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Coop Research

 

Natural Stand Research

Oak Enrichment Planting
New Oak Enrichment Planting Initiative
Oak and Yellow Poplar Individual Tree Release
Preliminary Herbicide Trial for Herbaceous Management and Tree Release
Continuing Studies of Constraints to Productivity in Very Young Stands
Understanding Density – Productivity Relationships in Young Stands
Thinning and Fertilization in a Seven-Year-Old Stand
Measuring the Impact of Edge Effects on Productivity
Stocking and Competition Management in Young Stands (Strip-Thinning), RW Study No. 70
Modeling Natural Stand Growth and Yield, RW Study No. 55
Assessing Alternative Regeneration Systems for Southern Hardwoods, RW Study No. 35

Plantation Research

Sweetgum Tolerance and Resistance to Defoliation
Sweetgum Seedling Family Screening and Heritability Estimations
Seedling Screening of Sweetgum, Loblolly Pine, Tecunmani Pine and Willow/Poplar
Sweetgum and Sycamore Tree Improvement, RW Study No. 90
Sycamore Disease
Sycamore Pulping
Sweetgum Rooted Cuttings
New Oak Rooted Cutting Initiative
Site Preparation Study for Sycamore, Sweetgum and Cherrybark Oak
Fertilization and Liming Response of Plantation Hardwoods, RW Study No. 46
Sweetgum Individual Tree Fertilization Trial
Sweetgum Foliar Nutrient Dynamics
SPAD Meter Nitrogen Diagnostics
Sweetgum Family Genotype X Fertility Interactions
European Black Alder Studies Revisited, RW Study No. 62

 Other Projects/Developments/News

HRC Web Page
HRC Member News
HRC Meetings
HRC Staff and Graduate Student News

Region-Wide Study Summaries

Active Region-Wide Studies
Inactive Region-Wide Studies

Recent Publications of HRC Staff and Students

 

 

 

 

 

 

Natural Stand Research

Oak Enrichment Planting

In March 1998 an enrichment planting study was installed on two sites in the NC Piedmont; a former mature hardwood stand salvage clearcut in winter 1996/1997 on the NC State Schenck Memorial Forest, and on a former loblolly pine plantation salvage clearcut in winter 1996/1997 on the NC State Hill Forest. On both of these sites, northern red and white oak seedlings (1-0) from the Georgia State Nursery and the Virginia State Nursery were randomly planted in three blocks into the regenerating clearcuts at a 3.1 x 3.1 m spacing. Additional information on these methods is included in the 1998 HRC Annual Report. Equal numbers of trees from each species/source (n=216 each) were treated soon after planting with a 0.9 x 0.9 m Vis Pore TM weed mat, 50 g diammonium phosphate (DAP) fertilizer per tree, weed mat + DAP, or untreated control.

During winter 2000/2001 each seedling was relocated and height and basal diameter measured and the three-year growth increment calculated (Table 1). Approximately 46% of the red oaks and 50% of the white oaks had been browsed (or for other reasons experienced height lose over the three years). Data were analyzed either for all surviving trees, or only for trees with > 0 growth. Initial seedling size within species/source did not differ, but did differ among species and sources. Blocking and site effects were not significant, and so data was pooled for the two sites. Given the independence among individual seedlings, each seedling within a species/source/treatment combination was used as a single tree plot in the analysis.

The data suggest that Georgia red oak and Virginia white oak responded positively to the treatments (Table 1). Seedlings treated with fertilizer, weed mat, or fertilizer + weed mat generally grew better than the controls. The response differences among the species/sources cannot be explained. These findings suggest a potentially positive impact of enrichment planting with treatments to improve the representation of oak in the developing overstory. These results can be compared to those in the "Oak and Yellow Poplar Individual Tree Release" section below, where natural oak regeneration on the same sites was similarly treated. These trees will be remeasured in future years.

This effort has been conducted by the staff and students of the HRC, with supplemental support from the Hardwood Forestry Fund of the Hardwood Plywood and Veneer Association.

 

Table 1. Mean height and basal diameter three-year growth increment measured three years after planting 1-0 stock into NC Piedmont clearcuts with four treatments. P value indicates the significance of the treatment effects for each species/source combination by ANOVA using initial height as a covariant.

 

Species/Source

Treatment

3-Year Height

Increment (cm)

P Value for Height

3-Year Basal Dia.

Increment (mm)

P Value for

Diameter

 

n

- - - -- - - - - - - - - - - - For All Seedlings Including Those with Height Increment < 0 - - - - - - - - - - - - - - - -

Red Oak / Georgia  

0.22

 

0.09

 
  Control

12

 

2.3

 

55

  Fertilized

23

 

2.9

 

54

  Weed Mat

27

 

4.2

 

52

  Fert + Weed

22

 

4.3

 

55

Red Oak / Virginia  

0.71

 

0.99

 
  Control

22

 

3.0

 

56

  Fertilized

32

 

3.4

 

54

  Weed Mat

28

 

2.7

 

50

  Fert + Weed

34

 

2.9

 

50

White Oak / Georgia  

0.81

 

0.82

 
  Control

40

 

5.8

 

51

  Fertilized

43

 

3.8

 

54

  Weed Mat

50

 

4.9

 

51

  Fert + Weed

47

 

4.6

 

56

White Oak / Virginia  

0.07

 

0.02

 
  Control

23

 

2.4

 

57

  Fertilized

30

 

1.7

 

53

  Weed Mat

29

 

2.6

 

54

  Fert + Weed

33

 

4.3

 

48

 

- - - - - - - - - - - - - - - - - - - - - For Seedlings with Height Increment > 0 - - - - - - - - - - - - - - - - - - - - - - - -

 
Red Oak / Georgia  

0.12

 

0.06

 
  Control

32

 

4.4

 

27

  Fertilized

42

 

4.0

 

22

  Weed Mat

40

 

4.7

 

26

  Fert + Weed

47

 

7.2

 

26

Red Oak / Virginia  

0.57

 

0.84

 
  Control

37

 

4.7

 

26

  Fertilized

41

 

4.1

 

22

  Weed Mat

47

 

5.6

 

24

  Fert + Weed

40

 

5.4

 

23

White Oak / Georgia  

0.80

 

0.89

 
  Control

48

 

5.1

 

39

  Fertilized

51

 

5.4

 

34

  Weed Mat

57

 

5.8

 

35

  Fert + Weed

58

 

6.3

 

36

White Oak / Virginia  

0.22

 

0.05

 
Control

37

 

4.7

 

28

Fertilized

41

 

4.1

 

33

Weed Mat

47

 

5.6

 

25

Fert + Weed

40

 

5.4

 

28

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New Oak Enrichment Planting Initiative

A USDA Special Grant was awarded to the NC State College of Natural Resources, for 2001/2002, with potential annual renewal for five years. Included in this grant is an initiative to expand the HRC’s oak enrichment planting and release work to the NC mountains. This effort will begin during summer 2001.

 

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Oak and Yellow Poplar Individual Tree Release
  1. One- and Two-Year-Old Trees

On the same sites as described in the "Oak Enrichment Planting" section above, naturally occurring oak regeneration was located in early spring 1998, and again in early spring 1999. This regeneration was from seed, root- or seedling-sprout origin, and while much of it may have been considerably older than one or two years (particularly the root systems), it was of the same size class as the seedlings planted in the Enrichment Study described above. This natural oak regeneration was dispersed around the sites, and consisted of a variety of upland oak species, pooled for analysis. Data from the two sites were pooled, and each tree used as a single-tree plot. Height and basal diameter of each tree were measured in the spring they were first identified, and then treatments applied: control, 0.9 x 0.9 m Vis Pore™ weed mat, 50 g DAP fertilizer, or weed mat + DAP. Height and basal diameter were remeasured in winter 2000/2001, 3 years or 2 years after treatments were applied in spring 1998 or 1999, respectively. Incremental growth was calculated (Table 2). Initial size of these seedlings did not vary among treatments, and no survivors showed a height lose during the measurement interval.

 

    Table 2. Mean height and basal diameter increment growth of natural mixed oak regeneration treated one or two years after regeneration, and remeasured three or two years later, respectively, on NC Piedmont sites. P value indicates significance of the treatment effects by ANOVA.

     

    Treatment

    Height

    Increment (cm)

    P Value for Height

    Basal Diameter Increment (mm)

    P Value for

    Diameter

     

    n

    - - - - - - - - - - - For Oaks Identified One Year After Clearcutting, 3-Year Increment - - - - - - - - - - - - - - -

         

    0.16

     

    0.02

     
      Control

    89

     

    11.8

     

    18

      Fertilized

    106

     

    17.3

     

    18

      Weed Mat

    70

     

    12.0

     

    18

      Fert + Weed Mat

    110

     

    19.7

     

    16

    - - - - - - - - - - - For Oaks Identified Two Years After Clearcutting, 2-Year Increment - - - - - - - - - - - - - - -

         

    0.75

     

    0.58

     
      Control

    34

     

    9.1

     

    38

      Fertilized

    46

     

    10.9

     

    41

      Weed Mat

    38

     

    9.8

     

    42

      Fert + Weed Mat

    38

     

    9.5

     

    36

     

The results suggests that oaks identified at the start of the second growing season following clearcutting on these sites, grew significantly better when treated with fertilizer (Table 2, top). Those oaks from this cohort treated with the weed mat showed no gain. Oaks identified at the start of the third season following clearcutting did not substantially benefit from the treatments (Table 2, bottom).

  1. Six- , Eight- and Fourteen-Year-Old Trees

On the NC State Hill Forest, in the NC Piedmont, former hardwood and mixed pine-hardwood stands that had been clearcut regenerated in 1985, 1990 and 1992 were used to assess the growth response of red/black oak, white oak, and yellow poplar to release treatments, initiated in fall 1998. Stems of these species, not from obvious stump sprout origin, were identified in dense six-, eight- and fourteen-year-old stands on an approximate 6.2 x 6.2 m grid with 3 blocks across the sites. In each block 18 to 29 trees of each species were identified, and treatments (see below) randomly assigned to them in approximately equal proportions. At the time of treatment, the six-year-old stand had a density of 33,358 stems per ha, and mean height of all species of 1.0 m; the eight-year-old stand had a density of 37,806 stems per ha and mean height of all species of 2.2 m; and the fourteen-year-old stand had a density of 13,111 stems per ha and mean height of all species of 4.2 m.

The following treatments were applied - -

  1. C = Control
  2. M = Manual release from woody stems by mechanically clearing a 1.8 m radius area in fall 1998
  3. M+Yr1R = Manual release as above, plus immediate treatment of cut woody stems with 50% Garlon™ herbicide
  4. M+Yr1R+F = Manual release as above, plus Garlon™ application as above, plus spring 1999 fertilization with DAP at 286 g per tree (560 kg per ha equivalent)
  5. M+Yr2R = Manual release as above, plus spring 2000 chemical release from woody sprouts and herbaceous competition with a tank mix application of 2.5% Accord™ and 0.0009% Oust™ herbicides

Height and DBH were measured at the time of initial treatment, and again during winter 2000/2001. Two-year growth increments were calculated (Table 3).

 

Table 3. Mean height and DBH two-year increment of individually treated stems on NC Piedmont sites (treatment explanations contained in text). "ANOVA" indicates level of significant differences among treatments.

 

 

6-Year-Old-Stand

- - - Increment - - -

8-Year-Old Stand

- - - Increment - - -

14-Year-Old Stand

- - - Increment - - -

Treatment

(Statistic)

Height

(m)

DBH

(cm)

Height

(m)

DBH

(cm)

Height

(m)

DBH

(cm)

- - -- - - - - - - - - - - - - - - - - - - - - - - - - - - - -Yellow Poplar - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

Control

0.93

0.61

1.40

1.04

1.31

0.74

M

0.80

0.89

0.86

1.11

0.87

0.80

M+Yr1R

0.86

0.92

1.25

1.02

0.97

0.93

M+Yr1R+F

0.79

0.85

1.12

1.04

1.01

0.79

M+Yr2R

0.79

0.90

0.80

0.96

1.64

1.03

(ANOVA)

P=.86

P=.39

P=.04

P=.96

P=.02

P=.32

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - -Red/Black Oak - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

Control

1.09

0.75

0.99

0.77

1.23

0.89
M

0.84

0.93

0.70

0.91

1.13

1.13

M+Yr1R

0.70

0.91

0.91

1.22

1.18

1.14

M+Yr1R+F

1.00

1.44

0.66

1.17

0.87

1.22

M+Yr2R

0.83

0.98

0.58

0.97

1.34

1.15

(ANOVA)

P=.02

P=.06

P=.11

P=.39

P=.64

P=.31

- - -- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - White Oak - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

Control

1.18

0.98

1.13

0.77

0.95

0.82
M

0.87

1.40

0.80

0.91

1.24

0.97
M+Yr1R

0.86

1.48

0.95

1.22

0.94

1.08

M+Yr1R+F

1.01

1.49

0.89

1.17

0.85

1.25

M+Yr2R

0.83

1.34

0.76

0.97

0.83

1.11

(ANOVA)

P=.03

P=.02

P=.06

P=.02

P=.29

P=.68

 

The data from this release study do not indicate any clear patterns of statistically significant positive effects of the treatments on individual tree growth. However, there does appear to be a depression of height growth with the treatments relative to the control in most of the age/species combinations. Diameter growth responded positively to the treatments in eight of the nine age/species combinations. When comparing the diameter growth of controls to the average response to all treatments for each species/age combination, the treatment effects appear substantive. Considering the data in this fashion, suggests that the treatments, on average, generated a 20 to 46 % diameter increase over the controls. Tree growth will continue to be monitored in future years. It is too early to make any conclusions from this experiment, although current (early) results are promising.

