Yule Roberta Ferreira Nunes

Changes in tree and liana communities along a successional gradient in a tropical dry forest in south-eastern Brazil

We investigated changes in species composition and structure of tree and liana communities along a successional gradient in a seasonally dry tropical forest. There was a progressive increase in tree richness and all tree structural traits from early to late stages, as well as marked changes in tree species composition and dominance. This pattern is probably related to pasture management practices such as ploughing, which remove tree roots and preclude regeneration by resprouting. On the other hand, liana density decreased from intermediate to late stages, showing a negative correlation with tree density. The higher liana abundance in intermediate stage is probably due to a balanced availability of support and light availability, since these variables may show opposite trends during forest growth. Predicted succession models may represent extremes in a continuum of possible successional pathways strongly influenced by land use history, climate, soil type, and by the outcomes of tree–liana interactions.

Aspectos ecológicos da aroeira (Myracrodruon urundeuva Allemão- Anacardiaceae): fenologia e germinação de sementes

Myracrodruon urundeuva Allemao, especie arborea conhecida como aroeira, constitui-se em um importante componente das Florestas Estacionais Deciduais do norte de Minas Gerais. Apesar disso, a aroeira vem sofrendo um processo de exploracao intensa, de forma predatoria, o que vem causando a devastacao de suas populacoes naturais. Este trabalho teve como objetivo conhecer os padroes fenologicos reprodutivos e vegetativos, bem como a capacidade germinativa da aroeira, na Area de Preservacao da COPASA em Juramento, MG. Foram feitas observacoes fenologicas quinzenais, no periodo de janeiro/2002 a novembro/2003, de 20 individuos arboreos, sendo ainda coletadas sementes, submetidas a diferentes tratamentos de escarificacao tegumentar (mecânico, termico, quimico e controle). A especie apresentou as fenofases reprodutivas e vegetativas influenciadas diferencialmente pelas variaveis ambientais de precipitacao e temperatura. Na estacao seca ocorreram a floracao, frutificacao e queda foliar, e a estacao chuvosa favoreceu o brotamento da especie. A capacidade germinativa dos diasporos de aroeira variou entre os tratamentos utilizados, com potencial germinativo e velocidade de germinacao altos no tratamento-controle, indicando ausencia de dormencia. Nesse sentido, estudos basicos sobre as especies florestais ameacadas podem ser precursores de modelos e mecanismos para manejo e recuperacao de suas populacoes naturais.

Cerrado to Rupestrian Grasslands: Patterns of Species Distribution and the Forces Shaping Them Along an Altitudinal Gradient

Due to clear variations in a relatively small area, mountains represent natural laboratories for evolutionary and ecological studies. In a large degree, these variations are driven by changes in climate and soil that occur along altitudinal gradients and influence the ecology, evolution and geography of species. In spite of being old and eroded, the southern Brazilian mountains provide enough variation and heterogeneity to influence species distribution and diversity. The best-known Brazilian mountain range is the Espinhaco (the Backbone mountains). The Espinhaco is a large natural watershed divider of major ecological importance in eastern Brazil. The altitudinal gradient in the Espinhaco Mountains is low when compared to other tall mountains in the world as it only varies from ca. 650 to 2.072 m a.s.l. at the Sun Peak (Pico do Sol). This chapter synthesizes the results of 10 studies that have collectively examined the soil, climate to better understand patterns and processes associated with biodiversity of key groups of organism, including of plants, termites, dung beetles, ants, butterflies, arbuscular mycorrhizal fungi, insect herbivores and birds in an altitudinal gradient (from 800 to 1400 m a.s.l.) at Espinhaco mountain range. In this mountain range, the soils are primarily poor and the vegetation is dominated by rupestrian grasslands, and both are known to vary along the altitudinal gradient hence providing opportunities for variation in the associated organisms.

