Variations in tree community composition and structure in a fragment of tropical semideciduous forest in southeastern Brazil related to different human disturbance histories

In an area of tropical seasonal semideciduous forest, the soil characteristics, floristic composition, physiognomic structure, and the distribution of three regeneration and three dispersal guilds were studied for four stands within the forest that had documented histories of varying degrees of human disturbance. The aim was to study forest regeneration in areas of preserved forest and secondary forest, with parts of both types of forest experiencing either 'intensive' or 'occasional' cattle trampling. The study was carried out in the Sebastiao Aleixo da Silva Ecological Station, Bauru, São Paulo State, Brazil. Two stands were called 'secondary' because they corresponded to forest tracts that were felled and occupied by crops and pastures in the past and then abandoned to forest regeneration ca. 40 years before this study. The other two stands, called 'preserved', corresponded to areas of the fragment where the forest has been maintained with only minor human impacts. The arboreal component of the tree community (diameter at breast height or dbh greater than or equal to 5 cm) was sampled in 20 plots of 40 m x 40 m, and the subarboreal component (diameter at the base of the stem or dbs < 5 cm and height greater than or equal to 0.5 m) in subplots of 40 m x 2 m. Physiognomic features, such as canopy height and density of climbing plants, were registered all over a 5 m x 5 m gridline laid on the sample plots. Soil bulk samples were collected for chemical and textural analyses. Most detected differences contrasted the secondary to the preserved forest stands. The soils of the secondary stands showed higher proportions of sand and lower levels of mineral nutrients and organic matter than those of the preserved stands, probably due to higher losses by leaching and erosion. Compared to the secondary stands, the preserved ones had higher proportions of tall trees, higher mean canopy height, lower species diversity, higher abundance of autochorous and shade-tolerant climax species, and lower abundance of pioneer and light-demanding climax species. Despite the high proportion of species shared by the preserved and secondary stands (108 out of 139), they differed consistently in terms of density of the most abundant species. on the other hand, the secondary and preserved stands held similar values for tree density and basal area, suggesting that 40 years were enough to restore these features. Effects of cattle trampling on the vegetation were detected for the frequency of trees of anemochorous and zoochorous species, which were higher in the stands under occasional and intensive cattle trampling, respectively. The density of thin climbers was lower in the stands with intensive trampling. (C) 2004 Elsevier B.V. All rights reserved.

Ecological interaction between Atta sexdens (Hymenoptera: Formicidae) and the vegetation of a mesophyll semideciduous forest fragment in Botucatu, SP, Brazil

Among 89 plants species growing in a subtropical dry forest fragment located in Botucatu, State of São Paulo, Brazil, 35 species were cut by Atta sexdens, representing 39.34% of the current plants existing in this area. A. sexdens L., 1758 (Hymenoptera: Formicidae) has a selective preference for the following species: Alchornea triplinervia, Faramea cyanea, Cariniana estrellensis and Casearea obliqua, with the first being the most cut species. The frequency and absolute densities of the plant families and species significantly influence the selection process. When comparing the absolute frequency regarding the 10 most cut plant species and the cutting frequency, significant data were obtained only for the euphorbiaceous A. triplinervia species, proving the preference of A. sexdens for this species in particular. These interactions are discussed based on ecological and management factors in agro-ecosystems.

