Forest structure and live aboveground biomass variation along an elevational gradient of tropical Atlantic moist forest (Brazil)

Live aboveground biomass (AGB) is an important source of uncertainty in the carbon balance from the tropical regions in part due scarcity of reliable estimates of live AGB and its variation across landscapes and forest types. Studies of forest structure and biomass stocks of Neotropical forests are biased toward Amazonian and Central American sites. In particular, standardized estimates of aboveground biomass stocks for the Brazilian Atlantic forest are rarely available. Notwithstanding the role of environmental variables that control the distribution and abundance of biomass in tropical lowland forests has been the subject of considerable research, the effect of short, steep elevational gradients on tropical forest structure and carbon dynamics is not well known. In order to evaluate forest structure and live AGB variation along an elevational gradient (0-1100 m a.s.l.) of coastal Atlantic Forest in SE Brazil, we carried out a standard census of woody stems >= 4.8 cm dbh in 13 1-ha permanent plots established on four different sites in 2006-2007. Live AGB ranged from 166.3 Mg ha(-1) (bootstrapped 95% CI: 1444,187.0) to 283.2 Mg ha(-1) (bootstrapped 95% CI: 253.0,325.2) and increased with elevation. We found that local-scale topographic variation associated with elevation influences the distribution of trees >50 cm dbh and total live AGB. Across all elevations, we found more stems (64-75%) with limited crown illumination but the largest proportion of the live AGB (68-85%) was stored in stems with highly illuminated or fully exposed crowns. Topography, disturbance and associated changes in light and nutrient supply probably control biomass distribution along this short but representative elevational gradient. Our findings also showed that intact Atlantic forest sites stored substantial amounts of carbon aboveground. The live tree AGB of the stands was found to be lower than Central Amazonian forests, but within the range of Neotropical forests, in particular when compared to Central American forests. Our comparative data suggests that differences in live tree AGB among Neotropical forests are probably related to the heterogeneous distribution of large and medium-sized diameter trees within forests and how the live biomass is partitioned among those size classes, in accordance with general trends found by previous studies. In addition, the elevational variation in live AGB stocks suggests a large spatial variability over coastal Atlantic forests in Brazil, clearly indicating that it is important to consider regional differences in biomass stocks for evaluating the role of this threatened tropical biome in the global carbon cycle. (C) 2010 Elsevier B.V. All rights reserved.

CHARACTERIZATION OF THE TREE COMPONENT IN A SEMIDECIDUOUS FOREST IN THE ESPINHACO RANGE: A SUBSIDY TO CONSERVATION

This study was conducted in the Private Reserve Mata do Jambreiro (912 ha), localized in the Iron Quadrangle, Minas Gerais, southeastern portion of the Espinhaco Range, which is predominantly covered by semideciduous seasonal montane forest. Three topographically and physiognomic similar areas located within a continuum forest fragment, distant by 1.3 to 1.5 km were sampled by the point-quadrat method. In each area, 30 points were marked. Individuals with a minimum perimeter at the breast height (PBH) of 15 cm were sampled, totaling 111 species belonging to 40 families. The most representative family was Fabaceae, with 14.29% of the total number of species. Low floristic similarity (5.3% to 34.4%) was observed between the areas, pointing out the importance of distribution of sample units in continuous fragments. Shannon diversity index (H') found was 4.22 and Pielou equability (J) 0.894. Soil analysis showed some differences in chemical composition between the three studied areas and was an important component for the interpretation of the floristic variation found. The low floristic similarity observed here for close areas justify the requirement of more detailed inventories by Brazilian Environmental Agencies for the legal authorization procedures prior to the establishment of new enterprising projects. Also, the professionals that conduct rapid inventories, mainly the Environmental Consultants, should give more attention to this kind of floristic variation and to the methods used to inventory complex forests.

