Waldir Mantovani

Effects of habitat fragmentation on plant guild structure in the montane Atlantic forest of southeastern Brazil

Abstract Habitat fragmentation is a major cause of biodiversity erosion in tropical forests. The Brazilian Atlantic forest has both high species richness and a long history of anthropogenic disturbance, beginning with colonial agriculture in the sixteenth century. Here we examine the species composition and guild structure of woody plants within five montane Atlantic forest fragments of the Tiet River basin, State of Sao Paulo, southeastern Brazil, ranging from 5 to 7900 ha in area. We found a negative relationship between fragment size and the relative importance of tree and shrub species that (1) depend on abiotic modes of seed dispersal, (2) are shade-intolerant, and (3) occupy the forest canopy. As fragment size decreased, there was a marked rise in the relative importance of ruderal species, primarily in the Compositae, Euphorbiaceae, Solanaceae, and Leguminosae. There also was a 9% average decline in smaller fragments in relative importance of Myrtaceae, Lauraceae, Sapotaceae, and Rubiaceae, which are the main sources of fleshy fruits for vertebrate frugivores in these forests. Our results suggest that predictable shifts in plant guild structure occur as tropical forest fragments are reduced in size, and that small fragments may become dominated by edges and the surrounding habitat matrix. We suggest that small forest fragments will be unlikely to preserve intact plant and animal assemblages of Brazils Atlantic coastal forest

A regeneração de uma floresta tropical montana após corte e queima (São Paulo - Brasil)

Slash-and-burn has been the main kind of disturbance in the Atlantic montane forest. We analyzed the change in vegetation structure, woody species composition, species richness and diversity and plant guild composition after the cutting and burning of a mature forest. According to our results the rate of vegetation change is related to the forest attribute analyzed. In the first moment, the disturbed forest had the species richness and diversity restored, followed by plant guild composition, species composition and finally its physical structure. A forty year old forest site showed between 38.8% and 117.1% of the values recorded in the mature site, suggesting that this forest regenerates following patterans observed in other tropical forests. In addition to disturbance intensity, this montane forest has particular features as the average size of diaspores and tree species richness, which are thought to provide this forest higher resilience. Changes in woody species composition can be described by successional models formed by three or four stages, depending on the disturbance intensity. Models are characterized by pioneer species of Imperata, Pteridium, Baccharis, Tibouchina and Alchornea genera.

A riqueza de espécies arbóreas na floresta atlântica de encosta no estado de São Paulo (Brasil)

The atlantic forest in Sao Paulo state, has been described in the scientific literature as having high floristic diversity. Such statement is based on data and conclusions of local floristic and phytosociological studies. However, the studies supporting this idea seldom give a clear definition of the plant group analysed, the scale of the study, nor, most significantly, the forests used for comparisons. Here we compare woody species richness data (³ 2.5 cm dbh) from the atlantic forest in Sao Paulo to similar data from other neotropical forests. Thereafter, we discuss the major relationships between historical and ecological processes and woody species richness in neotropical forests. Neither data on woody species richness nor characteristics of latitude, altitude, rainfall and soil in the atlantic region is able to support the idea of high woody species richness in the Sao Paulo atlantic forest. Studies using comparable data sets are required in order to characterise woody species richness in all types of the atlantic forest, as well as to suggest the mechanisms responsible for plant richness in different scales.

The soil seed bank during Atlantic Forest regeneration in Southeast Brazil

A survey was conducted to determine the density and species composition of viable seeds buried in four stands of a tropical montane forest at Parque Estadual Intervales, Brazil. The objective was to understand: (1) how numbers and composition of the soil seed bank change as the forest regrows, and (2) how such changes affect the species available for regeneration if forests of different ages are cut down. In each forest stand (5, 18, 27-yr-old and a mature forest), 57 soil samples were collected (0-2.5 and 2.5-5 cm deep). Viable seed density of herbaceous species ranged between 11,003 seeds. m-2 (5-yr-old vegetation) and 482 (mature forest), and between 25 (5-yr-old vegetation) and 389 seeds. m-2 (mature forest) for woody plant species in the 0-5 cm soil layer, suggesting a decrease in seed stocks in the course of forest regeneration. Seeds buried in the 0-2.5 cm soil layer represented between 56.9% and 67.4% of all viable seeds. Most of the viable seeds belonged to weeds of Asteraceae, Poaceae, Malvaceae and Solanaceae. The results provide evidence that, in forests of different ages, the soil does not store seeds of the same key ecological groups involved in the regeneration of Atlantic forest. Allochthonous seeds from remaining patches of forest, as well as their vertebrate dispersers, are needed for forest regeneration since the soil seed bank does not store large seeds of shade-tolerant species.

