Trace Gas Cross-Site Comparison: A TRAGNET Project

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9416813 Ojima This project will establish a database and model analyses to be used in determining general relationships of trace gas exchange across a broad environmental gradients in climate, atmospheric deposition of N, and soils to better quantify fluxes of these biogenic radiatively active trace gases across North America. Trace Gas Network (TRAGNET) sites will be used, an International Geosphere-Biosphere Programme/International Global Atmospheric Chemistry (IGBP/IGAC) Midlatitude Activity of a network of locations around the U.S., as the core set of study sites. This network includes many LTER sites and other long-term research sites, where fluxes of CO EMB1 2, CH4, and N2O and possibly other trace gases are being measured and locations where trace gas model development is being conducted. Measurement of biogenic trace gas across a network of sites in North America and comprehensive analysis of these data are critical to understanding the factors controlling biogenic trace gas production and consumption. Ecosystems in this region are major contributors of these important radiatively active biogenic trace gases. Human activities modify gas fluxes both directly and indirectly. Directly, agricultural and forest management practices affect soil physical and biological properties, including those that control gas fluxes. Indirectly, air pollution and acid deposition affect fluxes and modifying biogeochemical cycles associated, especially N dynamics, with trace gas fluxes. Natural systems are both sources and sinks of trace gases, but the magnitudes of these fluxes are not known. Although trace gas flux measurements in temperate ecosystems have been made for decades, measurements have generally been infrequent (rarely extending beyond a growing season), usually small-scale, e.g., plot size treatments and may not always be comparable to other flux data collected at other sites. A coordinated analysis of biogenic trace gas flux measurements is essential to understanding these sour ces and sinks in a regional and global context. Three critical research needs are : (1) improved estimates of net fluxes of methane, nitrous oxide and carbon dioxide and of environmental factors which control these fluxes; (2) identification and quantification of other potentially important regions of significant fluxes, particularly those from geographic areas that have been neglected in past research; and (3) development of models to quantify how trace gas fluxes will respond to climatic, N deposition, and land management changes. The effort will bring together data from on going trace gas flux projects and provide the integrated database to researchers involved in the study. {PAGE \# "'Page: '#' '"|Page: 1 } EMB1