[Show abstract][Hide abstract] ABSTRACT: Estudos baseados nas relações entre os diferentes estratos da comunidade vegetal podem contribuir para o entendimento da dinâmica futura nas comunidades vegetais. Este estudo objetivou avaliar a composição florística, diversidade e estrutura nos estratos adulto e regenerante na Mata de Galeria do Capetinga na Fazenda Água Limpa, Distrito Federal. A mata foi alvo de distúrbios no passado, incluindo incêndios e consequente presença de espécies superdominantes. As árvores (DAP – diâmetro a altura do peito ≥ 5 cm) foram amostradas em 100 parcelas de 10 x 10 m, dispostas em quatro transectos, enquanto os regenerantes (DAP < 5cm) foram amostrados em duas categorias: arvoretas, indivíduos maiores que 1 m de altura, e mudas, indivíduos com até 1 m de altura, em subparcelas de 5 x 5 m e 2 x 2 m, respectivamente. Foi determinada a diversidade de Shannon (H’) para cada estrato e a similaridade entre os mesmos foi verificada por meio do índice de Chao-Sørensen. A categoria árvores apresentou 85 espécies, arvoretas 73 e mudas 51; a diversidade foi de 3,73, 3,76 e 3,20, respectivamente. Dentre as 85 espécies de árvores, 83% foram amostradas na regeneração em pelo menos uma das duas categorias. Apesar da elevada similaridade florística entre os estratos, diferenças nas proporções entre os grupos ecológicos foram registradas para as dez espécies mais abundantes em cada estrato. Este resultado indica um rearranjo estrutural do estrato adulto com redução na densidade das espécies pioneiras e consequente aumento das tolerante à sombra, desde que a ocorrência de distúrbios se mantenha reduzida.
[Show abstract][Hide abstract] ABSTRACT: Seasonally dry tropical forests (SDTFs) have high tree species richness and endemism,
whose dynamics and succession depend on natural regeneration (NR). To test whether NR
is influenced by the mature stratum and environmental variables, we compared structural
and floristic patterns of mature trees [Mt (DBH ≥ 5 cm)] with the NR of a SDTF on limestone
outcrops in Central Brazil. Additionally, we tested for effects of environmental variables on
species abundance in these different strata. Within NR categories [JuvA (total height < 100
cm) and JuvB (total height ≥ 100 cm and DBH < 5 cm)], we recorded 597 individuals in 69
angiosperm species. Within NR and Mt we recorded 110 species distributed in 33 families,
and 54 were common to both (~50% of total richness). Shannon diversity was 3.83, 3.13
and 3.33 for Mt, JuvA and JuvB, respectively. Besides the high number of exclusive species
recorded in Mt (23), JuvA (18) and JuvB (24), comparisons indicated high floristic similarity
(51%) between strata. Mt, JuvA and JuvB were influenced by different environmental variables,
indicating that species requirements change along the establishment process. This
highlights the importance of environmental variability for maintaining tree species diversity in
SDTFs, and the importance of this remnant for the conservation of SDTFs in Central Brazil.
[Show abstract][Hide abstract] ABSTRACT: Monodominant tropical forests occur on several continents, including the Brazilian Amazon. In this study, we tested the hypothesis that seedling escape from leaf herbivory contributes to the maintenance of the monodominant Brosimum rubescens forest. The study was undertaken both in a monodominant forest of B. rubescens and in an adjacent seasonal forest in the transitional zone between the Cerrado and the Amazonian forest biomes. Percentage of leaf area damaged and herbivory rates were evaluated on young and mature leaves of seedlings of Brosimum rubescens, Protium pilosissimum and Tetragastris altissima in the understory and in the gap between the monodominant and seasonal forests. Little evidence of any signiﬁcant relationship between leaf herbivory and seedling density indicates that the monodominant species does not follow the hypothesized pattern of an intensive herbivore attack in areas of higher seedling density. The escape of Brosimum rubescens from herbivore pressure under conditions of high seedling density may be part of a set of conditions that determine the maintenance of this monodominant forest.
[Show abstract][Hide abstract] ABSTRACT: Studies of temporal dynamics for grassland sites report that fire suppression plays a crucial role in floristic changes. The objective of this study was to verify whether after seven years without fire, communities showed variations in terms of composition, life forms, pollination and dispersal syndromes. The first survey (T0) was conducted from September 1999 to October 2000, while the second (T1) took place from August 2006 to August 2007. The floristic results in T1 were compared with the survey in T0 through the Sorensen similarity index and Chi-square tests. Over time, there were differences in the composition, life forms and pollination and dispersion syndromes. The evidence of changes suggests that the frequency of the fire regime can be considered the main agent for change in the flora of these communities.