Environmental solutions of recovery of Amazonian forest mining operations

In order for the projects of recovery of degraded areas to be successful, it is necessary to have a perfect recovery of the soil where the revegetation will be implanted as an initial action in the recovery of the whole process. The use of native forest species fully adapted to these types of terrain is another aspect of great importance, once the non-selection of these species, even if abundant in the surrounding areas, as it is in our case, implies great mortality of individuals during the planting and their low fixation during the process. The establishment of a monitoring program that contemplates the advancements obtained in the soil, the vegetation and the return of wild animals also collaborate in the evaluation of the success of the process. And, finally, the effective participation of the mining company, accepting and applying the techniques tested and indicated by research, even if, initially, the return time is longer than expected, also guarantees the success of the process. The mining company not only implemented a partnership with important universities in Brazil to obtain solutions for the environmental problems but also applied the developed techniques and the monitoring program. In the present work, we have attempted to summarize important aspects to evaluate the advancements in the rehabilitation plan for those areas, being here presented some results of the monitoring of areas under different levels of recovery, in accordance with the techniques adopted. Biological parameters of the soil were used to verify the efficiency of these different techniques in the recovery process. This work is part of the monitoring program of areas in rehabilitation by the mining company, implemented as of 1999 and in partnership with universities. The microbial activity was determined through the quantification of the carbon and nitrogen microbial biomass (BMC and BMN) and the activity of the dehydrogenase evaluated in the mining floor and tailing areas in different levels of soil preparation and planting of native species. The analysis of the parameters studied revealed that the preparation of the soil, following the three years proposed by the methodology, was important for the success in establishing the rehabilitation process. Some of the areas analyzed already show some parameters with values close or superior to those found in the capoeira (secondary forest), the latter being the non-treated area. © 2010 WIT Press.

Use of space by frugivorous bats (Chiroptera: Phyllostomidae) in a restored Atlantic forest fragment in Brazil

We studied patterns in the use of space for foraging and roosting by two frugivorous bat species in a five-year-old restored Atlantic forest located in a fragmented landscape in southeastern Brazil. Ten individuals of Carollia perspicillata and eleven individuals of Artibeus lituratus were monitored through radio-telemetry in five sampling sessions. Each session lasted 3-8. days for each individual, with an average of 25.4 ± 10 locations for each C. perspicillata individual and 19 ± 4.4 for each A. lituratus individual. We described an average range of 124.4. ha and an average commuting distance of 1158.8. m for A. lituratus and an average range and commuting distance of 32. ha and 489. m, respectively, for C. perspicillata. We demonstrated a consistent pattern in habitat use and movements for both studied species, where they strictly used forests (restored or not) for day roosting, roosting in the foliage of trees located only in secondary forest remnants and restored areas, while restored areas were their main feeding habitat. We demonstrate that newly restored forests can be readily incorporated as foraging and roosting habitats by these species, and that C. perspicillata alters its roosting behavior in relation to preferred food availability. These results, when combined with data on the diet of the studied species, show consistent evidence of the potential that bats have to improve species diversity of anthropogenic plantings with their own natural seed dispersal. © 2012 Elsevier B.V.

Changes in plant species composition and functional traits along the successional trajectory of a restored patch of Atlantic Forest

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Euterpe edulis Seedlings in the Understory of Two Forest Fragments

The palm Euterpe edulis is one of the most exploited due the intense illegal extraction, which is very harmful because this species dies right after the cutting process. This study aimed to assess the palms' development as an enrichment plant in a forest fragment belonging to a Preservation Area and the Biosphere Reserve of the Green Belt of Sao Paulo State, in Embu das Artes city. The seeds were obtained from the Instituto Florestal, which follows all the regulations for seeds, in order to get seedlings with a high genetic variation. The seedlings were planted in two successional stages: secondary forest with low trees (SFLT) and secondary forest with medium trees (SFMT). The seedlings survival and growth were periodically assessed and the results were compared by the variance analysis. Both areas presented high rates of survival, which were superior comparing to other similar studies with Euterpe edulis. Despite the successional difference between the areas, the development of the seedlings did not show significant difference on the analysis of variance regarding leaf number, height growth, stem diameter and survival, except for plant height at 60 days after planting, when seedlings planted in SFLT reached higher height (21.38 cm) than when planted in SFMT (19.31 cm).

Forest destructuring as revealed by the temporal dynamics of fundamental species - Case study of Santa Genebra Forest in Brazil

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Carbon content in Amazonian Oxisols after forest conversion to pasture

