Parameter sensitivity of Amazonian ecosystem processes and vegetation dynamics using the LPJ dynamic vegetation model
Poulter, Potsdam Institute for Climate Impact Research (PIK), email@example.com
Cramer, Potsdam Institute for Climate Impact Research, firstname.lastname@example.org
Langerwisch, Potsdam Institute for Climate Impact Research, email@example.com
Dynamic vegetation models (DVM) provide spatially continuous information on carbon and water fluxes and vegetation distribution. In tropical regions, DVMs are necessary to resolve large-scale questions related to carbon cycling and disturbance and for evaluating field-based data from eddy covariance or biomass measurements. Current challenges in tropical ecophysiology include determining rooting distributions for deep soils and seasonal patterns of phenology. We evaluate the sensitivity of these parameters in the LPJ-DVM by comparing biomass, plant functional type distribution (PFT), and carbon fluxes against field and remote sensing observations. Based on literature review, we adjusted the range of rooting distributions, sapwood to heartwood turnover rates, and the development of phenology (leaf longevity and response to drought) within LPJ. We found that rooting distributions were most sensitive in the southern and eastern Amazon where water is more frequently limiting. Carbon allocation and phenology were most sensitive in the wetter regions of the Amazon and strongly influenced the competitiveness and biogeography of PFTs. The optimal distribution of parameters is likely more variable than the number of PFTs in use; this suggests that dynamic sub-modules rather than fitted parameters may be required for determining rooting and phenology patterns.