Abstract: In order to understand the characteristics of soil nematode community in the Abies georgei var. smithii forest gaps in southeast Tibet, an investigation was conducted to study the variations of soil nematode community at different depths of 0-30 cm soil layer in the gaps and nongaps. The nematode individual density, diversity index, and trophic group index were taken to analyze the composition and structural characteristics of the soil nematode community. A total of 26801 soil nematodes belonging to 2 classes, 5 orders, and 64 genera were collected by shallow dish method. The nematode individual density was averagely 3552 ind·100 g^-1 dry soil, and the individuals had a highly surface-gathering characteristics. In the gap soils, the dominant genera were Tylencholaimus and Filenchus, while the dominant trophic group was bacterivores. The soil organic matter was decomposed by both bacteria and fungi. The ecological index results showed that the nematodes diversity and richness were related to gap size. The characteristics of soil nematode community in the gaps were different from those in closed stand and forest open land, and this difference indicated the potential for using nematodes as the environmental indicator species.

Key words: soil animal, alpine forest, biological diversity, microhabitat, Tibet.