This study was installed by students from the Hill Forest work crews, with support from the NC State School Forest Trust Fund, and the Hardwood Forestry Fund of the Hardwood Plywood and Veneer Association with principle funding from the Triangle Pacific Corporation. Larry Jervis, particularly, and Heather Williams, Brandon Greco and Corbitt Simmons were instrumental in this work.

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Preliminary Herbicide Trial for Herbaceous Management and Tree Release

In an effort to explore the potential for broadcast herbicide application for the control of competition in regenerating natural stands, a screening trial was installed at NC State’s Hill Forest in the NC Piedmont. The site was formerly occupied by a mixed pine-hardwood stand, clearcut and then burned during 1999. In February 2000, 25 sq. m plots were delineated in the 1-year-old stand, for treatment with three preemergent control herbicides, replicated six times. In this preliminary trial, only a single rate of each herbicide was applied to examine the potential efficacy of this approach for enhancing tree growth. In each plot, nine to 13 trees (seedling, stump or root origin) of various species were tagged and height and basal diameter measured prior to herbicide treatment. In winter 2000/2001 these tree were remeasured and the one-year growth increment calculated (Table 4).

 

Table 4. Mean height (cm) and basal diameter (mm) one-year growth increment (n=6 replications) of regeneration during the second growing season following clearcutting and burning of an upland Piedmont natural hardwood forest in North Carolina, and treatment prior to budbreak of the growing season with herbicide, plots size of 25 sq. m.

 

Control

Casoron

Oust

Plateau

ANOVA

P Value

All Species          
Height Increment

44.8

50.3

53.9

42.1

0.009

Diameter Incr.

7.0

5.4

8.5

5.0

0.417

Total n All Reps.

73

53

79

62

 
Sweetgum          
Height Incr.

55.6

65.6

58.6

46.5

0.289

Diameter Incr.

7.0

9.7

6.7

5.5

0.032

Total n All Reps.

23

22

34

24

 
Mixed Oaks          
Height Incr.

34.5

19.5

52.7

38.3

0.154

Diameter Incr.

4.3

4.3

7.2

3.4

0.289

Total n All Reps.

16

8

18

12

 
Mixed Pines          
Height Incr.

52.0

50.1

60.9

39.8

0.115

Diameter Incr.

7.0

6.5

10.3

6.2

0.190

Total n All Reps.

19

8

7

18

 
Note: In all cases except for mixed pines, initial height was a significant covariate in the ANOVA across herbicide treatments by species. Casoron™ (dichlobenil) applied at 6.725 kg/ha active ingredient, Oust™ (sulformeturon) applied at 0.158 kg/ha active ingredient, and Plateau™ (imazipic) applied at 0.210 kg/ha active ingredient.

 

Results suggest a mixed tree growth response to the treatments, but considerable potential for using this technique to enhance productivity in very young stands. This corroborates other HRC studies of weed competition effects on regenerating stems, reported elsewhere in this Annual Report. In this study, initial height was a highly significant factor, and was used as a covariate in the statistical analyses, except for pine. The findings suggest that at the rates and conditions tested, the herbicide Oust™ most consistently provided a growth advantage to the trees, while Plateau™ and Casoron™ yielded more variable results. It is not possible to conclude very much from this preliminary trial, except that this silvicultural approach is worth further study.

This study was conducted by HRC staff, in collaboration with Joe Neal and Robbie Wooten of the NC State Department of Horticulture.

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Continuing Studies of Constraints to Productivity in Very Young Stands

The growth and development of very young natural even-aged hardwood stands is not well understood. The relative importance of biotic and abiotic constraints such as overstocking, herbaceous competition, tree nutrition, and pest impacts have not been widely studied in these types of stands. Earlier HRC work has demonstrated significant tree growth response (2- to 20-fold) to release from these constraints. Here we report on the continued measurement of these plots through year 4, and on a new series of plots in 1- and 3-year-old stands that have been followed for 1.5 years. Treatments imposed include thinning, herbaceous competition control, fertilization, and combinations of these treatments. These experiments are beginning to show the potential of very early stand interventions to shorten rotation ages in upland hardwoods. These efforts are part of a broader set of initiatives across the South by the HRC to explore early interventions for stocking and competition control as a silvicultural option in managing hardwoods.

The first study, initiated in spring 1998, was installed on three clearcut sites in the NC Piedmont. The sites are located on two of the NC State University owned forests, the Schenck Memorial Forest (Wake County) and the Hill Forest (Durham County). Each site was salvage clearcut during the winter of 1996/97, prompted by Hurricane Fran. The three sites previously held stands of mixed pine-hardwoods, natural mixed hardwoods, and a loblolly pine plantation. All sites have south-facing aspects and Cecil sandy loam soils on 2-10% slopes.

Four treatments were applied to 10 sq. meter square plots with 1 m borders in a randomized complete block design with 4 replications. The treatments, applied during the growing seasons of 1997 and 1998 (years 1 and 2 after clearcutting), consisted of—

  1. Pesticide = an insecticide, fungicide, and mammal repellant sprayed periodically over the vegetation
  2. Weeded = hand shearing of all non-hardwood vegetation
  3. Full = pesticide + weeded treatments
  4. Untreated control

Due to space restrictions, site 1 had all four treatment plots, site 2 only treatments 3 and 4, and site 3 had treatments 1, 3 and 4. The data reported include the two years when treatments were applied (age 1-2) and the two years after treatments were discontinued (age 3-4).

In the second study, treatments were established on two other upland NC Piedmont sites. The Hill site (Hill Forest), formerly a 2 ha loblolly pine stand with a small component of hardwoods, was clearcut logged in 1999. The Duke site (Duke Forest, Orange County), formerly a 5 ha mature mixed oak stand, was salvage clearcut in 1996/97 in response to damage from Hurricane Fran.

Ten sq. m circular plots with 1 m borders were randomly located, insofar as each plot contained at least 2 yellow-poplar and 2 oak trees. Each site contained a total of 8 treatments replicated in 4 blocks. The treatments were initiated in July 1999 and continue to the present. The treatments were installed in a 2 x 2 x 2 factorial design with the main factors being--

  1. Weeded vs. unweeded = hand removal of all non-arborescent vegetation
  2. Fertilized vs. unfertilized = 90 kg/ha of nitrogen and 100 kg/ha of phosphorus applied as diammonium phosphate
  3. Thinned vs. unthinned = stem density reduced to 4 stems/plot, consisting of 2 yellow-poplar and 2 oak trees

The data reported here for the second study is far the 5 most dominant yellow-poplar in each of the unthinned plots and the 2 yellow-poplars in each thinned plot. Therefore, the data represented a total of 8 stems on thinned and 20 on unthinned plots. This was done to reduce the error associated with different species composition among treatments and blocks. Yellow-poplar was selected for comparison because it represents an important timber species in the region, it existed in all plots, and as a fast-growing shade intolerant species it provides a rapid measure of treatment effects.

In the first experiment there were significant gains attributed to weeding and full treatments for the first 2 years (Figure 1). After 4 years of growth (treatments were applied during the initial 2 years) the full treatment still has greater cumulative heights and diameters, but significant differences (P<0.05) only occurred for height growth. By year 4, the pesticide and control treatments marginally surpassed the weeded treatments in height and diameter growth. These trends suggest convergence among treatments.

However, the application of the treatments inadvertently complicated the study. For the weeded and full treatments, all non-hardwood vegetation, including pine trees, were periodically sheared for 2 years. As a result, we are seeing the effects of loblolly pine on the control and pesticide treated plots (where they were not removed) beginning to out compete the hardwood seedlings on these shallow Cecil soils with southerly-facing slopes. On the control and pesticide treated plots at the end of year 4, loblolly pine accounted for roughly 50 and 75% of the stem count, respectively. By the end of the 4th growing season (2000), the loblolly pine component was accumulating more diameter and height growth than the hardwoods. By examining the curves and either mentally factoring pines into the full and weeded plots, or factoring them out of the pesticide and control plots, in Figure1, and either mentally factoring pines into the full and weeded plots,or factoring them out of the pesticide and control plots, the trends suggest a continuing positive effect of the treatments.

 

Figure 1. Mean (3 sites, 8-12 plots per treatment) height (top) and basal diamter (bottom) of natural regeneration following winter 1996/97 clearcutting on NC upland piedmont sites. Different letters indicate statistical differences at P=0.05 using ANOVA protected LSD means separation procedure. The arrow indicates the time when treatments were discounted.

wpe2.jpg (32365 bytes)

 

In the second set of experiments, initial height measurements were significantly different (P<0.05) among treatments for both sites, and were used as a covariate in the analysis. Fertilization significantly improved yellow-poplar height growth (+54%) after 1.5 years on the 2-year-old Hill site (Figure 2a). The combination of fertilization + weeding showed a positive interaction (P=0.0791), as did thinning + weeding (P=0.0587). Results suggest that weeds compete more strongly than seedlings with the dominant yellow-poplar trees. However, when both competitors were removed large gains in height growth were observed.

Fertilization significantly enhanced yellow-poplar height growth (+15%) after 1.5 years, on the 4-year-old Duke site (Figure 2b). Again, weeding and thinning treatments had no measurable positive effect on dominant yellow-poplar height growth. Fertilization out performed all other treatments except for the combined effects of thinning + fertilization + weeding. Even when thinning, weeding, and fertilization treatments were combined, yellow-poplar trees only grew 10% more than with fertilization alone.

Collectively, these findings suggest that early stand interventions can substantially increase hardwood growth, and that broad-cast fertilization may have good potential as a low-cost tool to enhance productivity in these stands. Weeding also can generate a substantial growth increase, and if it can be accomplished in a commercially efficient manner, it too may offer promise for accelerating natural stand growth, especially when coupled with fertilization. Thinning at these very young ages does not appear to benefit productivity unless coupled with another treatment.

This study is being conducted by Jamie Schuler of the HRC as a portion of his Ph.D. research, including the continued measurement of the plots in the "first experiment" (described above) established in 1998 by Mark Romagosa from his M.S. research with the HRC. 

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Understanding Density - Productivity Relationships in Young Stands

Stocking guides have not been devised for young natural hardwoods, and for density management to become a useful tool it will be necessary to know optimal densities to best enhance growth, form and perhaps species composition. The growth of individual stems within a mixed forest is influenced by the interaction of factors such as density (competition), genetics and microsite. In this study we are examining density/competition relationships for hardwood timber species in mixed natural even-aged stands in the NC Piedmont, from a sequence of age classes. On the NC State Hill Forest and the Duke Forest, individual dominant stems in stands aged 5 to 30 years have been measured and cut for stem analysis, and all trees with crowns touching the study tree have also been measured. This work began in summer 2000, and will continue through 2001/2002. It is hoped that the effect of density/competition on individual stem growth can be ascertained, and used to craft a stocking guide as a tool for interventions in young stands. This work is a portion of Jamie Schuler’s Ph.D. research for the HRC.

 

Figure 2. Mean (+SE) height of dominant yellow-poplar at age 2 (1.5 years of treatment) at the Hill Forest (top), and at age 4 (1.5 years of treatment) at the Duke forest (bottom).

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Thinning and Fertilization in a Seven-Year-Old Stand

Young even-aged hardwood stands undergo a period of intense competition and self-thinning during the early years of stand development. During this time relatively little growth is accumulated by stems which will persist until rotation age. This study reports on an experiment in a seven-year-old stand in northeastern NC, in which growth responses to thinning to 3000 trees per ac and fertilization with N and P were evaluated. Accelerating the growth of naturally regenerated hardwood stands is an important goal of forest managers. Across the southern U.S. many of these stands are even-aged, having regenerated following clearcutting. Through the natural processes of regeneration (including stump and root sprouts, and seedlings), stand consolidation and self-thinning, timber typically reaches merchantable size in 40 to 60 years. Common methods of promoting the growth of these stands take place when the timber is at least pole-sized, often 20 to 30 years old, and stand density has naturally declined to a few thousand stems per ac. Fertilization and thinning in younger stands may accelerate the rate of stand development, concentrating growth on fewer and more valuable stems, and reducing rotation age. These changes could have significant economic advantages.

Studies in natural hardwoods have long demonstrated that thinning can have many positive benefits in production forestry, provided damage to the residual stand and soils are prevented. Few studies have reported on thinning in stands less than 10 years old. Most reports are from Appalachian uplands. Fertilization in natural stands has been infrequently studied, with reports indicating a variety of stand responses. It is well established that enhancing site resources through fertilization, and reducing inter-tree competition (and herbaceous competition) through density control, and these factors in combination, can enhance productivity, often for many years following treatment. In the current study we report initial findings from a fertilization and thinning trial in a young coastal plain upland hardwood stand.

