Effects of soil microarthropods on plant litter decomposition across an elevation gradient in the Wuyi Mountains

Soil microarthropods are considered to be among the strongest determinants of plant litter decomposition in warm, humid sites. Little is known, however, about the regulation of plant litter decomposition dynamics along an elevation gradient in such sites. Our study examined the contributions of soil microarthropods to leaf litter decomposition of a single substrate (Castanopsis carlesii) along an elevation gradient across four types of zonal vegetations in southeastern China: evergreen broadleaf forest (EVB): coniferous forest (COF): dwarf forest (DWF): and alpine meadow (ALM) during April 2007 to March 2008. Leaf litter decomposition of C. carlesii was significantly accelerated by the presence of fauna in all four sites. After 360 days in the field, mass loss rates with the full decomposer assemblage and in the reduction of microarthropods were 62.9% and 41.2% in EVB, 48.1% and 30.6% in COF, 36.4% and 27.8% in DWF, 30.3% and 23.7% in ALM, respectively. The percentage of total decomposition due to the presence of soil fauna was 37% in EVB, 25% in COF, 12% in DWF, and 8% in ALM, thus showing strong systematic variation along the elevational gradient. The mass losses in control plots at the four sites were significantly correlated with the abundances of total Acari, Collembolans, and Mesostigmata mites. Although the proportion of Oribatid mites at EVB was not the highest among the four sites, there were elevated proportions of Mesostigmatid and Prostigmata mites, many of which were microbe-consuming species and induce an indirect influence on litter decomposition. Moreover, Shannon Index (F = 2.455, p = 0.093) and Group Number (F = 5.830, p = 0.005) both decreased along the elevation gradients. Mass losses were also found to be distinctively related to H′ (r² = 0.984, p = 0.016), and GN (r² = 0.952, p = 0.048) across the four sites. Our results suggest that the faunal contribution to plant litter decomposition varies markedly across environmental gradients that differ in litter faunal diversity.