Semideciduous Forest In Southeastern Brazil Research Articles

Human impacts affect tree community features of 20 forest fragments of a vanishing neotropical hotspot.

The loss in forest area due to human occupancy is not the only threat to the remaining biodiversity: forest fragments are susceptible to additional human impact. Our aim was to investigate the effect of human impact on tree community features (species composition and abundance, and structural descriptors) and check if there was a decrease in the number of slender trees, an increase in the amount of large trees, and also a reduction in the number of tree species that occur in 20 fragments of Atlantic montane semideciduous forest in southeastern Brazil. We produced digital maps of each forest fragment using Landsat 7 satellite images and processed the maps to obtain morphometric variables. We used investigative questionnaires and field observations to survey the history of human impact. We then converted the information into scores given to the extent, severity, and duration of each impact, including proportional border area, fire, trails, coppicing, logging, and cattle, and converted these scores into categorical levels. We used linear models to assess the effect of impacts on tree species abundance distribution and stand structural descriptors. Part of the variation in floristic patterns was significantly correlated to the impacts of fire, logging, and proportional border area. Structural descriptors were influenced by cattle and outer roads. Our results provided, for the first time, strong evidence that tree species occurrence and abundance, and forest structure of Atlantic seasonal forest fragments respond differently to various modes of disturbance by humans.

Floral biology and breeding system of Bauhinia forficata (Leguminosae: Caesalpinioideae), a moth-pollinated tree in southeastern Brazil

Floral biology and breeding system of Bauhinia forficata (Leguminosae: Caesalpinioideae), a moth-pollinated tree in southeastern Brazil. Bauhinia trees have a wide variety of pollination and breeding systems that are affected by geographic distribution. Bauhinia species with nocturnal anthesis are usually chiropterophilous and/or sphingophilous. B. forficata Link has floral features that are typical of the sphingophilous condition and this report describes the floral biology, pollination, and breeding system of a population of this species in a small fragment of semideciduous forest in southeastern Brazil. Flowers lasted 18 h, anthesis started at dusk, and pollen release and nectar production occurred at 8:00 and 10:00 pm, respectively. Flowers were protandrous and the stigma became receptive around 11:00 pm with the bisexual phase ending at 12:00 am. Nectar was produced continuously; the mean total nectar volume/flower was 15.11 μL and the mean total nectar concentration was 25.9 %. B. forficata is a strictly sphingophilous species that is pollinated exclusively by Manduca sexta L., the body morphology and behavior of which favor pollen transfer. Visitation by the bees Eulaema nigrita Lepeletier and Xylocopa brasilianorum L. (Apidae) occurred in the morning, but these species were considered occasional and not legitimate pollinators. Despite the geographic distance separating the Brazilian B. forficata from the Venezuelan B. aculeata, both species show very convergent pollination systems but differs in their faunal composition. B. forficata is homomorphic and predominantly self-incompatible; cross-pollination produces twice as much fruit as natural open pollinations, indicating a pollen limitation and relative inefficiency of the pollinator, the latter effect may reflect habitat disturbance that favors geitonogamous pollination and decreases the efficiency of pollination. More studies are necessary to investigate the relationship between habitat disturbance and geographic distribution on the pollination and breeding systems of Bauhinia species.

Maximized sampling of butterflies to detect temporal changes in tropical communities

