温度和水分对中亚热带人工林生态系统呼吸的调控作用

The Regulation of Soil Temperature and Water on Ecosystem Respiration of a Subtropical Plantation under the Seasonal Drought

全球气候变化导致的降水格局改变影响陆地生态系统碳收支状况。陆地生态系统所固定的碳主要通过呼吸作用返回到大气中,而温度和水分是调节生态系统呼吸的重要因素。ChinaFLUX千烟洲中亚热带人工林通量站夏季雨热不同季而造成的季节性干旱为探讨温度和水分对生态系统呼吸的调控作用提供了天然的试验条件。研究利用该生态系统2003—2010年涡度相关和常规气象数据,阐述了生态系统呼吸对温度和土壤含水量的响应特征,对比分析了只考虑温度与同时考虑温度和土壤含水量对生态系统呼吸的季节模式和年呼吸量的影响。研究表明,生态系统呼吸的季节变异主要受土壤温度的控制,呈现指数响应特征。但是,在干旱胁迫条件下,土壤含水量对生态系统呼吸的季节变异起到明显的调控作用。参考温度下的生态系统呼吸(Rref)明显受土壤含水量的影响。生态系统年呼吸量为1 289.4±73.9 gC.m-2.a-1,两类模型的估算结果没有显著差异。但是在生态系统的季节变异上,两类模型估算存在显著差异,同时考虑温度与土壤含水量的模型更适合模拟遭受干旱胁迫的生态系统呼吸。

Abstract： The carbon balance has been affected by altered precipitation patterns caused by global climate changes. The carbon sequestrated by terrestrial ecosystems returns to the atmosphere mainly through respiration, of which temperature and water are two essential factors in regulating ecosystem respiration （Reco）. Seasonal drought caused by the imbalance of heat and rain provides natural experimental conditions to investigate the regulation of temperature and water on ecosystem respiration in the ChinaFLUX Qianyanzhou subtropical plantation. Based on the eddy covariance and conventional meteorological data collected from 2003 to 2010, this study analyzed the response of ecosystem respiration to temperature and soil water content, and explored the effects of tempera- ture or both temperature and soil water content on ecosystem respiration seasonality and annual res- piration. The study showed that the seasonal variations of ecosystem respiration were mainly con- trolled by soil temperature, and Reco was an exponential function of soil temperature. Only under drought condition can soil water content play a significant role in regulation. With only temperature taken into account, the ecosystem respiration rate at the reference temperature （Rref） was signifi- cantly affected by soil water content; while with temperature and soil water content taken into ac- count, the ecosystem respiration under reference temperature was not affected by soil water content. There was no evident difference between considering temperature alone and both temperature and soil water content, the ecosystem respiration amount was 1289. 4 ±73.9 g C ·m-2·a-1 But the seasonal variations of ecosystem respiration had signifieant differenees between 2003 and 2010 whether a seasonal drought existed or not.