RANGELAND CO_2 FLUXES: IMPLICATIONS OF RESULTS FROM THE USDA-ARS FLUX NETWORK

摘要

Atmospheric concentrations of carbon dioxide (CO_2) have doubled since the end of the last Ice Age and increased over 30% since the beginning of the Industrial Age, almost 200 years ago. Concern that increasing levels of CO_2 and other greenhouse gases may alter the intensity of Earth's greenhouse effect and alter the climate has led to efforts to reduce greenhouse gas levels, both by reduction of emissions and by biotic removal and storage of CO_2-C in plant biomass and soils as organic carbon by agriculture and forest management. Long-term measurements of CO_2 fluxes in major terrestrial ecosystems are required to define the magnitude of C exchange between the biosphere and the atmosphere, and to determine which ecosystems account for the "missingC." The large C sink thought to exist in North America likely consists of smaller sources and sinks of unknown magnitudes. Considerable information has accumulated regarding C storage in soils used for crop production, and networks such as AmeriFlux aremeasuring net C accumulation in forests and other ecosystems. Little information is available regarding the role of grasslands and shrublands in the global C balance, despite their extensive distribution. Less information exists relative to their potential for sequestering C.