中文摘要：

土壤碳是森林生态系统最大的碳库,是其森林生态系统碳循环的极其重要组分。森林土壤呼吸时陆地生态系统土壤呼吸的重要组成部分,其动态变化对全球碳平衡有着重要的影响,然而目前对藏东南地区森林土壤呼吸的研究还比较薄弱。为探讨不同林型土壤呼吸差异及其影响因子,采用Li-8100便携式土壤呼吸测定仪,研究了藏东南色季拉山4种原始森林生态系统（高山灌丛AS、方枝柏SS、杜鹃RF、急尖长苞冷杉AGSF）的土壤碳动态。结果表明：（1）藏东南色季拉山寒温带森林土壤呼吸具有明显的日变化和季节变化。在日变化方面,CO2的排放通量存在明显的日变化规律,排放通量在白天16：00左右最高,最低值出现在凌晨6：00左右,一天内土壤呼吸作用均呈单峰型曲线变化。季节变化方面,CO2排放的通量的季节变化趋势表现为6月份随着天气转暖和植被生长土壤呼吸作用逐渐增大,7月份气温最高时土壤呼吸作用也达到最大值随后,9月份气温逐渐下降,土壤呼吸作用也逐渐降低。（2）4种森林类型的土壤呼吸速率在植物生长季内与土壤表层（10 cm）土壤温度均呈不同程度的正相关,而与土壤含水量的相关性较弱。土壤温度是决定藏东南色季拉山土壤呼季节变化的主要因子。该研究为明确森林生态系统土壤呼吸变化规律及其影响因素的控制提供参考,同时对估算地区碳平衡、评估区域碳源汇具有重要意义。

英文摘要：

Being the largest carbon pool of the forest ecosystem,soil carbon is a very important component of the carbon cycle in the system,and being a vital part of the soil respiration of the terrestrial ecosystem,soil respiration of the forest ecosystem influences significantly the global carbon balance. However,so far little research has been done on soil respiration of the forest ecosystems in southeastern Tibet. Therefore,in order to investigate soil respiration and its influencing factors relative to type of the forest ecosystem,a field experiment was conducted using an LI-8100（Nebraska,USA）to measure soil respirations in four different types of forests [Alpine shrubs（AS）,Sabina saltuaria（SS）,Rhododendron forest（RF）and Abies georgei var. smithii forest（AGSF）],typical of the Sygera Mountains of the Southeast Tibetan Plateau,for analysis of soil respiration dynamics and their major affecting factors therein. Results show that the soil respirations varies sharply in a day and with the seasons. Diurnally,CO2 emission flux follows an apparent one-peak pattern of peaking around 16：00 and bottoming around 06：00,while seasonally,it did another of beginning to rise in June when the weather turns warm and the vegetation starts to grow in June,peaking in July,when the air temperature is the hottest in a year in that region,and starting to decline in September,when the air temperature begins to descend. In the four types of forest ecosystems,soil respiration rate during the vegetation growth season is positively related soil temperature of the surface layer（10 cm）to a varying extent,but not so much to soil moisture content. In terms of soil respiration rate,the 4 different types of forest ecosystems follows an order of AGSF 〉 RF 〉 SS 〉AS. The determination coefficient（R2）of the relationship between soil respiration and soil temperature varies with the type of the forest ecosystem in the range of 0.47~0.72,demonstrating that the relationship reaches the significant level. On such a basis,it