Coexistence of forest and savanna in an Amazonian area from a geological perspective

Question: How can the coexistence of savanna and forest in Amazonian areas with relatively uniform climates be explained? Location: Eastern Marajo Island, northeast Amazonia, Brazil. Methods: The study integrated floristic analysis, terrain morphology, sedimentology and delta(13)C of soil organic matter. Floristic analysis involved rapid ecological assessment of 33 sites, determination of occurrence, specific richness, hierarchical distribution and matrix of floristic similarity between paired vegetation types. Terrain characterization was based on analysis of Landsat images using 4(R), 5(G) and 7(B) composition and digital elevation model (DEM). Sedimentology involved field descriptions of surface and core sediments. Finally, radiocarbon dating and analysis of delta(13)C of soil profile organic matter and natural ecotone forest-savanna was undertaken. Results: Slight tectonic subsidence in eastern Marajo Island favours seasonal flooding, making it unsuitable for forest growth. However, this area displays slightly convex-up, sinuous morphologies related to paleochannels, covered by forest. Terra-firme lowland forests are expanding from west to east, preferentially occupying paleochannels and replacing savanna. Slack, running water during channel abandonment leads to disappearance of varzea/gallery forest at channel margins. Long-abandoned channels sustain continuous terra-firme forests, because of longer times for more species to establish. Recently abandoned channels have had less time to become sites for widespread tree development, and are either not vegetated or covered by savanna. Conclusion: Landforms in eastern Marajo Island reflect changes in the physical environment due to reactivation of tectonic faults during the latest Quaternary. This promoted a dynamic history of channel abandonment, which controlled a set of interrelated parameters (soil type, topography, hydrology) that determined species location. Inclusion of a geological perspective for paleoenvironmental reconstruction can increase understanding of plant distribution in Amazonia.

Effects of bamboo stands on seed rain and seed limitation in a rainforest

Bamboos often negatively affect tree recruitment, survival, and growth, leading to arrested tree regeneration in forested habitats. Studies so far have focused on the effects of bamboos on the performance of seedlings and saplings, but the influence of bamboos on forest dynamics may start very early in the forest regeneration process by altering seed rain patterns. We tested the prediction that the density and composition of the seed rain are altered and seed limitation is higher in stands of Guadua tagoara (B or bamboo stands), a large-sized woody bamboo native from the Brazilian Atlantic Forest, compared to forest patches without bamboos (NB or non-bamboo stands). Forty 1 m(2) seed traps were set in B and NB stands, and the seed rain was monitored monthly for 1 year. The seed rain was not greatly altered by the presence of bamboos: rarefied seed species richness was higher for B stands, patterns of dominance and density of seeds were similar between stands, and differences in overall composition were slight. Seed limitation, however, was greater at B stands, likely as a resulted of reduced tree density. Despite Such reduced density, the presence of trees growing amidst and over the bamboos seems to play a key role in keeping the seeds falling in B stands because they serve as food sources for frugivores or simply as perches for them. The loss of such trees may lead to enhanced seed limitation, contributing ultimately to the self-perpetuating bamboo disturbance cycle. (C) 2008 Elsevier B,V. All rights reserved.

Impact of seedling removal on regenerating community structure of a seasonal semideciduous forest

(Impact of seedling removal on regenerating community structure of a seasonal semideciduous forest). Transplanting seedlings and saplings from natural forests has been considered an alternative to producing saplings of native species for forest restoration purposes, but the possible impact of this procedure on plant community regeneration has not been investigated. This work evaluates the impact of different treatments of shrub and tree-seedling (up to 30 cm) removal from a seasonal semideciduous forest fragment located in southeastern Brazil on the natural regeneration process. Eighty 2x2 m plots were installed in two habitats (forest edge and interior) and submitted to four seedling-removal treatments (I, II - 100% removal with or without soil mixing; III - 50% removal without soil mixing: and IV - control treatment Without seedling removal). Regeneration density and richness were evaluated before treatment as well as 6, 12 and 18 months later. The results were compared among treatments for each evaluation period and among periods within treatments. There were similarities between edge and interior. The natural regeneration process did not improve with soil mixing. Plots submitted to seedling removal partially recovered plant density; however, these plots had lower species richness when compared to the control and to the initial values before treatment. Seedling removal has a negative impact on the regeneration process of low-density species, thus the use of natural regeneration as a sapling source for forest restoration purposes should focus only on high-density species with well-known regeneration strategies and not on the community as a whole.

