川西亚高山、高山森林土壤微生物生物量和酶活性动态特征

为深入了解川西亚高山/高山森林冬季生态学过程，于2008年11月─2009年10月，在土壤冻结初期、冻结期和融化期及植被生长季节，研究了不同海拔岷江冷杉林（Abies faxoniana）土壤微生物生物量和酶活性动态。各海拔森林土壤在冬季维持着较高的微生物生物量含量和酶活性，并随土壤冻融过程不断变化。土壤有机层和矿质土壤层冬季微生物生物量碳和氮含量及转化酶和尿酶活性均表现出受冻结初期土壤冻融循环影响显著降低，在冻结期变化不明显，在融化期急剧增加至融化后显著降低的趋势，且土壤有机层微生物生物量含量和酶活性在融化期具有一个明显的年高峰值。海拔变化显著影响了土壤酶活性，但对土壤微生物生物量不显著。土壤温度与土壤微生物生物量含量相关显著。这表明季节性冻融期是土壤生态过程的重要时期，土壤冻融格局显著影响川西亚高山/高山森林土壤微生物生物量和酶活性动态。

Dynamics of Soil Microbial Biomass and Enzyme Activity in the Subalpine/Alpine Forests of Western Sichuan

In order to deeply understand winter ecological processes in the subalpine/alpine forests of western Sichuan, three fir （Abies faxoniana） forests, including primary fir forest at 3 582 m of altitude, fir and birch mixed forest at 3 298 m of altitude, and secondary fir forest at 3 023 m of altitude, were taken as study subject. Soils were collected in different stages as the onset of soil freezing period, soil frozen period, soil thawing period, and growing season from November 2008 to October 2009. The contents of soil microbial biomass carbon and nitrogen and activities of soil invertase and urease were measured. As comparing with growing season, the contents of soil microbial biomass carbon and nitrogen and activities of soil invertase and urease kept relatively high level during the winter in the sampled forests. Moreover, the dynamics of soil microbial biomass and enzyme activity changed with the processes of soil freeze-thaw. In both the soil organic layer and mineral soil layer, the contents of soil microbial biomass carbon and nitrogen and activities of soil invertase and urease respectively experienced a significantly decreasing dynamic in the onset of soil freezing period and a significantly increasing dynamic in the of soil thawing period, and they showed little change in the soil frozen period. However, soil microbial biomass and enzyme activity in the two layers significantly increased in the soil thawing period, and they reached to an obvious annual peak in the soil thawing period. Additionally, the altitude had significant effects on soil enzyme activity, but insignificant for soil microbial biomass. The soil temperature showed significant correlation with soil microbial biomass, but insignificant for soil enzyme activity. These results suggested that seasonal freeze-thaw period is crucial stage for soil ecological processes, and soil freeze-thaw pattern significantly influenced the dynamic of soil microbial biomass and enzyme activity in the subalpine/alpine forests of western Sichuan.