[Show abstract][Hide abstract] ABSTRACT: This study described and compared the floristic similarity in four Deciduous Seasonal Forest fragments, and assessed the floristic relations between the tree (adult), the treelet and the sapling stratum. The fragments studied are distributed in Minas Gerais State and in Bahia State, Brazil. The vegetation sampling method followed the protocol of the "Rede de Parcelas Permanentes nos biomas Cerrado e Pantanal" for the tree, treelet and sapling strata. The floristic similarity between the fragments was obtained based on Jaccard and Czekanowski indices. Besides the similarity indices, Venn diagrams were drawn for the strata within each area. The four fragments and the three strata of each fragment presented low degrees of species sharing. The floristic differences among the strata may be due to environmental variations throughout time as well as the reproductive capacity of the species differentiated among the years. Besides the geographic distance (neutral theory), the environmental variations between the areas and the vegetation contacts (ecotones) with other biomes may have favored the occurrence of species adapted to the conditions of each fragment, which contributed to the distinct floristic composition.
[Show abstract][Hide abstract] ABSTRACT: This study was carried out on a fragment of semi-deciduous forest in Pirenópolis, Goias, Brazil and investigated the changes in the photon flux density in relation to silvicultural interventions that aimed at increasing growth of tree species but without allowing invasion by exotic species that could influence the dynamics of natural regeneration. The design was a randomized block in factorial, testing the differences between silvicultural treatments, seasons and heights in the understory (1.30 m versus at the ground level). We tested two intensities of selective cutting of individual trees and vines in the forest. The treatments were sufficient to alter the understory light, both in the dry season and rainy season, in agreement with the hypothesis tested. The shading in the control area was 97% in the rainy season and 86% in the dry season, showing significant differences with the shading associated with silvicultural treatments, which ranged from 93% to 94% in the rainy season and from 77% to 80% in the dry season. This study may assist this forest management system for semi-deciduous forests in Central Brazil, and should be linked to population studies and community, preserving the forest fragments found in the region and generating numerous environmental benefits and extra income for the rural population.
[Show abstract][Hide abstract] ABSTRACT: The study was conducted in a Brosimum rubescens Taub. monodominant forest in Nova Xavantina, Mato Grosso state (14 49.8 0 S and 52 9.6 0 W), in the transition zone between the Cerrado and Amazonian Forest in central Brazil. The structure and dynamics of the natural regeneration was compared over a five-year period to identify patterns that affect seedling establishment and explain the maintenance of B. rubescens dominance. We raised the following questions: how does the structure and dynamics of a mono-dominant forest regeneration vary over time? What patterns affect seedling establishment and help to explain the maintenance of the monodominance of B. rubescens? Natural regeneration was sampled in 30 plots of 1 m Â 1 m (seedlings), 2 Â 2 (saplings), 5 Â 5 (poles) and 10 Â 10 (treelets). In the first inventory, the natural regeneration structure was characterized by a higher concentration of individuals in lower height classes and the largest number of seedlings of B. rubescens may be related to rainfall distribution in previous years. Seedling establishment may be limited by drier periods such as "El Niño" events, or by specific light conditions reaching the forest floor. Formation of a persistent seedling bank may provide a competitive advantage for the regeneration of B. rubescens in conditions of gaps pre-opening thus contributing to monodominance maintenance.
[Show abstract][Hide abstract] ABSTRACT: A large number of studies describes the structure and composition of cerradão, however there is no standardization regarding data collection, rendering it difficult to conduct ample comparisons and the emergence of a structural and floristic profile for the cerradão. Our aim is to establish a structural-floristic profile of the cerradão woody component and verify the overlap of forest, savanna and generalist species. We conducted the vegetation survey in sites in six states: DF, MG, MS, MT, PI and TO. The cerradão did not present a homogenous structure or floristic consistency among sites, presenting itself as a heterogeneous phytophysiognomy. Structurally it presented great variations, with both open and closed formations (density 652-1732 ind. ha-1; basal area 12.83-22.45 m2 ha-1). Species richness varied from 49 (MS) to 129 (MT). Floristical variation and dissimilarity was strong among the six sites with only six species occurring in all sites, where as 184 species are exclusive to one site. Although species composition is comprised of a mixture of forest and savanna species, we detected a greater participation of savanna species, with the exception of the MT site that presented a larger proportion of forest species. The general floristic and structural dissimilarity pattern observed indicate a great heterogeneity of cerradão woody flora distribution following the general patter for the Cerrado biome.
