Biogeochemical Cycling of Carbon and Nitrogen in Chaparral Dominated Ecosystems

Abstract

The controls and trajectories of biogeochemical dynamics in chaparral dominated ecosystems are highly diverse. This breadth of diversity in chaparral biogeochemical dynamics is caused by a combination of diverse biogeophysical drivers, self-organization, and sensitivity to historical legacies. The high topographic heterogeneity and decoupling of moisture inputs and energy inputs in the winter precipitation dominated climates imposes unique ecohydrologic adaptations that influence plant and microbial metabolic activities and distributions throughout chaparral landscapes. Chaparral biogeochemical dynamics, especially interactions among carbon, nitrogen, and hydrologic cycling, may have important implications for the ecosystem services and disservices provided by these ecosystems, including greenhouse gas emissions and pollutants to air and water, and influence the vulnerability of chaparral biological communities to global change drivers. These ecosystems may have a large capacity for carbon storage and sustained carbon sequestration at rates comparable with those of old-growth forests. In other places, chaparral ecosystems may have low pools of carbon and low rates of sequestration. While commonly considered nitrogen limited, chaparral dominated ecosystems may also have large nitrogen emissions through atmospheric and hydrologic pathways. Future trajectories of chaparral biogeochemical dynamics are also variable. Unprecedented interactions among global change drivers, including climate, nitrogen deposition, fire frequency, and invasion risks, are pushing many of these systems to tipping points of reorganization and type-conversion to grass dominated states with uncertain biogeochemical consequences. Management for maintaining ecosystem services associated with biogeochemical dynamics can be improved with growing opportunities provided by a suite of environmental sensors and next generation modeling approaches.