海拔梯度上西南亚高山-高山土壤微生物生物量碳季节动态

Seasonal Dynamics of MBC along Elevational Gradients of Subalpine-alpine in the Southwestern China

【目的】分析在高海拔地带海拔因素对土壤微生物生物量季节动态的影响规律。【方法】以亚高山-高山3250～4098m不同海拔生境下原位培养的均质化重装土柱为研究对象，测定0～10cm和10～20cm的土壤微生物生物量碳（microbial biomass carbon，MBC）含量、微生物生物量氮（microbia lbiomass nitrogen，MBN）及碳氮比的季节变化。【结果】低温季节（11月-3月）亚高山一高山土壤表层与表下层MBC仍处于较高水平（均高于l_3g／kg），且MBC沿海拔升高而降低，而5月～9月高海拔的MBC高于低海拔土壤；对于不同深度的土壤MBC季节差异，低温季节所有海拔均是下层（10～20cm）MBC高于表层（0～10cm），7月所有海拔土壤MBC均是表层高于下层，季节转换的5月和9月，海拔3250m和3438m均是表层低于下层，而高海拔处则是表层高于下层；沿海拔梯度土壤微生物生物量碳氮比变化明显，9月、11月和3月各海拔O～10cm和10~20cm土壤微生物生物量碳氮比多低于4；在5月和7月，仅低海拔（3250m和3438m）土壤微生物生物量碳氮比仍低于4。[结论]川西亚高山-高山土壤MBC季节动态，在海拔梯度上、土壤深度（O～10cm和10～20cm）上差异显著，而且微生物生物量碳氮比的变化规律也明显不同。

[Objective] The aim of the study was to determine seasonal dynamics of soil microbial biomass carbon （MBC） as affected by altitude in the subalpine-alpine of western Sichuan. 14VIeth- od] Topsoil cores （0--20 era） were in situ incubated along an altitudinal gradient （3 250--4 098 m）. Soil cores were sampled in September, November, March, May and July, respectively. MBC, microbial biomass nitrogen （MBN） and their ratios were analyzed. [Results＇l During the cold season （from November to March）, subalpine-alpine soil MBC in both soil layers kept a high level （〉1.3 g/kg） and decreased with the increase in elevation. While soil MBC at higher altitude were higher than those at lower altitude from May to September. For seasonal variations of soil MBC in different soil depth, MBC were higher in 10--20 cm than in 0--10 cm at all altitudes dur- ing the cold season but the opposite was true in July. MBC in 0-- 10 cm were lower than that in 10 -- 20 cm at 3 250 m and 3 438 m in May and September while there was a contrary tendency at high altitude. There were significant differences in MBC/MBN among elevational gradients. The ratios of MBC to MBN in the two soil layers were generally lower than 4 at each altitude in September, November and March. However, the values were still lower than 4 only at 3 250 m and 3 438 m in both May and July. [Conclusion] There were significant differences in MBC between elevavtions and soil depths （0--10 cm and 10--20 era）. Moreover, clear seasonality in the ratio of MBC to MBN was observed.