四川盆地亚热带常绿阔叶林不同物候期凋落物分解与土壤动物群落结构的关系

Abstract

Litter decomposition is one of the essential processes in terrestrial forest ecosystems,which could contribute to material turnover and plant productivity. Although primary decomposition of litter is ultimately the result of the catabolic activities of soil microbes,soil faunas have been well known that they can accelerate the rates of litter decomposition and nutrient cycling in forest ecosystems. Soil faunas have body sizes large enough to disrupt physical structure of litter directly by fragmenting and comminuting of litter,and promote litter decomposition indirectly by altering litter surface and regulating microbial activities. However,both litter quality and microclimate play important roles of soil fauna communities during litter decomposition. The annual critical phenological stages in plant growth do not only represent the change of climate environment,but also indicate the nutrients needs in plant growing. Therefore,in order to understand the relationships between litter decomposition and plant growth,the structure dynamics of soil fauna community were studied at plant phenological stages,including leave falling stage,leave budding stage,leaf expanding stage,leave maturing stage,leave graving period and leave senescing stage according to local plant phenology from November 2011 to October 2012. Four kinds of foliar litter were sampled as Pinus massoniana and Cryptomeria fortune from their plantations,and Cinnamomum camphora and Quercus acutissima from their secondary ecosystems in subtropical regions of Sichuan basin in southwestern China,respectively. Litterbags with different mesh sizes( 0. 04 mm and 3 mm) were used to exclude soil fauna during litter decomposition. We captured a total of 8047 soil fauna individuals in all litterbags,which belonged to 22 orders and 73families. Soil fauna individuals showed: C. fortunei( 2341) C. camphora( 2105) P. massoniana( 2046)Q. acutissima( 1555). Soil fauna community structure was significantly varied with different litter substrate at different key stages as litter decomposition proceeding,indicating liter quality could have close relationships to soil fauna during litter decomposition. The leave falling stage,leave budding stage and leaf expanding stage,predatory soil fauna dominated soil fauna community during P. massoniana litter decomposition,and fungivore dominated the other stages. Fungivore also dominated soil fauna community at leave falling stage and leave senescing stage during C. camphora decomposition,but predatory dominated the other stages. In contrast,soil fauna community during C. fortunei litter decomposition was dominated by fungivore at all investigated stages. Although fungivore dominated soil fauna community at early three stages during Q. acutissima litter decomposition,phytophagy dominated the later stages. Correlation analysis showed that the individual density of soil fauna was significantly related to Nitrogen and Phosphorus content in leave falling stage and leave budding stage,but which closely related to lignin content at leave senescing stage. Moreover,the contribution of soil fauna to litter decomposition showed a significantly relationships with the individual density of soil fauna at leave falling stage,which significantly related to the group density and the soil faunal functional group at other critical stages during litter decomposition.