新疆巴音布鲁克天鹅湖高寒湿地土壤呼吸对水分条件的响应

为了揭示干旱半干旱区高寒湿地不同水分梯度对土壤呼吸规律的影响,以及土壤温度与含水量对土壤呼吸影响的差异性,以新疆巴音布鲁克天鹅湖高寒湿地为研究对象,在2014年植物生长季利用LI-8100土壤碳通量自动测量系统对不同水分条件(常年积水区、季节性积水区、常年干燥区)下的土壤呼吸速率进行测定,分析土壤呼吸日变化、季节性变化特征及其与土壤温度、土壤体积含水量的关系. 结果表明:①不同水分条件下巴音布鲁克天鹅湖高寒湿地土壤呼吸速率日变化均呈明显的单峰曲线,常年积水区、季节性积水区、常年干燥区土壤呼吸速率最大值分别为1.97、7.39、8.83 μmol/(m2·s),均出现在13:00—15:00；土壤CO₂日累积排放量季节性变化明显,差异性达到极显著水平(P<0.01),三者的最大值分别为0.12、0.45、0.40 mol/m2,地表积水显著抑制了土壤呼吸,提高了土壤碳稳定性. ②不同水分条件下土壤呼吸速率与土壤温度、土壤体积含水量之间均呈极显著正相关(P<0.01),常年积水区、季节性积水区和常年干燥区的Q₁₀(土壤呼吸温度敏感性)差异性极显著(P<0.01),其大小表现为常年干燥区(1.54)<常年积水区(2.22)<季节性积水区(3.36),各水分区域6月典型日的Q₁₀最大,表现为常年干燥区(2.56)<季节性积水区(4.30)<常年积水区(4.75),说明水分条件显著影响Q₁₀. ③巴音布鲁克天鹅湖高寒湿地土壤呼吸受地下5 cm处土壤温度(T)与0~5 cm土壤体积含水量(W)的综合影响,季节性积水区土壤呼吸速率与二者之间满足最佳拟合模型R_s=-1.113+0.041W-0.366T+0.008WT,常年干燥区则满足最佳拟合模型R_s=1.470+0.023W-0.027T+0.002WT. 

Dynamics of Soil Respiration under Different Water Conditions in an Alpine Wetland of the Xinjiang Bayanbulak Swan Lake

In order to study the effect mechanism under different water conditions on soil respiration rate, and the influence of soil temperature and water content to soil respiration rate under different water conditions in an alpine wetland, this study measured the soil respiration rate under different water conditions using a Li-8100 automated soil CO₂ flux system (LI-COR, Lincoln, Nebraska, USA) from June to October 2014 at Bayanbulak Swan Lake alpine wetland. The dynamics of diurnal and seasonal soil respiration rate and the correlations between soil respiration rate and soil temperature and soil volumetric water content were also evaluated. The results showed that:1) The diurnal variation of soil respiration rate under different water conditions peaked once at 13:00-15:00, and the maximum value of soil respiration rate in perennial water area, seasonal water area and perennial dry area were 1.97,7.39, and 8.83 μmol/(m2·s), respectively. 2) The cumulative daily soil respiration was significantly different (P<0.01) between different seasons, and the maximum values at perennial water area, seasonal water area and perennial dry area were 0.12,0.45 and 0.40 mol/m2, respectively. Surface water at the study area significantly inhibited soil respiration and increased soil carbon stability. 3) The positive correlation between soil respiration rate and soil temperature and soil water content was significant (P<0.01). Soil water content had great effect on the temperature sensitive of soil respiration (Q₁₀), and Q₁₀ was significantly different under different water conditions. Q₁₀ was greatest at seasonal water area (3.36), followed by perennial water area (2.22), and the perennial dry area had the smallest values (1.54). 4) Results of the exponential model showed that the best fitting model of soil respiration rate and 5 cm soil temperature and 0-5 cm volume water content was R_s=-1.113+0.041W-0.366T+0.008WT in seasonal water area and R_s=1.470+0.023W-0.027T+0.002WT in perennial dry area. Soil temperature and soil water content could explain 62.0% and 47.6% of the variations for seasonal water area and perennial dry area, respectively. These results indicated that soil respiration rate was significantly influenced by water content and soil temperature at Swan Lake alpine wetland.