Forest production is strongly dependent on nutrient uptake; however, sustainable management of intensively managed plantations requires an improved understanding of this relationship when fertilization occurs frequently across short rotations. Here, we studied temporal nitrogen (N) concentration ([N]) and content (Nc) dynamics under different silvicultural practices (herbicide, fertilization, and planting density) throughout early loblolly pine (Pinus taeda) stand development (5 years). We describe relationships of [N] and Nc of different stand components (foliage, branches, stem, roots, and competing vegetation) with carbon and biomass. Our results demonstrate that [N] of perennial loblolly tissues do not respond to silvicultural practices and progressively decrease through development. While foliar [N] was most responsive to resource availability, it was not consistent across time. Controlling competing vegetation was crucial to promote the use of site resources by the crop tree and increased loblolly Nc by >500%. However, increased N uptake and expedited growth is dependent upon fertilization early in stand development. At age 5, herbicide plus reduced and full fertilization rates exhibited similar aboveground Nc, which was 32% higher than with herbicide only. Increasing planting density resulted in increased above- and belowground loblolly Nc; however, increases in Nc were not proportional with increases in planting density. Net primary productivity and N uptake were linearly related, but age/development strongly controlled N use efficiency. Our study helps to understand complex relationships between N, biomass, and silvicultural practices during early stand development and demonstrates that temporal evaluation of nutrient dynamics is crucial to better understand loblolly pine growth, carbon sequestration potential, and to inform sustainable silvicultural practices across short rotations.

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

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:

*all properties are from loblolly pine trees but “cptveg”, which refers to competing vegetation

 

needlesperN – needles (foliage) nitrogen (N) concentration [N] – in %

branchesperN – branch [N] in %

stemperN – stem [N] in %

rootsperN – root [N] in %

cptvegperN – competing vegetation [N] in %

need15N – foliage δ¹⁵N (‰)

branch15N – branch δ¹⁵N (‰)

stem15N – stem δ¹⁵N (‰)

root15N – root δ¹⁵N (‰)

cptveg15N – competing vegetation δ¹⁵N (‰)

needlesN – foliage N content (kg N ha^-1)

branchesN – branch N content (kg N ha^-1)

stemN – stem N content (kg N ha^-1)

rootN – root N content (kg N ha^-1)

abvN – loblolly pine aboveground N content⁺ (kg N ha^-1)

⁺sum of needle, branch, and stem N content

cptvegN – competing vegetation N content (kg N ha^-1)

needlesCN – foliage Carbon:Nitrogen (C:N) ratio (unitless)

branchesCN – branch C:N ratio (unitless)

stemCN – stem C:N ratio (unitless)

rootCN – root C:N ratio (unitless)

abvCN – loblolly pine aboveground C:N ratio (unitless)

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

"-" indicates no measurements or calculations were performed for this variable at this period.