There are few papers describing long-term fluctuations and general patterns of temporal diversity in butterfly assemblages in the Neotropical region. The present paper presents a long-term study on the variation in richness and composition of butterflies in a fragment of semi-deciduous forest in Southeastern Brazil, and examines the viability of using maximized butterfly transect counts as a methodology to rapidly and adequately access the local characteristics of butterfly communities. Based on the eight annual standard lists, 518 species in six butterfly families were recorded, representing 74 % of the total butterfly fauna known from the study site. Hesperiidae was the richest family (248 species), followed by Nymphalidae (154), Lycaenidae (49), Riodinidae (29), Pieridae (26), and Papilionidae (12). The accumulation curves show that 8 years of sampling were not enough to result in stable species totals for all butterfly families, especially Hesperiidae and Lycaenidae, which are still increasing in number of species. A great similarity in species composition was observed among all the years (54 %). Comparing the similarity between two standard lists at different time intervals (from 1 to 8 years), a clear pattern of increasing dissimilarity was observed in most families. Our results show that the maximized sampling method is effective in revealing temporal patterns of diversity across several years and could be valuable in monitoring temporal variation in butterfly assemblages for conservation purposes, since the obtained standard lists can be successfully compared to temporal patterns over large periods of time.

Functional groups in a semideciduous seasonal forest in Southeastern Brazil

This study was carried out in a semideciduous forest in Southeastern Brazil. Five ecological attributes were used to define the functional groups: dominant stratum of the species, light demand of the plant, seed dispersal, likely pollinator, and deciduousness. The groups were formed through a species matrix and its attributes, and they were delimited according to the Jaccard similarity coefficient and a dendrogram generated by the group average (UPGMA). The analysis used was satisfactory, indicating the formation of four coherent groups with distinct functions both with regard to the community and the ecosystem. The results indicate a tree community in a late successional stage, with relations between flora and fauna species.

Arthropod recolonization in the restoration of a semideciduous forest in southeastern Brazil

The use of arthropods for monitoring habitat changes has grown widely in the last decades. In Brazil, however, most of the studies in restored areas have involved only vegetation changes. The present study aimed at investigating recolonization patterns of epigeic arthropods in recently restored sites of semideciduous forests in southeastern Brazil. We compared the community structure of adjoining sites 5, 17, 29 and 36 months old with that at a nearby forest remnant (reference site). We also determined the most abundant species and looked for ecological indicator species of each site age. Arthropods were sampled using pitfall traps, and their assemblages were described and compared with multi- and univariate statistical methods. Species abundance and richness equivalent to the reference site were reached at five months after planting, however species composition was very distinctive not only in relation to the reference site, but also among restored sites. Some of the main species found in this restoration stage are common in agroecosystems or cerrado vegetation. Nevertheless, there was a clear trend of arthropod fauna in restored sites moving toward the fauna in the forest remnant over time. Our results also highlighted ants and termites because of their abundance and ants because of their high value as ecological indicators of restoration age.

Repeated disturbances and canopy disturbance regime in a tropical semi-deciduous forest

Abstract:The canopy disturbance regime and the influence of gap methods on the interpretation of forest structure and dynamics were evaluated in a tropical semi-deciduous forest in south-eastern Brazil. We encountered a gap density of 11.2 gaps ha−1and an average size which varied from 121 to 333 m2depending on the gap delimitation method considered (minimum gap size was 10 m2). Although average size was slightly higher, the median value obtained (78 m2) was comparable to other tropical forest sites and the gap size-class distribution found supported the pattern described for such forest sites. Among 297 gap makers, snapping and uprooting were the most common modes of disturbance. The number and basal area of gap makers were good predictors of gap size. Almost 25% of all gaps suffered from repeated disturbance events that brought about larger gap sizes. Such processes, along with delimitation methods, strongly influenced the estimation of turnover rate and therefore the interpretation of forest dynamics. These results demonstrated the importance of further studies on repeated disturbances, which is often neglected in forest studies.

Effects of Patch Size and Floral Herbivory on Seed Set in Trichogoniopsis adenantha (Asteraceae) in Southeastern Brazil1

ABSTRACTThe effects of patch size and floral herbivory on reproductive success of Trichogoniopsis adenantha (Asteraceae) were studied in a semideciduous forest in southeastern Brazil. Plants in large patches and capitula not attacked by endophagous insects had higher seed set. The consequences of living in large or small patches for plant reproductive success are discussed.

