Species of leaf litter are more important than urbanization effects for litter mass loss in semi-arid river

Abstract

Leaf litter mass loss plays a crucial role in ecosystem processes, and understanding the factors that influence this process is essential, particularly in semi-arid riparian zones. This study investigated the impact of plant species (Erythrina velutina, Anacardium occidentale, Tabebuia aurea, Croton sonderianus, and Hymenaea courbaril) and environmental conditions (before and after urban) on leaf litter mass loss in these ecosystems. We utilized litter bags containing senescent leaves to evaluate the density and richness of invertebrates, shredder and scraper abundance and measured the mass loss of litter after oven drying. We observed that plant litter with higher palatability characteristics experienced faster mass loss when exposed to less palatable leaf resources, suggesting a "fertility islands" effect driven by increased invertebrate density and scraper abundance. Additionally, river sections downstream of urban areas exhibited higher mass loss, likely attributed to elevated nutrient concentrations and water temperature. The prevalence of larger-bodied scraper species (leaf tissue fragmentation by radulae) indicates their role in driving mass loss processes. Thiaridae, Lymnaeidae, and Planorbiidae can act as intermediate hosts for various parasitic diseases affecting humans and animals, with special concern for Thiaridae downstream of urban areas due to increased human waste, increasing the risk of contamination. It is important to consider both biotic and abiotic factors in leaf litter mass loss, emphasizing this process as a valuable environmental indicator.