RUI: Fluctuating Resources and Mechanisms of Invasibility Along the Prairie-Forest Border

入侵生态学理论需要变得更加机械化、量化和预测性，需要野外实验和更好的模型来帮助完成这一目标。这项拟议项目的最初目标是测试最近提出的侵袭性的机制假说，并开发一个定量的经验模型，可以用来预测环境随时间变化的侵袭性。被检验的假说提出，入侵性和资源可获得性之间存在机械关系，入侵性的变化通常是由于来自栖息植被的竞争强度的变化，而这反过来又是资源可获得性波动的结果。该项目将在明尼苏达州沙地平原的原生草地环境中进行。因此，该项目的第二个目标是增加我们对与半干旱环境中草原和林地/草原交错带相关的入侵动态的了解。这些目标将在一项由三部分组成的研究中实现。在第一阶段，将利用野外实验的数据建立入侵能力的经验模型，在该实验中，资源可获得性(水)的时间模式将在被实验入侵的地块中进行调整。在这一阶段，现场试验的数据也将被用来直接检验资源可获得性波动假说的预测。之所以选择水作为处理资源，是因为以前对雪松溪育苗的研究表明，草本植物和植物的建立成功与土壤水分条件最密切相关。在第二阶段，将使用现有的机械土壤水模型，在各种气候(温度和降雨)数据集下，在研究地点产生长达一季的土壤水分剖面，包括研究地点在项目期间记录的气候数据，该地区的历史气候数据，以及如果气候变化，未来可能出现的各种假设的温度和降水状况。在第三阶段，由机械模型产生的长达一季的水面线将被用作入侵性经验模型的输入。将经验模型和机械模型相结合产生的侵袭性预测与研究期间进行的单独的野外实验所获得的侵袭性数据进行比较。如果综合模型的预测是成功的，那么它将与历史和假设的气候数据一起使用，以确定过去天然草原的年变化不可侵入性的程度，以及未来如果温度和/或降水制度发生变化，可侵入性可能改变的程度。本研究的目的是促进生态学理论和对特定环境的生态学理解。除了测试最新的可侵入性机械理论外，这项研究还将开发一种方法来建模和预测可移植到其他环境中的入侵能力。最近的证据表明，草原和老田比其他生物群对降水的波动更敏感，而草原和稀树草原等水资源有限的环境可能是受未来气候变化影响最大的一些生物群。因此，通过在雪松溪水资源有限的草原-森林交错带中测试特定的入侵机制理论，并进行实验研究，最终开发出入侵能力模型，这项研究将有助于建立重要的知识池，这将是预测和准备这些环境中全球环境变化可能产生的生态后果所必需的。

0208125DavisIt is widely agreed that invasion ecology theory needs to become more mechanistic,quantitative, and predictive and that field experiments and better models are required to helpaccomplish this goal. The initial goal of the proposed project is to test a recent mechanistichypothesis of invasibility and to develop a quantitative empirical model that can be used topredict the changing invasibility of an environment over time. The hypothesis tested proposesthat a mechanistic relationship exists between invasibility and resource availability, and thatchanges in invasibility are often due to changes in the competition intensity from residentvegetation, which in turn result from fluctuations in resource availability. This project will beconducted in a native grass environment located on a Minnesota sand plain. Thus, a second goalof the project is to increase our understanding of the invasion dynamics associated withgrasslands and woodland/grassland ecotones in semi-arid environments. These goals will beaccomplished in a study consisting of three parts.During the first stage, an empirical model of invasibility will be developed using datafrom a field experiment in which temporal patterns of resource availability (water) will bemanipulated in plots being experimentally invaded. During this stage, data from the fieldexperiments will also be used to directly test predictions of the fluctuating resource availabilityhypothesis. Water was selected as the resource to be manipulated because previous studies ofseedling establishment at Cedar Creek have shown that establishment success of herbaceous andplants was most strongly correlated with soil water conditions. During the second stage, anexisting mechanistic soil water model will be used to produce season-long soil water profiles atthe study site under a variety of climatological (temperature and rainfall) data sets, includingclimatological data recorded at the study site during the project, historical climatological data forthe region, and various hypothetical temperature and precipitation regimes that might occur inthe future if the climate changes. During the third stage, the season-long water profiles producedby the mechanistic model will be used as input for the empirical model of invasibility. Theinvasibility predictions produced by the integration of the empirical and mechanistic models willcompared to invasibility data obtained from a separate field experiment conducted during thestudy. If the integrated model is successful in its predictions, then it will be used with thehistorical and hypothetical climatological data to determine the extent of annual variability ininvasibility of native grasslands in the past, and the extent to which invasibility may change inthe future if temperature and/or precipitation regimes change.The goals of the proposed study are both to advance ecological theory and the ecologicalunderstanding of specific environments. In addition to testing a recent mechanistic theory ofinvasibility, the study will develop a method to model and predict invasibility that is intended tobe transferable to other environments. Recent evidence has shown that grasslands and old fieldsare more responsive to fluctuations in precipitation than other biomes and that water limitedenvironments such as grasslands and savannas are likely to be some of the biomes most affectedby future climate change. Thus, by testing a specific mechanistic theory of invasibility in thewater limited grassland-forest ecotone at Cedar Creek with an experimental study culminating inthe development of a model of invasibility, this study will contribute to the important pool ofknowledge that will be necessary to predict and prepare for the possible ecological consequencesof global environmental change in these environments.