La colonización y descomposición biológica de la hojarasca en un arroyo subtropical

Abstract

In small streams, aquatic community obtains energy mainly from leaves of the riparian vegetation. Processing these leaves involves physical, chemical and biological factors that may differ among leaf species. We assessed the effects of li�er quality on leaf decomposition and colonization by aquatic invertebrates in a subtropical stream. Leaves from two native, highly represented tree species common in subtropical riparian areas, Ficus luschnathiana and Casearia sylvestris, were incubated in coarse mesh bags in a stream. Bags were sampled weekly during an incubation of 28 days. The decomposition rates were higher in leaves of F. luschnathiana than in those of C. sylvestris. In the first seven days of the experiment, leaves of F. luschnathiana lost ~60% of the initial mass, while Casearia sylvestris lost around 30%. The leaves of C. sylvestris were initially more palatable than the leaves of F. luschnathiana, perhaps due to their lower lignin and cellulose content, and lignin to N ratio (Lignin:N). These structural compounds enhance leaf toughness thereby protecting them from herbivores and detritivores. However, leaves of F. luschnathiana were comparatively softer, which apparently facilitated fungal colonization and conditioning. Thus, leaves of F. luschnathiana a�ained high shredders density, which was reflected in a higher leaf mass loss. Our results suggest that li�er decomposition was sensitive to fungal biomass and leaf toughness. We observed that microbial conditioning, rather than the initial chemical quality of the leaf li�er, decreased leaf toughness thereby stimulating further colonization by shredders and enhancing the decomposition process. The fungal community has a key-role in the degradation process within aquatic environments, breaking down even low-quality li�er (i.e., F. luschnathiana) and promoting changes in the composition and structure of the invertebrate community.

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

“…A mass loss of around 40% for both litter types in 30 days is a relevant result that supports this inference. After leaching (usually compounds against herbivory), the litter becomes less toxic and more palatable(Marsaro et al 2023), allowing for the colonization of the decomposer community(Biasi et al 2016), also justifying the higher invertebrate density on E. velutina and T. aurea (by increase of nitrogen and protein content) compared to other plant species litter, and consequently, its leaf litter breakdown(Rezende et al, 2018(Rezende et al, , 2014bBrandão et al, 2022).…”