New records of Rhagomys rufescens (Rodentia : Sigmodontinae) in the Atlantic forest of Brazil

Since it was trapped in the XIX(th) century, Rhagomys rufescens has been considered a rare endangered sigmodontine rodent and an endemic species of the Atlantic forest. Only a handful of vouchers of this taxon were known by Thomas, 1886. Recently, eight new individuals were collected, providing new geographical, morphological and phylogenetic (based on molecular evidence) information on this species. In the present work we report the southernmost occurrence record for R. rufescens at Indaial, Santa Catarina State, with the largest collected series of this species, the northernmost occurrence record at Santa Teresa, Espirito Santo State, and new records from Pocos de Caldas, Minas Gerais State, from Ibiuna and Ribeirao Grande, Sao Paulo State.

Herbicide distribution in soils of a riparian forest and neighboring sugar cane field

Riparian forests are protected by Brazilian law to preserve rivers and their margins. A sugar cane field adjacent to a strip of young riparian forest bordering an older riparian forest along a stream was used to study the riparian forest as a buffer zone to prevent pesticides pollution. Concentrations of the herbicides diuron, hexazinone and tebuthiuron were determined in different soil layers of a Red Yellow Oxisol during 2003 and 2004. The determination was done by High Performance Liquid Chromatography with reverse phase C-18 column, through two mobile phases. Diuron and hexazinone concentration diminished between the sugar cane and riparian forest as buffer strip demonstrating a protective effect. However, tebuthiuron had about four times higher concentrations in the old riparian forest compared to the other areas. Concentrations were higher in the surface and decreased in deeper soil layers in the old riparian forest suggesting that this herbicide probably was introduced by air pollution. This pesticide concentrated in the canopy could be washed by rain to the soil adjacent to the stream. Our data suggest that climate conditions were responsible for enhanced volatilization exposing the old riparian forest to more air pollution that was captured by the higher canopy. (C) 2010 Elsevier B.V. All rights reserved.

Out of Amazonia again and again: episodic crossing of the Andes promotes diversification in a lowland forest flycatcher

Most Neotropical lowland forest taxa occur exclusively on one side of the Andes despite the availability of appropriate habitat on both sides. Almost all molecular phylogenies and phylogenetic analyses of species assemblages (i.e. area cladograms) have supported the hypothesis that Andean uplift during the Late Pliocene created a vicariant barrier affecting lowland lineages in the region. However, a few widespread plant and animal species occurring in lowland forests on both sides of the Andes challenge the generality of this hypothesis. To understand the role of the Andes in the history of such organisms, we reconstructed the phylogeographic history of a widespread Neotropical flycatcher (Mionectes oleagineus) in the context of the other four species in the genus. A molecular phylogeny based on nuclear and mitochondrial sequences unambiguously showed an early basal split between montane and lowland Mionectes. The phylogeographic reconstruction of lowland taxa revealed a complex history, with multiple cases in which geographically proximate populations do not represent sister lineages. Specifically, three populations of M. oleagineus west of the Andes do not comprise a monophyletic clade; instead, each represents an independent lineage with origins east of the Andes. Divergence time estimates suggest that at least two cross-Andean dispersal events post-date Andean uplift.

Allometric models for estimating the phytomass of a secondary Atlantic Forest area of southeastern Brazil

The purpose of this study was to develop and validate equations to estimate the aboveground phytomass of a 30 years old plot of Atlantic Forest. In two plots of 100 m², a total of 82 trees were cut down at ground level. For each tree, height and diameter were measured. Leaves and woody material were separated in order to determine their fresh weights in field conditions. Samples of each fraction were oven dried at 80 °C to constant weight to determine their dry weight. Tree data were divided into two random samples. One sample was used for the development of the regression equations, and the other for validation. The models were developed using single linear regression analysis, where the dependent variable was the dry mass, and the independent variables were height (h), diameter (d) and d²h. The validation was carried out using Pearson correlation coefficient, paired t-Student test and standard error of estimation. The best equations to estimate aboveground phytomass were: lnDW = -3.068+2.522lnd (r² = 0.91; s y/x = 0.67) and lnDW = -3.676+0.951ln d²h (r² = 0.94; s y/x = 0.56).