O solo desempenha importante papel no ciclo do C, porém a substituição da floresta tropical por áreas cultivadas altera a dinâmica e o estoque desse elemento. Em uma frente pioneira de colonização no município de Itupiranga (PA), na Amazônia Oriental, foi desenvolvido este estudo com o objetivo de avaliar as consequências da substituição de floresta nativa por pastagens de Brachiaria brizantha no conteúdo de C de um Latossolo Amarelo distrófico. As amostras de solo foram coletadas em área de floresta nativa (FN), floresta secundária de 8–10 anos (FS), pastagens de 1–2 anos (P1-2), de 5–7 anos (P5–7) e de 10–12 anos (P10–12), nas camadas de 0–2, 2–5 e 5–10 cm, para avaliar os teores e o estoque de C e realizar um fracionamento granulométrico da matéria orgânica. Após o desmatamento, a densidade do solo aumentou até a profundidade de 5 cm, sendo esse aumento maior nas pastagens mais antigas. As maiores mudanças no conteúdo de C ocorreram na camada superior do solo, havendo aumento nesse conteúdo com o tempo de implantação das pastagens. Nas camadas de 2–5 e 5–10 cm, o conteúdo de C se mostrou estável entre os tipos de cobertura vegetal avaliados. As maiores concentrações de C foram encontradas na fração silte, mas os maiores conteúdos de C ocorreram na fração argila, independentemente do tipo de cobertura vegetal. Um aumento da quantidade de C associado à fração areia, na forma de resíduos orgânicos pouco decompostos, foi observado nas pastagens, confirmando a maior sensibilidade dessa fração às mudanças de uso do solo.

Litterfall and leaf decomposition in forest fragments under different successional phases on the Atlantic Plateau of the state of Sao Paulo, Brazil

Litterfall and litter decomposition are vital processes in tropical forests because they regulate nutrient cycling. Nutrient cycling can be altered by forest fragmentation. The Atlantic Forest is one of the most threatened biomes in the world due to human occupation over the last 500 years. This scenario has resulted in fragments of different size, age and regeneration phase. To investigate differences in litterfall and leaf decomposition between forest successional phases, we compared six forest fragments at three different successional phases and an area of mature forest on the Atlantic Plateau of Sao Paulo, Brazil. We sampled litter monthly from November 2008 to October 2009. We used litterbags to calculate leaf decomposition rate of an exotic species, Tipuana tipu (Fabaceae), over the same period litter sampling was performed. Litterfall was higher in the earliest successional area. This pattern may be related to the structural properties of the forest fragments, especially the higher abundance of pioneer species, which have higher productivity and are typical of early successional areas. However, we have not found significant differences in the decomposition rates between the studied areas, which may be caused by rapid stabilization of the decomposition environment (combined effect of microclimatic conditions and the decomposers activities). This result indicates that the leaf decomposition process have already been restored to levels observed in mature forests after a few decades of regeneration, although litterfall has not been entirely restored. This study emphasizes the importance of secondary forests for restoration of ecosystem processes on a regional scale.

Habitat structure and food resources for wildlife across successional stages in a tropical forest

Tropical forests are experiencing an increase in the proportion of secondary forests as a result of the balance between the widespread harvesting of old-growth forests and the regeneration in abandoned areas. The impacts of such a process on biodiversity are poorly known and intensely debated. Recent reviews and multi-taxa studies indicate that species replacement in wildlife assemblages is a consistent pattern, sometimes stronger than changes in diversity, with a replacement from habitat generalists to old-growth specialists being commonly observed during tropical forest regeneration. However, the ecological drivers of such compositional changes are rarely investigated, despite its importance in assessing the conservation value of secondary forests, and to support and guide management techniques for restoration. By sampling 28 sites in a continuous Atlantic forest area in Southeastern Brazil, we assessed how important aspects of habitat structure and food resources for wildlife change across successional stages, and point out hypotheses on the implications of these changes for wildlife recovery. Old-growth areas presented a more complex structure at ground level (deeper leaf litter, and higher woody debris volume) and higher fruit availability from an understorey palm, whereas vegetation connectivity, ground-dwelling arthropod biomass, and total fruit availability were higher in earlier successional stages. From these results we hypothetize that generalist species adapted to fast population growth in resource-rich environments should proliferate and dominate earlier successional stages, while species with higher competitive ability in resource-limited environments, or those that depend on resources such as palm fruits, on higher complexity at the ground level, or on open space for flying, should dominate older-growth forests. Since the identification of the drivers of wildlife recovery is crucial for restoration strategies, it is important that future work test and further develop the proposed hypotheses. We also found structural and functional differences between old-growth forests and secondary forests with more than 80 years of regeneration, suggesting that restoration strategies may be crucial to recover structural and functional aspects expected to be important for wildlife in much altered ecosystems, such as the Brazilian Atlantic forest. (C) 2012 Elsevier B.V. All rights reserved.

