Biodiversidade e funcionamento de ecossistemas naturais e implantados

• Autor(a) principal: Muscardi, Dalana Campos
• Data de Publicação: 2013
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/917
• topic: Funcionamento; Decomposição; Diversidade; Agrofloresta; Operation; Decomposition; Diversity; Agroforestry; CNPQ::CIENCIAS BIOLOGICAS::ECOLOGIA

The conversion of natural habitats due to agricultural activity is the main cause of biodiversity loss. This biodiversity loss can be expressed as loss of function which maintains the ecosystem functioning. The ecosystem functioning can be defined as a set of biogeochemical processes responsible for the matter and energy flow. The diversity loss affects the ecosystem functioning throw many ways, according to the importance of species that are lost. Several estimates of diversity and ecosystem processes have been used in studies of biodiversity and ecosystem functioning. The most common diversity estimates in BEF studies are taxonomic diversity, functional diversity and phylogenetic diversity. Decomposition and nutrient cycling can be used as measures of ecosystem functioning. Decomposition is the progressive breakdown of organic matter into smaller pieces, until the organic molecules are mineralized in its primary constituents: water, carbon dioxide and mineral elements. The release and nutrients cycling litter layer promote the nutrients absorption by plants and maintains soil fertility and productivity. The process of decomposition and nutrient release can be modulated by edaphic biota, and the effect of these organisms on such processes can be changed by litter diversity and environment characteristics of where they occur. This thesis aimed to investigate the effects of litter diversity and edaphic arthropods in decomposition and nutrient release. In addition, we analyzed the effect of different management intensities (forest fragments, conventional coffee systems and agroforestry coffee systems) on the decomposition and nutrient release. We used leaf litter decomposition as a model of ecosystem function, presenting a flowchart of processes that affect decomposition, and relating these processes to litter diversity. We detail some relationships between fauna involved in litter breakdown from a simplified trophic web. Moreover, we used litter bags methodology containing coffee and tree leaves of plant species present in the coffee systems. Biocide was used to diminish arthropod diversity. This study aimed to test whether the decomposition and nutrient release increased with the diversity of arthropods and plant litter, and if there were higher in areas with less intensive management. The diversity of arthropods was affected by the management, the biocide and the litter diversity. The decomposition was affected by the litter diversity and nutrient release was affected by litter diversity, arthropods diversity and management. The lack of management effect on decomposition and nutrient release may be due to the fact that the abundance of mites and collembolans did not varies in among the studied environments. The management effect on carbon release is possibly due to the use of fertilizers, which can alter nutrient cycling in agroecosystems compared to natural environments. However, in a smaller scale of analysis, we can observe a decrease in abundance of mites and collembolans due to the presence of biocide, and this decrease diminish decomposition. Furthermore, naphthalene has a fungicidal effect and may decrease the activity of decomposers in degradation of leaf material. We can account that it was not through the route resource heterogeneity to arthropods , that litter diversity enhance litter decomposition. The mechanism behind this effect may lie in increasing activity and diversity of decomposers by litter species richness. This increase in microbial activity can occur via edaphic microclimate variation or increased litter quality, both factors derived from litter diversity. We observed the importance of litter species richness and edaphic arthropods diversity in decomposition and nutrient release processes in our study. We also note that managed environments must be included in BEF research, due to their effects on decomposition and soil fauna community. We also recommend that litter composition, soil fauna diversity and decomposers have to be analyzed together. Finally, our study stands out by manipulating the diversity of litter and soil fauna. The use of manipulative experiments may clarify the patterns in BEF studies.