The study site is located on International Paper Company land (formerly a Union Camp Corporation site) in northeastern NC (Northampton County) on a coastal plain mineral flat of somewhat poorly to poorly drained silty clay loam soil (Lenoir series). These soils can be phosphorus-deficient, with relatively low productivity. The stand consists of naturally regenerated mixed pine-hardwoods, which grew following a commercial clearcut of the prior natural stand in 1990. The current dominant species are sweetgum and red maple.

The experimental design was a 2 x 2 factorial (thinning and fertilization as main effects) with three blocks. Treatments were imposed when the stand was 7 years old with a density of approximately 8500 stems per ac. Treatment plots measure 166 ft. x 166 ft., with interior measurement plots of 100 ft. x 100 ft. Within each measurement plot there were 13 circular 154 sq. ft. subplots. Thinning was done in winter 1997 by reducing density to circa 3000 stems per ac with a brushcutter, using spacing and desirable species as a guide. Fertilizer was hand broadcast applied in spring 1998 as 200 lbs. per ac N (in urea and diammonium phosphate [DAP]) and 50 lbs. per ac P (in DAP).

Here we present data on mean tree size (Height and DBH) at age 10 (measured winter 2000/2001), and the 3 year increment between age 7 (measured May 1997) when treatments were applied and age 10. Stand volume, and increment, by treatment are also presented. Volume was estimated by summing subplot standing volumes for each treatment plot, and using an expansion factor to express them on a per ac basis. DBH and height were measured for all stems >4.5 ft. tall and >1.5 in. diameter (DBH). Stem volume was calculated as (DBH2*Height)*(0.002). Canopy cover was estimated with a spherical densiometer in mid-August 2000.

Differences in tree size and cover among the treatments were visually apparent 3 years after thinning and fertilization. Densiometer readings of canopy cover were, control 77%, fertilized 86%, thinned 56%, and thinned + fertilized 83 %. Ground cover patterns, data not reported here, reflected the inverse of the densiometer readings, and trees were noticeably larger in the treatment plots than the controls. Given the demonstrated positive relationships between leaf area, as approximated by densiometer readings in this case, and productivity, we would expect that the treatment plots with high canopy cover would be more productive.

There were no significant differences (P>0.10) in height, DBH or estimated volume among treatment plots in May 1997 immediately post treatment. Three years after the treatments were applied, mean height, DBH and volume, and 3-year cumulative increments for these measures, differed significantly among treatments (Table 5). The interaction between thinning and fertilization was only significant for the volume estimates. Blocking effects were significant at age 10 for all parameters (P<0.05). In general, the control and thinned plots did not differ, and had smaller trees than the fertilized and thinned + fertilized plots, which were similar to each other. For all parameters measured, the thinning effect was not significant (P>0.10), and the fertilization effect was significant (Table 5).

The data suggest that height growth was more responsive to the treatments than diameter growth, and that thinning alone did not generate a substantial growth response, whereas fertilization did. Observations of the thinned only plots suggests that thinning in this stand resulted in site resources being made available to competing plants (herbaceous, woody shrubs [notably wax myrtle], and stump sprouts of cut trees), without benefit to the residual stand. When thinning was coupled with fertilization, however, the residual stand was apparently able to capture a significant portion of the newly available and added site resources, and exhibit a positive growth response. Fertilization alone resulted in increased growth for most parameters, and suggests that this low-cost silvicultural intervention may have good operational potential. Although thinning coupled with fertilization did not appreciably increase growth over fertilization alone, the data trends and significant interaction between these treatments suggest that over time, the combined effect may be greater than either individual treatment.

The treatments in the current study do not indicate what the effect of thinning + weed control might have been, however, other studies suggest that the positive aspects of density reduction can be realized in young stands when weed control is used. Further, it cannot be determined which fertilizer element was responsible for the positive effects recorded in this study, nor does this study reveal optimum rates or timing for fertilization. However, the results reported here suggest that substantial productivity gains may be realized in very young stands with these types of interventions.

 

Table 5. Mean growth response after 3 years of trees treated at age 7, in a naturally regenerated NC coastal plain upland. Means within a column followed by different letters are significantly different at P=0.10, by protected LSMeans. "ANOVA" indicates the statistical analysis for each parameter across treatments, and "Fertilization" and "Thin X Fert" indicate the significance of the main effect or treatment interaction for each parameter. Thinning was not a significant main effect.

Treatment

(Statistics)

Height (ft.)

DBH (in.)

Volume (cu. ft. per ac.)

- - - - - - - - - - - - - - - - - - - - Measures at Age 10 - - - - - - - - - - - - - - - - - - - - - - -

Control   22.7 ab   2.43 a   353 a
Thinned   22.0 ab   2.44 a   317 a
Fertilized   23.8 ab   2.52 a   557 b
Thinned + Fertilized   24.6 b   2.82 b   660 c
(ANOVA)   P=0.025   P=0.018   P=0.0002
(Fertilization)   P=0.030   P=0.070   P=0.0001
(Thin X Fert)   P=0.327   P=0.233   P=0.056

- - - - - - - - - - - - - - - 3-Year Cumulative Increment Age 7 to 10 - - - - - - - - - - - - -

Control   4.2 a   0.33   266 a
Thinned   4.5 a   0.35   220 a
Fertilized   5.8 b   0.50   479 b
Thinned + Fertilized   6.1 b   0.70   538 b
(ANOVA)   P=0.011   P=0.145   P=0.0002
(Fertilization)   P=0.010   P=0.040   P=0.0001
(Thin X Fert)   P=0.972   P=0.434   P=0.086

 

This study is being conducted by Leslie Newton for her M.S. research with the HRC. Supplementary funding for this work was provided by Union Camp Corporation, and the initial study design and installation was conducted by Jerry Hansen of Union Camp Corporation, now with International Paper Company.

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Measuring the Impact of Edge Effects on Productivity

Given the HRC’s interest in density control in young stands, and the potential to employ strip-thinning as an operational broad-scale tool to accomplish this (see "Stocking and Competition Management in Young Stands" section below), it is important to understand the relationships between thinned (cleared) strip width and depth into the residual stand that a positive growth impact might be found. There may also be strip-thinning x species interactions to consider. When the study described above, "Thinning and Fertilization in a Seven-Year-Old Stand," was installed, each plot (total of 12) was delineated by clearing a 3.1 m wide corridor around the entire plot (51 m on each side), and treating it during the initial year with Accord herbicide to control regrowth. These cleared corridors were essentially strip-thinnings through a 7-year-old stand. Two years after they were installed (winter 1999/2000) tree measurements were taken from the edge of each plot next to the cleared corridor, into the plot itself, to evaluate the growth impacts of such thinning.

Using the three "control" plots, on each side of these plots, three sample transects 1.8 m wide by 9.2 m deep were delineated (n=12 transects per plot) , and every woody stem measured (height and DBH) and their distance from the edge recorded. Data were examined graphically to determine if trees near the edge were growing at a rate faster than those more distal from the edge. Preliminary findings weakly suggest that there may be a positive growth effect for trees 1 to 2 m from the edge. Stems closer to the edge did not benefit, and those more than 4 to 5 m deep in the stand also did not benefit from the cleared strip. These relationships were most evident for the largest trees measured. When only the largest trees were considered, there was a distinct growth advantage to being closer to the cleared strip. Small trees were found and were not effected at any distance from the edge. Some of the trees measured in the first 1 to 2 m of the stand were from stump sprouts along the edge of the cleared strip, and others small stems that might not have survived except for the light entering from the edge itself. While further analysis is underway, several factors have already become important to consider. Although the benefit of an edge effect is readily seen in many older trees growing next to open areas in many places (a common observation worldwide), it is not clear at what rate this effect emerges after the clearing. Further, in this study, two years of growth in such a young stand may not have been sufficient to generate much of a gradient effect. However, given that growth is cumulative, the edge effect may emerge more strongly as the stand matures. These initial findings may have significance for the HRC’s study on strip-thinning (see below).

This work is being conducted by Leslie Newton and Peter Birks.

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Stocking and Competition Management in Young Stands (Strip-Thinning), Region-Wide Study No. 70

A region-wide study of stand response to strip-thinning and associated treatments was designed by the HRC in early 1999, and was installed by HRC member Temple-Inland Forest Products Corporation in 1999/2000. Other HRC members may also install this study. In even-aged hardwood stands in the 3 to 5 year-old age class, and/or in the 8 to 10 year-old age class, 3.1 m wide strips every 3.1 m are mechanically cut through the stand and maintained vegetation-free with herbicides. Within the 3.1 m wide leave strips, various combinations of individual tree release, fertilization and herbaceous weed control are deployed, with appropriate controls. Stand growth and development is then monitored. This approach may result in an operational means of treating young stands to capture their growth potential as demonstrated in other HRC studies in young stands. This study was described in detail in the 2000 HRC Annual Report. Response data will not be available for several years.

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Modeling Natural Stand Growth and Yield, Region-Wide Study No. 55

The HRC has begun the process of developing a suite of natural stand hardwood growth and yield models with data collected since 1968 from G&Y plots on member lands. In the mid-1990s, HRC member Georgia-Pacific Corporation (now The Timber Company) used this data to privately develop G&Y models. They have now provided the model forms from their effort to the HRC for reparameterization. This work was begun by HRC visiting scientist Xiaoyi Cheng (sponsored by the Jiangsu Provincial Bureau of Forestry, China) in 1999/2000, with substantive assistance from John Paul McTague of HRC member Champion International Corporation. During 2000/2001 this effort has been taken over by Joe Roise of the NC State Department of Forestry. The initial work should be completed during 2001, and models made available to HRC members. Later, model accuracy testing, development of stand level attribute models, linkage of model output to volume equations, and development of a user-friendly interface may be undertaken.

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Assessing Alternative Regeneration Systems for Southern Hardwoods, Region–Wide Study No. 35

On a variety of southern hardwood forest types (Coastal, Piedmont, and Appalachian), this study was designed to evaluate the quality, quantity, species composition, and development of natural hardwood regeneration and aesthetic responses of the forest to different harvesting (regeneration) systems. Treatments were unharvested control, clean-cut, two-stage shelterwood, and deferment cut. Immediately after overstory harvest, 0.01 ha permanent overstory plots and 0.0004 ha permanent understory plots were established in each treatment. The overstory plots were measured immediately after the experimental harvests, including species, diameter, height (total and merchantable) and condition (crown/bole/epicormic sprouts). Both the overstory and understory plots are scheduled for remeasurement at five year intervals. The understory plots will be first measured five years after the experimental harvest, recording species and size of all trees. The study was installed at 15 sites between 1993 and 1995. These include one each in TN, MS, WV, FL and AL, two each in SC and GA, and six in NC. During the first growing season after installation of the harvests was complete, regeneration on three sites (NC coastal plain, NC Piedmont, WV mountains) was studied in detail and reported in an M.S. Thesis (M.M. McKinney, 1996) under the direction of Ted Shear at NC State, and in the Proceedings of the First North American Forest Ecology Workshop, 24-26 June 1997, Raleigh, NC. The initial five-year remeasurement was accomplished at two of the sites in 2000 and 2001. Data analysis will be conducted as resources allow.

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Plantation Research

Sweetgum Tolerance and Resistance to Defoliation

Sweetgum is an important hardwood plantation species in the U.S. south, and the focus of considerable HRC genetic and silvicultural research and development. While having a high degree of native pest resistance sweetgum remains susceptible to defoliation by the outbreak species gypsy moth, Lymantria dispar, and forest tent caterpillar, Malacosoma disstria, among others. While the gypsy moth continues to spread throughout the range of sweetgum, the forest tent caterpillar is a common native pest of sweetgum in the region. The work described here is conducted within an integrated plantation research and genetic tree improvement effort by the HRC. Genotypic families used in this work are the focus of other detailed ecophysiological studies by the HRC, and field work is within the context of intensively managed/operational plantations. This work will provide a basis for determining economic injury levels on young sweetgum, and provide a beginning foundation for assessing the utility of screening for generalist insect folivore resistance in the sweetgum genetic improvement program of the HRC.

I. Artificial Defoliation

This work is being performed in an operational sweetgum plantation in eastern North Carolina (Hertford Co.) on International Paper Company land. The plantation was established with 1-0 seedlings on a clearcut coastal plain site following mechanical and chemical site preparation, and received annual operational fertilization and weed control treatments during its first two growing seasons. On trees beginning their second field season, artificial defoliation treatments of 0, 33, 67, or 99 % were applied over a two-week spring period in 1999 using rough-cut scissors. Defoliation consisted of progressive cutting of outer crown leaves followed by inner crown leaves and buds to mimic the temporal and spatial nature of folivore feeding. Trees were selected prior to defoliation for overall tree and site uniformity (n=12/treatment). There were no significant differences in tree size prior to installation of the treatments. In spring 2000, plots were split (n=6/treatment) and defoliation treatments applied again to half the trees in the same manner as described above.

Tree growth response to the defoliation treatments was assessed by measuring height and diameter increment growth after the first growing season following the year 1 defoliation treatments, and again after the second growing season of the experiment following additional defoliation on half of the study trees in year 2 (Table 6).

