Collaborative Research: Nutrient co-limitation in young and mature northern hardwood forests

北方阔叶林幼林和成熟林的养分共同限制长期以来，温带森林被认为是氮（N）限制的，但随着时间的推移，空气污染造成的慢性N沉降应减少N限制，理论表明，生态系统生产力应受到多种养分的共同限制。在温带森林系统中缺乏氮与磷限制的实验测试。 本研究将结合联合收割机模拟和实地研究，探讨管理阔叶林生态系统演替过程中的养分吸收。 提高对资源利用的生态系统优化的理解，包括维持共同限制，对森林管理、环境保护和基础科学知识都很重要。平衡的养分循环对维持森林的可持续性至关重要，白色山国家森林的科学家和管理人员将根据拟议研究的结果评估造林做法。 例如，它们的森林管理计划要求从森林获取养分用于再生长的能力方面说明密集采伐的理由。 当养分有限时，矿物风化的生物增强等反馈明显与此相关。多元素限制（MEL）模型从资源优化理论和生态系统地球化学的角度代表了共同限制。我们已经扩展了模型，包括P以及N，碳，光，和水，并将其应用于模拟初级和次级演替在北方阔叶林。在3个林龄的林分中，采用N单施、P单施、N+P单施的养分添加方式，（~20年，30年和100年）在新罕布什尔州的巴特利特实验森林，我们将测试模型预测的资源限制模式和多种分配机制的努力，以获得N和P。该模型预测，地上生产力对N+P的响应比单独N或P更大。在较老的立场，它预测一个更大的响应N比P此外，但在年轻的立场，该模型表明，从碎屑N的供应应该是足够的创建P限制。

Nutrient Co-limitation in Young and Mature Northern Hardwood ForestsTemperate forests have long been thought to be nitrogen (N) limited, but chronic N deposition from air pollution should reduce N limitation over time, and theory suggests that ecosystem productivity should be co-limited by multiple nutrients. Experimental tests of N vs. phosphorus (P) limitation in temperate forest systems are lacking. This study will combine modeling and field studies to explore processes mediating nutrient colimitation in relation to successional change in managed hardwood forest ecosystems. An improved understanding of ecosystem optimization of resource use, including the maintenance of co-limitation, is important to forest management, environmental protection, and basic scientific knowledge. Balanced nutrient cycling is essential to maintaining forest sustainability, and scientists and managers at the White Mountain National Forest will evaluate silvicultural practices in light of results from the proposed research. For example, their forest management plans require justifying intensive harvest removals in terms of the ability of forests to acquire nutrients for regrowth. Feedbacks such as the biological enhancement of mineral weathering when nutrients are limiting are clearly relevant to this appraisal.The Multi-Element Limitation (MEL) model represents co-limitation from the perspective of resource optimization theory and ecosystem biogeochemistry. We have extended the model to include P as well as N, carbon, light, and water, and applied it to simulate primary and secondary succession in northern hardwood forests. Using nutrient additions of N alone in some forest stands, P alone in some forest stands, N+P in some forest stands, in replicated stands of three ages (~20, 30, and 100 years) at the Bartlett Experimental Forest in New Hampshire, we will test the patterns of resource limitation predicted by the model and multiple mechanisms of allocation of effort to acquire N and P. Specifically, the model predicts a greater response of aboveground productivity to N+P than N or P alone. In older stands, it predicts a greater response to N than to P addition, but in younger stands, the model suggests that the supply of N from detritus should be sufficient to create P limitation.