Frugivory and seed dispersal of golden lion tamarin (Leontopithecus rosalia (Linnaeus, 1766)) in a forest fragment in the Atlantic Forest, Brazil

The influence of the golden lion tamarin (Leontopithecus rosalia) as a seed disperser was studied by monitoring two groups of tamarins from December 1998 to December 2000 (871.9 hours of observations) in a forest fragment in south-east Brazil. The tamarins consumed fruits of 57 species from at least 17 families. They ingested the seeds of 39 species, and 23 of these were put to germinate in the laboratory and/or in the field. L. rosalia is a legitimate seed disperser because the seeds of all species tested germinated after ingestion, albeit some in low percentages. These primates do not show a consistent effect in final seed germination, because they benefit some species while damaging others. Feces were examined for seeds that had been preyed upon or digested.

Birds from cerradão woodland, an overlooked forest of the Cerrado region, Brazil

The Cerrado region still receives relatively little ornithological attention, although it is regarded as the only tropical savanna in the world considered to be a biodiversity hotspot. Cerradão is one of the least known and most deforested Cerrado physiognomies and few recent bird surveys have been conducted in these forests. In order to rescue bird records and complement the few existing inventories of this under-studied forest type in the state of São Paulo, we looked for published papers on birds of cerradão. Additionally we surveyed birds at a 314-ha cerradão remnant located in central São Paulo, Brazil, from September 2005-December 2006 using unlimited distance transect counts. Out of 95 investigations involving cerradão bird studies, only 17 (18%) investigations teased apart bird species recorded inside cerradão from those recorded in other physiognomies of Cerrado. Except for one study, no research found more than 64 species in this type of forest, a result shared within many regions from Brazil and Bolivia. Differences in species richness do not seem be related with levels of disturbance of landscape or fragment size. Considering all species recorded in cerradão in Brazil and Bolivia, a compilation of data accumulated 250 species in 36 families and 15 orders. In recent surveys at central São Paulo, we recorded 48 species in 20 families, including the Pale-bellied Tyrant-Manakin Neopelma pallescens, threatened in São Paulo, and the Helmeted Manakin Antilophia galeata, near threatened in the state and endemic to the Cerrado region. Among the most abundant species inside this fragment, none was considered to be neither threatened nor endemic.

A comparison of the leaf-litter ant fauna in a secondary atlantic forest with an adjacent pine plantation in southeastern Brazil

We investigated the influence of Pinus afforestation on the structure of leaf-litter ant communities in the southeastern Brazilian Atlantic Forest, studying an old secondary forest and a nearly 30 year-old never managed Pinus elliottii reforested area. A total of 12,826 individual ants distributed among 95 species and 32 genera were obtained from 50 1 m² samples/ habitat. Of these, 60 species were recorded in the pine plantation and 82 in the area of Atlantic forest; almost 50% of the species found in the secondary forest area were also present in the pine plantation. The number of species per sample was significantly higher in the secondary forest than in the pine plantation. Forest-adapted taxa are the most responsible for ant species richness differences between areas, and the pine plantation is richer in species classified as soil or litter omnivorous-dominants. The specialized ant predators registered in the pine plantation, as seven Dacetini, two Basiceros, two Attini and two Discothyrea, belong to widely distributed species. The NMDS (non-metric multidimensional scaling) ordination also suggested strong differences in similarity among samples of the two areas. Furthermore, this analysis indicated higher sample heterogeneity in the secondary forest, with two clusters of species, while in the pine plantation the species belong to a single cluster. We applied the ant mosaic hypothesis to explain the distribution of the leaf-litter fauna and spatial autocorrelation tests among samples. We argue that the results are likely related to differences in quality and distribution of the leaf-litter between the pine plantation and the secondary area.

