Altered litter and cellulose decomposition across an anthropogenic habitat modification gradient in Sulawesi, Indonesia

Abstract

Many tropical regions in Southeast Asia have experienced extensive habitat modification, creating a mosaic of forested and agricultural land. The capacity of these human-modified tropical landscapes to support biodiversity and ecosystem functions and services is of considerable practical interest. Decomposition of plant material is a key process maintaining the nutrient cycle in both natural and agro-ecosystems, but few studies have documented the relative contributions of different guilds of decomposers, acting on different plant substrates, across different tropical land-uses. We measured decomposition of leaf litter and cellulose across a gradient of anthropogenic habitat modification (forest, shrubland, and corn farmland) within Panua Nature Reserve, Sulawesi, Indonesia. The influence of fungi and the litter invertebrate community were investigated experimentally. Decomposition of both substrates was significantly lower in corn plantations than in forest sites. Partial exclusion of litter invertebrates, but not fungi, significantly reduced decomposition, but the feeding guild composition of the litter invertebrate community did not differ significantly across habitat types. Our results confirm that even small-scale agricultural areas adjacent to forest fragments can experience impaired ecosystem functions. These changes can be linked to reduced invertebrate activity, apparently independent of the functional structure of the litter invertebrate community. Effective management of human-modified landscapes will be needed to maintain nutrient cycling, even in areas where agroecosystems and tropical forests occur in close proximity. Keywords: Tropical forest, Sulawesi, decomposition, substrate, fungus exclusion, and litter invertebrate community.