Interactions between invertebrate and microbial communities in decomposing camphor and Masson pine litter varied with seasonal rainfall

Abstract

To reveal the changes in the interactions between invertebrates and microbes in decomposing litter with seasonal rainfall, litterbags containing camphor (Cinnamomum longepaniculatum) and Masson pine (Pinus massoniana) litter were therefore in situ incubated on the floor of Masson pine-camphor mixed plantations in the subtropical region of China. Different mesh sizes of litterbags were used to control the access of the invertebrates. The invertebrates in litterbags were collected by funnel method, and microbial communities were detected by phospholipid fatty acid (PLFA) method in slightly rainy season (SRS; November 1–December 24), micro rainy season (MRS; December 25–March 7), early rainy season (ERS; March 8–June 15) and rainy season (RS; June 16–October 31) during two decomposition years. The abundance and composition of microbial and invertebrate communities varied significantly with seasonal rainfall and tree species. Invertebrate exclusion generally decreased the bacterial and fungal biomass, and the biomass of Gram-positive bacteria and Gram-negative bacteria in Masson pine needle litter, but generally increased these indices in camphor foliar litter. Invertebrate exclusion decreased the mass loss rate of Masson pine litter, but increased the mass loss rate of camphor litter. Total microbial biomass and bacterial biomass in both foliar litters were generally higher in SRS and MRS than these in ERS and RS during the first decomposition year, whereas the situation reversed during the second decomposition year. The abundance of invertebrates increased gradually from the first SRS to the second SRS and decreased gradually afterwards. Briefly, the interactions between invertebrate and microbial communities varied greatly with litter types and seasons. Positive and negative interactions between invertebrate and microbes were respectively observed in Masson pine and camphor litters, and differential responses of microbial biomass and mass loss rate to invertebrate exclusion were found in two litter types. In turn, the interactions between invertebrates and microbes run the litter decomposition.