凋落物分解过程中土壤微生物群落的变化

Changes in soil microbial communities during litter decomposition

凋落物分解是生态系统碳循环和营养物质循环的关键过程,受多种因素共同影响。土壤微生物是影响凋落物分解的重要因素,其群落组成在一定程度上依赖于所处植物群落的特征。因此,研究分解过程中微生物群落组成的变化及其对植物多样性的响应,有利于对凋落物分解机制的理解。本文采用分解袋野外原位分解的方法,对凋落物分解过程中微生物群落的变化及其对所处森林环境中树木的种类和遗传多样性的响应进行了研究。结果表明:(1)凋落物分解183天后,土壤中微生物群落的多样性降低,并且森林群落的物种多样性与微生物群落多样性呈负相关关系;(2)凋落物分解前后,土壤中真菌和细菌群落的磷脂脂肪酸(PLFA)量均有所增加,说明凋落物分解为微生物生存和繁殖提供了养分;(3)地形因素是影响微生物群落变化最显著的因素,可解释微生物群落变化的29.55%;其次是凋落物的基质质量,可以解释15.39%;最后是森林群落的多样性,可以解释8.45%;这3种因素共同解释率为2.97%。综上所述,与森林群落的植物多样性相比,样地的地形因素与凋落物的基质质量对微生物群落的影响更显著。

Litter decomposition is an important ecosystem function, and is an indispensable process for car- bon and nutrient cycling. Litter decomposition is influenced by many factors, especially soil microbial com- munities, which are subject to their corresponding plant communities. It is necessary to study changes in soil microbial communities during litter decomposition and how these changes respond to plant diversity in cor- responding forest communities to understand the mechanisms of decomposition. In the present study, we in- vestigated these changes and responses using a litter bag method. Our results showed： （1） After 183 days of litter bag placement, microbial diversity decreased, and there was a negative correlation between plant spe- cies diversity and microbial diversity; （2） Soil microbial communities varied before and after the placement of plant litter bags. In particular the PLFAs of fungi and bacteria after the placement of litter bags were much higher than those before the placement of litter bags; （3） Topography was the most important factor corre- lated with the soil microbial community, and explained 29.55% of the variation of microbial communities. In contrast, litter quality and plant diversity explained 15.39% and 8.45%, respectively, and the interaction of the three factors explained 2.97% of the variation of the microbial communities. In conclusion, we find plant diversity plays a less important role than topography in determining soil microbial diversity, and litter quality influences soil microbial communities during litter decomposition.