Influência da matriz de pastagem na dispersão de espécies lenhosas de cerrado
Data
2020-03-26
Orientadores
Vieira, Elisa Hardt Alves 
Tipo
Dissertação de mestrado
Título da Revista
ISSN da Revista
Título de Volume
Resumo
A redução da conectividade funcional da paisagem pode ser causada por processos de fragmentação, perda de habitat e atividades antrópicas de diferentes tipos e intensidades na matriz. As áreas de pastagem são exemplos de influências antrópicas responsáveis pela perda da maior parte do Cerrado no estado de São Paulo, tendo potencial de alterar as respostas da dispersão das espécies da flora. Diante desta problemática, esta dissertação teve como objetivo entender os potenciais efeitos da matriz de pastagem sobre a dispersão de espécies lenhosas do Cerrado em duas abordagens diferentes que visaram: i) compreender as relações de correspondência entre medidas estruturais e de conectividade funcional da paisagem na avaliação da conservação do Cerrado utilizando ambiente de Sistema de Informação Geográfica (SIG); e ii) identificar limiares de distância de dispersão na matriz, a partir da quantificação do estabelecimento de espécies lenhosas regenerantes in loco e em experimento ex situ de viabilidade de propágulos em sistema controlado. Foram selecionadas três paisagens fragmentadas no Domínio do Cerrado com remanescentes de cerradão e ocorrência de manchas de Floresta Estacional Semidecidual do bioma Mata Atlântica inseridos em matriz de pastagem. O mapeamento das paisagens foi realizado em software ArcGIS®. A análise da paisagem em SIG consistiu no cálculo de métricas estruturais e funcionais nos programas Fragstats® e Conefor®. Foram realizados levantamentos em unidades amostrais estratificadas para testar a hipótese de que existe um gradiente habitat-matriz decrescente para variáveis de composição (riqueza), estrutura (abundância, altura, diâmetro e volume) e diversidade da flora lenhosa. Em campo também foram realizadas coletas de solos para a quantificação da compactação medida pela porosidade total e densidade do solo e a realização de um experimento controlado para avaliação da viabilidade de propágulos (germinação e rebrota). Os resultados mostraram que todas as paisagens avaliadas possuem baixas taxas de cobertura e conectividade funcional (IIC) entre habitats. As métricas estruturais e funcionais não são correspondentes e, algumas vezes, apresentaram interpretações antagônicas. A aplicação de métricas de conectividade funcional no planejamento da conservação depende da disponibilidade de dados sobre dispersão das espécies, especialmente em diferentes usos e coberturas e da definição de uma espécie representativa para dada área. A matriz de pastagem parece reduzir a conectividade funcional da flora, especialmente para espécies zoocóricas. Apesar da condição da matriz influenciada por Urochloa sp. e pelo pisoteio e forrageio do gado não impedir o estabelecimento de plantas, ela altera a composição da comunidade vegetal, priorizando espécies de ocorrência em formações campestres e de dispersão do tipo autocórica. Não foi possível identificar um gradiente habitat-matriz para as variáveis estudadas, o que pode ter sido mascarado pela maior compactação do solo observada próximo a borda do habitat e, possivelmente, pelo uso de consórcio gramínea-leguminosa nos pastos. A dispersão por rebrote e por germinação de espécies autocóricas do banco de sementes da matriz de pastagem reforçam o potencial de regeneração natural da flora lenhosa do Cerrado como estratégia de restauração do bioma, desde que acompanhada de ações de manejo adequadas.
