Differing environmental conditions in terrestrial and aquatic ecosystems likely influence effects of plant litter species traits and species composition on ecosystem processes, yet cross-ecosystem comparisons of litter processing have been constrained by differences in temporal scale and analytical methods. Here, we compare published data on processing dynamics of single- and mixed-species leaf litter in riparian and stream habitats of a forested, southern Appalachian watershed that were collected at similar successional stages throughout breakdown. Using an information-theoretic approach, we determined that the most parsimonious models for both riparian and stream datasets contained litter species composition, chemical and biological parameters. 

Results/Conclusions

Species composition effects included species interactions in riparian litter and species presence/absence in stream litter. Litter C:N and fiber had positive effects and invertebrate abundance had negative effects on litter mass remaining in riparian habitats; whereas secondary compounds had positive effects and fungi had negative effects on litter mass remaining in stream habitats. Our results indicate that litter nutrient content, structural compounds, and invertebrate decomposers are the strongest traits associated with litter processing in terrestrial systems; whereas secondary compounds and fungi most determine litter processing in aquatic ecosystems. Although effects of litter species traits persisted during processing in both ecosystems, the relative importance of specific traits and species composition on litter processing varied between terrestrial and aquatic ecosystems. Identifying which species traits persist and interact to affect ecosystem function under varying environmental conditions may allow ecologists to make stronger predictions about functional consequences of species composition shifts across ecosystems.