RUI: Grass Effects on Tree Seedling Success in the Pairie-Forest Border: Competition and Facilitation along a Multiple Resource Gradient

9873673Davis尽管水分在干旱和半干旱环境中的重要性，以及围绕竞争和资源梯度进行的大量工作，但没有研究将根和梢竞争沿土壤水分梯度的影响分开。如果我们要了解草地群落木苗建立的生态学，这些信息是至关重要的。本研究将探讨干旱和半干旱环境下木本植物幼苗的建立。将在Cedar Creek LTER场地进行一项大型多因素田间试验，其中水输入、氮输入和草的竞争将被控制。本试验将定量测定禾本科植物在水氮梯度上的根、茎和全株竞争。它还将允许独立量化在上述每种组合中树苗（大栎和椭圆栎）之间的根和梢竞争强度。本研究将为研究资源供给对草木竞争相互作用的影响提供重要的新信息。虽然在单一地点实施，但该研究应该对竞争理论具有广泛的意义，因为它涉及水和养分，并预测植物对自然和人为干扰的反应。本研究的发现将有助于理解全球和区域环境变化（包括氮沉降水平的增加、降水的变化和外来草取代本地草）如何影响草地群落木本幼苗的建立。

9873673Davis Despite the importance of water in arid and semi-arid environments and the numerous amount of work centered around competition and resource gradients, no studies have been made to separate out the effects of root and shoot competition along a soil water gradient. This information is critical if we are going to understand the ecology of wood seedlings establishment in grassland communities. This research will examine the establishment of woody seedlings in arid and semi-arid environments. A large multi-factor field experiment will be undertaken at the Cedar Creek LTER site in which water input, nitrogen input and competition from grasses will be manipulated. This experiment will permit the quantification of root, shoot and whole plant competition by grasses along the water-nitrogen gradient. It will also allow an independent quantification of root and shoot competition intensity between the tree seedlings (Quercus macrocarpa and Q. ellipsoidalis) in each of the above combinations. This research should provide important new information on the effect of resource supply on competitive interactions between grasses and trees. Although implemented at a single site, the research should have broad implications for competition theory as it relates to water and nutrients and for predicting plant response to natural and human-caused disturbance. Findings from this proposed research should help in understanding how global and regional changes in the environment involving increased levels of nitrogen deposition, changes in precipitation, and replacement of native by exotic grasses my be affecting woody seedling establishment in grassland communities.