Fatores reguladores da decomposição foliar: uma abordagem sobre fragmentadores e decompositores

Abstract

According to the River Continuum Concept, in small rivers, corresponding to ~ 80% of river basins, the main energy source for the trophic chain is the material produced in riparian zones, especially leaves. This material goes through the process of decomposition, which is responsible for the nutrients cycling and maintenance of aquatic communities. In this context, the objective of this study is to investigate the effects of physical, chemical and physiological traits of plant species on microbial activity and fragmentation, and as a consequence on decomposition rates. In the first chapter we investigated the activity of Phylloicus fragmentation in relation to food resources with different leaf traits. We found that the shredders have their food activity stimulated by substrate with less amount of lignin, which facilitates fungus conditioning and promotes the palatability of the detritus. In the second chapter, we investigated the feeding preference and assimilation of C3 and C4 carbon by Phylloicus and Aegla longirostri. We found that the shredders consume more the C4 species, but do not alter its isotopic signature and the intense activity of the hyphomycetes in the leaves C4 stimulated the consumption by the shredders. In the third chapter we investigated the effect of nutrient enrichment on soil and water on leaf nutritional quality and decomposition rates. We showed that the fertilized trees promoted leaves more nutritious than leaves of unfertilized trees. In addition, we found that the effect of nutrient enrichment on water was stronger than the nutrient enrichment of leaves in the decomposition process. Within the three chapters, we verified that the activities of the shredders and fungi are influenced by the characteristics of the leaves and are related to the riparian vegetation, especially by C3 carbon. We verified that the structural compounds are determinant for the microbial colonization and consequently for the fragmentation and litter decomposition. We also verified that the enrichment of nutrients in the water may be more important for the process of leaf decomposition than the nutrients in the leaves.