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

为了解植物生长不同物候时期凋落物分解过程中土壤动物群落结构动态及其与凋落物分解的关系,以四川盆地亚热带常绿阔叶林典型人工林树种马尾松和柳杉,次生林树种香樟和麻栎凋落物为研究对象,采用凋落物分解袋试验研究,凋落物分解过程中土壤动物的群落特征。4种凋落物分解袋共获得土壤动物8047只,其中,柳杉(2341只)>香樟(2105只)>马尾松(2046只)>麻栎(1555只)。其中,秋末落叶期、萌动期和展叶期,马尾松凋落物袋中主要以捕食性土壤动物为优势类群,而后以菌食性土壤动物为主;香樟凋落物袋中除秋末落叶期和叶衰期以菌食性土壤动物为主要优势类群外,其他各时期均以捕食性土壤动物为主要优势类群;柳杉凋落物分解各时期均以菌食性土壤动物为主要优势类群;麻栎凋落物分解在前3个时期以菌食性为主,而后以植食性土壤动物为主要优势类群。相关分析表明,在秋末落叶期和萌动期土壤动物的个体密度主要和氮、磷含量及其格局密切相关,叶衰期主要和难分解组分木质素显著相关。除在秋末落叶期土壤动物对凋落物分解的贡献率与土壤动物的个体密度显著相关外,其余主要物候关键时期均与土壤动物的类群密度及其食性显著相关。

The dynamics of soil fauna community during litter decomposition at different phenological stages in the subtropical evergreen broad-leaved forests in Sichuan basin

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 73 families. 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.