Population dynamics, age structure and sex ratio of the bromeliad-dwelling jumping spider, Psecas chapoda (Salticidae)

In this study, the population fluctuations, phenology and sex ratio of the bromeliad-dwelling jumping spider Psecas chapoda were investigated in an area of semi-deciduous forest in south-eastern Brazil. Psecas chapoda occurred and reproduced on Bromelia balansae (Bromeliaceae) throughout the year. The number of egg sacs increased at the beginning of the rainy season (September to December), but the population size and phenology were stable over time and correlated weakly with rainfall and temperature. The principal factor affecting the dynamics of P. chapoda was the blooming of B. balansae, which expelled spiders because of the drastic change in plant architecture. Male spiders were more frequent than females during the juvenile phase, whereas females were more frequent than males during the subadult and adult phases, suggesting a sex ratio that favoured males. The biotic and abiotic factors that influence the population dynamics and sex-dependent vulnerability determination are discussed.

Phenology, sex ratio, and spatial distribution among dioecious species of Trichilia (Meliaceae).

The flowering, sex ratio, and spatial distribution of four dioecious species of Trichilia (Meliaceae) were studied in a semi-deciduous forest in southeastern Brazil. All reproductive trees (T. clausseni, T. pallida and T. catigua) with dbh > or = 5 cm within a 1-ha plot were collected, sexed, mapped and, for individuals of each species, the distances to the nearest neighbour of the same and opposite sex were measured. For the shrub species T. elegans (dbh < 5 cm), all reproductive individuals were sampled randomly in 10 samples of 10 x 10 m. The reproductive phenology was observed at weekly to monthly intervals from May 1988 to January 1990. The species are strictly dioecious, did not present any sex-mixed trees or sex switching during the study, and sex ratio did not differ significantly from 1 : 1. The size distributions and the relative size variation were not significantly different between sexes. There was no significant segregation or clumping between individuals of either sex and no fruit production without pollination. Onset of flowering and flowering peak were synchronous between male and female plants for all species studied. Flower synchrony was related to outcrossing and pollinator attraction rather than climatic factors.

Effects of flooding regime and woody bamboos on tree community dynamics in a section of tropical semideciduous forest in South-Eastern Brazil

The influence of a population of the understorey woody bamboo Merostachys riedeliana and different flooding regimes on tree community dynamics in a section of tropical semideciduous forest in South-Eastern Brazil was examined. A forest section with an area of 1.6 ha composed of 71 adjacent plots was located on a slope ending at the river margin. The section was divided into five topographical sectors according to the mean duration of river floods. In 1991 and 1998 all trees with a diameter at the base of the trunk ≥ 5 cm were measured, identified and tagged, and all live bamboo culms were counted. Annualised estimates of the rates of tree mortality and recruitment, gain and loss of tree basal area, and change in bamboo density were calculated for each of the 71 plots and five topographical sectors as well as for diameter classes and tree species. To segregate patterns arising from spatially autocorrelated events, geostatistical analyses were used prior to statistical comparisons and correlations. In general, mortality rates were not compensated by recruitment rates but there was a net increase in basal area in all sectors, suggesting that the tree community as a whole was in a building phase. Tree community dynamics of the point bar forest (Depression and Levee sectors) differed from that of the upland forest (Ridgetop, Middle Slope and Lower Slope sectors) in the extremely high rates of gain in basal area. The predominant and specialised species, Inga vera and Salix humboldtiana, are probably favoured by relaxed competition in an environment stressed by long-lasting floods. In the upland forest, mortality rates were highest at the Middle Slope, particularly for smaller trees, while recruitment rates were lowest. As bamboo clumps were concentrated in this sector, the locally higher instability in the tree community probably resulted from the direct interference of bamboos. The density of bamboo culms in the upland forest was negatively correlated with the rates of tree recruitment and gain in basal area, and positively correlated with tree mortality rates. Bamboos therefore seemed to restrict the recruitment, growth and survival of trees.

