Nutrient cycling drives plant community trait assembly and ecosystem functioning in a tropical mountain biodiversity hotspot

M Dantas de Paula, M Forrest, L Langan… - New …, 2021 - Wiley Online Library
New Phytologist, 2021Wiley Online Library
Community trait assembly in highly diverse tropical rainforests is still poorly understood.
Based on more than a decade of field measurements in a biodiversity hotspot of southern
Ecuador, we implemented plant trait variation and improved soil organic matter dynamics in
a widely used dynamic vegetation model (the Lund‐Potsdam‐Jena General Ecosystem
Simulator, LPJ‐GUESS) to explore the main drivers of community assembly along an
elevational gradient. In the model used here (LPJ‐GUESS‐NTD, where NTD stands for …
Summary
  • Community trait assembly in highly diverse tropical rainforests is still poorly understood. Based on more than a decade of field measurements in a biodiversity hotspot of southern Ecuador, we implemented plant trait variation and improved soil organic matter dynamics in a widely used dynamic vegetation model (the Lund‐Potsdam‐Jena General Ecosystem Simulator, LPJ‐GUESS) to explore the main drivers of community assembly along an elevational gradient.
  • In the model used here (LPJ‐GUESS‐NTD, where NTD stands for nutrient‐trait dynamics), each plant individual can possess different trait combinations, and the community trait composition emerges via ecological sorting. Further model developments include plant growth limitation by phosphorous (P) and mycorrhizal nutrient uptake.
  • The new model version reproduced the main observed community trait shift and related vegetation processes along the elevational gradient, but only if nutrient limitations to plant growth were activated. In turn, when traits were fixed, low productivity communities emerged due to reduced nutrient‐use efficiency. Mycorrhizal nutrient uptake, when deactivated, reduced net primary production (NPP) by 61–72% along the gradient.
  • Our results strongly suggest that the elevational temperature gradient drives community assembly and ecosystem functioning indirectly through its effect on soil nutrient dynamics and vegetation traits. This illustrates the importance of considering these processes to yield realistic model predictions.
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