Litter Decomposition, and Associated Invertebrate Communities, in Wetland Ponds of the Copper River Delta, Alaska (USA)

High-latitude wetlands provide vital ecological functions, many of which rely on the decomposition of plant litter, but little understanding exists of how decomposition rates vary across space, and among common plant species. We investigated the litter decomposition of seven plant species in six wetland ponds on the Copper River Delta (Alaska, USA), and the litter-associated invertebrates. The ponds exist on common geomorphic surfaces of the delta: surfaces created by glacial retreat and outwash, and those resulting from uplifted intertidal area following a powerful 1964 earthquake. An eight-fold range in decomposition rates existed across litter species and correlated with phosphorus (r = 0.63), but not nitrogen and carbon content of the litter. Macroinvertebrate abundance also differed among leaf species. Litter-decay rates did not differ between pond types when expressed on a percent-mass-loss per-day basis; however, on a per-degree-day basis, decomposition in outwash ponds was more rapid. Litter in outwash ponds also had greater invertebrate abundance than uplift ponds, a pattern driven by collector-gatherer chironomids. Invertebrate activity was deemed a minor source of litter-mass loss relative to microbial decomposition. Results suggest that litter-associated invertebrate communities differ between pond types, but that differences in plant-litter decomposition are subtle.