Seed bank and seed rain in a seasonal semi-deciduous forest in south-eastern Brazil

To examine the influence of seasonality on the abundance and composition of species in the community, we studied the seed rain and the seed bank in a seasonal, semi-deciduous forest in south-eastern Brazil. Soil samples (depth 3 cm, 0.25 m2) were collected within a 1-ha plot in the dry seasons of 1996 and 1997 and the rainy season of 1997 (84 samples per collection). Thirty-five seed traps (0.25 m2 each) were placed randomly in the forest from March 1997 to February 1998. The greatest density of seeds in the soil occurred in samples collected during the rainy season, the period which coincides with the main fruiting period in this forest. The Sørensen similarity index values for the seed bank composition among the three periods were high (&gt; 0.50). The fallout of propagules was strongly seasonal, with more than half of the annual total number of seeds being caught in the two months around the end of the dry season and beginning of the rainy season. The mean density of seeds in the soil bank was nearly 86% lower than the seed rain density. There was no clear evidence of seasonal effects on species density and richness in this forest.

Pollination Biology of Piperaceae Species in Southeastern Brazil

Phenology, floral biology and breeding system are described for 14 Piperaceae species at two sites covered by semi-deciduous forest in southeastern Brazil. Flowering occurred continuously throughout the year, with a peak during the windy months. All species had minute odorous and nectarless flowers visited by insects; five of them showed a substantial degree of self-compatibility, and one was andromonoecious. Seven species were wind pollinated, and three were exclusively pollinated by insects. Flower visitors were mainly hoverflies and bees.

Effects of past disturbance and edges on tree community structure and dynamics within a fragment of tropical semideciduous forest in south-eastern Brazil over a five-year period (1987–1992)

Tree community structure and dynamics of a 5.8 ha fragment of montane semideciduous forest in south-eastern Brazil are described based on two successive surveys of trees with dbh ≥5 cm carried out in 1987 and 1992 in 126 20 × 20 m quadrats. The main purpose was to assess whether the spatial variation of dynamic and structural variables were related to edge-effects and past disturbance regimes. The totals for the two surveys were, respectively, 6528 and 6770 trees, and 94.89 and 108.53 m2 of basal area. The forest fragment was at an aggrading sylvigenetic phase, indicated by an overall net increase in density and basal area, and by a declining proportion of trees of smaller size. The overall annual mortality and recruitment rates were 2.6% and 3.0%, respectively. The dynamic process, however, was strongly affected by spatial heterogeneity. The more severely disturbed sectors had lower average canopy heights and basal areas per hectare, and higher tree densities, proportions of smaller trees, and relative area of canopy gaps. They also had higher mortality and recruitment rates, resulting in higher turnover rates compared to the sectors which suffered only moderate disturbance regimes. Edge sectors were also affected by different past disturbance regimes. However, they stood out by having a particularly high frequency of liana tangles and the highest rates of net increase both in density and basal area. A canonical correspondence analysis indicated that the effects of past disturbance regimes and edges were highly related to the species distribution in the area. Pioneer species were concentrated on the edges and more severely disturbed sectors, shade-tolerant species were particularly more abundant on the moderately disturbed sites, while light-demanding ones were more widely distributed. Tree community structure was also undergoing important changes, with less common species enjoying higher recruitment rates and density increase compared to the more common ones. Shade-tolerant species were increasing in relative abundance and had comparatively lower mortality rates and higher recruitment rates. On the other hand, pioneer species were under retreat, with a decreasing relative abundance, higher mortality rates and lower recruitment rates. Nomenclature: Oliveira-Filho et al. 1994a,d.

