In this collaborative project scientists at the Institute of Ecosystem Studies and Syracuse University will continue long-term biogeochemical studies at the Hubbard Brook Experimental Forest (HBEF) in New Hampshire to evaluate trends in atmospheric deposition, streamwater chemistry and cycling of critical nutrient elements. During the past three decades, dramatic changes in atmospheric deposition, streamwater chemistry, vegetation biomass and soil chemistry were observed at the HBEF. These changes have important ecological implications for the management of base-poor forest ecosystems, which are widespread throughout the northeastern U.S. In particular, a decline in atmospheric inputs of base cations has increased the sensitivity of forest and aquatic ecosystems to continuing high inputs of acidic deposition, as well as to forest management practices, such as harvest by clearcutting. Neither the decline in atmospheric inputs nor declines in forest floor concentrations of base cations observed during this period were predicted from existing knowledge or from models of nutrient cycling for forest ecosystems. Significantly, the pattern of recovery following anthropogenic acidification suggests that acidification may not be a fully reversible process. %%% Long-term efforts at synthesis and integration of biogeochemical information at Hubbard Brook will be continued. Results from this research will improve the understanding of biogeochemical flux and cycling in forest ecosystems of the northeastern U.S. In addition, the continuation of the long-term record of precipitation, streamwater and soilwater chemistry at Hubbard Brook will provide a basis for interpreting the effects of changing atmospheric deposition on biogeochemical processes in terrestrial and associated aquatic ecosystems.