The landscape functional connectivity reduction can be caused by fragmentation processes, habitat loss, and anthropogenic activities of different types and intensities in the matrix. The pasture areas are examples of these anthropic influences that are responsible for the loss of most of the Cerrado in the São Paulo state, with the potential to modify the responses in the flora species dispersal. Given this problem, this dissertation aimed to understand the potential effects of the pasture matrix on the woody species dispersal in the Cerrado, with two approaches that aimed: i) to understand the correspondence relationships between landscape structural and functional connectivity measures in the conservation evaluation of Cerrado using Geographic Information System (GIS) environment; and ii) to identify dispersion distance threshold in the matrix, based on the quantification of the regenerating woody species establishment in loco and with an ex-situ propagation viability experiment in a controlled system. Three fragmented landscapes were selected in the Cerrado Domain with remnants of cerradão and the occurrence of seasonal Semideciduous Forest patches of the Atlantic Forest biome inserted in a pasture matrix. Landscapes mapping was carried out using ArcGIS® software. The GIS landscape analysis consisted of calculating structural and functional metrics in the Fragstats® and Conefor® programs. Surveys were carried out in stratified sample units to test the hypothesis that there is a decreasing habitat-matrix gradient for variables of composition (richness), structure (abundance, height, diameter, and volume) and diversity of woody flora. In the field, the soil was also collected for compaction quantification by measuring the soil total porosity, soil density, and carrying out a controlled experiment to evaluate the propagule's viability (germination and resprout). The results showed that all evaluated landscapes have low rates of coverage and functional connectivity (IIC) between habitats. The structural and functional metrics do not correspond and, sometimes, they had antagonistic interpretations. The application of functional connectivity metrics in conservation planning depends on the availability of species dispersal data, especially related to different land use and land coverages and the definition of representative species for a given area. The pasture matrix seems to reduce the flora functional connectivity, especially for zoochoric species. Although matrix condition influenced by Urochloa sp. and for trampling and foraging cattle does not avoid the plant establishment, it alters the plant community composition, prioritizing species that usually occur in Cerrado grasslands and with autochory dispersal. It was not possible to identify a habitat-matrix gradient for the study variables, which may have been masked by the greater soil compaction observed near the habitat’s edge and by the, possibly by the grass-leguminous mixture use. The dispersal by resprouting and by autochoric species germination from the pasture matrix seed bank fortified the potential of the Cercado’s woody flora for natural regeneration as a strategy for restoring the biome since it is accompanied by appropriate management actions.
The landscape functional connectivity reduction can be caused by fragmentation processes, habitat loss, and anthropogenic activities of different types and intensities in the matrix. The pasture areas are examples of these anthropic influences that are responsible for the loss of most of the Cerrado in the São Paulo state, with the potential to modify the responses in the flora species dispersal. Given this problem, this dissertation aimed to understand the potential effects of the pasture matrix on the woody species dispersal in the Cerrado, with two approaches that aimed: i) to understand the correspondence relationships between landscape structural and functional connectivity measures in the conservation evaluation of Cerrado using Geographic Information System (GIS) environment; and ii) to identify dispersion distance threshold in the matrix, based on the quantification of the regenerating woody species establishment in loco and with an ex-situ propagation viability experiment in a controlled system. Three fragmented landscapes were selected in the Cerrado Domain with remnants of cerradão and the occurrence of seasonal Semideciduous Forest patches of the Atlantic Forest biome inserted in a pasture matrix. Landscapes mapping was carried out using ArcGIS® software. The GIS landscape analysis consisted of calculating structural and functional metrics in the Fragstats® and Conefor® programs. Surveys were carried out in stratified sample units to test the hypothesis that there is a decreasing habitat-matrix gradient for variables of composition (richness), structure (abundance, height, diameter, and volume) and diversity of woody flora. In the field, the soil was also collected for compaction quantification by measuring the soil total porosity, soil density, and carrying out a controlled experiment to evaluate the propagule's viability (germination and resprout). The results showed that all evaluated landscapes have low rates of coverage and functional connectivity (IIC) between habitats. The structural and functional metrics do not correspond and, sometimes, they had antagonistic interpretations. The application of functional connectivity metrics in conservation planning depends on the availability of species dispersal data, especially related to different land use and land coverages and the definition of representative species for a given area. The pasture matrix seems to reduce the flora functional connectivity, especially for zoochoric species. Although matrix condition influenced by Urochloa sp. and for trampling and foraging cattle does not avoid the plant establishment, it alters the plant community composition, prioritizing species that usually occur in Cerrado grasslands and with autochory dispersal. It was not possible to identify a habitat-matrix gradient for the study variables, which may have been masked by the greater soil compaction observed near the habitat’s edge and by the, possibly by the grass-leguminous mixture use. The dispersal by resprouting and by autochoric species germination from the pasture matrix seed bank fortified the potential of the Cercado’s woody flora for natural regeneration as a strategy for restoring the biome since it is accompanied by appropriate management actions.