Ant community richness and composition across a gradient from Eucalyptus plantations to secondary Atlantic Forest

Secondary forests and exotic tree plantations are expanding across tropical landscapes. However, our current understanding of the value of these human-dominated forest landscapes for invertebrate biodiversity conservation is still very poor. In this paper, we use the leaf-litter ant fauna to assess invertebrate diversity in one commercially managed Eucalyptus plantation (four years old), two abandoned plantations of different regeneration ages (16 and 31 years), and one neighboring secondary Atlantic Forest in Southeastern Brazil. There was a clear gradient in species richness from the secondary forest to the managed Eucalyptus plantation; richness and diversity peaked in secondary forest and in the older regenerating Eucalyptus plantation. Significantly more species were recorded in secondary forest samples than in Eucalyptus plantations, but Eucalyptus plantations had a similar level of richness. Furthermore, a non-metric multidimensional scaling analysis revealed clear differences in species composition between the younger managed Eucalyptus plantation (understory absent) and habitats with sub-developed or developed understory. Eucalyptus plantations were characterized by an assemblage of widespread, generalist species very different from those known to occur in core forest habitats of southeastern Brazil. Our results indicate that while older regenerating Eucalyptus plantations can provide habitat to facilitate the persistence of generalist ant species, it is unlikely to conserve most of the primary forest species, such as specialized predators, Dacetini predators, and nomadic species.

Frog diversity in the Floresta Nacional de Chapecó, Atlantic Forest of southern Brazil

The Atlantic Forest is considered one of the world's biological diversity hotspots but is nevertheless increasingly threatened with the rapid destruction and fragmentation of its natural areas. In the state of Santa Catarina, southern Brazil, remnants of the mixed ombrophilous forest and seasonal deciduous forest exist as islands within large areas of agriculture, pastures and human settlements. Here we present information on species richness and habitat use by anurans in the Floresta Nacional de Chapecó, located in the western portion of the state of Santa Catarina. Anurans were surveyed by active search of potential reproductive sites from December 1998 to December 2001. A total of 29 species were recorded, most of which have a known distribution restricted to southern Brazil and adjacent countries (Argentina, Paraguay, and Uruguay) and use open areas for reproduction. The species composition was most similar to other areas of mixed ombrophilous forest and seasonal deciduous forest from the extreme south of Brazil. The information in this study may support the implementation of conservation and management strategies in the area.

Analysis of mangrove forest succession, using sediment cores: a case study in the Cananéia -Iguape coastal system, São Paulo Brazil

Sediment cores are an essential tool for the analysis of the dynamics of mangrove succession. Coring was used to correlate changes in depositional environments and lateral sedimentary facies with discrete stages of forest succession at the Cananéia-Iguape Coastal System in southeastern Brazil. A local level successional pattern was examined based on four core series T1) a sediment bank; T2) a smooth cordgrass Spartina alterniflora bank; T3) an active mangrove progradation fringe dominated by Laguncularia racemosa, and; T4) a mature mangrove forest dominated by Avicennia schaueriana. Cores were macroscopically described in terms of color, texture, sedimentary structure and organic components. The base of all cores exhibited a similar pattern suggesting common vertical progressive changes in depositional conditions and subsequent successional colonization pattern throughout the forest. The progradation zone is an exposed bank, colonized by S. alterniflora. L. racemosa, replaces S. alterniflora as progradation takes place. As the substrate consolidates A. schaueriana replaces L. racemosa and attains the greatest structural development in the mature forest. Cores collected within the A. schaueriana dominated stand contained S. alterniflora fragments near the base, confirming that a smooth cordgrass habitat characterized the establishment and early seral stages. Cores provide a reliable approach to describe local-level successional sequences in dynamic settings subject to drivers operating on multiple temporal and spatial scales where spatial heterogeneity can lead to multiple equilibria and where similar successional end-points may be reached through convergent paths.