Biotic Control of Calcium Supply: Distinguishing Sources to Regrowing Forests

摘要：在森林生态系统环境胁迫的研究中，森林经营的影响以及与林分发展相关的变化没有得到足够的重视。钙的收支表明，年轻的北方阔叶林(30年生)将钙从矿质土壤转移到地上植被、森林地面和排水中，而较老的林分处于大致稳定的状态。这种差异对于理解酸雨在美国东北部钙耗竭中的相对重要性很重要。此外，如果幼龄林分利用了老林分无法获得的土壤钙，那么重复采伐不会像根据老林分的出口和风化速率所预测的那样，导致钙的迅速枯竭。另一方面，如果幼林对钙的快速吸收加速了随时可用的库的枯竭，可持续林业可能会受到威胁。我们的目标是确定矿物土壤中可风化钙的非硅酸盐来源的重要性，以及林分年龄对矿物土壤中可活化钙的来源和数量的影响。我们将使用锶同位素和元素比率来确定不同土壤钙库对满足更新森林的钙需求的相对重要性。BROADER影响：多所大学将通过分包合同参与这项研究，至少将培训3名研究生和2名本科生。这项工作将提供信息，使森林管理者和政策制定者能够就营林作出更好的决策。

ABSTRACT: The effects of forest management, and the changes associated with stand development, have not been given sufficient emphasis in studies of environmental stress in forested ecosystems. Calcium budgets indicate that young northern hardwood stands (30 yrs old) transfer Ca from mineral soil into aboveground vegetation, forest floor, and drainage water, whereas older stands are in approximate steady state. This difference is important to understanding the relative importance of acid rain in Ca depletion in the northeastern United States. Futhermore, if young stands tap a pool of soil Ca unavailable to older stands, then repeated harvest will not result in rapid Ca depletion, as has been predicted based on rates of export and weathering in older stands. If, on the other hand, rapid Ca uptake by young stands hastens the depletion of readily available pools, sustainable forestry may be threatened. Our objectives are to determine the importance of non-silicate sources of weatherable Ca in the mineral soil, and the effect of stand age on the source and magnitude of Ca mobilized from the mineral soil. We will use Sr isotopes and element ratios to identify the relative importance of different soil Ca pools to meeting the Ca needs of regenerating forests.BROADER IMPACTS: Multiple Universities will be involved in this research through subcontracts, and at least 3 graduate students and 2 undergraduates will be trained. This work will provide information that will enable forest managers and policy makers to maker better decisions about silviculture.