Mechanisms Controlling Metal and Phosphorus Dynamics in an Experimentally Acidified Watershed in Maine

缅因州熊溪流域(BBWM)是一项长期(14年以上)的全流域实验，旨在研究生态系统对酸沉降的反应。自以来，某流域每两个月进行一次氮硫直升机治理。结果证明，土壤和溪流逐渐酸化，土壤养分(如钙)大量流失，氮循环增加，树木叶片化学发生变化。对磷这一生态系统中的关键营养物质的研究很少。该项目将通过研究土壤、土壤溶液、溪水和生物群(例如，树叶、根和土壤微生物)来评估长期流域酸化对金属活化(侧重于铝和铁)的影响，以及对生物多样性的关联影响。由于酸化、氮饱和和盐基阳离子耗竭等已知的生态效应，政策制定者将重点放在控制氮和硫的排放法规上。关于这些生态变化将如何反过来影响磷循环，人们知之甚少。了解这一关键营养物质的变化可能对了解森林衰退和地表水质量的根本机制至关重要，因此将是政策和管理规划的基础。

The Bear Brook Watershed in Maine (BBWM) is a long-term (14+ years), whole-watershed experiment designed to study ecosystem responses to acid deposition. One watershed has been treated bimonthly by helicopter with nitrogen and sulfur since 1989. Results have documented progressive acidification of soils and streams, substantial losses of soil nutrients (e.g., calcium), increased nitrogen cycling, and changes in tree foliar chemistry. Little research has been done on phosphorus, a critical nutrient in ecosystems. This project will evaluate the effects of long-term watershed acidification on metal mobilization (focusing on aluminum and iron) and linked effects on phosphorus at BBWM by studying soils, soil solutions, stream water, and biota (e.g., foliage, roots, and soil microorganisms).Policy makers have focused on emissions regulations to control nitrogen and sulfur due to known ecological effects on forests and streams such as acidification, nitrogen saturation, and base cation depletion. Little is known about how these ecological changes will, in turn, affect phosphorus cycling. Understanding changes in this key nutrient may be pivotal to understanding underlying mechanisms of forest decline and surface water quality, and will therefore be fundamental to policy and management planning.