The effects of gap size and litter species on colonization of soil fauna during litter decomposition in Pinus massoniana plantations

Litter decomposition is a major component of the nutrient cycle in forest ecosystems. It is generally accepted that higher initial quality and litter mixture contribute to increased mass loss, and the effects of soil fauna on litter decomposition is context-dependent. Meanwhile, the formation of gaps alters the hydrological and thermal conditions of the forest through the redistribution of light and precipitation, ultimately influencing the distribution and activity of the soil biota. Previous studies have focused on the effects of either litter species or forest gaps on soil microbes. However, the combined effects of litter species and gap size on the composition and structure of the soil fauna during litter decomposition have not been thoroughly examined. By analyzing litter collected over the course of one year from a Pinus massoniana plantation, shifts in the soil fauna, including indicator groups and guilds based on feeding habits, were correlated with changes of litter substrate, gap size, and incubation time. It was also observed that mesofauna (including microarthropods, nematodes, etc.) were more susceptible to these examined factors than macrofauna. Furthermore, litter type has higher influence on the abundance and richness of soil fauna than litter diversity. In general, small to intermediate sized gaps improved soil fauna diversity, richness, and functional diversity of indicator taxa. The relative abundance of guilds varied with gap size, litter species, and incubation time. The relative abundance of carnivores increased with gap size, whereas fungivores and detritivores increased with incubation time. The observed relative abundance of herbivores was higher in P. massoniana leaf litter than in Cinnamomum camphora and mixed-species leaf litters. Overall, the data presented here indicated that the creation of small to intermediate sized gaps will increase the diversity of soil fauna and accelerate litter mass loss in P. massoniana plantations. The subsequent effects on the return of bioavailable nutrients and soil carbon storage require additional long-term studies.