Implications for estimating processes from Earth System Models
These results have important implications for the use of earth system models (ESMs) for estimating ecosystems processes across scales. Most ESMs treat traits as constants, disregarding variation among species within plant functional types and intraspecific variation driven by the environment (Ghimire et al., 2016, Lawrence et al., 2019, but see attempts at integrating more flexible strategies like Fisher et al., 2015). This was justified by previous evidence suggesting that only interspecific variation mattered at continental scales (Messier et al. 2010). However, our results demonstrate that even at near-continental scales intraspecific variation holds meaningful information that needs to be addressed (Figures 1, 5). The need to incorporate intraspecific variation is magnified when models are applied at smaller scales where the environment affects traits-tradeoffs to move away from the global LES (Fisher et al., 2018). Because different regions exhibit different directional shifts from the species-only models (Figure 4) we need to understand environmentally driven intraspecific traits variation to accurately model regional ecosystem processes.