Abstract: Japanese larch (Larix kaempferi) was introduced into China in the 1970s and has been planted in many parts of the country ever since, but its impact, as an alien species, on soil biodiversity is poorly documented. Field investigations were carried out in a Japanese larch plantation with stands different in development stage to explore community characteristics of the soil macrofauna community in forest floor of the plantation in the western part of the Qinling Mountains. Results demonstrate that in terms of density and richness in class group of soil macrofauna community in forest floor, the stands displayed an order of 10a old > 32a old > 20a old. Significant changes also occurred in composition of the nutritional function group of the macrofauna. With rising age of the stand, the predator group increased first and then decreased in proportion, while the group of saprophagous+ominivores did reversely and the group of herbivores increased all the way. Densities of the groups of Gastropoda, Lumbricidae, Diplopoda, Lithobiomorpha, Pselaphidae, Staphylinidae, Carabidae, Curculionidae, Diptera and Formicidae varied sharply between stands different in age, thus triggering changes in structure and in composition of the nutritional function groups of soil macrofauna. Soil macrofauna in the forest floor are very sensitive to changes in environment with the age of the Japanese larch stands and hence can be used as indicator of changes in soil environment under forests.

Key words: western part of the Qinling Mountains, Larix kaempferi, development stage, soil macrofauna, community structure