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

缅因州的熊溪流域（BBWM）是一个长期（14年以上）的全流域实验，旨在研究生态系统对酸沉降的响应。 自1989年以来，每两个月用直升机用氮和硫处理一个流域。 结果表明，土壤和溪流逐渐酸化，土壤养分大量流失（例如，钙），增加氮循环，并在树叶化学变化。 磷是生态系统中的一种关键营养素，但对磷的研究很少。 该项目将通过研究土壤、土壤溶液、溪流水和生物群（例如，由于已知的对森林和溪流的生态影响，例如酸化、氮饱和和碱阳离子耗尽，决策者已经关注排放法规以控制氮和硫。 人们对这些生态变化如何反过来影响磷循环知之甚少。 了解这一关键营养素的变化可能是了解森林衰退和地表水质量的根本机制的关键，因此对政策和管理规划至关重要。

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.