The effect of contrasting crown attributes in clonal Pinus taeda trees on forest growth, stand dynamics, and biomass distribution
Overview
Objectives
The primary objective of this study is to examine how the differing crown attributes produced by three clonal varieties and one family of loblolly pine (Pinus taeda) affect forest growth, biomass distribution, and stand dynamics. Here we report the contrast for two Clones: A and B
A secondary objective is to examine how these crown attributes correspond to the thinning response of the different genotypes.
Summary / Lessons Learned / Additional Thoughts
Two clones differed in their crown characteristics. Clone B added more height and had a cleaner (no branches) bole under narrow spacing than clone A. This suggests genetics could be used to select for desirable traits but the effect may depend on tree spacing.
Future reporting will include updates on the thinning response of the two clones. Clone A has a larger crown than Clone B, suggesting it will respond more to thinning.
Long Description of Practice
The previous slash pine plantation (established approximately in 2002) was whole-tree harvested in 2009. Prior to this harvest, the site was treated with glyphosate herbicide (Makaze, 5.2 dm3 ac-1, 2 quart ac-1) with a surfactant (Li700, 0.585 l ha-1, 8 oz ac-1).
The trees were treated with 36.8% permethrin at a rate of 1.9 liters (2 quarts) per 100,000 individuals just prior to planting. The study site was hand-planted with containerized seedlings in February 2010. Genetic entries consisted of three loblolly pine clones (Clone A, Clone B, and Clone C) derived from somatic embryogenesis, and a loblolly pine full-sib seedling family (Family B) (see notes on data collection process below for plot design specifics).
For the three years after planting, weed competition was treated as needed with glyphosate (5%), sulfometuron methyl (Sulfomet XP, 0.11 l ha-1,1.5 oz ac-1), clopyralid Sp (Transline, 1.17 l ha-1, 16 oz ac-1), and mowing. This kept the understory relatively free of vegetation while the overstory developed. In April 2010, trees were treated with fipronil (PTM, 1 ml chemical + 9 ml water per tree injected into root zone) to protect against infestation by Nantucket pine tip moth (Rhyacionia frustrana (Comstock)). In May 2010, any dead trees were replaced with the same genotype from extra trees stored on site in container racks. In September 2011, the entire experiment was broadcast fertilized with 535 kg ha-1 of a 10-10-10 + micronutrient blend with 0.05% Mn, 0.07% Zn, 0.17% Fe, 0.02% Cu, and 0.02% B.
Results
Tree Diameters Table
| Date (month / year) | Species | ||
|---|---|---|---|
Tree Heights Table
| Date (month / year) | Species | |||
|---|---|---|---|---|
Volume Table
| Date (month / year) | Species | ||
|---|---|---|---|
Other Table
| Date (month / year) | Species | Clone | Spacing (ft) Narrow=6 x 12 Wide = 12 x 12 | DBH (in) | Height (ft) | Ht. to Base of Live crown |
|---|---|---|---|---|---|---|
| 3/2021 (age 10) | Loblolly pine | A | Narrow | 7.3 | 47.9 | 24.0 |
| 3/2021 (age 10) | Loblolly pine | A | Wide | 8.6 | 51.2 | 24.0 |
| 3/2021 (age 10) | Loblolly pine | B | Narrow | 7.2 | 59.4 | 26.2 |
| 3/2021 (age 10) | Loblolly pine | B | Wide | 8.2 | 46.9 | 20.3 |
Silvicultural Application(s) Used in Study
What did the study investigate?
Other Investigations
Genetics (Clonal and family variation)
If silviculture included a harvest, what type(s)?
Information not provided.
Silvicultural Action(s) Timings and Types / Intensities
Information not provided.
Are there any local forest health threats to your target species?
Yes
Plans for Future Treatments
'To-be-thinned' plots were thinned. This data will be added to a future report.
Only the significant contrast for Clone A and B are shown in this report.
Plans for Future Measurements
Future measurements in this trial will enable us to examine how different varieties respond to thinning; how previously-observed differences in crown dimensions and growth responses are affected by thinning; whether different varieties begin self-thinning at different relative densities; and other stand dynamics and competition topics.
One prediction associated with narrow-crowned crop ideotypes is that they might have increased carrying capacity or stockability, possibly realized through increased individual tree resource efficiency and an associated potential to carry higher relative density (At age 10 years, the narrow spacing treatments in the current study had just reached relative density consistent with the onset of density-dependent mortality). The study was subsequently thinned at age 11, and so at the time of writing contains a wide range of relative density conditions, from free-to-grow to experiencing density-dependent mortality, conditions favorable for testing the stockability of clones across this gradient.