 

Table 6. Mean one– or two-year height and DBH increments of plantation sweetgum defoliated in the spring of their 2nd field growing season (defoliated only in year 1 of the study), or defoliated in the spring of their 2nd and 3rd growing seasons (defoliated in year 1 and year 2 of the study), in northeastern NC.

%

   

Defoliation

(ANOVA)

- - - - - - - - - - - Defoliated Only in Year 1 - - - - - - - - - - - -

Defoliated in Year 1 and Year2

(same amount each year)

 

Height (cm)

Increment

Year 1

DBH (mm)

Increment

Year 1

Height

(cm)Increment

Year 2

DBH (mm)

Increment

Year 2

Height (cm)

Increment

Year 2

DBH (mm)

Increment

Year 2

0

69

21

126

32

126

32

33

63

24

125

32

117

31

67

57

20

142

27

104

26

99

42

17

143

31

91

17

(P value)

<0.05

<0.05

>0.05

>0.05

<0.05

<0.05

 

Results of the artificial defoliation study indicate that sweetgum stem growth is tolerant of mechanical foliage loss. Results may differ with actual pest defoliation, and as site, cultural, genetic and timing/age factors change. The findings in the current study do provide substantial guidance for dealing with expected and measured foliage loss in this species in the absence of additional experience and research. In this study, a single season of defoliation resulted in a substantive growth loss only when defoliation exceeded 67%. If this level of defoliation was not followed by a subsequent year of defoliation, then in the second year there was no measurable growth loss. This suggests that during the first year of defoliation, protecting foliage through insecticide applications is not warranted. However, when a second (consecutive) year of defoliation is expected, then substantive growth reductions are likely in trees defoliated more than 67%, and pest management may be useful. These trees will be measured again in fall 2001 to assess growth 3 years after the initial treatment. A small follow-on study was initiated in spring 2001, in which four 4-year-old trees from each of two sweetgum families at the NC State Reedy Creek Experimental Farm were defoliated 99% (and controls identified), to investigate genotype X defoliation tolerance interactions in sweetgum.

II. Bioassay Screening for Differential Resistance Among Families

The HRC has focused its eco-physiological studies on a subset of 16 families with a broad genetic background from the approximately 400 families in the sweetgum tree improvement program. These 16 families will be used to develop an understanding of the behavioral and developmental interactions of the forest tent caterpillar with sweetgum. It is hoped that these experiments will help to evaluate the utility of two screening methods for determining genetic control of differential resistance to defoliation among sweetgum families, and contribute to our understanding of induced resistance due to defoliation. All assays will be conducted on young, fully expanded early-season leaves.

Leaves from these 16 families from a 3-year-old HRC progeny trial at the NC State Reedy Creek Experimental Farm were collected in May 2000 for bioassays. Forest tent caterpillars were reared from field collected eggs (from northern Michigan collected by Mike Young, International Paper Company) on artificial diet until reaching the second instar in preparation for the bioassays.

Behavioral preference assays were conducted in petri dishes, with leaf disks from each sweetgum family randomly arranged around the edge, and L2 larvae allowed to make selective feeding choices among the families. Relative consumption of each family was used to assess behavioral preference (Figure 3).

 

Figure 3. Feeding (24 hours) by second instar forest tent caterpillars in a multi-choice petri-dish behavioral preference bioassay among 16 sweetgum families.

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Developmental performance assays were conducted in rectangular plastic rearing boxes with single leaves from each sweetgum family placed in each box with their petiole in a water vial. Ten L2 larvae were placed in each box and allowed to feed freely. After six days the change in insect weight was recorded to assess developmental performance on these families (Figure 4).

                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 

Figure 4. Feeding (six days) by second instar forest tent caterpillars in a no-choice rearing-box developmental performance bioassay of 16 sweetgum families.

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The results of the behavioral preference and developmental performance assays indicate significant differences among families in their natural resistance to feeding by the forest tent caterpillar. Inasmuch as the forest tent caterpillar is a generalist folivore, and plant resistance to it is likely to be correlated with resistance to other similar folivores, this approach may be a way to assess the relative resistance of sweetgum families to this type of insect in the HRC tree improvement program. Such an approach could be useful in developing an advanced breeding strategy.

Additional feeding bioassays are planned for spring/summer 2001. This work is being conducted by HRC M.S. student Robert Jetton.

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Sweetgum Seedling Family Screening and Heritiability Estimations

This experiment was described in the 1999 and 2000 HRC Annual Reports. The intent of this work is to investigate the ranking and range of growth and ecophysiological responses to stress treatments among sweetgum families, and to discover if through stress treatments and various methods of data analysis first year seedling growth might be well correlated with field growth. These goals are important to the HRC tree improvement effort. As these efforts progress, it will be desirable to screen families (and eventually clones) for stress tolerance, as well as good growth rates; and it would be efficient to be able to effectively screen families (clones) for growth potential at very young ages. The application of stress, and perhaps the use of multivariate analyses, may provide more accurate production potential ranking of seedlings than has previously been found for seedlings.

In summer 1997, seed from 22 sweetgum families were sown in a greenhouse at NC State. Sixteen of these families were from the HRC sweetgum clone bank in St. George, SC, and six were provided by Union Camp Corporation. Eight treatments in a split-split plot design were applied: with and without 33% shade, with and without 73% artificial defoliation, and with high and very low fertility. Tree growth and a variety of associated traits (i.e., foliar nutrient concentrations, leaf area, biomass by plant component, etc.) were measured periodically throughout the first season and at the end of the first season of growth in the greenhouse. At the end of the season, about one-third of the seedlings were removed for field planting at the NC State Reedy Creek Experimental Farm, in a modified progeny test design. These same families are also in the HRC region-wide progeny trials.

Among the traits measured on all families - - light, fertility, defoliation, light by fertility interactions and family were found to be significantly different at P<0.10 for all traits. No significant differences were found for light by defoliation, fertility by defoliation and family by defoliation, or any three way interactions for any trait. Light had the greatest effect on all tree morphological characteristics, except leaf area, which was most strongly effected by fertility. The fertility treatment was second most important for all morphological treatments, except leaf area. The defoliation treatment was consistently third in importance. Significant differences among families were found for all morphological traits. Means separation showed greater separation between families grown under the more stressful treatments than under the other treatments. The data has also be used in the multivariate approach of Principle Components Analysis, and genetic heritability (h2) calculated for each trait. This work will be finalized soon, and an M.S. thesis and related publications produced. Here we report the results of the heritability analyses among the 16 HRC sweetgum families with data from the greenhouse work. The families provided by Union Camp Corporation were from a different genetic population and were not included in these analyses.

The genetical analyses were preformed using two methods, with variance components calculated using REML in the PROC VARCOMP procedure in SAS (Statistical Analysis System, 1990, SAS Cary, NC). Family heritability (h2) was estimated, 1) for each measured trait (e.g. height, diameter, foliar nutrients) under each of the eight treatments (considered "environments" in this analysis) separately, and 2) for each trait when all treatments were combined, and treatment and replication considered as random factors. For a number of trait / treatment combinations, h2 could not be calculated because there was as much variation between families within each plot, replication and/or treatment, as within families. Calculated h2 in these analyses ranged from 0.1 to 1.67. While an h2 >1 may be erroneous, in the current study they were most probably due to the small sample sizes. The standard errors (SE) associated with these large h2 estimates were modest.

There was a wide range of h2 values associated with each trait when calculated separately under each of the eight treatments. Twenty-one of the 64 h2 estimates were greater than 0.50. For cases in which the long form SE was not more than 50% of the h2 value, there was no discernable trend among traits across treatments. In two of the eight treatments, root collar diameter, leaf area, stem biomass and foliar %K each had an SE less than half of the h2 estimate. For a variety of other traits, h2 values were >0.75 in a single treatment. Overall, the treatments (environments) yielding the greatest number of large heritability estimates were full light / low fertility with or without defoliation, and shade / high fertility / defoliation. Generally the morphological traits had higher h2 values than the foliar nutrient traits. The heritability estimates calculated for traits with all treatments combined were all less than 0.50. However, in almost all cases the associated SE’s were very small relative to the h2 values. These results suggest that substantial amounts of variation in seedling performance can be assigned to genetic control, but that this may differ markedly in different environments. As trees mature these relationships may also change. These findings, when coupled with the univariate and multivariate approaches to measuring and analyzing sweetgum family performance in this study, support the notion that under appropriate environmental conditions it may be possible to correctly rank families for future field performance. Such a ranking is unlikely to be a precise determination of relative performance, but rather a means to separate those expected to be higher performing families for which more genetic improvement investment is justified, from those likely to perform poorly.

This work is being conducted by HRC M.S. student Peter Birks. The findings from this work have been used to select sweetgum families and techniques for a variety of other research studies described in this Annual Report, including the study described next, as well work on sweetgum resistance to defoliation, and genotype x fertility interactions.

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 Seedling Screening of Sweetgum, Loblolly Pine, Tecunmani Pine and Willow/Poplar

As a test of the hypothesis that the performance of seedlings under stress better predicts field performance than other seedling screening methods, a greenhouse trial was established building on the M.S. research of Peter Birks (see section above in this report, "Sweetgum Seedling Family Screening"). If a reliable method of seedling screening can be devised, then the efficiency of tree improvement efforts can be greatly increased. The underlying theory to this approach is that stress is what actually determines the success of various genetic entities in the field, and that only by challenging seedlings with stress can their performance potential be evaluated. This is contrary to the good growing conditions typically used in seedling screens and progeny tests. In this study we are testing (during spring/summer 2001) the growth of seedlings under high stress (low light and low fertility) and low stress (full light and high fertility) conditions in a greenhouse, in a seedling progeny test design. The design is 20 genetic entities per species, in 20 single-tree replicates, in each of two stress conditions. The genetic entities are - -

  1. Sweetgum (seed from 20 families) with as yet unknown field performance (the same as used in Birks’ research, and being tested in various HRC progeny trials)

  2. Loblolly pine (seed from 20 families) with known field performance (supplied by Steve McKeand of the NC State Tree Improvement Cooperative

  3. Mexican pine Pinus tecunumanii (seed from 20 families) with known field performance (supplied by Bill Dvorak and Gary Hodge of the NC State CAMCORE Cooperative)

  4. Willow and poplar (cuttings from 20 clones) with known field performance (supplied by Tim Volk and Larry Abrahamson of the SUNY College of Environmental Science and Forestry, Syracuse, NY Biomass Research Program.

These plants will be grown for several months in the greenhouse through summer 2001, and then rank order performance of the genetic entities under the high and low stress environments will be compared to their rank order performance in field trials. For this approach to be successful, it is not necessary for a high rank order correlation to be found, rather it only requires that the best half or two-thirds be separated from the poorer performing entities. Such a screening method would reduce the number of families/clones being established in field trials, and improve the efficiency of improvement. This work is being conducted as a special project by undergraduate Ben Brazell.

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Sweetgum and Sycamore Tree Improvement, Region-Wide Study No. 90

No additional sweetgum progeny tests were installed during the past year (Table 7). However, seed was distributed to HRC members from the remaining families located at the St. George, SC HRC clone bank/seed production area on South Carolina Forestry Commission property. Nearly 200 families are represented in this clone bank. Also distributed was seed from 74 Asian sweetgum families acquired by the HRC through a cooperative effect with Nanjing Forestry University, China. The HRC clone bank/seed production area in Goldsboro, NC at the NC Forest Service Tree Nursery, yielded seed in fall 2000. A collection was made, representing about 30 of the 140 families located there. This seed is available for progeny testing. The Goldsboro clone bank has suffered from poor tree health and growth since establishment, and many ramets had died over the years. During summer 2000 a major grafting activity was undertaken using scion from existing ramets at Goldsboro and scion provided by various HRC members from back-up clone bank sites. A total of 350 grafts were made onto seedlings in a greenhouse at NC State, representing 70 clones. After grafts were strong, the plants were moved outdoors under overhead irrigation to acclimatize. In late winter 2000/2001 these grafted trees were planted at the Goldsboro site, were fertilized, had weeds controlled, and have been hand-irrigated weekly through spring 2001. By June 2001, the overall success rate was 72%, and an additional 53 clones and 67 ramets are now represented in this clone bank. Several ramets were planted in each planting spot to ensure success.

In 2000, sycamore seed was distributed to interested HRC members from clones in the St. George, SC clone bank, and from many additional sources provided by Dave Foushee of Boise Cascade in Jackson, AL. This seed has not been planted.

 

Table 7. Summary of the HRC progeny tests installed and under development as of spring 2001.

Species / Source

HRC Member

Location

Planting Date

(Winter)

No. Sites

Approximate

No. OP Families

Sweetgum / Gulf Coast        
Boise Cascade South-Central AL

1998 / 99

1

68

International Paper West-Central MS

1998 / 99

1

75

International Paper Central MS

1999 / 00

1

82

International Paper ?

