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

我 摘要9628819 对大气中温室气体积累导致的全球气候变化的预测所依据的模型在很大程度上忽略了气候-生态系统的相互作用。然而，这种相互作用有可能对气候系统产生巨大的积极或消极反馈，从而加强或减轻气候变化的程度。为了量化这些反馈，需要对实验地块尺度上的气候-生态系统相互作用进行详细和机械的理解，沿着需要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。 一个广泛使用的技术，以获得生态系统对气候变化的反应的生态系统规模的理解是从整个景观的网站获得的数据开发一套相关的当地生态系统变量和当地气候条件之间的关系。这些相关性可以用来预测对气候变化的反应，但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。气候操纵实验提供了一种更基于机械的方法来预测对气候变化的反应，并可以确定影响这些反应的最重要的偶然因素（如年际气候变率），但实际困难排除了在许多地点进行这些许多景观。此外，影响生态系统对气候变化的反应的偶然因素的存在，排除了简单地假设从一个地点的试验地块上获得的信息将以直接的方式适用于一个景观上的所有类似生境（例如，基于植被分类）的扩大规模。 该项目将联合收割机操作与高程样带研究相结合，以1）加深对形成气候-生态系统反馈的机制和偶然因素的理解，2）评估和改进样带研究的使用，以外推生态系统响应和反馈到景观尺度的结果。重点将是两个相关的生态系统对气候变化的反应，已观察到超过四年的实验模拟气候变暖的混合灌木/草/杂类草栖息地在科罗拉多：1）加热引起的二氧化碳从生态系统的净流出和2）在占主导地位的植被从杂类草灌木的转变。由于二氧化碳是一种温室气体，而且植被覆盖的变化会改变与大气的能量和水分交换，因此这些对变暖的反应在更大范围内可能是对气候的重要反馈。 ??

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. ??