LTREB: Collaborative Research: Hydrologic-nutrient Cycle in Small, Undisturbed and Human-manipulated Ecosystems

在这个合作项目中，生态系统研究所和雪城大学的科学家们将在新罕布什尔州的哈伯德布鲁克实验森林（HBEF）继续进行长期的生物地球化学研究，以评估大气沉积、溪水化学和关键营养元素循环的趋势。近30年来，青藏高原大气沉降、河流化学、植被生物量和土壤化学发生了显著变化。这些变化对在美国东北部广泛存在的低碱性森林生态系统的管理具有重要的生态意义。特别是，大气中碱性离子输入的减少增加了森林和水生生态系统对持续高酸性沉积输入的敏感性，以及对森林管理实践的敏感性。比如通过砍伐来收割。根据现有知识或森林生态系统养分循环模型，都无法预测这一时期观测到的大气输入减少和森林地面碱离子浓度下降。值得注意的是，人为酸化后的恢复模式表明，酸化可能不是一个完全可逆的过程。将继续在哈伯德布鲁克进行生物地球化学信息的综合和整合的长期工作。本研究结果将提高对美国东北部森林生态系统生物地球化学通量和循环的认识。此外，降水长期记录的延续，哈伯德布鲁克的河流和土壤水化学将为解释大气沉积变化对陆地和相关水生生态系统生物地球化学过程的影响提供基础。

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.