Clareiras naturais e a riqueza de especies pioneiras em uma floresta Atlantica montana

Treefall gaps have been considered a mechanism for the maintenance of tree and shrub species diversity in tropical forests as they represent an essential site for the regeneration of pioneer plants. In a site of the Atlantic montane forest, Southeastern Brazil, we sampled all woody individuals taller than 1 m at thirty treefall gaps (30.3-500.5 m2). Two hundred and twenty tree and shrub species were sampled, where 24% were considered pioneers. Among pioneers, 88.7% were considered as short-lived, and 11.3 as large pioneers. Species of Miconia, Leandra and Rapanea genera represented 49% and 62.1% of pioneer species and individuals sampled. In this forest, gap age, gap area, canopy height and gap area covered by bamboo species explained between 20% and 73% on characteristics of gap colonization by pioneer species. We have found evidence that in the Atlantic montane forest: (1) at a landscape level there is a high richness of short-lived pioneer species such as those established in open habitats like edge streams and open forests on top mountains; (2) species of bamboo and bamboo-like species affect negatively the density, the diversity and the local richness of pioneer species, filling up their niche; and (3) ecological factors as few large gaps area responsible for the low local richness of pioneers in this forest.

Colonização de clareiras naturais na floresta atlântica no sudeste do Brasil

ABSTRACT - (Treefall gaps colonization in the southern Brazil coastal forest). The natural plant colonization was analyzed in 23 treefall gaps (34-256 m2) of two forest sites in the Atlantic coast southern Brazil. In both plots, small gaps (< 150 m2) were more abundant, comprising the largest area covering this type of disturbance (100-66%). Treefall gaps shown a common colonization pattern, where shade tolerant species were more abundant and frequent than shade intolerant ones. Relationships between gap area, guild composition and abundance of dominant species were not observed. The results suggest that the Atlantic forest has a reduced richness of shade intolerant species, mainly the large pioneer ones. The gap area is not the best predictor of floristic and ecological composition in treefall gaps.

O Banco de sementes de um trecho de uma floresta Atlântica montana (São Paulo - Brasil)

Soil seed bank of tropical forests is involved in the establishment of ecological groups and in woody species richness restoration during forest regeneration, after natural or antropic disturbances. In order to analyze the seed bank composition in a tropical montane forest, Southeastern Brazil, 57 soil samples were collected, inside a 2-hectare forest plot, representing 28,500 cm3 of collected soil. Along 17 months, 497 seeds germinated, 65% between 0 and 2.5 cm depth. They represented a density of 872 seeds/m2. The seed bank analyzed is characterized as having two components: one composed by 66 herbaceous taxa, belonging to families with high richness of pioneer species; and another composed by 19 pioneer shrub and tree species, most of them with diaspores shorter than 1 mm length. The results found in the study site suggest that in the Atlantic montane forest soil seed bank can be important for the establishment of woody species, which form ecological groups involved in forest regeneration, following slash-and-burn. After treefall gaps, seed bank is probably responsible for the establishment of Melastomataceae species, the richest and more abundant group of pioneer species sampled in gaps.

Estrutura do componente arbustivo-arbóreo da floresta atlântica de encosta, Peruíbe, SP

In this study the structure of the sub-montane Atlantic tropical rain forest tree and shrub component in different size classes was compared and their regeneration dynamics was discussed. The plants in each size class were sampled in plots of different size: Class I (individuals £15cm tall) in 250 1x1m plots taken in five main samples of 50 units, at three-months intervals, between July/95 and July/96; Class II (individuals >15cm and £ 1,3m tall) in ten 2,5x5m plots; Class III (individuals > 1,3m tall and < 5,0cm DBH) in ten 5x10m plots and Class IV (individuals³ 5cm DBH) in ten 10x20m plots. The highest diversity was found in intermediate size classes was due to a more even distribution of individuals among species. These classes had also the highest values of quantitative and qualitative species similarity indices. The majority of the species and the individuals were secondary-climax and under-story, suggesting that the present forest structure have favored the regeneration of these plant groups.

O método de pontos

The point method has been utilized in many situations, with or without modifications; it has also been compared to other methods and critically discussed. A review of the literature reveals the advantages (speed precision, minimum disturbance of the stand) and disadvantages (dependence on diameter of the needle, wind action). A new index is introduced and discussed. It is referred to as the cover index (CI) and is obtained by summing absolute frequency, which represents cover, and absolute vigor, which is associated with biomass.

MATURAÇÃO E DISPERSÃO DE MICONIA CINNAMOMIFOLIA (DC.) NAUD. NA RESERVA BIOLÓGICA DE POÇO DAS ANTAS, MUNICÍPIO DE SILVA JARDIM, RJ, BRASIL.

This paper evaluates the physiological maturation of seeds of Miconia cinnamomifolia (DC.) Naud. ¾ from an ecological point of view, i e., ripening processes associated to fruit dispersal. During two consecutive years seed rain samples were analysed and local seed production evaluated. Our results demonstrated that both green and black fruits have viable seeds during the whole harvest period (7-8 months). Fruit maturation is irregular in the canopy and in each inflorescence. Fortnightly harvests of target trees, observed from blooming to fruiting, reveal an intense predation of the black fruits. Seed physiological maturity could be associated to the middle of the harvest, when seed moisture is low and seed germination is high. Germination and seed moisture are good indicators of physiological maturation of this species; fruit color cannot be used as a good indicator, because both greenish and black fruits germinate equally well. Maturation percentage, i. e., the ratio of green and black to fruits totals proved to be a good indicator of maturity for Miconia cinnamomifolia, although the intense predation of black fruits at the end of the crop could obscure the results.