Gisele Cristina de Oliveira Menino

Floristic Variation within Seasonally Dry Tropical Forests of the Caatinga Biogeographic Domain, Brazil, and Its Conservation Implications

SUMMARY Seasonally Dry Tropical Forests (SDTF) are gaining recognition as a significant biome and poorly conserved tropical biodiversity refuge. Understanding floristic relationships within SDTF is essential for their effective conservation. This study examines the floristic variation within SDTF of the Caatinga Biogeographic Domain, in north-eastern Brazil. SDTF trees, shrubs and arborescent cacti were sampled in six localities in the Brazilian states of Minas Gerais and Bahia. A number of soil chemical attributes were also measured to analyse vegetation-soil relationships across the study sites. Five floristically distinct SDTF communities were delineated. Differences in these communities are attributable to influences from adjacent savanna and rain forest surrounding the study sites, and also to soil properties such as Al3+, base saturation and gravel content. The high species richness of, and species dissimilarity between communities reflect the need for judicious conservation planning for SDTF that account for biodiversity values and forest structural integrity.

ENVIRONMENTAL HETEROGENEITY AND NATURAL REGENERATION IN RIPARIAN VEGETATION OF THE BRAZILIAN SEMI-ARID REGION

This study investigated the structure, diversity and composition of the regenerating shrub-tree species community along a stretch of riparian vegetation in relation to environmental heterogeneity. In the Environmental Protection Area of Pandeiros River, southeastern Brazil, the regenerating stratum on 70 plots (25 m 2 ) divided into four groups according to their soil characteristics and natural barriers was sampled. For each plot observations were made of variables related to several soil properties, canopy openness and flooding regime. In addition to the traditional calculation of phytosociological parameters and diversity, a canonical correspondence analysis (CCA) to examine the existing relationships between environmental variables and species distribution was performed. The families with the highest species richness were Fabaceae and Myrtaceae and the species with the highest importance value indices were Zygia latifolia , Tapirira guianensis , Butia capitata , Bauhinia rufa and Hirtella gracilipes . The CCA largely confirmed the groups that were originally proposed. The stretch of riparian vegetation studied was highly heterogeneous with regard to both the abiotic variables tested and floristic structure and composition.

Caracterização física de frutos e putâmens e taxa de ataque por Carmenta sp. a pequizeiros (Caryocar brasiliense Camb.) no norte de Minas Gerais

The pequi tree is a native species of brazilian savanah, which fruits are explored in an extractivist form, having a huge economic importance. The long periods of availability of the fruits, together with the heterogeneity of the productive regions, leads to an inference of the existence of differences among their physical characteristics. Thus, this study aimed to compare the physical characteristics of pequi tree fruit collected in three municipalities in the north of Minas Gerais state, and to verify if the attack by insects is directly related to its biometrical characteristics. We sampled 10 individuals and collected 20 fruits from each tree, in Montes Claros, Mirabela and Japonvar, municipalities, totalling 200 fruits per area. The physical variables of the fruits and pits, the number of little fruits (frutilhos), pits and seeds, and the percentage of intact and damaged fruits and pits were determined. The results indicated that there are physical differences among the collected areas, with the region of Japonvar having the most vigorous pits, with the lowest rates of attack by the pequi fruit borer. In addition, skin thickness and length of fruits from Japonvar and Mirabela, respectively, had relations with the percentage of attack by Carmenta sp. These differences found among the areas may be associated with the climatic and edaphic influences of these regions, which may also highlight the linkage to the genetical composition aspects of the pequi.

Tree succession across a seasonally dry tropical forest and forest-savanna ecotone in northern Minas Gerais, Brazil

Aims: Understanding succession in tropical forest is an important aspect of vegetation science, but to date, successional processes in seasonally dry tropical forests (SDTFs) have received much less attention than evergreen humid tropical forests. We aim to fill this knowledge gap. Methods: We investigated vegetation succession in SDTF areas consisting of three different successional stages (early, intermediate, late), and a SDTF-savanna ecotone in the municipal district of Juramento, north of Minas Gerais State, Brazil. Using twelve 400 m(2) plots in each area, we compared vegetation parameters and structural variables (absolute density and basal area) and examined the floristic composition of the tree component to find gradients of change. Important Findings: We found evidence of species turnover along a successional gradient, with the intermediate stage showing the highest species richness and diversity. This was accompanied with a significant increase in the number of tree individuals and basal area from the early to intermediate successional stage. However, the intermediate and late SDTF successional stages were more similar in structure and floristics. The ecotone was the most species rich and was similar to the intermediate SDTF and early successional stage in species richness and floristic composition respectively. These results will have implications for guiding SDTF management and recovery programs.

