Biogeochemical effects of global change on US national parks

Federal parks and other public lands have unique mandates and rules regulat ing their use and conservation. Because of variation in their response to l ocal, regional, and globalscale disturbance, development of mitigation stra tegies requires substantial research in the context of long-term inventory and monitoring. In 1982, the National Park Service began long-term, watersh ed-level studies in a series of national parks. The objective was to provid e a more comprehensive database against which the effects of global change and other issues could be quantified. A subset of five sites in North Carol ina, Texas, Washington, Michigan, and Alaska, is examined here. During the last 50 years, temperatures have declined at the southern sites and increas ed at the northern sites with the greatest increase in Alaska. Only the mos t southern site has shown an increase in precipitation amount. The net effe ct of these trends, especially for the most northern and southern sites, wo uld likely be an increase in the growing season and especially the time soi l processes could continue without moisture or temperature limitations. Dur ing the last 18 years, there were few trends in atmospheric ion inputs. The most evident was the decline in SO42- deposition. There were no significan t relationships between ion input and stream water output. This finding sug gests other factors as modification of precipitation or canopy throughfall by soil processes, hydrologic flow path, and snowmelt rates are major proce sses regulating stream water chemical outputs.