青海湖流域南岸温性草原CO_(2)排放特征对模拟降雨变化的响应

Response of CO_(2)Emission Characteristics of Temperate Grasslands on the South Shore of Qinghai Lake Basin to Simulated Rainfall Changes

近20年,青海湖流域降雨量呈增加趋势。为准确揭示降雨变化对青海湖流域草地生态系统温性草原CO_(2)排放速率的影响及调控因素,本研究以温性草原为研究对象,原位监测不同降雨处理下CO_(2)排放特征,基于主成分和回归模型分析,解析CO_(2)排放特征的主要调控因素。研究结果表明生长季5—8月各降雨处理下温性草原CO_(2)基本为排放状态。5—8月五种实验处理下草地CO_(2)平均排放速率之和的顺序为J25>Z75>CK>Z25>J75。增雨控制下CO_(2)排放为自然对照的-3.53%~65.64%,减雨控制下CO_(2)排放为自然对照的-33.35%~83.85%。降雨变化显著影响土壤湿度、生物量及土壤理化性质,雨季未到时CO_(2)排放主要靠根系呼吸,雨季来临时土壤湿度对CO_(2)排放影响显著高于土壤温度。并通过逐步回归分析法将影响因子进行逐步筛选,建立与CO_(2)排放速率之间的回归方程模型,与各影响因子同CO_(2)排放速率的相关分析相互印证,这对未来青海湖流域暖湿化背景下的温性草原CO_(2)排放速率提供了参考。

In the past 20 years,rainfall in the Qinghai Lake basin has been increasing.In order to reveal the effects of rainfall changes on the CO_(2)emission rate of temperate grasslands in Qinghai Lake basin and the regulating factors,this study took that temperate grasslands as the research object,monitored the CO_(2)emission characteristics under different rainfall treatments in situ,and analyzed the main regulating factors of CO_(2)emission characteristics based on principal component and regression model analysis.The results showed that the CO_(2)emission of temperate grassland was basically in the state of emission under each rainfall treatment from May to August of the growing season.The order of the sum of the mean CO_(2)emission rates of grasses under the five experimental treatments from May to August was J25>Z75>CK>Z25>J75.CO_(2)emissions under rainfall increase control ranged from-3.53%to 65.64%of the natural control and-33.35%to 83.85%of the natural control under rainfall reduction control.Rainfall variation significantly affected soil moisture,biomass and soil physicochemical properties,and CO_(2)emission was mainly based on root respiration before the rainy season,while the effect of soil moisture on CO_(2)emission was significantly higher than that of soil temperature at the onset of the rainy season.The regression equation model between the influencing factors and CO_(2)emission rate was established by stepwise regression analysis,and the correlation analysis between the influencing factors and CO_(2)emission rate was corroborated,which provides a reference for the future CO_(2)emission rate of temperate grassland under the background of warming and humidification in Qinghai Lake basin.