Adaptive strategy of tree communities on an environmental harshness hinterland inselberg in Minas Gerais, Brazil

Trees and other plants growing in stressful environments can display adaptive strategies such as sprouting, which is considered to be a functional trait for the persistence niche. For example, inselbergs are rocky outcrops that impose limitations on many plant forms through selective pressure to adapt to these environments. The present research tested the hypotheses that environmental harshness enhances sprouting, and that multi-stemmed trees have different persistence dynamics compared with single-stemmed trees. We sampled vegetation in 2006 and 2011 across a soil depth gradient in three areas: riparian forest, inselbergs and a corridor between the first two areas. Trees with a diameter at the breast height (dbh) ≥5 cm were sampled, and sprouts were counted. Results showed that the inselberg had more sprouted individuals and a larger amount of sprouts than the other areas. Thus, sprouting as a survival strategy was efficient in dealing with the environmental harshness and may be considered an adaptive strategy of trees to enable them to persist in such environments. The dynamic of multi-stemmed trees differed from single-stemmed ones, and the inselberg was distinct from the other areas. Over the 5 years of the present study, sprouting proved to be a strategy of persistence in this habitat, a finding that is in accordance with our hypothesis. Factors contributing to the environmental harshness, such as soil depth, may be the cause of sprouting in trees.

INSELBERG COMO FONTE DE DIVERSIDADE β EM UMA MATRIZ VEGETACIONAL, NO MUNICÍPIO DE COQUEIRAL - MG

This study aimed to answer the following question: Does habitat heterogeneity affect the tree community? To answer that question, we evaluated the influence of the species composition and structure of the tree community of inselbergs on the tree community of the matrix where the inselberg is located. The correlations between environmental and vegetation gradients were analyzed by canonical correspondence analysis of a species composition matrix constructed from abundance data of 40 plots sampled in two areas, one composed of seasonal semideciduous forest (SSF) and another with riparian forests, a vegetation corridor, and inselbergs. A similarity dendrogram of the four areas was calculated using the Dice-Sorensen index and UPGMA linkage method. The species indicator analysis was used to evaluate which species were characteristic of each area sampled. The eigenvalues of the first two axes were high indicating high species turnover. The correlations between environmental variables and plots indicated the formation of three groups: the first one formed by the SSF patch plots with high clay content; the second group formed by the vegetation corridor and inselberg plots, which did not separate as sharply as the first group, with a small separation in organic matter content; and the third group, formed by the riparian forest plots, which are located in areas of highest soil fertility, with high content of calcium, sum of bases and base saturation. The results showed high species turnover among areas, indicating that even though the areas are geographically close, the occurrence of inselbergs increased habitat heterogeneity, directly affecting the variation in species composition and community structure among areas.

FLORÍSTICA E ESTRUTURA DE FLORESTAS TROPICAIS SAZONALMENTE SECAS

A floristic and structural survey of the tree community in different environments (slope, Arboreal Caatinga and ecotone to savannah) were carried out in Cavernas do Peruacu National Park, North of Minas Gerais. We aimed to test the following hypotheses: 1 - There is floristic differentiation among the environments; 2 - All environments have the same structural characteristics. Venn Diagrams were used to compare both the shared and unshared species among the environments. Tree distribution by diameter classes for each environment was made by means of frequency histograms. An Indicator Species Analysis and usual phytossociological parameters were used. A total of 305 species were found, distributed in 173 genera and 48 families, of which 166 were found in the slope, 204 in the Arboreal Caatinga and 155 in the ecotone. 54 species were exclusive to the slope, 65 to the Arboreal Caatinga and 35 to the ecotone and only 69 species were common to all three environments. 1391 individuals were sampled, yielding an estimated density of 1340.62, 1765 and 1280 individuals.ha-1 respectively for the slope, Arboreal Caatinga and ecotone. The basal area reached 47.64, 30.05 and 23.29 m2.ha-1, respectively for the slope, Arboreal Caatinga and ecotone. The Shannon diversity index and Pielous evenness were, respectively, 3.49 and 0.80 for the slope, 3.74 and 0.84 for the Arboreal Caatinga and 3.61 and 0.85 for the ecotone. The Arboreal Caatinga and the slope presented a gradual decrease in frequency towards the higher diameter classes whereas the ecotone tended to follow a normal distribution.