STRUCTURAL ASPECTS AND FLORISTIC SIMILARITY AMONG TROPICAL DRY FOREST FRAGMENTS WITH DIFFERENT MANAGEMENT HISTORIES IN NORTHERN MINAS GERAIS, BRAZIL 1

In order to produce useful knowledge to the initiatives of protection and management of forest fragments, more specifically for tropical dry forests which suffer with frequent anthropic activities, and due to the lack of specific studies, this article aimed describe the structure and the floristic similarity among three areas of dry forest with different management histories. The study was developed in Capitao Eneas municipality, Northern Minas Gerais, Brazil, where three fragments were evaluated, being one in regeneration for 30 years, another submitted to occasional fire and the third with selective cut in small scale. The sampling was developed through the point quarter method considering all the alive phanerophyte individuals with circumference at breast height (CBH) > 15 cm. In the three fragments, 512 individuals, distributed in 60 species, 47 genera, and 23 families were sampled. The most representative families were Fabaceae (26), Anacardiaceae (4), Bignoniaceae (3) and Combretaceae (3). However, fourteen families were represented by only one species. Only eight species were common to all fragments - Myracrodruon urundeuva standed out with 26.9% of all sampled individuals - while a great number of species were exclusive of each fragment. The floristic and structural differences between the fragments are possibly related to the history and intensity of management in each area besides the topography variations and the presence or absence of limestone outcrops. These results show the importance of each fragment, indicating that the loss of anyone would cause negative impacts on the regional flora and consequently to the associated biodiversity.

Phenology of Tree Species Populations in Tropical Dry Forests of Southeastern Brazil

Tropical dry forests (TDFs) are forest formations that occur in regions with two marked seasons (dry and wet) and are characterized by some degree of foliar deciduousness (Murphy & Lugo, 1986). Recent estimates show that 1,048,700 km2 of TDFs exist worldwide (Miles et al., 2006). The two largest continuous areas of this physiognomy are located in South America and include northeastern Brazil and the region incorporating southeastern Bolivia, Paraguay and northern Argentina (Miles et al., 2006).

STRUCTURE OF NATURAL REGENERATION IN RELATION TO SOIL PROPERTIES AND DISTURBANCE IN TWO SWAMP FORESTS

Veredas (palm swamps) is a type of vegetation associated with watercourses, characterized by the presence of Mauritia flexuosa palm trees. These systems are not well understood and suffer from high anthropogenic pressure. The aims of this study were to describe the natural regeneration of two swamp forests in vereda systems with different anthropogenic impacts and investigate if the variation in these plant communities are associated to edaphic conditions. The study was performed in preserved and impacted sites located in the Environmental Protection Area of the Pandeiros River in northern Minas Gerais. At each site, one hundred 25 m2 plots were established for surveying regenerating shrubs and trees (≥1 cm diameter at the base of the stem and < 3 cm diameter at breast height). Vegetation structure was evaluated by phytosociological parameters, similarity index, and size distribution of individuals. Regenerating strata was correlated with chemical and physical soil analyses. The vegetation at the preserved site was characterized by a higher number of individuals and a lower diversity but contained species that were typical of flooded areas. The results also showed differences in soil nutrient availability between sites that influenced the distribution of species at the two study sites.

Phenology of riparian tree species in a transitional region in southeastern Brazil

This study characterizes the phenological behavior of the most abundant species of riparian vegetation (Pandeiros river, southeast Brazil) in a transition region of Caatinga and Cerrado biomes and relates its phenophases to climatic variables. Among the ten most abundant species of each five sites studied between August 2008 through July 2009, individuals were marked for phenological monitoring, totaling 31 species and 964 individuals. For each sampled individual, the presence or absence of reproductive and vegetative phenophases was recorded and related to the climatic variables of precipitation, temperature, and relative humidity. The period with the greatest amount of vegetative and reproductive phenological activity was in the dry season. Among the climatic variables, the vegetative phenophases were most correlated by temperature, while the reproductive phenophases were most influenced by relative humidity. The species studied presented phenological behavior similar to their typical occurrence area, like in cerrado and caatinga phytophysiognomies, contradicting the phenological pattern expected for riparian forest. However, this behavior also demonstrated adaptations for survival in a transitional environment, leading to the formation of a phenological pattern that is unique to the riparian forest studied.

