Zhang Yan-Jun, Guo Sheng-Li
State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Institute of Soil and Water Conservation, Northwest A & F University, Yangling 712100, China.
Shaanxi Key Laboratory of Disaster Monitoring and Mechanism Simulation, College of Geography and Environment Engineering, Baoji University of Arts and Sciences, Baoji 721013, China.
Huan Jing Ke Xue. 2019 Mar 8;40(3):1446-1456. doi: 10.13227/j.hjkx.201705155.
Studying the effect of environmental factors on the variation of soil microbial respiration and its temperature sensitivity () at different time scales under field conditions is of great significance for accurately understanding the region's climate warming potential. From March 2008 to November 2013, in situ soil microbial respiration rates were determined using an automated CO flux system (Li~8100) in long-term bare fallow soil at the Changwu State Key Agro-Ecosystem Experimental Station, Shaanxi, China, for studying the effect of environmental factors on the variation of soil microbial respiration and at different time scales. At diurnal time scales, the daily variation of soil microbial respiration rates showed a single-peak curve, which was closely related to soil temperature (<0.05); whereas the daily mean soil microbial respiration rate and varied with soil moisture, with both showing the order of moderate soil moisture conditions > higher soil moisture conditions > lower soil moisture conditions[daily mean soil microbial respiration rate:1.20 μmol·(m·s) vs. 0.95 μmol·(m·s) vs. 0.79 μmol·(m·s); :2.12 vs. 1.93 vs. 1.59]. At seasonal time scales, both the seasonal mean soil microbial respiration rate and showed the order of rainy season > non-rainy season[seasonal mean soil microbial respiration rate:1.11 μmol·(m·s)vs. 0.90 μmol·(m·s); :1.96 vs. 1.59], which was consistent with the trend of soil temperature and moisture (soil temperature:20.39 vs. 14.50℃; soil moisture:49.2% vs. 38.6%). The bivariate model of soil temperature and soil moisture could explain the greater seasonal variability of the soil microbial respiration rate than did the univariate model of soil temperature or soil moisture (:0.45-0.82 vs. 0.32-0.67 vs. 0.35-0.86; the fitting coefficient between the simulated and measured soil microbial respiration rates:0.76 vs. 0.64 vs. 0.58). At annual time scales, the annual cumulative soil microbial respiration ranged from 226 to 298 g·(m·a), with an average of 253 g·(m·a), and the annual ranged from 1.48 to 1.94, with an average of 1.70. The annual cumulative soil microbial respiration and showed a negative quadratic correlation with annual mean soil moisture (<0.05), with the annual mean soil moisture explaining 39% and 54% of the annual variability of annual cumulative soil microbial respiration and , respectively. In the bare soil treatment, the soil organic carbon decreased from 6.5 g·kg at the beginning of the experiment to 5.5 g·kg at present; whereas, the annual cumulative soil microbial respiration was up to 255 g·(m·a) and the loss of annual cumulative soil microbial respiration was 20 times larger than the loss of soil organic carbon in the Loess Plateau region, China.
研究田间条件下不同时间尺度环境因素对土壤微生物呼吸及其温度敏感性（）变化的影响，对于准确理解该地区气候变暖潜力具有重要意义。2008年3月至2013年11月，在中国陕西长武国家重点农业生态系统试验站长年撂荒土壤中，使用自动CO通量系统（Li~8100）测定原位土壤微生物呼吸速率，以研究不同时间尺度环境因素对土壤微生物呼吸及其温度敏感性变化的影响。在日时间尺度上，土壤微生物呼吸速率的日变化呈单峰曲线，与土壤温度密切相关（<0.05）；而土壤微生物呼吸日均值及其温度敏感性随土壤湿度变化，均表现为土壤湿度适中条件>土壤湿度较高条件>土壤湿度较低条件[土壤微生物呼吸日均值：1.20 μmol·(m·s) 对0.95 μmol·(m·s) 对0.79 μmol·(m·s)；温度敏感性：2.12对1.93对1.59]。在季节时间尺度上，土壤微生物呼吸季节均值及其温度敏感性均表现为雨季>非雨季[土壤微生物呼吸季节均值：1.11 μmol·(m·s)对0.90 μmol·(m·s)；温度敏感性：1.96对1.59]，这与土壤温度和湿度的变化趋势一致（土壤温度：20.39对14.50℃；土壤湿度：49.2%对38.6%）。土壤温度和土壤湿度的二元模型比土壤温度或土壤湿度的一元模型能解释更大的土壤微生物呼吸速率季节变异性（温度敏感性：0.45 - 0.82对0.32 - 0.67对0.35 - 0.86；模拟与实测土壤微生物呼吸速率的拟合系数：0.76对0.64对0.58）。在年时间尺度上，年累积土壤微生物呼吸量在226至298 g·(m·a)之间，平均为253 g·(m·a)，年温度敏感性在1.48至1.94之间，平均为1.70。年累积土壤微生物呼吸量及其温度敏感性与年平均土壤湿度呈负二次相关（<0.05），年平均土壤湿度分别解释了年累积土壤微生物呼吸量和温度敏感性年变异性的39%和54%。在裸土处理中，土壤有机碳从试验开始时的6.5 g·kg降至目前的5.5 g·kg；而年累积土壤微生物呼吸量高达255 g·(m·a)，中国黄土高原地区年累积土壤微生物呼吸量的损失比土壤有机碳的损失大20倍。
