EROC: Ecosystem Feedbacks to Climate Changes: Extending Results from an Ecosystem-Warming Experiment to the Landscape Level

对大气中温室气体积累导致的全球气候变化的预测是基于很大程度上忽略了气候-生态系统相互作用的模式。然而，这种相互作用有可能对气候系统产生巨大的正反馈或负反馈，从而增强或减轻气候变化的幅度。为了量化这些反馈，需要在实验地块的尺度上对气候-生态系统相互作用有一个详细和机械的了解，以及将从生态系统实验中获得的知识外推到景观尺度的可靠方法。在景观尺度上了解生态系统对气候变化的响应，一种广泛使用的技术是从整个景观中获得的数据中发展出一套有关当地生态系统变量与当地气候条件之间的相关性。这些相关性可以用来产生对气候变化响应的预测，但是这种预测的价值取决于这样一个假设，即生态系统变量跟踪气候变化的方式与这些变量现在跟踪空间气候差异的方式相同。气候操纵实验为预测对气候变化的响应提供了一种更基于机械的方法，并且可以确定影响这些响应的最重要的偶然因素（如年际气候变率），但实际困难阻碍了在许多景观的许多地点进行这些实验。此外，影响生态系统对气候变化反应的偶然因素的存在妨碍了扩大规模，因为它简单地假设，在一个地点的试验田上获得的信息将以一种直接的方式应用于景观上所有类似的栖息地（例如基于植被分类）。该项目将结合海拔样带研究，以加深对形成气候-生态系统反馈的机制和偶然因素的理解，并评估和改进样带研究的使用，以推断生态系统响应和反馈到景观尺度的结果。重点将放在两种生态系统对气候变化的响应上，这两种响应是在科罗拉多州灌木/草/牧草混合栖息地进行的为期四年的气候变暖实验模拟中观察到的：1)由加热引起的二氧化碳从生态系统净流出；2)主要植被从牧草向灌木的转变。因为二氧化碳是一种温室气体，因为植被覆盖的变化会改变与大气的能量和水的交换，这些对变暖的反应，在更大的范围内，可能是对气候的重要反馈的来源。?？

I Abstract 9628819 Predictions of global climate change resulting from the buildup of greenhouse gases in the atmosphere are based on models that largely ignore climate-ecosystem interactions. Yet such interactions have the potential to generate large positive or negative feedbacks to the climate system, thereby either enhancing or alleviating the magnitude of climate change. To quantify these feedbacks, a detailed and mechanistic understanding of climate-ecosystem interactions on the scale of experimental plots is needed, along with reliable methods for extrapolating knowledge obtained from ecosystem experimentation to the landscape scale. A widely used technique for acquiring landscape-scale understanding of ecosystem responses to climate change is to develop from data acquired at sites across the landscape a set of correlations between the local ecosystem variable in question and the local climatic conditions. These correlations can then be used to generate predictions of response to climate change, but the value of such predictions hinges on the assumption that ecosystem variables track changing climate in the same way that such variables now track climate differences over space. Climate manipulation experiments provide a more mechanistically-based approach to forecasting responses to climate change, and can identify the most important contingent factors (such as interannual climate variability) that influence those responses, but practical difficulties preclude carrying these out at many sites over many landscapes. Moreover, the existence of contingent factors influencing ecosystem response to climate change precludes scaling up by simply assuming that information learned on experimental plots at one site will apply in a straightforward manner to all the similar habitat (based, say, on a vegetational classification) over a landscape. This project will combine manipulations with elevational transect studies to 1) deepen understanding of the mechanisms and contingent factors that shape climate-ecosystem feedbacks, and 2) evaluate and improve the use of transect studies for extrapolating results about ecosystem response and feedback to the landscape scale. The focus will be on two linked ecosystem responses to climate variation that have been observed over four years of an experimental simulation of climate warming in mixed shrub/ grass/forb habitat in Colorado: 1) a heating-induced net outflow of carbon dioxide from the ecosystem and 2) a shift in dominant vegetation from forbs to shrubs. Because carbon dioxide is a greenhouse gas and because a shift in vegetative cover will alter energy and water exchange with the atmosphere, these responses to warming, on a larger scale, could be a source of significant feedback to the climate. ??