SOBREVIVÊNCIA E CRESCIMENTO DE SETE ESPÉCIES ARBÓREAS NATIVAS EM UMA ÁREA DEGRADADA DE FLORESTA ESTACIONAL DECIDUAL, NORTE DE MINAS GERAIS

This study aimed to evaluate the growth and survival of seven native tree species in different treatments in a degraded area at COPASA Reserve (Juramento, MG). Approximately 1.2 ha area was used, where 899 seedlings were planted of seven native species (Anadenanthera colubrina, Copaifera langsdorffii, Dilodendron bipinatum, Miracrodruon urundeuva, Pterogyne nitens, Schinopsis brasiliensis and Senegalia polyphylla) followed for 24 months. The area was divided into five plots of 0.24 ha, which represented the following treatments: (T1) plot sown with grass (Brachiaria sp.); (T2) plot where the pits were treated with soil conditioner; (T3) plot sown with grass and legumes (Cajanus cajan) together; (T4) plot sown with legumes; and (T5) control. The mortality percentage was higher in T2 and lower in T3, and the species C. langsdorffii (43.66%) and S. brasiliensis (11.64%) were the ones with higher and lower mortality rate, respectively. The growth (height and diameter) of seedlings was higher in T2 (24.32 ± 26.05 cm and 0.51 ± 0.37 mm; respectively) and lowest in T1 (10,82 ± 22,57 cm and 0,26 ± 0,27 mm; respectively). The species with the largest growth in height were A. colubrina and S. polyphylla, and D. bipinatum and S. brasiliensis showed the highest growth in diameter. Pterogyne nitens showed the lowest growth, and highest mortality, presenting low ability to establish in degraded environments.

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.

EFFECTS OF PRE-GERMINATION TREATMENTS AND STORAGE ON GERMINATION OF Astronium fraxinifolium SCHOTT (ANACARDIACEAE) DIASPORES

Este trabalho teve como objetivo avaliar a germinacao e a capacidade de armazenamento de diasporos de Astronium fraxinifolium. Para o experimento de germinacao, utilizaram-se seis tratamentos pre-germinativos: tratamento controle (diasporos intactos); diasporos imersos em agua a temperatura ambiente (25o C) por 5 min.; diasporos imersos em agua a 70° C por 5 min.; diasporos imersos em agua a 100° C por 5 min.; diasporos imersos em solucao de hipoclorito de sodio (1:1000) por 2 min.; e diasporos escarificados mecanicamente, com lixa no 80. Para determinar a capacidade de armazenamento, foram testados dois diferentes tipos de embalagem (saco de papel permeavel e vidro transparente) e duas condicoes ambientais (câmara fria e condicoes de laboratorio). Foram realizados testes de germinacao antes do armazenamento (tempo zero) e apos 60, 120, 180, 240, 300 e 360 dias de armazenamento. Os efeitos dos diferentes tratamentos pre-germinativos e das condicoes de armazenamento na germinacao dos diasporos foram avaliados por meio da ANOVA, seguida do teste de Tukey. Em relacao aos tratamentos pre-germinativos, foram observadas altas taxas de germinacao nos tratamentos com imersao em hipoclorito (98,0 ± 4,22%), controle (97,0 ± 4,83%), imersao em agua destilada a temperatura ambiente (96,0 ± 6,99%) e imersao em agua aquecida a 70oC (83,0 ± 29,08%). Dessa forma, os diasporos de Astronium fraxinifolium nao apresentaram dormencia. No armazenamento, os diasporos permaneceram viaveis durante todo o periodo de estudo, apresentando altas porcentagens de germinacao, com excecao do tratamento em saco de papel acondicionado em câmara fria, que perdeu a viabilidade no oitavo mes de armazenamento, nao sendo, portanto, um metodo de armazenamento recomendado para esta especie.