Full-text · Article · Jun 2012 · Acta Botanica Brasilica
[Show abstract][Hide abstract] ABSTRACT: Cerradão vegetation shares many species with savanna and forest areas and is one of the most vulnerable phytophysiognomies in the Cerrado (Brazilian savanna) biome. The floristic composition of the Cerradão Biological Reserve was examined between September/2007 and November/2008. A total of 282 species distributed among 194 genera and 75 families were encountered, demonstrating proportions of 0.91 herbaceous species and 0.54 shrub species for each tree species. Fabaceae, Asteraceae, Rubiaceae, Poaceae, Myrtaceae, Malpighiaceae, and Melastomataceae were the most species-rich families. Fully 72.3% of the species of this dystrophic cerradão were shared by cerrado and forest vegetations, while 60.43% were shared by other cerradão sites, although the largest proportion of species (91%) were shared with cerrado sensu stricto. No species was found to be exclusive to this cerradão site, but approximately 95% of all species were native to the Cerrado biome.
Preview · Article · Dec 2011 · Brazilian Journal of Botany
[Show abstract][Hide abstract] ABSTRACT: The diversity parameters used to analyze community organization and floristics relationships can be used as a base to select priority areas for conservation. At the Paranã valley in northeastern Goiás State, Central Brazil, the seasonally dry tropical forests growing on limestone outcrops form a mosaic with the cerrado vegetation being preferential for conversion to cattle ranging and mining. Alpha (Shannon diversity index) and beta (Sørensen and Czekanowski similarity coefficients) diversity were analyzed for the tree layer of six fragments of dry forests on limestone outcrops aiming the definition of priority areas for conservation. Based on the results, three of the six fragments analyzed were selected: (1) Nica farm - Guarani (GUA) which showed the highest values of alpha and diversity plus density of threatened vegetation. (2), Forquilha farm - Monte Alegre (MAL) with high values of alpha and beta diversity and (3) São José farm - São Domingos (SD_SJ) with the highest beta diversity, therefore, the most dissimilar. This method detected well the variations in floristics and structure of a physiognomy along a geographical gradient and seems promising for the definition of priority areas for conservation.
No preview · Article · Sep 2011 · Bioscience Journal
[Show abstract][Hide abstract] ABSTRACT: Dendrometer bands are used to make repeated measurements of tree radial growth. Two types of dendrometers are used worldwide, the industrial and the homemade. Homemade dendrometers prevail in Brazilian forestry studies, but researchers have trouble constructing and installing them. An easier solution is to use industrial dendrometer bands, but they are not produced in Brazil and, therefore, are expensive and might not be appropriate for local environmental conditions. We analyzed trunk growth measurements each month (from February 2008 to January 2009) using both industrial (imported) and homemade (national components) dendrometer bands installed on 20 trees of Acacia tenuifolia in a seasonally dry forest on limestone outcrops in central Brazil. Cost-benefit comparative analysis of measurements and prices indicates that homemade dendrometer bands have all benefits, and none of the problems, of the imported industrial dendrometer bands, such as the following: (1) similar precision of measurements (correlation analysis: r > 0.930, P < 0.01; permutation t-test: P > 0.55), (2) much lower costs (10 to 15 times cheaper), (3) easily manipulated and installated in the field, and (4) absence of some damage to tree trunks that are caused by industrial dendrometers.
