新疆南部农田裸地土壤呼吸变化特征

Characteristics of Soil Respiration in Bare Soil of Farmland in the South of Xinjiang

于2012-06-28-2013-01-08在新疆焉耆盆地设置农田裸土桶装培养试验，采用动态密闭气室法（Li-8100，USA），监测地表温度和土壤呼吸地表通量的日变化和季节变化。试验包括3个处理：原土、含1．25％和2．5％玉米秸秆的混合土。结果表明：①土壤呼吸速率日变化特征均呈单峰型曲线，最高值出现在12：00-16：00，最低值在5：00-7：00。②土壤呼吸速率季节变化特征为：夏季最大，冬季最小。其中，在夏季有2个峰值：出现在7月中下旬和8月中下旬。通过相关性分析发现：3个处理土壤呼吸速率与地表温度的相关性在夏季均不显著（P〉0．05），在秋季均呈极显著相关（R^2〉0．90，P〈0．01），在冬季均呈显著相关（R^2〉0．40，P〈0．05）。夏季和冬季的土壤呼吸温度敏感性（用Q10值表示）分别为1．21～1．52和1．65～2．25。

Soil surface CO2 efflux, or soil respiration, is a major component of the global terrestrial carbon cycle because it may constitute about three-quarters of total ecosystem respiration. The changes in soil surface CO2 efflux, the primary CO2 source to the atmosphere from terrestrial ecosystems, directly influences the local and regional car- bon budgets. In this study, a incubation experiments were conducted in the Yanqi Basin using farmland bare soil from June 28,2012 to January 8,2013. Diurnal and seasonal variations of soil respiration and soil surface tempera- ture were determined under three treatments（ original bare soil and bare soil mixed with 1.25% and 2.5% of maize straw） by using an Automated Soil CO2 Efflux System（ LI -COR 8100）. The results indicated that there was obvious diurnal variation of soil respiration under all three treatments. The maximum rate of soil respiration occurred between 12：00 - 16：00（ Local time）, the minimum between 5：00 - 7：00. On average, the total amount of carbon released during daytime accounted for about 58% - 70% of that for the whole day. There were seasonal variations of soil res- piration under all three treatments, showing similar two-peaked curves in middle to late July and middle to late Au- gust. During the whole observation period, the total amount of carbon released was 370 g · m^-2,361 g · m^-2 and 329 g · m^-2 for the 2.5% straw ＋ soil, 1.25% straw ＋ soil and bare soil,respectively. The exponential relationships between the rate of soil respiration and soil surface temperature for all three treatments were highly significant in au- tumn （R^2 〉0. 9,P 〈0.01 ） ,significant in winter （R^2 〉0.4 ,P 〈0.05） but no significant in summer （P 〉0.05）. The Q10 values for the bare soil, 1.25% straw ＋ soil and 2.5% straw ＋ soil were all larger in winter（ 1.65 - 2.25 ） than in summer（ 1.21 - 1.52）.