2000 / 01

1

63

IP (Union Camp) Central SC

1998 / 99

1

75

IP (Union Camp) Central SC

1999 / 00

1

82

IP (Champion) Western FL

1998 / 99

1

73

IP (Champion) Western FL or SW AL

1999 / 00

1

81

NC State Central NC

1998 / 99

1

22

Smurfit-Stone Container Southeast AL

[1998 / 99]

1

71

Kimberly-Clark South AL

[1998 / 99]

1

71

Rayonier East-Central GA

1998 / 99

1

68

Temple-Inland East TX

1998 / 99

1

140

Westvaco Southeast SC

1998 / 99

2

74

Westvaco Southeast SC

1999 / 00

2

88

Westvaco SC

2000 / 01

1

63

Westvaco Western KY

?

?

81

Sweetgum / Asian        
International Paper ?

?

1

13

NC State NC

2001 / 02

1

13

Sycamore / Gulf Coast        
Boise Cascade South-Central AL

(1997 / 98)

1

43

Boise Cascade South-Central AL

2000 / 01

1

160

Champion International Western FL

(1997 / 98)

1

42

Champion International Western FL

2000 / 01

1

60

International Paper SC

1997 / 98

1

43

International Paper ?

2000 / 01

1

60

Temple-Inland East TX

1997 / 98

1

42

IP (Union Camp) East GA

1997 / 98

1

43

Westvaco Southeast SC

Spring 1997

1

42

Westvaco Southeast SC

2000 / 01

1

60

Westvaco Western KY

?

?

160

Note: Planting date in parenthesis indicates a test eliminated due to poor 1998 survival related to drought, dates in brackets indicate a trial planted by an HRC member that has subsequently left the Cooperative.

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Sycamore Disease

For the past decade a decline/dieback/disease syndrome has been observed on plantation sycamore in the Southern coastal plain and at low elevations inland. An HRC working group was formed, in close cooperation with US Forest Service (USFS) scientists, to evaluate the causes and potential management of this syndrome. Through pathology sampling and research, USFS scientists Kerry Britton (Southern Research Station (SRS), Athens, GA) and Ted Leininger (Southern Research Station, Stoneville, MS) identified the principle agent in coastal plain areas as the xylem-limited bacterial leaf scorch disease, Xylella fastidiosa. As part of this overall effort, HRC staff and members accomplished a literature review of sycamore silvics, silviculture and pest issues, and tree health surveys of HRC clone banks and member plantations. This HRC work was partly funded by the USFS SRS, through a cooperative agreement, "Development of Baseline Information to Understand Dieback and Decline Diseases in Sycamore Plantations in the Southern U.S." The HRC members most involved in this effort were Boise Cascade, Westvaco, Kimberly-Clark, International Paper, Union Camp, and Jefferson Smurfit Corps.

The following objectives were pursued by the HRC under this project - -

  1. Compile a database of information on the locations, histories, and relative health of sycamore plantations across the South.
  2. Conduct a thorough literature and historical record review of previous reports of sycamore dieback and decline.

These objectives were to lead to the development of hypotheses and new objectives for future research, by determining, 1) the magnitude of sycamore dieback and decline across the South, and 2) its ecological and silvicultural contexts. This work, coupled with USFS-SRS investigations into the casual agents of the disease syndrome, were meant to provide a broad basis for future focused research on pest management issues associated with this important hardwood plantation species.

"Database development" was conducted by the staff of the HRC. To fulfill this objective, the HRC developed a survey document for cooperating plantation owners (forest industry members of the HRC) to record the context and health of sycamore plantations. It was hoped that this information would reveal soil/site, silvicultural and plantation age conditions under which the dieback syndrome was more or less pronounced. Such information would provide a basis for plantation management research question development, and an understanding of the environmental component of the disease syndrome.

In addition to the "paper" survey of plantations conducted by forest industry cooperators from plantation records, cooperators and HRC staff directly surveyed sycamore clone-banks established across the South for the HRC. These clone banks are an integral component of an HRC genetic improvement program for sycamore, and include many of the same genotypes (clones), grafted onto seedling rootstock (no genetic control of the rootstock) in various locations for clone preservation and seed production for progeny testing. Surveys of these clone banks, it was hoped, would help reveal genetic aspects important to the dieback syndrome.

Results from the plantation survey revealed few consistent findings (Table 8). Six cooperators returned survey data (gleaned from paper records), representing 79 sycamore plantations; 22 in southern Alabama (13 having had dieback), 5 in western Florida (1 having had dieback), 4 in east Texas (2 having had dieback), 29 in central South Carolina (0 having had dieback), and 19 in western Kentucky (7 having had dieback). This survey is not necessarily representative of sycamore plantations across the South. Cooperators were asked to focus on younger plantations, not all regions reported and not all plantations were considered.

 

Table 8. Results from survey of paper records of HRC member sycamore plantations, 2000.

 

- - - - - - - - - - - - - - - - - - General Location - - - - - - - - - - - - - - - -

   

AL, FL, TX, SC

KY

Survey Factor

(% of plantations surveyed)

WITH DIEBACK

(n=16 plantations)

WITH DIEBACK

(n=7 plantations)

Dominate Site Type Coastal Plain Upland Alluvial Floodplain/Island
Dominant Flooding Condition Not Flooded Growing Season Floods 100%
% Surrounded by Agriculture / Forestry ca. 50 / 50 ca. 57 / 43
% Previously in Agriculture / Forestry ca. 62 / 38 ca. 14 / 86
% with Chemical / Mechanical Weed Mgmt ca. 100 / 0 ca. 0 / 100
% Receiving Fertilizer ca. 81 0
% Thinned 0 28
Age Range when Dieback Began 2-4 yrs. 8-10 years
Dieback Development 94% scattered individual trees 100% scattered individual trees

 

WITHOUT DIEBACK

(n=44 plantations)

WITHOUT DIEBACK

(n=12 plantations)

Dominate Site Type Coastal Plain Upland Alluvial Floodplain/Island (58%) 2ndary Drainage (25%), Fertigated (17%)
Dominant Flooding Condition Not Flooded Growing Season (50%), Dormant Season (17%), Not Flooded (33%)
% Surrounded by Agriculture / Forestry ca. 11 / 89 ca. 75 / 25
% Previously in Agriculture / Forestry ca. 84 / 16 ca. 42 / 58
% with Chemical / Mechanical Weed Mgmt ca. 100 / 0 ca. 17 / 83
% Receiving Fertilizer ca. 100 0
% Thinned 0 8

 

Plantation survey results for AL, FL, TX and SC combined, suggest that few obvious differences exist between plantations with and without dieback symptoms, for those factors investigated in this study. The only difference, which may be of interest, is a greater percentage of plantations impacted by dieback when agricultural fields surround the plantation. Survey results for KY do not reveal any obvious differences between those impacted and those unimpacted. In all cases, in both regions, where dieback was found, it developed in individual trees scattered throughout the plantation. Between the AL, FL, TX and SC region, and the KY region, the only obvious difference was the age of dieback onset, 2-4 years versus 8-10, respectively.

These results do not reveal any obvious soil/site, silvicultural or other environmental variables that may be linked to the syndrome. The only substantive finding is the regional difference in age of dieback onset. This may be related to different disease organisms. Kentucky field surveys have tended to find evidence of Ceratocystis disease, whereas in the other regions Xylella leaf scorch has been the dominate disease found in the field (K. Britton, USFS and R. Rousseau, Westvaco Corp., pers. comm.).

The results of the clone bank field surveys for crown condition are described below. These data were collected by different people at each location, and at different times during the 1999 growing season, when the trees (scion from mature trees grafted onto seedling rootstock) were in their 6th growing season. The clone banks (grafted material) for which data is available are the Rayonier site (formerly Jefferson-Smurfit) in southeast AL, International Paper (IP) site (formerly Champion) in western FL, the International Paper site (formerly Union Camp) in eastern GA, and the South Carolina Forestry Commission (SCFC) site in central SC.

The impact of the graft or the genetic properties of the rootstock on disease is unknown. Generally all of these sites were treated with weed control (chemical and/or mechanical) and fertilization. Not all clones were established at each location, and so there is little among site replication of the clones. At each site, generally, at least three (3), and sometimes as many as five (5) ramets of each clone were established. At several of the sites, some clones were in 1999 only represented by 1-2 ramets, the others having died. Additionally, at each site some clones died-out entirely. The cause of clone death cannot be attributed to any particular cause; some of it may have been due to graft incompatibility, other due to disease, injury, etc. No conclusions can be reached about dead ramets/missing clones. For those that remained in 1999, crown condition is the best general gauge of tree condition with respect to Xylella, Botryosphaeria, and Ceratocystis diseases. Additional data from the field sheets and summaries are available on request.

Listed below for each site are the clones, which, when at least 2 ramets were found, at least 60% of the ramets were in either the "dense" or "sparse" crown condition categories (Table 9). These clones may be those with some level of resistance to whatever causes the dieback syndrome in the most general sense (dense crowns), or those highly susceptible (sparse crowns). It is probable that many of the missing clones, or those with fewer than 2 ramets remaining, were even more susceptible to the disease, but this cannot be substantiated. The clones included in the table below may be useful in future disease screening research, especially if field surveys in the future reveal the "resistant" clones are still present.

 

Table 9. Putatively resistant or susceptible sycamore clones (42-_ _ _) to crown dieback syndrome at four HRC grafted clone bank sites (1999).

Rayonier Site

(Alabama)

IP (Champion) Site

(Florida)

IP (Union Camp) Site

(Georgia)

SCFC Site

(South Carolina)

- - - - - - - - - - - Putatively Resistant (at least 60% of ramets in "dense" crown category) - - - - - - - - - -

42 - 003

42 - 019

42 - 033

- 120

42 - 001

- 080

- 080

- 050

- 045

- 121

- 005

- 089

- 012

- 079

- 062

- 122

- 012

- 091

- 017

TX52

- 068

- 123

- 013

 

- 035

 

- 081

- 124

- 020

 

- 039

 

- 084

- 147

- 062

 
   

- 089

- 150

- 071

 
   

- 111

- 151

- 074

 
   

- 114

- 154

- 077

 

- - - - - - - - - - -Putatively Susceptible (at least 60% of the ramets in the "sparse" crown category) - - - - - - - - - -

- 037

- 025

- 118

 

-

 

- 040

 

- 128

     

 

The literature review of sycamore silvics, silviculture and pests was conducted for the HRC by a contracted consultant, Dr. James Solomon. This review (Solomon, J. 1999. A Literature Review of the Causes and Potential Management of a Region-Wide Sycamore Dieback Syndrome. NC State-HRC, Raleigh, NC. Internal Report. 32 pp.), including an executive summary, is available on request, and was distributed to HRC members at the 2000 Annual Meeting. Solomon’s review does an excellent job summarizing what was known about sycamore management and pests up until the initiation of the current work. His findings and conclusions, seem to underestimate the emerging understanding of the insect-vectored bacterium Xylella fastidiosa as the most important casual agent of the dieback syndrome. This new understanding has been developed primarily by recent research.

Colleagues in Mexico have been contacted and collaborative efforts are being planned to collect seed from high elevation Mexican sycamore stands for testing and research in the U.S. Infection by Xylella fastidiosa can be cured with cold temperatures, and therefore the disease is not found in the Appalachians, but is readily found in the Southern Coastal Plain. Mexican sycamore, however, despite not enduring cold temperatures, does not appear to be susceptible to this disease. Seed from these sources will be used to search for genetic resistance which might be used through hybridization with American sycamore, or through selection and breeding for cold tolerant Mexican varieties for use in the U.S. south.

In this anticipated work, the HRC has been assisted by Jesus Dorantes at the Institute of Forest Genetics at Chopingo University, Teo Eguiluz of Groupo Genfor, David Cibrian of the University of Chopingo, and Bill Dvorak of NC State’s CAMCORE Cooperative.

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Sycamore Pulping

Preliminary research was undertaken on the pulp characteristics of young sycamore coppice. Sycamore has great potential for use in short-rotation, high-density fiber/biomass production systems due to its rapid juvenile growth rate, capacity to tolerate high densities and to coppice after harvest without root sprouting, and its high quality fiber characteristics. The wood is light colored, and has specific gravity comparable to other important hardwood pulp species. In short-rotation (3 to 5 year harvest cycles) high-density (ca. 15,000 stems/ha) systems, the stand could be renewed through coppice regrowth (stump sprouting). Such systems maximize the use of site resources, providing productivity 2- to 5-fold greater than traditional plantation systems (having ca. 1,100 stems/ha, 15 to 25 year harvest intervals). At harvest, with agricultural type machinery, bark cannot be separated from the wood. However, sycamore bark is extremely thin, and can be pulped without great difficulty.

In this study three 16-year-old sycamore logs (DBH ca. 25 cm) to 5 cm diameter tops, and three complete stump sprout clumps from 4-year-old coppice (DBH of individual stems ranged from ca. 1 to 10 cm) were cut at the goundline in February 2000 by International Paper Company from 3 x 3 m spaced plantations in southeastern VA. All stems (logs and coppice sprouts) were cut into 1.2 m bolts, and the log pieces divided evenly in half. Half of the log pieces had the bark removed. The debarked logs, logs with bark, and coppice stems with bark were chipped separately, and used in pulping tests. In laboratory scale digesters, the three types of chips were pulped under a variety of conditions to examine the impact of bark (on logs or on coppice) on processes and yields (Table 10).

