Skip to main content
Dryad logo

Herbicide, fertilization, and planting density effects on intensively managed loblolly pine early stand development

Citation

Ferreira, Gabriel; Rau, Benjamin; Aubrey, Doug (2020), Herbicide, fertilization, and planting density effects on intensively managed loblolly pine early stand development, Dryad, Dataset, https://doi.org/10.5061/dryad.xksn02vbt

Abstract

Production forestry in the southeast US has been partially transitioned to intensively managed short rotations (~10 years), in which multiple silvicultural interventions are performed during forest development. Understanding the responses to silvicultural practices and continued refinement of site-specific recommendations is critical to sustainably maximize forest production. We evaluated the effects of silvicultural practices (herbicide, fertilization, and planting density) on growth, stand homogeneity, and above- and belowground biomass accumulation and partitioning of loblolly pine (Pinus taeda) throughout early stand development (age 5 years) in the southeastern US. Five treatments with eight replications each were tested: no herbicide and no fertilization (C); herbicide only (H); herbicide and half-reduced fertilization rate (R); herbicide and full fertilization (F); and increased stand density (60+ %; 1346 vs. 2152 trees per hectare) with herbicide and full fertilization rate (D). Allometric equations generated from destructive harvests were applied to annual diameter measurements to estimate plot-level biomass and allocation. Herbicide was crucial to promote stand uniformity and increase yield (~600+ % stem biomass compared with C at age 5). Aboveground biomass was similar in R and F treatments, which was, on average, ~25% higher than in H at age 5. Increasing planting density along with multiple herbicide and fertilizer applications yielded higher biomass without compromising individual tree size (diameter and height). There was little effect of silviculture practices on allocation patterns. Our results parallel what was found for fertilization with herbicide from a number of loblolly stands under similar conditions and indicate a ~28% volume gain with fertilization during early stand development. Similarly, our results were consistent with other studies implementing similar differences in planting density and suggest a ~26% volume gain through early stand development with an initial 60% increase in planting density. Our study helps to understand complex relationships between production and silvicultural practices during early stand development and demonstrates that silvicultural prescriptions can be optimized to increase sustainability of production forestry.

Methods

All study details (e.g., site description, experimental design, planting density, fertilization timing, rates and sources, plot sizes, measurement protocols, and biomass calculations) can be found in the manuscript linked to the data. 

Data file description:

- Treatment coding: 

1 – control: no herbicide and no fertilization (C)

2 - herbicide only (H)

3 - herbicide and half-reduced fertilization rate (R)

4 - herbicide and full fertilization (F)

5 - increased stand density (60+ %; 1346 vs. 2152 trees per hectare) with herbicide and full fertilization rate (D);

Variable coding and units:

height – Average tree height (m)

dgl – Diameter at the ground level (cm)

dbh – diameter at breast height (cm)

ba – Basal area (m2/ha)

vi – volume index (mha-1)

mai – mean annual increment (mha-1 yr-1)

need – Foliage (needles) biomass (Mg ha-1)

branc – Branch biomass (Mg ha-1)

stem – stem biomass (Mg ha-1)

abvg – aboveground biomass (needles + branches +stem) (Mg ha-1)

roots-coarse – Coarse roots (> 12 mm) biomass (Mg ha-1)

rmf – root mass fraction (unitless)

comp-vegetation – competing vegetation biomass (Mg ha-1)

Data is provided as plot means. - indicates no measurements or calculations were performed for this variable at this period

Funding

U.S. Forest Service, Award: 18-CS-11330140-087

U.S. Department of Agriculture, Award: 2013-67009-21405

U.S. Department of Agriculture, Award: 2013-67009-25148

U.S. Department of Agriculture, Award: 2019-67019-29906

U.S. Department of Energy, Award: DE‐EM0004391

U.S. Department of Energy, Award: DE-EM0003622