The effects of habitat loss, fragmentation, and matrix quality on metacommunity structure and ecosystem function

Background/Question/Methods

Habitat loss and fragmentation continue to threaten biodiversity. The quality of the intervening matrix habitat can drive the negative effects of habitat loss and fragmentation by serving as a dispersal barrier when the matrix is inhospitable. Alternatively, a more hospitable matrix may serve as a source of colonizers that can alter local dynamics. Resultant effects on metacommunity structure may affect ecosystem function. However, the effects of matrix quality, habitat loss and fragmentation per se are rarely studied experimentally. We used a fully-crossed experimental microcosm system of leaf litter metacommunities to examine (1) the effects of matrix quality, patch size and isolation on metacommunities, and (2) the resultant effects on an important ecosystem function: litter decomposition. Microcosms were formed of 1 m² landscapes comprised of oak and pine litter habitat. Large and small patches of oak litter were either connected or isolated, and surrounded by a matrix of either bare ground or pine litter habitat. Litter bags were used to quantify differences in leaf mass loss in oak litter patches among landscape types. Landscapes were sampled bi-monthly for one year and community composition was assessed using a combination of molecular methods: T-RFLP and Illumina sequencing.

Results/Conclusions

Results show that leaf litter communities at local and landscape scales change through time reflecting the differences in landscape structure and matrix quality. The rate of leaf litter decomposition was dependent on matrix quality but not patch size or isolation. The rate of leaf litter decomposition in oak litter patches was reduced in the presence of a pine litter matrix. This may be due to ecological processes: e.g., pine litter species invading oak litter habitat may be less efficient at breaking down oak litter. The lower rate of decomposition may also be due to abiotic effects; e.g., a change in oak litter pH as a result of leaching of relatively acidic rainwater from the pine litter matrix into oak litter patches.