These results indicate that pulping sycamore logs or coppice with bark requires greater amounts of chemicals than pulping debarked logs, and that coppice pulp yield is lower and dirt higher than either type of log sample. The amount of dirt found in the samples could be the result of how the wood was handled during collection and processing, and it is probable that the dirt found in coppice could be reduced. The lower yield and higher chemical needs of the coppice material as compared to the debarked logs is estimated to add about 5% to the current cost of pulping. These results are encouraging in that they indicate sycamore can be successfully pulped with bark, suggesting that energy savings may be had by eliminating the debarking of sycamore logs, and the potential for using high-density ultra-short high productivity rotations for coppice sycamore pulpwood production.

This work was a collaborative effort between the HRC and Hasan Jameel, Hou-Min Chang and Jim McMurray of the NC State Department of Wood and Paper Science, including matching financial support. Jerry Hansen of International Paper Company provided the sample material.

 

Table 10. Sycamore pulping conditions and results.
 

- - Pulping Conditions - -

- - Pulping Results - -

- - Bleaching Results - -

Sycamore Material

%AA

H Factor

Kappa

% Pulp Yield

Brightness

% ISO

Dirt

(ppm)

Debarked Log

14.5

300

54.0

48.5

-

-

 

16.0

300

43.0

48.1

-

-

 

14.5

600

27.0

43.2

-

-

 

16.0

800

16.7

45.0

89.7

28

 

14.5

1000

16.0

44.5

-

-

Log with Bark

14.5

300

46.0

47.4

-

-

 

16.5

300

36.0

46.0

-

-

 

14.5

600

28.0

42.4

-

-

 

16.5

800

16.3

44.0

87.8

37

 

14.5

1000

18.0

42.0

-

-

Coppice with Bark

14.5

300

65.0

43.7

-

-

 

17.5

300

40.1

42.5

-

-

 

14.5

600

44.0

43.4

-

-

 

17.5

800

16.0

40.3

88.4

42

 

14.5

1000

24.0

46.5

-

-

Note: In all cases pulping sulfidity = 25%, and Liquuor:Wood ratio = 4. Bleaching conducted by D(EOP)D sequence.

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Sweetgum Rooted Cuttings

Research efforts on optimizing sweetgum rooted cutting production have continued. Earlier findings are reported in the 1999 and 2000 HRC Annual Reports. While sweetgum are not difficult to root from greenwood cuttings, such a system must be operationally efficient to reduce associated costs, and to maximize the utility of elite clones. Clonal selection and deployment is likely to be a key factor in the economic viability of sweetgum plantations. A clonal forest system will rapidly capture genetic gain, provide uniformity of response, and overcome the large variability among individuals common in sweetgum, even in superior families. This variability has a significant impact on plantation productivity, and may be efficiently overcome through the use of clonal stock. In our rooted cutting research efforts, we are investigating a variety of means to make the system infrastructure, cutting collection, and cutting root and shoot growth responses more efficient.

In the past year an experiment was conducted with two clones (UC1 and 2074) established in the HRC’s cutting hedges at the NC State Reedy Creek Experimental Farm, in Raleigh, NC. Fifteen cm greenwood (semi-hardwood) cuttings were collected in June 2000, and within two weeks (stored in a cooler) dipped in 0.8% IBA rooting hormone, and stuck in the misthouse in, 1) Ray LeachTM tubes containing 1:1 peat:perlite, 2) Jiffy Horticultural (30 mm) PelletsTM (lime treated peat) in plastic Winstrip TraysTM , or 3) Grow-tech Flexi-plug (#72) TM pellets (peat:pine bark) in Winstrip Trays. At the same time cuttings were stuck (with 0.8% IBA dip) in an outdoor rooting bed containing loamy sand field soil that had overhead spray irrigation and 50% shade clothe. There were six experimental treatments, as follows - -

  1. Stuck directly into outdoor bed

  2. Stuck in Ray Leach tubes in the misthouse for 14 weeks, and then moved outdoors in tubes in racks

  3. Stuck in Jiffy pellets in the misthouse, and transplanted in the pellet to the outdoor bed after 11 or 13 weeks in the misthouse

  4. Stuck in Grow-tech plugs in the misthouse, and transplanted in the pellet to the outdoor bed after 11 or 13 weeks in the misthouse

These treatments were established during spring/summer 2000, and the cuttings overwintered in the outdoor rooting bed, or in the case of cuttings in Ray Leach tubes in racks, within the outdoor bed area, but not into the bed itself. Immediately prior to transferring/transplanting rooted cuttings from the misthouse to the outdoor bed, % rooting was assessed from a subsample of cuttings for each clone in the Jiffy Pellets and the Grow-tech Plugs, at the 11 and 13 week intervals (Table 11).

 

Table 11. Rooting % of sweetgum clone cuttings in two media after different lengths of time in a misthouse, immediately prior to transfer/transplanting into an outdoor bed.

Time in Misthouse

- - - - - - - - - Clone UC1 - - - - - - - - -

- - - - - - - - - Clone 2074 - - - - - - - -

 

Jiffy Pellets

Grow-tech Plugs

Jiffy Pellets

Grow-tech Plugs

11 Weeks

97

83

97

67

13 Weeks

100

90

93

87

 

In April 2001, overwintering survival of cuttings outdoors was assessed by recording bud expansion and leaf emergence, and then cuttings were destructively harvested and root biomass (with the original cutting removed) measured (Table 12). There was little or no shoot growth during the entire experiment and so no aboveground measures were recorded. This experiment suffered three uniform stress events during its course that may make the results conservative. During summer 2000 the irrigation system did not function during a single very hot day, and most cuttings defoliated over the following days, during winter 2000/2001 a very heavy snowfall caused the shade clothe to collapse onto the cuttings and some broken tops were suffered, and during late winter 2000/2001 the soil in the outdoor bed alternatively thawed and froze and there was considerable frost heaving among the cuttings.


Table 12. Survival (% rooted) and root biomass of spring sweetgum cuttings from two clones after initial rooting and then overwintering under various environmental conditions.

 

- - - - - - - - - Clone UC1 - - - - - - - - -

- - - - - - - - - Clone 2074 - - - - - - - -

 

 

Treatment

% Survival

After Winter

In Outdoor Bed

Mean Root

Dry Weight (g)

After Winter

% Survival

After Winter

In Outdoor Bed

Mean Root

Dry Weight

After Winter

Stuck Directly in Outdoor Bed

48

0.314

23

0.143

Stuck in Ray Leach Tubes in Misthouse for 14 Weeks, Then Transferred Outside

72

0.347

47

0.305

Stuck in Jiffy Pellets in Misthouse For 11 Weeks, then Transplanted Into Outdoor Bed

77

0.175

78

0.152

Stuck in Jiffy Pellets in Misthouse For 13 Weeks, then Transplanted Into Outdoor Bed

98

0.294

75

0.144

Stuck in Grow-tech Plugs in Misthouse For 11 Weeks, then Transplanted Into Outdoor Bed

70

-

43

-

Stuck in Grow-tech Plugs s in Misthouse For 13 Weeks, then Transplanted Into Outdoor Bed

87

-

37

-

 

Differences in overwintering survival among the various transplant treatments (Table 12) can be partly explained by the % rooting at the time of transfer (Table 11). Overall, both clones performed better in the Jiffy Pellets than in the Grow-tech Plugs. However, survival in both media was sufficiently high to suggest that by altering other environmental conditions, notably irrigation and or tray type, that very high survival could be achieved in either media type. Transplanting after 11 weeks in the misthouse was better for clone UC1 then after 13 weeks, and the opposite was found for clone 2074. The transplant systems generally resulted in better rooting/survival than did the "standard" completely containerized system of Ray Leach tubes in the misthouse followed by overwintering outdoors in the tubes. The direct outdoor stick yielded the lowest survival for both clones among all treatments, but average or high root biomass for the clones as compared to the other treatments. Root weight could not be determined for cuttings in the Grow-tech plugs due to difficulty in separating roots from the plug itself. Considering the three stress events the outdoor direct stuck cuttings endured, these results provide compelling evidence that a direct outdoor sticking system can be optimized, and potentially represent significant cost savings in rooted cutting production for sweetgum.

A new series of related experiments have been initiated in 2001, including direct outdoor sticking of dormant and greenwood sweetgum cuttings, investigating the relationship between degree days and rootability of greenwood cuttings, and the effects of artificial cold periods and coppicing on shoot growth of previously rooted cuttings.

This work is being conducted by HRC M.S. student Matt Gocke, in cooperation with Barry Goldfarb of the NC State Department of Forestry.

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New Oak Rooted Cutting Initiative

A USDA Special Grant to the NC State College of Natural Resources, awarded for 2001/2002, and anticipated to last 5 years, includes funding for an initiative to learn how to root northern red oak cuttings. Oaks are difficult to root, and considerable work is needed to develop a system which will provide high rooting percentages. This research will examine time of year, hedge shading and nutrition, rooting environment, and rooting hormones as factors influencing rooting. A northern red oak hedge – cutting orchard has been developed at the NC State Reedy Creek Experimental Farm, consisting of oak seedlings which will be hedged beginning winter 2001/2002, and cutting collection beginning spring 2002. This orchard includes oaks from a Pennsylvania provenance, a North Carolina provenance, a Missouri provenance and two half-sib families from Tennessee. The Tennessee families are being provided cooperatively by Scott Schlarbaum of the University of Tennessee. This work will be in conjunction with the "New Oak Enrichment Planting Initiative" described above. Matt Gocke will lead the technical aspects of this work, and Barry Goldfarb of NC State Department of Forestry will be a co-principle investigator.

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Site Preparation Study for Sycamore, Sweetgum and Cherrybark Oak

Effective establishment and efficient growth of hardwood plantations requires thorough weed management through the processes of site preparation and post-planting competition control. Hardwoods are more sensitive to competition than are pines, and poor weed management most often leads to plantation failures, or at best plantation growth rates no faster than in unmanaged natural stands. Early stand weed management has been an almost insurmountable challenge to hardwood plantation management for decades. Without effective weed management there is little use in fertilization or the deployment of genetically improved stock. Greater understanding of the interactions between planted hardwoods and weed intensity, both herbaceous and woody competition, and knowledge of herbicides suitable for weed management, are needed to overcome these challenges. In 1999 HRC member American Cyanamid Corporation (now BASF Corporation) developed a special project with the HRC, and funded a trial to investigate the use of the herbicide Chopper™ (imazapyr) as a site preparation tool, and a means to explore weed-productivity relationships through the use of a variety of control treatments.

The study was installed on a flat red river bottom terrace above the Roanoke River in eastern NC near Oak City (Bertie County). Soils on the site were moderately-well drained, fine sandy loams with pH about 4.8. The site was clearcut of planted loblolly pine in 1998 and bedded at 3.1 m intervals. In spring 1999 three replications of plots 6.1 m long across 10 beds were delineated for installation of 30 treatments. In June, July and September 1999, the herbicide Chopper™ was applied at four rates (1.1, 2.2, 3.4 and 4.5 L/ha active ingredient) over the emerging woody and herbaceous weed vegetation. No other site preparation treatments were applied between the 1998 bedding and tree planting in February 2000. In February 2000 the plots were planted with 10 tree subplot rows (across the beds), with 1.2 m between trees on beds. Four species were planted - - cherrybark oak, sweetgum and sycamore as 1-0 stock, and a cottonwood clone as a dormant cutting. Within two weeks of planting, while trees were still dormant, half the plots were treated with the herbicide Oust™ (sulfometuron) as a broadcast spray at 0.15 L/ha a.i. On the other half of the plots, weeds were mechanically sheared at the soil surface in late winter, and then treated in May and July with a directed spray of the herbicide Accord™ (glyphosate) + surfactant as a 2% solution. Three types of control plots were included, 1) no treatment post-bedding, 2) Oust™ only in February 2000, and 3) Accord™ only in May and July 2000. There were also Chopper™ only plots from June, July and September (data not reported here). During the season prior to tree planting, and periodically throughout the first season, weed coverage and tree symptoms of phytotoxicity were assessed. At the end of the first growing season, fall 2000/2001, tree survival, height and basal diameter were recorded.   Tree height after the first season is reported here (Figure 5).  Tree height will again be measured at the end of the second growing season, fall 2001. Cottonwood mortality was very high during the first few weeks after planting, due to hot dry conditions on the site, and it was dropped from the experiment.

Analysis of height data (initial height by species did not differ at the onset of the experiment) by ANOVA for main effects, indicated that the time of Chopper™ application was a significant factor for sycamore and sweetgum (P<0.10), but not for cherrybark oak. Chopper™ rate was significant only for sycamore (P<0.05), and the rate x time interaction was only significant for sycamore (P<0.05). For all species, Oust™ and Accord™ were significant factors (P<0.05). For sycamore (Figure 5, top), height growth was enhanced by the use of Accord™ over Oust™, by June over July over September for Chopper™ application, and variable by Chopper™ rate, although the highest rate provided the best results. For sweetgum (Figure 5, middle), height growth was best with Accord™ over Oust™, and Chopper™ application in June over July over September, with no effect of Chopper™ rate. Cherrybark oak responded similarly to all Chopper™ combinations (Figure 5,bottom), but did better with Accord than Oust™ treatments.

