Define Future challenges for scaling from individual to ecosystems?
Scaling of biogeochemical fluxes in terrestrial systems has confirmed much harder. While ecosystem ecologists frequently scale "from leaf-to-globe" in one or two steps (Ehleringer and Field 1993, Fitz et al. 1996), population and community ecologists have insisted that variability within and between populations and species should be incorporated in this scaling process. Such scaling is biologically and mathematically non-trivial. Though, scaling from leaves to individuals, functional ecologists have found it difficult to develop common models that can predict plant responses to increases in CO2 and temperature (Bernacchi et al. 2000). The problem obtains even harder when plants balance their requirements for multiple nutrients; interact with other plants, soil microbes, or herbivores; respond to their environment through acclimating (showing phenotypic plasticity); or respond by modifying their development (showing ontogenetic shifts). We need both data, and models that can incorporate the data, for the influences of spatial variation in populations caused by disturbance and environmental variation at a within-grid spatial scale (Moorcroft et al. 2001); successional and climate-driven shifts of species composition and functional guild composition within a specified habitat; and movement of species range limits while climates change rapidly (Pitelka et al. 1997).)
The mathematical, statistical and computational challenges here are formidable. We should come up with ways for consistently constraining large models with continental-scale databases, and for estimating the future behavior of species assemblages in a changing climate. More basically, we need to find ways that models can be sped up to the point where they can be coupled with global-scale simulation models, by some combination of computational advances (algorithmic and parallel-computation techniques) and mathematical advances which aggregate the details of models while retaining quantitative accuracy in physical and biogeochemical properties at a larger scale. The critical biological question, which can just only be answered by exploration, is whether the signature of individual interactions along with the abiotic environment is reliably transmitted up multiple levels of organizational scale, or if the frequency- dependent and idiosyncratic nature of community interactions blurs these regularities at the ecosystem scale. With appropriate attention to both the mathematical rules of scaling and to the regularities observed in the way that broad classes of organisms have solved their ecological problems (Reich et al. 1997), we should be capable to develop a new class of tools that greatly increase our power to understand and predict biological dynamics throughout a range of scales.