The Roles of Decaying Logs in Harboring Soil Invertebrate Communities are Affected by Gap Positions

Abstract

Both forest gaps and coarse wood debris resulting from tree mortality might profoundly affect soil biodiversity. However, the knowledge regarding the interactive effects of decaying logs and canopy gaps on the structure and function of soil invertebrate communities is limited. To fill this gap, Minjiang fir (Abies faxoniana) logs of decay classes I-V were incubated on the floor from gap center to closed canopy in a primary Minjiang fir forest on the eastern Qinghai-Tibet Plateau, and soil invertebrate communities in litter and topsoil layers beneath and away from decaying logs were simultaneously investigated in the growing season after 6 years. The taxa composition and structure of soil invertebrate communities beneath decaying logs differed greatly from those away from coarse woody debris. Meanwhile, the composition and structure of soil invertebrate communities in both litter and topsoil layers beneath the logs varied with decay process, and higher invertebrate alpha diversity indices were observed in topsoil layer beneath the logs of III - IV decay classes. Additionally, the taxa composition and diversity indices of soil invertebrate communities changed markedly with critical periods, and invertebrate density and alpha diversity indices in litter layer decreased from early to later growing seasons, but those in topsoil layer increased. Besides, the structure of detrital food web beneath decaying logs differed significantly from that away from logs, and changed markedly with gap positions, soil layers and critical periods. Briefly, decaying logs exerted differential roles in harboring soil invertebrate diversity and maintaining the structure of detrital food web, but were strongly affected by gap positions. These findings contribute to our understanding of the effects of climate change on soil biodiversity.

Keywords: soil biodiversity, soil invertebrate, forest gap, coarse woody debris, Minjiang fir, subalpine coniferous forest