With respect to the controls, both sycamore and sweetgum grew best with the Accord™ treatment, intermediate with Oust™, and poorest in the untreated control. Cherrybark oak grew the same in all controls. For sycamore and sweetgum almost all chopper treatments grew better than the untreated control, most grew better than the Oust™ only control, and some grew better than the Accord™ only control. For cherrybark oak, most Chopper treatments grew better than the various controls. These findings, while limited to this site, suggest that sycamore growth can benefit from any the tested combinations of treatments, and may perform best with an early summer application of Chopper™ at about 4.5 L/ha a.i. the season prior to planting, coupled with first season application of Accord™ or Oust™, or products or techniques which provide weed control similar to Accord™. Sweetgum responded only marginally to any of the Chopper™ treatments relative to the Accord™ control, and Oust™ was marginally effective when coupled with lower rates of Chopper™ applied early in the prior season. Cherrybark oak generally grew better with Chopper™ at any time in the prior season plus first season Accord™, than with Chopper™ plus Oust™. As the Chopper™ rate increased it marginally improved height growth of this species.

 

Figure 5. First year field height growth of sycamore (top), sweetgum (middle), and cherrybark oak (bottom) seedlings as affected by Chopper™ herbicide applied at 4 rates during 3 spray periods compared with a group of control treatments. Accord™ vs. Oust™ treatments were superimposed over the rate x time Chopper™ treatments. For each Chopper™ rate, the three bars to the left indicate the June, July and September Chopper™ treatments + Accord™, and the three bars to the right are the three Chopper™ application times + Oust™. The statistical significance of these treatments are described in the text.

wpe9.jpg (53593 bytes)

 

The control data suggests that cherrybark oak was tolerant under these conditions of Oust™, while both sweetgum and sycamore did not grow as well with Oust™ as they did with Accord™ as the control. The Accord™ applications in this study were very carefully applied and effective, and there was no observable damage to the measured trees. The Oust™ treatments resulted in partial control of competing vegetation (as compared to the full control offered by the Accord™ applications), and therefore growth under the Oust™ treatments may have been effected by either the remaining weed competition, or phytotoxic effects of Oust™ on the trees through root or dormant bud/bark absorption.

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 Fertilization and Liming Response of Plantation Hardwoods, Region-Wide Study No. 46

The HRC’s Region-Wide No. 46 study on fertilization and liming responses of plantation hardwoods, principally sweetgum, completed four years of growth on all sites (as of end 1999). Results of these trials were reported in detail in HRC’s 2000 Annual Report. A supplementary report will also be prepared from this study. Significant foliar nitrogen and stem growth responses were found on a number of sites. However, most sites after 4 years still did not demonstrate substantial responses to the fertilizer treatments. It is anticipated that responses will become increasingly apparent with the cumulative effect of additional years of growth, especially on treatment plots receiving periodic nitrogen inputs. There are a number of possible reasons for this delayed or muted response to the treatments, including weed competition and potentially early biomass allocation to crowns and roots. Continued monitoring of this study, in conjunction with other sweetgum nutrition studies, will provide important information on sweetgum fertility requirements and expected productivity. For some of the 14 RW-46 sites, data will be available after 6 years of growth, and this will be added to future summaries of the study.

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 Sweetgum Individual Tree Fertilization Trial

This study was initiated in spring 1999 to examine the utility of using single tree plots for assessing sweetgum response to fertilization. A two-year-old operational plantation on International Paper Company land (somewhat well-drained coastal plain site) in southeast NC was used. Twenty-three fertilizer treatment combinations and controls (principally seven N levels from 0 to 300 lbs./ac and three P levels from 0 to 50 lbs./ac) were installed. At the end of the first growing season of the study, there were significant growth responses, generally following an expected trend of greater growth at higher N and P levels, and with significant nutrient interactions. This study was not continued beyond the first season of response due to budgetary constraints. This approach may be useful for efficiently testing a large number of treatment combinations (nutrient/dose/frequency/timing). Year one results were reported in detail later in the HRC’s 2000 Annual Report.

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Sweetgum Foliar Nutrient Dynamics

Foliar N, P, K, Ca and Mg concentrations were studied in young plantation sweetgum in eastern NC from June to October during the 1997 and 1999 growing seasons. Samples were taken every few weeks from upper, middle and lower crown positions. Foliar nutrients can be affected by factors such as soil nutrient and water availability, temperature, day length, canopy leaching, defoliation, retranslocation, competition, season and crown position, and this poses a challenge for forest managers in deciding the best time for collecting foliar samples for nutrient diagnosis and fertilizer recommendations. Optimizing the timing and position of hardwood foliar sample collection will improve our ability to correctly diagnose plantation hardwood nutritional status, and maximize the efficiency of nutrition management. It is also important to understand the between-year variation in foliar nutrient status, in order to ensure that standard protocols for sampling account for this variation.

Samples were collected from 3-(1997) and 5-(1999) year-old trees. They had received 50 kg/ha N and 56 kg/ha P as a preplant application of diammonium phosphate when they were established, within the context of a larger NC State Hardwood Research Cooperative fertilization study (RW 46) installed by Union Camp Corporation (now International Paper Company) in Gates County, (northeastern) NC. The site is a well-drained coastal plain ridge (soil classified as Typic Paleudults).

Five fully expanded sun leaves were collected from 6 to 9 trees in each of the three "very low N+P’’ replicates within the larger fertilizer study. There were seven sample periods from 25 June to 28 October in 1997, and five from 7 July to 12 October in 1999.

Repeated measures analysis of variance for the 1997 data showed that there was no crown position by sampling date interaction for N, P, and K. However, crown position and sampling date did have a significant interaction for Ca and Mg. Sampling date was significant for all elements, and the significance of crown position varied among the elements and sample dates. For all crown positions combined, 1997 N and K concentrations gradually decreased from late June to late October, circa 1.7 to 1.4%, and 0.75 to 0.55%, respectively. Foliar P concentration was generally stable throughout the season, about 0.14%, and Ca and Mg concentrations gradually increased through the season, 0.7 to 1.1%, and 0.24 to 0.30%, respectively. Some of this data can be found in the HRC’s 1999 Annual Report.

Foliar nutrient concentrations in the 1999 growing season were very different for N, P and K, but very similar for Ca and Mg, as compared with the 1997 growing season. Foliar N, regardless of crown position, was generally more stable and lower in the 1999 than in the 1997, ranging on average from about 1.2% in early July to 1.3% in mid-October. Nitrogen concentration differed between the upper crown and the lower/mid crown positions only in the last two sampling dates (mid-September and mid-October) in 1999. Foliar P concentrations increased continuously in the 1999 growing season, rising from circa 0.1 to 0.2% during the season; without substantial differences among crown positions. This P dynamic differed markedly from the 1997 findings. Foliar K concentrations were lower in 1999 than in 1997, differed little among crown positions, and ranged from 0.45 to 0.55% during the season.

These findings generally corroborate earlier studies of deciduous tree foliar nutrient fluctuations. They also add depth to our understanding of sweetgum dynamics, and demonstrate the rapidity with which nutrient concentrations can change within a season, and the large differences between similar sample dates between years. These dynamics are important with respect to using foliar nutrition as a diagnostic and monitoring tool in nutrition and fertilization management. Sampling foliage during late-summer early-fall (late August to early October), as is common, is supported by this work, but not without a recognition that large changes in foliar nutrient concentrations can occur during this period. The crown positional effect on foliar nutrient concentration was consistent over the two growing seasons, suggesting that any non-shaded crown position in young sweetgum could be sampled for foliar nutrient status, so long as the position sampled was consistent. The findings indicate substantial differences in nutrient concentrations within and between seasons, suggesting caution in the use of these measures as diagnostic/monitoring tools in plantation nutrition and fertilization management.

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SPAD Meter Nitrogen Diagnostics

A SPAD(Minolta Co.) meter is a portable/field device that measures the transmittance of light through a leaf, and provides a unitless index value (ranging from 0 to 100) of the amount of transmission. This device has proved useful in a number of agricultural systems for estimating foliar nitrogen, which is correlated with foliar greenness and chlorophyll content. In 1997 the HRC began testing this meter for use in estimating hardwood foliar nitrogen. Such a rapid diagnostic method for foliar N could be an important tool in research and operational plantings – avoiding the time and cost of chemical analysis in prescribing and evaluating tree nitrogen nutrition, or minimally to focus such chemical analysis on critical samples. In 1997 the SPAD was found to do an excellent job of predicting sweetgum foliar N. In 1998 it was tested on sweetgum, sycamore, green ash and cottonwood, and for all species the relationship between SPAD value and foliar N was statistically significant (see 1999 HRC Annual Report).

In 1999 the SPAD meter was tested on sweetgum leaves from different crown positions, and at various times during the growing season. Three crown positions (lower, mid and upper) were sampled on five dates (July to October) in a low-N only treatment in an HRC Region-Wide No. 46 study in Gates County, NC (International Paper). Results suggest that the linear relationship between the SPAD meter value and foliar nitrogen concentration was not affected by crown position and sampling date. For all crown positions and sample dates combined, the relationship between SPAD value and foliar N concentration was %N = 0.542 + 0.020 x SPAD, r2=0.3910, P<0.0001; and for SPAD and foliar N content it was N per unit leaf area = -0.662 + 0.054 x SPAD, r2=0.5515, P<0.0001. These results confirmed and validated data obtained in earlier work. In 2000, independent samples from the low and high N fertilizer rate plots at the same HRC RW-46 study in Gates County, NC were used to test the accuracy of the established SPAD-foliar N relationships in sweetgum. This data is not yet available.

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 Sweetgum Family Genotype X Fertility Interactions

Genotype x fertility interactions may affect the suitability of sweetgum for specific sites or the efficiency of nutrient use. To gain a better understanding of these interactions, 2-year-old sweetgum seedlings from two half-sib families from the HRC tree improvement program were tested for growth response to N (0 and 100 kg/ha equivalent) and P (0 and 50 kg/ha equivalent) for one season in an outdoor pot study. These two families had in earlier work demonstrated substantially different responses to high and low fertility levels. The aim of this work was to develop an understanding of the proportion of growth response attributable to genotype x fertility interactions. If such interactions are significant, then fertilization decisions could be made for specific genotypes. In the current study we specifically examine N and P fertility effects.

This experiment was conducted in pots (22 cm diameter by 25 cm deep) out-of-doors at the Horticulture Field Laboratory of North Carolina State University in Raleigh, NC. Seed from two half-sib sweetgum families in the NC State-HRC program (F10022 and F10023), collected from a seed production area in St. George, SC (SC Forestry Commission land) were used in this work. Stratified seed were sown, two per pot from the same family, on 22 July 1999, into pots containing peat:vermiculite:field soil in a 6:3:1 (volume) ratio. The field soil (Congoree silt loam) was collected from an area with naturally occurring sweetgum in Raleigh, NC. After germination, all pots received a one-time application of 1.45 g of OsmocoteTM slow-release fertilizer (14-14-14) to ensure adequate nutrition for healthy seedling development in the first growing season. Seedlings were thinned to one per pot in September 1999, to leave similarly sized plants among pots. Seedlings were over-wintered outdoors and experimental treatments applied in the second growing season. Pots were widely spaced throughout the experiment to eliminate shading.

On 6 July 2000, four treatments were applied to both families, 1) no N or P (control), 2) no N and 50 kg/ha equivalent P, 3) 100 kg/ha equivalent N and no P, and 4) 100 kg/ha equivalent N and 50 kg/ha equivalent P. There were three pots for each family within each treatment. Fertilizers were applied as granular ammonium nitrate and triple superphosphate. Pots received daily overhead irrigation.

Initial seedling size (ground-line basal diameter, total height, unit leaf weight, unit leaf area, and specific leaf area [SLA]) was measured on 23 June 2000. Leaf weight and area (then used to calculate SLA) were estimated by sampling five mid-crown fully expanded leaves from every tree. Final seedling size (same parameters as above, plus crown dimensions [height and width]) was measured on 7 September. Leaf samples were dried at 65 C and weighed. Crown volume was calculated as a conoid from height and width measurements.

All initial seedling size measurements were compared by ANOVA among treatments. None differed significantly at P<0.05 among treatment or family effects, or with any interactions. A few of the initial size measurements differed among treatments and families at P<0.10. These were leaf weight among N, P and family factors, SLA by P levels, and height by family.

At the time of final measurements (two months after the treatments were applied) SLA was significantly (P<0.01) affected by N, P, and an N x P interaction, but not by family (Figure 6a). Without N addition seedling sweetgum SLA did not respond to P. Initial and final basal diameters were significantly correlated, however initial and final heights were not. Basal diameter was affected by the experimental factors; family (P<0.01), N (P<0.1), and P (P<0.05) (Figure6b). Family F10023 consistently had greater basal diameter than F10022, nitrogen addition was marginally significant at each P level, and P addition was significant regardless of the rate of N application. There were no interactions among these three factors with respect to diameter.

Seedling height was significantly affected by family (P<0.05) and N application (P<0.05) (Figure 6c). However, in contrast to the findings for basal diameter growth, family F10022 was consistently taller than family F10023. No interactions with respect to height were found.

