Soil animal communities in the litter of the evergreen broad-leaved forest at five succession stages in Tiantong

Soil animals are aboundant in forest litter layer, but little attention has been paid to the vertical distribution of community structure of soil animals in the layer at different plant community succession stages. Forest litter layer can be divided into fresh litter layer (L), fermentation layer (F) and humus layer (H), which may represent different litter decomposition stages. The aim of the study is to ascertain the vertical distribution feature of soil animal community structure among the three litter layers and the change in the succession process of the evergreen broad-leaved forest (EBLF) in Tiantong, Zhejiang Province. Five plant communities at different succession stages were investigated in winter of 2003. Soil animals, which were extracted by using Tullgren funnels, amounted to a total of 13, 381 in number, falling into 2 phyla, 8 classes and 20 orders. The dominant groups were Arcarina and Collembola, accounting for 94.24% of the total individuals, with the number of Arcarina individuals 7.66 times that of Collembola. The common group was Diptera. The results indicated that there was a distinctive vertical distribution of the soil animal communities in the forest litter layer, but it differed from that in soil below the litter layer. Opposite to those in the soil, the soil animals in the litter layer generally tend to increase from top fresh litter layer to bottom humus layer both in group richness and density; altogether 19 groups and 59.03% of total individuals were found in the bottom layer, while only 8 groups and 5.35% of the individuals were seen in the top. Moreover, there were some variations in the distribution of the soil animals at different plant succession stages; 85.19% of Homoptera and 100% of Symphyla were found in the litter layer at the climax succession stage, while 75.61% of Thysanoptera found at the intermediate succession stage. Therefore these groups might be seen as indicative groups. The total numbers of soil animal groups and individuals in the litter layers greatly changed in the succession process of the EBLF. They both were greatest at the climax, moderate at the intermediate and smallest at the primary succession stage. However, the main soil animal groups in the litter at the different succession stages were essentially the same; they were Arcarina, Collembola, Diptera and Lepidoptera. Although similarity analysis revealed that the soil animal communities in the litter at the intermediate succession stage were most similar to those at the climax succession stage, they differed greatly from each other in the Shannon-Wiener diversity index. The Shannon index was highest at the climax succession stage and lowest at the intermediate succession stage. The Shannon-Wiener diversity index well represented the diversity of the soil animal communities in the litter at the five succession stages but was in negative correlation with the Simpson dominance index. Finally, the paper discussed the following three questions: the role of soil animals as indicators for different plant community succession stages; the role of different soil animal groups in litter decomposition at different stages; the major factors affecting the composition and distribution of soil animals in the litter. This paper would provide a new perspective for the research on the succession mechanism of plant communities and soil animals' decomposition functions.