Ecologia de Florestas Atlânticas com ocorrência do muriqui (Brachyteles spp.): diversidade, sucessão secundária e estrutura nutricional / Atlantic Forests ecology holding muriqui (Brachyteles spp.): diversity, secondary succession and nutritional structure

AUTOR(ES)
DATA DE PUBLICAÇÃO

2008

RESUMO

This study has three chapters which mainly aimed the understanding on the role of forests variables affecting distribution, abundance and range ecology of primates belonging to Brachyteles genera. The first chapter specifically aimed on characterization and comparisons of tree species diversity and secondary succession among three forests holding Brachyteles hypoxanthus in Minas Gerais State: Rio Doce State Park (RDSP), a private property Mata do Sossego (Sossego) and Brigadeiro State Park (BSP). In order to reach such aim 800 trees measuring at least 5 cm DBH (diameter at breast height) scattered on 200 quarter points were sampled in each forest. The Shannon diversity index (H), equability (J), the successional stage and the distribution between the numbers of individuals by diameter classes were assessed. Additionally, comparisons based upon the species compositions were taken into account by Jaccard index (S) in order to evaluate the similarity among forests. Different diversity structure emerged from these three forests. The RDSP showed the smallest and largest alfa and beta diversity respectively, the smallest equability, and was the most advanced forest in terms of succession. Most of these results in RDSP occurred due to the prevalence of Senefeldera multiflora (Euphorbiaceae). S. multiflora has never seen as food resource for muriquis. Thus, their massive abundance powndered food resources offer leading to an energy budget improvement and eventually may lead to lower muriquiss density. Sossego and BSP forests showed larger diversity index and equability values than RDSP. Yet, Sossego forest is more advanced than BSP in terms of succession considering both the number of late secondary species and the number of diameter classes. Such characteristics favor a bigger food resource offer besides favor the occurrence of alternative items when favorite ones are scarce, which may promote higher muriquis density onto these two forests. Chapter two aimed on the investigation whether food resource offer can improve muriqui density. For this purpose a number of data set were compiled from available papers considering those genera used by muriquis as food resource (resource-genera). Data of six forests with both vegetation features (species composition and structure) and muriquis densities were also compiled. Three of these forests were the same studied in the first chapter. Data from two new forest spread out São Paulo State and one from Espírito Santo State were added to our current data set. The presences of those resource-genera were checked on each species composition and structure lists, which were divided on two new ones: one comprising the resource-genera and another with non-resource genera. The relative density and biomass from each genera modality were summed. Additionally the density and biomass ratios between genera modalities were assessed. Muriquis densities have entered as response variable, whereas food resource estimators have entered as explanatory variable in statistical model. Multiple regressions were performed using generalized linear models. Only the biomass ratio in addition to its interaction with density ratio was statistically significant to explain muriquis densities. It means that forests carry supports are linked to species composition holding resource- genera, and such genera are represented by big trees in contrast to non-resource genera. Generally the ratio was 3:1 for both biomass and density. Big trees are important due to security promoted by their strong branches during muriquis locomotion besides they can offer more food allowing cohesive groups while foraging, low home range at same time that weaken inter group competition. The actions toward muriquis conservation account to the enlargement of forested areas by planting favorite trees species and the construction of corridors among fragments. It is suggested the planting of at least 60% of trees belonging to resource-genera, and forestry favoring the gain of biomass for such genera. The third chapter aimed to investigate the role of forest successional stage, structure and chemical profile (foliar protein to fiber ratio) on B. hypoxanthus range ecology between two forests at BSP. The choices of these two sites were based on the usage differences by muriquis. Hereafter these two sites are called core area and non core area. The standard sampling methods presented in chapter one were repeated on these two sites at BSP. For chemical profile assessment leaves from three different individuals of those species comprising 80% of community importance value (IV) were sampled regardless their integrity and ontogeny within each site. The chemical analyses account for nitrogen, protein, fiber and protein to fiber ratio (P/F). The P/F was evaluated between sites and among regeneration guilds. In order to spatially correlate the structural variables with muriquis abundance 50 buffers measuring 20m of ray were put between two vegetation sampling points. The stem density, mean basal area and P/F were assessed for each buffer. Other 50 concentric buffers measuring 50 m of ray were overlaid in order to trap muriquis counts. The number of muriquis was the response variable, and the stem density, mean basal area and mean P/F were the explanatory variable inserted on statistical model using multiple regression. None statistical difference was detected between sites considering P/F, but in the non core area the late successional species showed lower P/F, whereas the core area was chemically more homogeneous than non core area, and none statistical differences emerged across regeneration guilds in core area. The most important structural difference between sites occurred due to massive bamboos clumps spread out in non core area. The massive bamboos clumps regeneration is supposed to has occurred as a response to logging in the past. Bamboos clumps generate gaps in the canopy besides harm the regenerating tree species below them by physical injuries caused by fallen branches. Such forest dynamics favor opened canopies increasing muriquis energy budget by improving their horizontal and vertical routes when gaps are faced while traveling. Thus one may expect that muriquis avoid these sites. These results point out that the pathway taken by secondary succession favored bamboos clumps regeneration at non core area. It is suggested as short term actions that weaken non resource genera as bamboos clumps at BSP and S. multiflora at RDSP are taken into account on forestry planning seeking habitat enrichment and muriquis persistence. The secondary succession monitoring is also suggested as an additional tool for those studies aiming muriquis conservation.

ASSUNTO(S)

botanica diversity mata atlântica brachyteles hypoxanthus sucessão succession protein/fiber relation relação proteína/fibra atlantic forest diversidade brachyteles hypoxanthus

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