The Effects of Phosphorus Cycle Dynamics on Carbon Sources and Sinks in the Amazon Region: A Modeling Study Using ELM v1

Abstract

Tropical forests play a crucial role in the global carbon cycle, accounting for one third of the global net primary productivity and containing about 25% of global vegetation biomass and soil carbon. This is particularly true for tropical forests in the Amazon region, as these comprise approximately 50% of the world's tropical forests. It is therefore important for us to understand and represent the processes that determine the fluxes and storage of carbon in these forests. In this study, we show that the implementation of phosphorus (P) cycle and P limitation in the version 1 of the Energy Exascale Earth System Model land model (ELM v1) improves simulated spatial pattern of wood productivity. The P‐enabled ELM v1 is able to capture the declining west‐to‐east gradient of productivity, consistent with field observations. We also show that by improving the representation of mortality processes using soils data, ELMv1 is able to reproduce the observed spatial pattern of above ground biomass. Our model simulations show that the consideration of P availability leads to a smaller carbon sink associated with CO2 fertilization effect and lower carbon emissions due to land use and land cover change. Our simulations suggest P limitation would significantly reduce the carbon sink associated with CO2 fertilization effects through the 21st century. We conclude that P cycle dynamics affect both sources and sinks of carbon in the Amazon region, and the effects of P limitation would become increasingly important as CO2 increases. Therefore, P limitation must be considered for projecting future carbon dynamics in tropical ecosystems.

Rapid Net Carbon Loss From a Whole‐Ecosystem Warmed Peatland

“…Previous versions of ELM‐SPRUCE were used to conduct uncertainty analyses of net C exchange (Griffiths et al, 2017), and those simulations indicated relatively modest responses to warming. Here we modified ELM‐SPRUCE to include land biogeochemistry improvements for version 1 of the Energy Exascale Earth System Model (E3SM and thus ELM for the land model component; Golaz et al, 2019; Yang et al, 2019). Key model improvements include the addition of phosphorus cycling, C and nutrient storage pools, and improved phenology.…”

An Introduction to the E3SM Special Collection: Goals, Science Drivers, Development, and Analysis

“…Building from CLM4.5, E3SM Land Model (ELM v1) includes new options for representing soil hydrology and biogeochemistry, featuring a variably saturated flow model (Bisht et al 2018) and a new module for phosphorus dynamics (Yang et al 2019). To understand the effects of nutrient limitations on carbon-climate feedbacks and their sensitivity to model structural uncertainty, two biogeochemistry approaches are included in ELM v1 to contrast a mechanistic (Equilibrium Chemistry Approximation or ECA; Tang, 2015;Tang and Riley, 2017;Zhu et al, 2016;Zhu et al, 2017) and a conceptual (Converging Trophic Cascade or CTC; Mao et al, 2016;Raczka et al, 2016;Duarte et al, 2017) framework for representing nutrient competition between microbes, plants, and abiotic processes.…”

Modeling the hydrology and physiology of <i>Sphagnum</i> moss in a northern temperate bog

“…Developed by multiple DOE laboratories, E3SM consists of atmosphere, land, ocean, sea ice, and land ice components, linked through a coupler that facilitates across-component communication (Golaz et al, 2019). ELM was originally branched from the Community Land Model (CLM4.5, Oleson et al, 2013), with new developments that include representation of coupled carbon, nitrogen, and phosphorus controls on soil and vegetation processes, and new plant carbon and nutrient storage pools (Ricciuto et al, 2018;Yang et al, 2019;Burrows et al, in review). The model version used in this study is designated ELM_SPRUCE, and includes the new implementation of Sphagnum mosses as well as the hydrological dynamics of lateral transport between hummock and hollow microtopographies.…”