Topography drive species diversity, structure and ecosystem function in tropical Atlantic forest

• Ano de defesa: 2018
• Autor(a) principal: Rodrigues, Alice Cristina
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Universidade Federal de Viçosa
• Palavras-chave em Português: Biodiversidade florestal - Viçosa (MG); Serviços ambientais; Mata Atlântica - Manejo; Mata Atlântica - Conservação; Fitogeografia
• Link de acesso: http://www.locus.ufv.br/handle/123456789/21184

The Brazilian Atlantic forest is considered one the most important centers of diversity of vascular plants in the world providing various ecosystem services. Nevertheless, the region is also one of the most threatened tropical forests in the world, due mainly to habitat fragmentation. Comprehending the role played by environmental drivers, such as topographic variables that determine the community assembly and ecosystem functioning of tropical forests is fundamental to establishing conservation and management strategies. Nevertheless, research that study the relationship of these drivers on the biodiversity, structure and ecosystem function of Atlantic Forest tree communities remains scarce. The objective of this research was to evaluate the relative contribution of topographic drivers on forest attributes and ecosystem functioning . The study was conducted in a seasonal semi deciduous Atlantic forest fragment (at Viçosa municipality, Minas Gerais state, Brazil. We selected two sampling areas with contrasting topographic conditions (a Southeast area and a Northeast area one). Each area (100 × 100 m) was sub-divided into 100 plots of 10 × 10 m a total 200 plots (2 ha). From each plot, all trees having diameter at breast height ≥ 3.2 cm were sampled and identified to the species level. In each plot we measured three topographic variables (slope, elevation, and convexity) using a Total Station and measure the soil physicochemical properties. We performed multivariate regression tree (MRT) analysis to classify habitat types according to topographic variables and species composition. We estimated the maximum number of species required accounting for 50% of stem abundance and biomass in each area and we considered as ‘biomass hyperdominants’ and ‘stem hyperdominants’ the species that accumulated 50% of the total biomass and stems, respectively. The two study areas showed significant differences in spatial distribution of topographical variables. According to the MRT, the Southeast area was topographically less heterogeneous whith five habitat types, whereas the Northeast area was topographically more heterogeneous with seven habitas types. All species richness indices differed significantly between areas, but only in Southeast area did they also differ between habitat types. Species richness in the Northeast area is 48% higher than that of Southeast area. Structural attributes and AGB did not show differences between areas. However when analyzed at the area scale, basal area, tree height and AGB showed significant differences between low valleys and high plateaus in the Southeast area. The number of stem hyperdominants varied significantly between areas. In the Southeast area, only two species accounted for 50% of the number of stems hyperdominants, while in the Northeast area 10 species accounted for 50% of stems hyperdominants. In the Southeast area, only two species were classified as biomass hyperdominants, in the Northeast area, on the other hand, five species accumulated 50% of the AGB. Our results showed that the diversity and distribution pattern of hyperdominant species were significantly correlated with topography in both areas, and that the structural and AGB attributes vary in the topographic gradient of the Southeast area . We presume that the relative functional contributions of species may substantially vary from one species to another, regardless of their abundance. Thereby, some particularly abundant species may not in fact contribute substantially to ecosystem processes. The variation of forest attributes among habitats is probably due to the heterogeneous distribution of resources such as water and nutrients because of the great difference in elevation between the extremes of the topographic. This fact can also be correlated with the existence of a marked fine-scale edaphic gradient in soil parameters among habitats in the Southeast area. In addition, species redundancy may explain the weak relation between richness and AGB found in our study . We conclude that topography is an important driver that determines the structure, diversity and ecosystem functioning . Our study is of great importance in the analysis of impacts on tropical forests on a local scale with global repercussions, which favors the establishment of basic criteria for conservation and management.