Background/Question/Methods Plant decomposition is driven largely by activity of extracellular enzymes produced by bacteria and fungi. Decomposition tends to be slower at ecosystem edges (ecotones) between forest and field ecosystems due to changes in moisture and temperature regimes. However, the effects of edges between forest types on decomposition are still unclear. In previous studies, we found unexplained variation in the bacterial community relative to changes in soil characteristics at ecotones. The goal of our study was to evaluate whether microbial communities at ecotones are poorly adapted for the abiotic conditions, altering decomposition rate. To test this, we used leaf litter bags of red oak, sugar maple, or shagbark hickory in each of three forest ecosystems (upland, bottomland, and riparian forests), and at ecotones between each pair of these ecosystems. Litter bags were deployed in December 2017 and collected every six months for eighteen months. Remaining litter was dried, weighed, and ashed to measure decomposition. Further, enzyme assays were performed as a proxy for microbial community investment for the acquisition of carbon, nitrogen, and phosphorus. Results/Conclusions Decomposition was slower in ecotones than ecosystem centers (cores) for the labile leaf types (shagbark hickory and sugar maple), but not for recalcitrant red oak. Among ecosystem cores, decomposition was faster in the bottomland than other ecosystems for all leaf types. Among ecotone types, decomposition rate was faster for all leaf types in the bottomland-upland transition than in the riparian-bottomland or upland-riparian transitions. Despite decomposition being slower in ecotones, enzymatic activity did not differ between ecotones and ecosystem cores in a linear mixed model. These preliminary findings suggest that decomposition is fastest in the wettest parts of the forest, but slower than expected in ecotones. Further analyses are needed to best explain why there are no ecotone effects on enzymatic activity despite changes in decomposition. Overall, it appears that microbial communities may be poorly adapted to ecotones, resulting in slower decomposition in these transitional areas of the forest.