Physiological responses to nutrient additions often appear first in foliar characteristics and crown expansion. Crown width in the current study was significantly correlated with initial seedling height (P<0.05), and was affected by N (P<0.01) and P (P<0.01) additions (Figure 7a). Differences in crown width between the families were not significant, nor were there any significant treatment interactions. Crown height was significantly correlated with initial SLA (P<0.05), and was affected by family (P<0.05) and N (P<0.01) application (Figure 7b). For crown height (similar to total height, family 10022 was greater than family 10023. When crown width and height were integrated into crown volume, family differences were not significant (Figure 7c), although N and P additions increased crown volume. No interaction between N and P was found. The significant effects of the N and P treatments on crown volume and SLA (Figure 6a) may be responsible, through their relationship with photosynthetic area, for the seedling growth responses found. With respect to basal diameter, N, P and family explained 37, 21 and 10 % of the growth response, respectively.

N and P application affected the growth rate of two-year-old sweetgum seedlings, two months after treatment. The two half-sib families responded to the N and P treatments differently, indicating significant genotype x fertility variation in sweetgum. Results suggest the need to balance N and P applications to seedling sweetgum, and that N generally limits the response to P. Nitrogen, P and family genotype explained 37, 21 and 10 % of the response in basal diameter growth, respectively. The data suggest that screening sweetgum families for nutrient use efficiency may be worthwhile, and that balanced N and P applications are important for promoting seedling growth.

 

Figure 6. Mean + SE (n=4) response of 2-year-old sweetgum to N and P application, and family (F10022 and F10023), by specific leaf area (SLA), seedling basal diameter (BD) and height (Ht), two months after treatment. The top graph (a) shows the interaction between N and P (P<0.05) treatments on SLA when family was not significant. In the middle graph (b), N (P<0.10), P (P<.0.05) and family (P<0.05) were significant; and in the bottom graph (c), N and family (P<0.05) were significant.

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Figure 7. Mean + SE (n=4) response of 2-year-old sweetgum to N and P application, and family (F10022 and F10023), by crown width, crown height and crown volume, two months after treatment. In the top graph (a), N and P were significant (P<0.05); in the middle graph (b), N and family were significant (P<0.05); and in the bottom graph (c), N and P were significant (P<0.05).

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European Black Alder Studies Revisited, Region–Wide Study No. 62

The Hardwood Research Cooperative developed interest in growing black alder in the early 1970s. Several members of the HRC had plantings on their lands and found black alder to perform well in the Piedmont of North Carolina and in the Upper Coastal Plain of Alabama. Those early interests lead to the eventual installation of a Region-Wide black alder study in 1980 for provenance testing of seed sources (RW 62). That effort was discontinued in 1983/1984 because most of the plantings failed due to severe drought or because they were planted off-site. Some trials planted on moist sites survived, but growth rates were often less than other hardwood species. There remains, however, substantial potential for black alder to be used in a variety of forestry/reclamation activities, and there are reports of good growth by this species in a variety of situations. Past performance of this species in the South was a result of inappropriate genetic-stock and site selection, and ineffective weed control. The first two are the factors the HRC began to effectively explore in the 1970-80s, and it may be possible to relieve these constraints with additional focused research on genetics and plantation development. An HRC report on black alder will be prepared.

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Other Projects / Developments / News

HRC Web Page

The HRC web page can be accessed through the NC State – College of Natural Resources – Department of Forestry Home Page, or directly at www2.ncsu.edu/unity/lockers/project/hardwood/index.htm. The site consists of the HRC Annual Report, and will be expanded to include other features. The most recent addition is a link to the previous years’ Annual Report, and a listing of HRC theses through the "Graduate Research" button. HRC administrative assistant Robin Hughes has been responsible for this effort.

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HRC Member News

Fiscal year 2000/2001 has seen a dramatic reduction in HRC membership. Since the May 2000 Annual Advisory Board Meeting, the following members have left or will leave the organization - - Champion International Corporation was acquired by International Paper Company (summer 2000), Westvaco Corporation is leaving to focus their efforts on specific hardwood plantation issues (leaving effective 1 July 2001), The Timber Company is leaving to focus research on pine (effective 1 July 2001), Weyerhaeuser Company is leaving due to a lack of interest in hardwood research (effective 1 July 2001), South Carolina Forestry Commission is leaving due to state budget reductions (effective 1 July 2001), and International Paper Company is leaving to reduce their overall cooperative support budget (effective 1 January 2002). These changes have a significant effect on HRC activities and budgets, and will require a realignment of HRC research. These issues have been discussed at length with the remaining members, and will be the focus of discussions at the 2001 Annual Meeting.

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HRC Meetings

The May 2000 Advisory Board Meeting included invited presentations from Sharon Friedman, US Forest Service (USFS Hardwood Initiatives) and Jerry Tuskan, Oak Ridge National Laboratory (Advanced Breeding Strategies for Hardwoods); as well as speakers from the HRC and collaborating organizations. The 2001 Annual Meeting will include invited presentations from Ted Shear and Joe Neal of NC State. The FY 2000/2001 HRC Contact Meeting was hosted by Temple-Inland in east Texas in October 2000. Although attendance was very low, the two days spent visiting forestry research and operations sites were excellent. They did a terrific job hosting the meeting.

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HRC Staff and Graduate Student News

The people that make up the HRC at NC State remained fairly constant during FY 2000/2001, with few exceptions. Robin Hughes continued as our Administrative Assistant, and Peter Birks as the Assistant Director for Technical Management. Peter will soon complete his M.S. as well, and get that albatross to fly away from him! Scott Chang, Associate Director, left at the end of March 2001 for the University of Alberta, Canada, and his position will not be filled due to budget constraints. M.S. students Leslie Newton, Robert Jetton and Matt Gocke continued on course, as has Ph.D. student Jamie Schuler. Robert will finished by end 2001, and begin a Ph.D. program in the NC State Department of Entomology. Matt will finish in spring 2002, but beginning summer 2001 he will work full-time on the new USDA funded oak enrichment and rooted cutting project. Leslie will finish in spring 2002, and will spend one month during summer 2001 as a teaching assistant at Western Carolina University. Among our technicians, Karin Hess has continued on a part-time basis, David Gadd has worked full-time but will leave the HRC in summer 2001 to study environmental law at the Vermont Law School or University of Maryland. Jim Bridges is continuing full-time, Chris Miller will leave for summer work with the USFS, Pantaleo Munishi completed his Ph.D. with Ted Shear and returned to Tanzania as a lecturer at Sokoine University of Agriculture, and Tzu-Ming Liu returned to Taiwan in August 2000 and has been applying to Ph.D. programs in forest economics in the U.S. Ben Brazell, an undergraduate in the Natural Resources program of the Department of Forestry began work with the HRC on a special project in January 2001, and will continue on a variety of tasks.

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Region-wide (RW) Study Summaries

 

ACTIVE STUDIES

RW-32 Determining Tolerable Amounts of Residuals in Hardwood Regeneration Cuts

This study is designed to determine the amount of residual basal area that can be tolerated before the number and quality of trees in the subsequent stand are significantly affected, and to develop regeneration guidelines for residual control in harvested southern hardwood stands. Four treatments (0, 10, 25, and 40 ft2 residual basal areas) were applied beginning in 1984 at 10 installations on eight different forest types.

RW-33 Development of Southern Hardwood Stands from Natural Regeneration

This study compares the effectiveness of several even-aged natural regeneration systems on productive hardwood forest sites. The four treatments used are: (1) clearcut to remove all merchantable trees, (2) clearcut to remove all merchantable timber and shear all remaining woody plants, (3) clearcut all merchantable trees and inject all woody stems >1.6 inches dbh, and (4) clearcut all merchantable trees and chop and burn all remaining woody plants. Measurements have been collected from 16 installations since 1977.

RW-35 Assessing Alternative Regeneration Systems for Southern Hardwoods

On a variety of southern hardwood forest types (Coastal, Piedmont, and Appalachian), this study was designed to evaluate the quality, quantity, species composition, and development of natural hardwood regeneration and aesthetic responses of the forest to different harvesting (regeneration) systems. Treatments are: (1) unharvested control, (2) clean-cut, (3) two-stage shelterwood, and (4) deferment cuts. The study was installed at 14 sites in 1993.

RW-46 Determining Fertilization and Liming Response in Intensively-Cultured Hardwood Plantations

The objectives of this study are to determine growth and nutritional responses of commercially important hardwood species (sweetgum, sycamore, yellow-poplar, and cottonwood) to lime and nutrients (N, P, K, Ca, Mg, S, Fe, Mn, Cu, B, Zn) across a range of soil types, and to develop diagnostic criteria (e.g., foliar nutrient concentrations, leaf area index) for nutrition management in hardwood plantations. A total of 17 study plantations were established in 1994 and 1995.

RW-55 Growth and Yield of Natural Hardwood Stands

This study is designed to: (1) develop a working plan for a growth and yield study applicable to hardwood land management over a wide range of forest site types, age classes, stand densities, stand composition, and soil capabilities, (2) amass field data through a cooperative effort on a scale that would be prohibitive for any one organization to attempt, (3) compile the data by geographic province, forest site type, age, stand density, species, soil structure, soil productivity, and other desired combinations, and (4) model stand growth and yield for natural mixed hardwood stands. Data have been collected for 27 species at 203 installations across the South since 1969, covering 10 forest site types and age classes ranging from 10 to more than 60 years old.

RW-56 Growth and Yield of Plantation Hardwoods

The objectives of this study are to: (1) develop volume and biomass equations for plantation hardwoods, (2) develop yield tables on a volume, green weight, and dry weight basis for selected plantation species, and (3) develop stock and stand tables. Data have been collected from 91 installations since 1974 for sweetgum, sycamore, green ash, yellow-poplar, water-willow oak, cottonwood, and other species.

RW-70 Competition and Stocking Management in Young Even-Aged Hardwood Stands (Initiated 1999)

This study examines the effect of mechanical + chemical strip thinning in 3 to 5 and 8 to 10 year-old natural hardwood stands on growth and development of trees in the leave strips. Leave strips are treated with various combinations of individual tree release, herbaceous control and fertilization. Two installations were established in 2000.

 RW-90 Sweetgum & Sycamore Clone Banks & Progeny Testing (Initiated 1990, named 1999)

This study includes the establishment of grafted clone bank / seed production areas for both species, with genetic selections made from the RW-99 study, and other sources. Half-sib family seed collected from these selections is used for progeny testing across the South as part of the overall HRC tree improvement program. The study was initiated in 1990, with primary clone banks developed at Goldsboro, NC and St. George, SC. The goal is for each of the primary clone banks to contain 200 unique clones for each species, and for these to be field tested in progeny trials.

INACTIVE STUDIES

RW-34 Hardwood Coppice Study

The goals of this study were to: (1) determine the best season of harvest to ensure the maximum and/or minimum coppice sprout stimulation as desired by management objectives, (2) measure stand biomass from seedling and coppice origin stands, and (3) determine the site index of seedling and coppice origin stands. Measurements were collected from four installations from 1972-1992.

RW-45 Nitrogen Fertilization Requirements of Mid-rotation Hardwood Plantations

The objectives of this study were to characterize the nitrogen status of hardwood plantations at mid-rotation and develop guidelines for predicting the magnitude of response to various rates of applied N. Trials received four treatment rates of ammonium nitrate or urea. Soil, foliage, and tree measurements were collected from eight installations from 1979-1983.

RW-61 Site Evaluation for Estimating the Suitability of Southern U.S. Sites for Eucalyptus Plantations

The objectives of this study were to evaluate the growth of a wide variety of Eucalyptus selections on multiple sites across the south, and to obtain estimates of site index and volume at various ages. Thirty-eight installations were measured from 1978-1982.

RW-62 Seed Source Testing of European Black Alder

This study tested the potential of various sources of European black alder on sites in the Piedmont, Atlantic and Gulf Coast regions. Survival, height, diameter, form, adaptability, pest resistance and wood properties were measured from 1979-1982 at seven installations.

RW-66 Sweetgum Provenance Study

Dbh, volume, stem-form, and crown characteristics of various sweetgum provenances established on a variety of sites were measured from 1967-1981 at 47 installations.

RW-77 Precommercial and Early Commercial Thinning of Young, Natural Hardwoods

This study assessed the response of hardwoods to various thinning regimes. In densely stocked stands 7 to 12 years old, stocking was reduced to various levels through density control, and in densely stocked stands 15 to 22 years old, stocking was reduced to various levels through basal area control. Thirty-seven installations were studied from 1970-1994.

RW-88 Standardized Plan for Species-Site Testing

The objectives of this study were to: (1) delimit sites best suited for hardwood production, including conifer-hardwood transition zones, and (2) evaluate the growth of various species on a range of sites. Fifty-two installations were studied from 1966-1990.

RW-99 Standardized Plan for the Open-Pollinated ("Mother Tree") Testing of Hardwood Species

This activity located phenotypically average or better-than-average trees of promising species from natural stands across the South and collected open-pollinated seed from these trees for progeny testing. Progeny tests were used to determine the breeding value of parents, to identify the best individuals in the best families, and to establish seed orchards for the production of genetically improved seed from the parent trees and/or the best of the progeny. Installations were studied from 1972-1994.

 

 

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