[Show abstract][Hide abstract] ABSTRACT: This study evaluated the floristic and structural dynamics of a community of herbaceous-shrub species in an area of moist grassland in Alto Paraíso de Goiás. The first inventory was undertaken in 2000 (T0) and the second in 2007 (T1). Shannon's diversity between the periods was compared by Hutchesonśs t-test, and the fl oristic similarity by the Chao-Sørensen similarity index. Floristic composition and cover, between periods and lines, were evaluated by detrended correspondence analysis (DCA). We sampled 98 species, 88 at T0 and 67 at T1; 31 were unique to T0 and 10 to T1. Floristic diversity in the community was high in both periods, but different between them (t = 7.12, p <0.001), due to variation in species number and coverage. Similarity between the two surveys was high (Chao-Sørensen CI = ± 0.841 ± 0.074). The DCA ordination indicated relationships between the floristic composition and cover with a gradient of moisture and organic matter in the soil identified in T0. There were changes in the lines in the seasonal zones, which became more similar in those constantly saturated with water. During an interval of seven years the moist grassland showed changes in floristic composition and mainly in structure due to increased cover of the clumped tussock perennial species, which were favored by higher soil moisture due to high rainfall in the region.
Full-text · Article · Jun 2011 · Acta Botanica Brasilica
[Show abstract][Hide abstract] ABSTRACT: The natural regeneration in forest environments is dynamic, variable in space and time and it is in the development cycle of forests. In seasonal tropical forests, due to seasonal climatic changes, natural regeneration depends mainly on availability of soil moisture, which affects patterns of seed production and germination, survival and development of seedling as well. The objective of this study was to analyze the dynamics of natural regeneration in a seasonal semideciduous secondary forest in Pirenópolis, Goiás, Brazil, by analyzing the changes in floristic composition of seedlings and small trees over time and relating them to environmental factors of plots in the study area by using Canonical Correspondence Analysis (CCA). The results indicated that seedlings were more dynamic than small trees mainly because of climate. This occurred because of the greater susceptibility of the seedling to soil water stress and the increase of solar radiation and temperature in the dry season. It was found a high floristic similarity (± 50%) among population of natural regeneration and the tree community, indicating an advanced stage of natural regeneration of the forest, with Diversity Index higher than 3.0 nats.indv -1. Canonical Correspondence Analysis grouped the species according to the environmental gradient of moisture and shade versus soil cover, placing near to each other, species of humid environments versus species of typical cerrado dry environments.
[Show abstract][Hide abstract] ABSTRACT: Initial development of Dipteryx alata Vogel and Myracrodruon urundeuva Allemão planting in enrichment in a semideciduous secondary forest. This study evaluated the initial development of Dipteryx alata and Myracrodruon urundeuva planted in enrichment system in a secondary semi-deciduous seasonal forest along an environmental gradient. The survival and growth in height and diameter were made 12 months after planting. There was 10% mortality for M. urundeuva and 45% for D. alata. Twenty-five months after replanting, the mortality was 15% for both species. There was no association between mortality of the species and environmental gradient (χ 2) and also there were no statistical differences in diameter increment between species (ANOVA). Myracrodruon urundeuva and D. alata grew on average 0.96 and 0.52 mm.yr -1, respectively. The average growth in height was 9.6 and 4.0 cm.yr -1 for M. urundeuva and D. alata, respectively, statistically different. The smaller growth in height of D. alata versus M. urundeuva should not be used determine the adaptation to the environment and may be linked to different patterns of growth, adaptation strategies, or different ecological needs, showing differences in efficiency in the use of available resources. This study highlighted the potential use of these species in enrichment systems.
No preview · Article · May 2011 · Bioscience Journal
[Show abstract][Hide abstract] ABSTRACT: The goal of this work was to investigate the floristic and structural changes in a seasonally dry deciduous forest on limestone outcrops in the municipality of Iaciara (14º03'53"S; 46º29'15"W), northeast Goiás, Central Brazil, after a 6-year interval (2000-2006). Due to the biotic limitations of marked seasonality and stressful edaphic conditions (rocky and shallow soils), we hypothesized that the tree community would show rapid dynamics, but without pronounced changes in floristic composition and structure. Changes in floristics and structure were investigated through comparisons between two consecutive inventories in permanent plots (25 sampling units of 20 x 20 m randomly located in the forest) for the years 2000 and 2006. All trees with dbh > 5 cm were sampled, measured, and structural, phytosociological and diversity parameters were calculated. Rates of mortality and recruitment were calculated, and indirect gradient analyses (DCA) were applied to test the structural changes between the plots. The rates of mortality (2.77 %.year-1) and recruitment (4.43 %.year-1) were high showing rapid community dynamics. However, the rapid dynamics did not promote qualitative (species richness) and quantitative (phytosociological structure, diversity and gradient analysis) changes, supporting the hypothesis and showing high stability across the interval.
Full-text · Article · Mar 2011 · Acta Botanica Brasilica