2020 ESA Annual Meeting (August 3 - 6)

COS 174 Abstract - Identifying plant resource acquisition and allocation strategies for nutrient-enabled ELM-FATES

Elizabeth Agee, Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, Ryan Knox, Earth Sciences Division, Lawrence Berkeley National Lab, Charles D. Koven, Earth and Environmental Sciences Area, Lawrence Berkeley National Laboratory, Berkeley, CA, Rosie A. Fisher, Climate & Global Dynamics, National Center for Atmospheric Research, Boulder, CO, Stuart J. Davies, Forest Global Earth Observatory, Smithsonian Tropical Research Institute, Washington, DC and Anthony Walker, Environmental Sciences Division and Climate Change Science Institute, Oak Ridge National Laboratory, Oak Ridge, TN
Background/Question/Methods

The allocation of biomass to leaf, stem, and root is intimately linked to the acquisition of key resources needed to support plant function. Within a community, there exist numerable strategies for acquiring and allocating resources, operating within developmental and competitive spaces, ultimately shaping the structure and function of ecosystems over long time scales. Of particular interest are the resource allocation and acquisition strategies of tropical forests—with soil nutrient concentrations (nitrogen and phosphorous) hypothesized to dampen primary production and regulate forest growth. Size-structured or cohort-based models provide the means to test hypothesized allocation and acquisition strategies and quantify the impacts of the costs and benefits of these strategies on co-existence under resource limitation. The Functionally Assembled Terrestrial Ecosystem Simulator (FATES) model is a demographic vegetation model fully integrated with the E3SM Land Model (ELM). A newly implemented nutrient acquisition module was used to explore the impacts of acquisition traits on carbon uptake within a tropical forest.

Results/Conclusions

Analysis was performed along a soil nutrient gradient (soil types ranging from sandstone-derived loam to shale-derived clay) for plots within Lambir Hills, Malaysia. Site-level measurements from ForestGEO were coupled with data from trait databases to assemble multiple plant functional types (PFTs) with resource acquisition strategies ranging from acquisitive to conservative. Acquisitive strategies favor uptake over storage, with generally higher maximum uptake rates and phosphatase activity. Alternatively, conservative strategies favor slower turnover of nutrients, with higher rates of translocation of nutrients and higher values of nutrient use efficiency. Nutrient-enabled, single PFT simulations were compared to carbon-only simulations within ELM-FATES, confirming nutrient controls on gross primary production. Further simulations utilizing multiple PFTs highlight the co-existence of diverse functional types within the same landscape—with relative abundance determined by the underlying substrate. Model results signal the importance of representing nutrient dynamics in size structured dynamic vegetation models in order to capture the response of tropical forests to changing climate.