The metacommunity concept is a synthesis of longstanding ideas in ecology that has helped to advance our understanding of species coexistence through an appreciation of multiscale interactions.  However, metacommunities are most often experimentally studied in systems with distinct local community boundaries surrounded by an inhospitable matrix (e.g., aquatic communities in a terrestrial matrix). The intervening matrix in such studies serves only as a dispersal barrier and may not reflect dynamics in more continuously structured systems with indistinct local community boundaries, where the matrix also serves as a source of potential colonizers (e.g., in a patchy forest landscape). Ecosystem processes might also be influenced if the species that perform essential functions are influenced by matrix quality.

We used a microcosm system of leaf litter arthropod communities to examine (1) how the quality of the matrix mediates the effects of patch size and isolation on metacommunities, and (2) how the resultant metacommunity structure (diversity, composition) affect the rate of an important ecosystem function, leaf litter decomposition. Microcosms were formed of 1 m² landscapes comprised of oak and pine litter habitat. Large and small oak litter patches were arranged in either connected or isolated patterns, and surrounded by a matrix of either bare ground (inhospitable) or pine litter habitat.  Litter bags were used to quantify differences in leaf mass loss among landscape types.  Landscapes were sampled bi-monthly for one year.

Results/Conclusions

Results show that arthropod 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 also dependent on landscape type. Initial results indicate that patch size, isolation, and matrix quality each influence the rate of litter decomposition.