Tree species distribution along soil catenas in a riverside semideciduous forest in southeastern Brazil

Summary The relationships between topography, soil taxonomic categories and tree species distribution were analysed in a riverside semideciduous forest on the margins of the Rio Grande, in Conquista, state of Minas Gerais, Southeastern Brazil. The forest was sampled by two transects made up of 50 contiguous 15 × 15 m2 quadrats (total 1.125 ha). Each transect started at the river margin and extended upslope so that they could include two soil catenas: the first with the sequence Ustifluvent, Haplustox and Ustorthent, and the second with Ustifluvent followed by Haplustult. A quick but more extensive survey was carried out in the whole forest fragment covering the same soil habitats in order to assess the extension of soil-species relationships found in the transects. A canonical correspondence analysis indicated that the species’ abundance distribution was significantly correlated with the soil habitats. Differences in soil drainage classes among the soils rather than their chemical properties appeared to be the leading factor: tree species distribution was strongly correlated with a wide hydrosequence ranging from poorly drained to strongly drained soils. The 55 most abundant species were classified according to their ecological group (regeneration guild) within the forest dynamics. A tentative ecological classification of those species combining their habitat preference in terms of soil drainage class and their growth strategy suggested that these factors play and important role in promoting the coexistence of tree species in that type of forest.

Ant Dispersal of Croton priscus (Euphorbiceae) Seeds in an Tropical Semideciduous Forest in Southeastern Brazil

Seed dispersal of C. priscus was studied in a semideciduous forest in S.E. Brazil. C. priscus is a pioneer tree, with abundant capsules containing three elaiosome-bearing seeds. The seeds are explosively dispersed and the mean ballistic dispersal distance for two trees were 3.2 and 3.4 m. The explosive ejection of seeds is followed by ant exploitation. Eleven ant species were attracted to the elaiosomes of the seeds, but only two species regularly removed seeds. On average, Atta sexdens and Pheidole sp. 1 move seeds 2.5 and 1.0 m, respectively. The ants usually deposit the seeds in the nest. The seed removal rate was 88 percent (N = 100) over the first 24 hr of exposure. Our results indicate that elaiosome removal by ants probably does not improve germination rates in C. priscus. Seeds without elaiosomes and seedlings of C. priscus were frequent on refuse piles of ant nest in the study area, suggesting that transport of the seeds by Attini and Pheidolini may provide beneficial effects in the Croton system.

Structure and Dispersion of Four Tree Populations in an Area of Montane Semideciduous Forest in Southeastern Brazil

Structure and Dispersion of Four Tree Populations in an Area of Montane Semideciduous Forest in Southeastern Brazil

Reproductive Phenology of Climbers in a Southeastern Brazilian Forest

The reproductive phenology of the entire dimber community (96 species of lianas and 40 species of vines) in a semideciduous forest in Southeastern Brazil (22o49'45t'S; 47006'33'W and 670 m altitude) was observed from March 1988 to February 1991. Phenological observations were made weekly by walking along a 10.5 km trail in the interior and at the forest edges of the Santa Genebra Reserve (SGR). The most species-rich families of dimbers were Bignoniaceae (22), Malpighiaceae (17), Sapindaceae (12) and Asteraceae (12). Flowering patterns for woody lianas and herbaceous vines differed. Lianas had two flowering peaks: a minor peak in March in the transition from wet to dry season, and a major peak in October during the transition from dry to wet season. The flowering peak for herbaceous vines was in April. Fruiting of lianas was highly seasonal, with one peak in the late dry season (JulyAugust). Fruiting for vines was less seasonal with a slight peak in March. These differences were consistent with the predominance of wind-dispersed fruits among lianas (72% of species) versus vines (52%). Low rainfall, high leaf fall, and strong winds during the dry season favor wind dispersal. More species of vines (40%) have animal-dispersed seeds than lianas (19%), and most vines fruited during the wet season. Phenological patterns of climbers and trees and treelets at SGR differed. The life form of lianas and their system of reserve economy may allow them to reproduce during periods unfavorable to trees. Displacement of peak flowering periods of trees and climbers pollinated by bees and small generalist insects may decrease competition for pollen vectors among species of these two groups of plants. Whereas the fruiting patterns of wind-dispersed trees and climbers at SGR were similar (most species fruiting during the dry season), animal-dispersed trees and treelets fruited throughout the year while animal-dispersed climbers exhibited a pronounced peak in late wet season. The distinct phenological patterns of climbers, generally complementary to those presented by trees, resulted in constant availability of flowers and fruits throughout the year and enhances the importance of this plant group in Neotropical forests.

