PNAS:气候变化与加利福尼亚草原的植物生长
美国赖斯大学一项研究模拟了持续性全球气候变化中的4个主要成分将如何影响生态系统，这项研究发现，未来的气候变化预计将降低美国加利福尼亚草原和类似生态系统的总年度植物生长。预测生态系统将如何对全球气候变化做出响应是一个挑战，这是由于相互作用因素的数量与复杂性。Kai Zhu、Chris Field和他们的同事把来自一个17年的多因素实验的直接观测与统计分析结合起来，通过模拟在温度、降水量、大气二氧化碳和氮污染的许多组合下的未来条件，研究了美国加利福尼亚草原的年度植物生长即净的初级生产。这组作者把植物生长精密调整到了平均条件下，结果发现偏离长期平均值导致了净的初级生产的减少。这组作者说，由于加利福尼亚草原几乎没有表现出在一个变化的气候中截存额外的碳的趋势，未来缓解气候变化的举措可能需要把致力于降低和能源有关的系统的排放的策略整合进来。
原文链接：
Nonlinear, interacting responses to climate limit grassland production under global change
原文摘要：
Global changes in climate, atmospheric composition, and pollutants are altering ecosystems and the goods and services they provide. Among approaches for predicting ecosystem responses, long-term observations and manipulative experiments can be powerful approaches for resolving single-factor and interactive effects of global changes on key metrics such as net primary production (NPP). Here we combine both approaches, developing multidimensional response surfaces for NPP based on the longest-running, best-replicated, most-multifactor global-change experiment at the ecosystem scale—a 17-y study of California grassland exposed to full-factorial warming, added precipitation, elevated CO2, and nitrogen deposition. Single-factor and interactive effects were not time-dependent, enabling us to analyze each year as a separate realization of the experiment and extract NPP as a continuous function of global-change factors. We found a ridge-shaped response surface in which NPP is humped (unimodal) in response to temperature and precipitation when CO2 and nitrogen are ambient, with peak NPP rising under elevated CO2 or nitrogen but also shifting to lower temperatures. Our results suggest that future climate change will push this ecosystem away from conditions that maximize NPP, but with large year-to-year variability.
作者：Kai Zhu
