中文摘要：

开展土壤呼吸对全球气候变化的响应研究对预测全球碳循环具有重要作用.采用红外辐射加热器模拟增温结合外施氮肥的方法,研究川西亚高山针叶林两种主要树种幼苗——云杉（Picea asperata）和岷江冷杉（Abiesfaxoniana）土壤呼吸动态变化对增温和施肥的短期响应.结果表明：在试验处理期间（2008年9月～2009年7月）,空气平均温度和5 cm土壤平均温度分别比对照提高了2.03℃和4.10℃.两种幼苗样地土壤呼吸速率在各处理下都表现出明显的季节和日动态.增温对两种幼苗土壤呼吸速率的影响总体表现为促进作用,而施肥处理则表现为抑制效应.但两种幼苗土壤呼吸对增温和施肥处理的响应又存在一定的差异,且与季节密切相关.增温使云杉幼苗土壤呼吸年通量在非施肥和施肥条件下分别增加了22.30%和8.82%,而使冷杉土壤呼吸速率年通量分别仅增加了4.85%和4.45%.两种幼苗在各处理下土壤呼吸速率与地下5 cm土壤温度之间具有显著的指数关系.增温和施肥处理均提高了两种幼苗土壤呼吸速率的Q10值,但云杉幼苗土壤呼吸对温度变化的响应比冷杉更为敏感.总之,不同树种土壤呼吸特征对全球气候变化的响应差异进一步增加了对该区森林碳源/汇功能预测的不确定和复杂性,其内在机理有待进一步深入研究.

英文摘要：

Responses of soil respiration to experimental warming and nitrogen addition can provide insights into C source/sink functions of forest ecosystems in climates change.An infrared heater was used to determine the short-term effects of two levels of air temperature（ambient and warmed） combined with nitrogen addition（N,0 and 25 g m-2 a-1） on soil respiration in Picea asperata plots and Abies faxoniana plots.The results showed that the warming manipulation increased mean air temperature and soil temperature at 5 cm depth by 2.03℃ and 4.10 ℃,respectively.Soil respiration displayed strong seasonal and diurnal patterns.In general,simulated warming increased soil respiration,while nitrogen addition decreased the soil respiration of the two conifer plots during the whole experiment.However,the responses of soil respiration to experimental warming and nitrogen addition were strongly dependent on both tree species and seasons.Warming increased the carbon fluxes of soil total respiration by 22.30% and 8.82% in the unfertilized and fertilized P.asperata plots,and 4.85% and 4.45% in the unfertilized and fertilized A.faxoniana plots,respectively.Significant exponential relationships were found between the soil respiration rates and soil temperature at 5 cm depth.Warming and nitrogen addition both increased the Q 10 values in the two conifer plots,but Q 10 value was generally higher in P.asperata plots.Therefore,the soil respiration in P.asperata plots was more sensitive to temperature changes than A.faxoniana plots.As a result,the response differences to warming and nitrogen addition between tree species add more uncertainty and complexity in C sink/source dynamics in changing climate,and the underlying mechanism should be further studied.