Integration of Ecophysiological and Biogeochemical Approaches to Ecosystem Dynamics

Abstract

Our ability to predict the extent to which climate change will influence the composition, structure, and function of ecosystems is contingent on understanding and integrating the response of organisms across all levels of ecological organization (i.e., physiological, population, community, and ecosystem levels). The integration of ecophysiology and biogeochemistry holds promise for working across levels of ecological organization and for increasing our understanding of ecosystem dynamics. In this chapter, ecophysiology is integrated with biogeochemistry using the C cycle of terrestrial ecosystems as a primary example. The fixation, redistribution, and loss of C from terrestrial ecosystems are largely controlled by the physiological activities of plants and soil microorganisms; however, there are several key gaps in our understanding of plant and microbial ecophysiology that limit our ability to predict the response of the terrestrial C cycle to a changing climate. The most significant gap in our understanding lies belowground and centers on the physiological links among the allocation of C to the production and maintenance of fine roots, the longevity of these structures, and the extent to which the metabolism and longevity of plant roots influence substrate availability for microbial activity in soil. In this chapter, we identify how a physiologically based understanding of fine-root production, maintenance, and longevity can be used to understand ecosystem-level patterns of C allocation. We then explore the extent to which the amount, timing, and biochemistry of root-associated C inputs influence the composition and function of microbial communities in soil. Understanding the ecophysiological links between plant roots and soil microorganisms lies at the heart of understanding the belowground C budget of terrestrial ecosystems.