Zhou Xuhui, Weng Ensheng, Luo Yiqi
Department of Botany and Microbiology, University of Oklahoma, Norman, Oklahoma 73019, USA.
Ecol Appl. 2008 Mar;18(2):453-66. doi: 10.1890/07-0626.1.
It is commonly acknowledged that ecosystem responses to global climate change are nonlinear. However, patterns of the nonlinearity have not been well characterized on ecosystem carbon and water processes. We used a terrestrial ecosystem (TECO) model to examine nonlinear patterns of ecosystem responses to changes in temperature, CO2, and precipitation individually or in combination. The TECO model was calibrated against experimental data obtained from a grassland ecosystem in the central United States and ran for 100 years with gradual change at 252 different scenarios. We primarily used the 100th-year results to explore nonlinearity of ecosystem responses. Variables examined in this study are net primary production (NPP), heterotrophic respiration (R(h)), net ecosystem carbon exchange (NEE), runoff, and evapotranspiration (ET). Our modeling results show that nonlinear patterns were parabolic, asymptotic, and threshold-like in response to temperature, CO2, and precipitation anomalies, respectively, for NPP, NEE, and R(h). Runoff and ET exhibited threshold-like pattern in response to both temperature and precipitation anomalies but were less sensitive to CO2 changes. Ecosystem responses to combined temperature, CO2, and precipitation anomalies differed considerably from the responses to individual factors in terms of response patterns and/or critical points of nonlinearity. Our results suggest that nonlinear patterns in response to multiple global-change factors were diverse and were considerably affected by combined climate anomalies on ecosystem carbon and water processes. The diverse response patterns in nonlinearity have profound implications for both experimental design and theoretical development.
人们普遍认为生态系统对全球气候变化的响应是非线性的。然而，这种非线性在生态系统碳和水过程中的模式尚未得到很好的描述。我们使用一个陆地生态系统（TECO）模型来研究生态系统对温度、二氧化碳和降水变化单独或组合变化的非线性响应模式。TECO模型根据从美国中部一个草地生态系统获得的实验数据进行校准，并在252种不同情景下以逐渐变化的方式运行100年。我们主要使用第100年的结果来探索生态系统响应的非线性。本研究中考察的变量有净初级生产力（NPP）、异养呼吸（R(h)）、生态系统净碳交换（NEE）、径流和蒸散（ET）。我们的模拟结果表明，对于NPP、NEE和R(h)，响应温度、二氧化碳和降水异常时，非线性模式分别为抛物线型、渐近型和阈值型。径流和ET对温度和降水异常均表现出阈值型模式，但对二氧化碳变化不太敏感。生态系统对温度、二氧化碳和降水综合异常的响应在响应模式和/或非线性临界点方面与对单个因素的响应有很大不同。我们的结果表明，对多种全球变化因素的非线性响应模式是多样的，并且受到气候综合异常对生态系统碳和水过程的显著影响。非线性中多样的响应模式对实验设计和理论发展都有深远影响。
