Control of Productivity and Plant Species Segregation by Nitrogen Fluxes to Wetland Beaver Meadows

约翰斯顿等人DEB-9615326 海狸创造的池塘和草地是北美大面积地区整体水和养分通量调节的关键组成部分。 这些海狸池塘和草地发生在景观位置，非常适合接收地表径流，溪流和地下水排放的上游来源，使海狸池塘和草地的水文控制功能不成比例地大于将推断其面积单独。 潮湿的禾本科草甸是一个关键阶段，通过河狸池塘通过在水文制度的变化，可能会统治这些景观的动态。 基于以前的研究表明，在这些草甸植物生长的氮限制，这项新的研究将试图量化海狸草甸不同的氮源的相对重要性，以及氮供应对植被的组成，结构和生产力的影响。 为了测试这些关系，海狸池塘和草地内的水文和养分收支的空间明确的模型将耦合到一个模型的植物生长，冠层分配，和垂直光梯度在不同的养分和水分制度。 该模型将使用收集在Voyageurs国家公园的水文数据，并使用温室和围隔生态系统的物种响应水，光和营养物质的实验参数化。 然后，该模型将测试对植被的空间格局沿着梯度的水深和养分的可用性在几个不同的水文草甸。 这项研究将提供显着的进展，了解景观控制植物物种隔离和生产力通过水和养分输送。 它也将促进了解禾本科物种的物种隔离和生产力的控制在潮湿的生态系统中，在短暂的冠层动态，而不是总的响应营养，可能会决定社区动态。

JOHNSTON et al. DEB-9615326 Ponds and meadows created by beaver are key components of the regulation of overall water and nutrient fluxes over large areas in North America. These beaver ponds and meadows occur in landscape positions ideally suited to receive surface runoff, stream flow, and groundwater discharge from upstream sources, giving beaver ponds and meadows a hydrologic control function disproportionately greater than would be inferred by their area alone. Moist graminoid meadows are a key stage through which beaver ponds pass during changes in hydrologic regimes which may govern the dynamics of these landscapes. Building on previous research that has shown N limitation of plant growth in these meadows, this new research will attempt to quantify the relative importance of different N sources in beaver meadows, and the effect of N supply to vegetation on its composition, structure, and productivity. To test these relationships, a spatially explicit model of hydrology and nutrient budgets within beaver ponds and meadows will be coupled to a model of plant growth, canopy allocation, and the vertical light gradient under different nutrient and water regimes. The model will be parameterized using hydrologic data collected in Voyageurs National Park and using greenhouse and mesocosm experiments on species responses to water, light, and nutrients. The model will then be tested against spatial patterns of vegetation along gradients of water depth and nutrient availability in several meadows of different hydrology. This research will provide significant advances in understanding of landscape controls on plant species segregation and productivity via water and nutrient delivery. It will also advance understanding of how species segregation and productivity of graminoid species are controlled in moist ecosystems, in which transient canopy dynamics, rather than total response to nutrients, may be determining community dynamics.