DOI: 10.5061/dryad.xksn02vbt
title: Herbicide, fertilization, and planting density effects on intensively managed loblolly pine early stand development

description: 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.
description: 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 (<i>C</i>) 2 - herbicide only
 (<i>H</i>) 3 - herbicide and half-reduced
 fertilization rate (<i>R</i>) 4 - herbicide and full
 fertilization (<i>F</i>) 5 - increased stand density (60+
 %; 1346 <i>vs.</i> 2152 trees per hectare) with herbicide and
 full fertilization rate (<i>D</i>); 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
 (m<sup>2</sup>/ha) vi – volume index
 (m<sup>3 </sup>ha<sup>-1</sup>) mai – mean annual increment
 (m<sup>3 </sup>ha<sup>-1</sup>
 yr<sup>-1</sup>) need – Foliage (needles) biomass
 (Mg ha<sup>-1</sup>) branc – Branch biomass (Mg
 ha<sup>-1</sup>) stem – stem biomass (Mg
 ha<sup>-1</sup>) abvg – aboveground biomass
 (needles + branches +stem) (Mg ha<sup>-1</sup>)
 roots-coarse – Coarse roots
 (&gt; 12 mm) biomass (Mg ha<sup>-1</sup>) rmf – root mass fraction
 (unitless) comp-vegetation – competing
 vegetation biomass (Mg ha<sup>-1</sup>) Data is provided as plot means. -
 indicates no measurements or calculations were performed for this variable
 at this period