Differentiation of streamside and upland vegetation in an area of montane semideciduous forest in southeastern Brazil

Summary The differences in plant community structure and soil properties between streamside and upland topographical sites were analysed in an area of montane semideciduous forest on the margins of the Camargos Reservoir, southeastern Brazil. The studied forest patch lies at the headwaters of two narrow streams and is surrounded by montane grasslands. The plant community was surveyed by one 30 × 150 m and one 30 × 165 m transects, both made up of 15 × 15 m contiguous quadrats. The first transect extended along one of the streams while the other linked the two streams by traversing the interfluve. Soil samples were collected from all quadrats and their texture and chemical properties were analysed in the laboratory. The streamside soils were tropical Podzolic Soils, characterised by clay depletion of the top layer with its accumulation in the deeper horizons. The upland soils were Cambisols, a 'maturing' soil type with no clear zonation. A canonical correspondence analysis indicated that the species' abundance distribution was significantly correlated with the two topographical sites as well as with some soil properties. The most abundant species appeared to vary from fairly exclusive streamside or upland preferentials to broadly indifferent for the two habitats. A tentative ecological classification of the 69 most abundant species according to their preference for streamside or upland habitat and to their growth strategy in the forest dynamics, is presented. An overall analysis of this classification along with the differences in soil properties between the two topographic sites gives evidence that the forest probably expanded from the two valley bottoms towards the upland sector occupying sites that were previously covered with montane grasslands.

Effect of flooding regime and understorey bamboos on the physiognomy and tree species composition of a tropical semideciduous forest in Southeastern Brazil

The interrelationship between river flooding regime, topography, soil properties and the distribution of tree and bamboo species was analysed in an area of tropical semideciduous forest on the margins of the Rio Grande, in Madre de Deus de Minas, Southeastern Brazil. A survey was carried out in a single forest plot (1.597 ha, 71 adjacent 225 m2 quadrats) located in the inner side of a river bend and extending from the point bar to the top of the slope. All trees (≥5 cm diameter at the base of the trunk) and bamboo culms were registered. Soil samples were collected and analysed for their properties and the river level was monitored during a two year period. In the point bar the forest was dominated by only two tree species, Salix humboldtiana and Inga affinis, that tended to occur in distinct areas. Differences in soil properties between these areas suggest variation in sedimentation dynamics. In the sloping part of the plot, a canonical correspondence analysis (CCA) indicated that the floristic composition was significantly correlated with three topographic sectors and their corresponding flood regimes. The Lower Slope corresponds to the sharp transition to the point bar forest, endures partial and annual floods and shows a very distinct flora that includes many light-demanding species. The Middle Slope is only occasionally reached by exceptional river floods and is characterised by a high density of the bamboo Merostachys neesii. The comparatively low density and basal area of trees, particularly for the smaller ones, provide evidence that the bamboos are problably interfering with the trees by restricting their recruitment. The Ridgetop lies entirely above the highest flooding level registered. The density of bamboos is lower and the understorey trees abundant.

Diet of the Scaly-Headed Parrot (Pionus maximiliani) in a Semideciduous Forest in Southeastern Brazil

The diet of the Scaly-headed Parrot (Pionus maximiliani) was studied during three consecutive years in a 250 ha semideciduous forest in southeastern Brazil. The parrots showed a generalist and seasonal diet. Seeds composed 70.4 percent of the diet of parrots, followed by flowers (20.3%), corn from plantations that surround the forest (7.7%) and fruit pulp (1.6%). In the dry season flowers constituted 38 percent of the diet and leguminous fruits comprised 41.2 percent of its diet. Parrots are important predispersal seed predators and have a high impact on the fitness of plants in semideciduous forests, due to their high consumption of seeds and flowers.