Temperate forest structural metrics respond to N and P addition
Abstract
Improvements in airborne laser scanning allow us to test the effects of nutrient availability on forest structure at scales not previously possible. Forests on geologically young soils are often assumed to be limited by N, but anthropogenic N deposition has pushed many ecosystems towards multiple element limitation. To explore nutrient limitation in temperate forests, the Multiple Element Limitation in Northern Hardwood Ecosystems (MELNHE) project has added N (as NH4NO3; 30 kg/ha/yr) and P (as NaH2PO4; 10 kg/ha/yr) to 0.25-ha plots in a factorial design in nine forested stands at the Bartlett Experimental Forest in New Hampshire since 2011. Five years after treatment, diameter growth was greater in P-amended plots (Goswami et al. 2018). Here we use three years of aerial laser scanning data collected by the National Ecological Observatory Networks Airborne Observation Platform (NEON AOP) to examine the effect of N and P on the 13 forest structural metrics developed by LaRue et al. (2020). To discern structural differences in forests amended with N versus P we used a linear mixed effect model with N addition, P addition, the interaction of N and P addition, and forest age as fixed effects; stand and year were random effects. We found that trees that received N were significantly taller than trees within the same stand that did not receive N (main effect of N, p = 0.02), and that there was a significant synergistic effect of N and P (p = 0.02) on tree height; i.e. height in N+P plots was greater than would be predicted by the main effects of N and P alone. However, trees that received P had greater canopy complexity (main effect of P, p < 0.001) suggesting greater exploitation of light environment that may be related to the diameter increase observed in 2015 (Goswami et al 2018). Airborne laser scanning holds promise for measuring aboveground structural attributes of ecosystems and relating them to nutrient limitation of productivity.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMB088...07Y
- Keywords:
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- 0414 Biogeochemical cycles;
- processes;
- and modeling;
- BIOGEOSCIENCES;
- 0416 Biogeophysics;
- BIOGEOSCIENCES;
- 0426 Biosphere/atmosphere interactions;
- BIOGEOSCIENCES;
- 0476 Plant ecology;
- BIOGEOSCIENCES