疏勒河源高寒草甸土壤微生物生物量碳氮变化特征

土壤微生物生物量是土壤有机质的活性部分，是反映土壤质量和碳氮循环机制的重要指标。本文以青藏高原东北缘疏勒河源高寒草甸为研究对象，对土壤微生物生物量碳（SMBC, mg/kg）和微生物生物量氮（SMBN, mg/kg）的不同季节（春、夏、秋、冬）和土层（0—10、10—20、20—30、30—40、40—50 cm）变化特征及其影响因素进行研究。结果表明：（1）不同土层SMBC均表现为春季开始逐渐升高、夏季达到最大值、秋季逐渐降低、冬季值最小，而SMBN春季开始逐渐降低、夏季值最小、秋季逐渐升高、冬季达到最大值。（2）SMBC、SMBN随着土壤深度的增加而下降，0—10 cm层SMBC、SMBN显著高于40—50 cm层，且SMBC、SMBN0—10 cm层的季节变幅显著大于40—50 cm层。（3）0—50 cm土层SMBC/SMBN表现为春季开始逐渐升高、夏季达到最大值、秋季逐渐降低、冬季值最小，其季节变化范围为8.77—23.59，处于较高水平。（4）SMBC、SMBN、SMBC/SMBN的季节和土层变化主要受植被地下生物量和土壤温度的影响。（5）各土层SMBC/SOC均表现为春季开始逐渐升高、夏季达到最大值、秋季逐渐降低、冬季值最小，而SMBN/TN春季开始逐渐降低、夏季值最小、秋季逐渐升高、冬季达到最大值。除夏季土层间无显著差异外，SMBC/SOC与SMBN/TN均表现为0—10 cm层显著高于40—50 cm层。（6）0—50 cm土层SMBC/SOC夏秋季显著高于冬春季且其季节变化范围为0.58%—1.18%，而SMBN/TN秋冬季显著高于夏季且其季节变化范围为0.39%—0.72%。综上，季节变化和剖面深度均对SMBC、SMBN产生显著影响且0—10 cm土层对SMBC、SMBN的累积能力最强。

Variations of soil microbial biomass carbon and nitrogen in alpine meadow of the Shule River headwater region

Soil microbial biomass is the active part of soil organic matter and an important indicator of soil quality and carbon and nitrogen cycling mechanism. The different season (spring, summer, autumn and winter) and soil layer (0-10, 10-20, 20-30, 30-40 and 40-50 cm) variations of soil microbial biomass carbon (SMBC, mg/kg) and microbial biomass nitrogen (SMBN, mg/kg) and their influencing factors were studied in alpine meadow of the Shule River headwater region in the northeast margin of Qinghai-Tibet Plateau. The results showed that (1) the SMBC of different soil layers increased gradually in spring, peaked in summer, decreased in autumn, and reached the minimum value in winter. While the SMBN decreased gradually in spring, reached the minimum value in summer, increased in autumn, and peaked in winter. (2) Both SMBC and SMBN decreased with the increase of soil depth. The 0-10 cm layer of SMBC and SMBN was significantly higher than the 40-50 cm layer. The season variations of SMBC and SMBN in the 0-10 cm layer was also higher than those in the 40-50 cm layer. (3) The SMBC/SMBN in the 0-50 cm layers increased gradually in spring, peaked in summer, decreased in autumn, and reached the minimum value in winter. Its season variation range was 8.77-23.59, which was at a relatively high level. (4) The season and layer variations of SMBC, SMBN and SMBC/SMBN were mainly influenced by belowground biomass of vegetation and soil temperature. (5) The SMBC/SOC in different soil layers increased gradually in spring, peaked in summer, decreased in autumn, and reached the minimum value in winter. While the SMBN/TN decreased gradually in spring, reached the minimum value in summer, increased in autumn, and peaked in winter. Except that there was no significant difference in soil layer variation in summer, SMBC/SOC and SMBN/TN showed that the 0-10 cm layer was significantly higher than the 40-50 cm layer. (6) In the 0-50 cm layers, SMBC/SOC was significantly higher in summer and autumn than that in winter and spring. Its season variation range was 0.58%-1.18%. while SMBN/TN was significantly higher in autumn and winter than in summer and its season variation range was 0.39%-0.72%. In conclusion, the variations of season and profile depth could affect SMBC and SMBN contents significantly. The 0-10 cm soil layer has the strongest accumulation ability on SMBC and SMBN.