Land-use and land-cover change in Atlantic Forest landscapes

The Atlantic Forest is one of the most threatened tropical biomes, with much of the standing forest in small (less than 50 ha), disturbed and isolated patches. The pattern of land-use and land-cover change (LULCC) which has resulted in this critical scenario has not yet been fully investigated. Here, we describe the LULCC in three Atlantic Forest fragmented landscapes (Sao Paulo, Brazil) between 1960-1980s and 1980-2000s. The three studied landscapes differ in the current proportion of forest cover, having 10%, 30% and 50% respectively. Between the 1960s and 1980s. forest cover of two landscapes was reduced while the forest cover in the third landscape increased slightly. The opposite trend was observed between the 1980s and 2000s: forest regeneration was greater than deforestation at the landscapes with 10% and 50% of forest cover and, as a consequence, forest cover increased. By contrast, the percentage of forest cover at the landscape with 30% of forest cover was drastically reduced between the 1980s and 2000s. LULCC deviated from a random trajectory, were not constant through time in two study landscapes and were not constant across space in a given time period. This landscape dynamism in single locations over small temporal scales is a key factor to be considered in models of LULCC to accurately simulate future changes for the Atlantic Forest. In general, forest patches became more isolated when deforestation was greater than forest regeneration and became more connected when forest regeneration was greater than deforestation. As a result of the dynamic experienced by the study landscapes, individual forest patches currently consist of a mosaic of different forest age classes which is likely to impact bio-diversity. Furthermore, landscape dynamics suggests the beginning of a forest transition in some Atlantic Forest regions, what could be of great importance for biodiversity conservation due to the potential effects of young secondary forests in reducing forest isolation and maintaining a significant amount of the original biodiversity. (C) 2012 Elsevier B.V. All rights reserved.

High Bee and Wasp Diversity in a Heterogeneous Tropical Farming System Compared to Protected Forest

It is a globally important challenge to meet increasing demands for resources and, at the same time, protect biodiversity and ecosystem services. Farming is usually regarded as a major threat to biodiversity due to its expansion into natural areas. We compared biodiversity of bees and wasps between heterogeneous small-scale farming areas and protected forest in northern coastal Belize, Central America. Malaise traps operated for three months during the transition from wet to dry season. Farming areas consisted of a mosaic of mixed crop types, open habitat, secondary forest, and agroforestry. Mean species richness per site (alpha diversity), as well as spatial and temporal community variation (beta diversity) of bees and wasps were equal or higher in farming areas compared to protected forest. The higher species richness and community variation in farmland was due to additional species that did not occur in the forest, whereas most species trapped in forest were also found in farming areas. The overall regional species richness (gamma diversity) increased by 70% with the inclusion of farming areas. Our results suggest that small-scale farming systems adjacent to protected forest may not only conserve, but even favour, biodiversity of some taxonomic groups. We can, however, not exclude possible declines of bee and wasp diversity in more intensified farmland or in landscapes completely covered by heterogeneous farming systems.

Secondary Forests and Local Livelihoods along a Gradient of Accessibility: A Case Study in Northern Laos

Rural livelihoods in developing countries can be enhanced by improving access to natural resources, services, and markets. In remote rural areas of the humid or semihumid tropics, forests represent an important resource for livelihoods. In countries like Laos, where most primary forest has been converted to secondary forest, and where an intricate and interlinked mosaic of forest and farmland prevails, people depend on secondary forests as a prime source of goods and services. The linkages between local livelihoods and secondary forest resources are subject to changes caused by improving accessibility. This article studies how accessibility affects the condition of forests and local livelihoods by comparing three villages along a gradient of accessibility in Phonxay district, Luang Prabang province, northern Laos. The results of this research show that accessibility strengthens the influence of the government and of markets, and that local livelihoods improve with increasing accessibility, while forest condition deteriorates.

Development of forest structure on cleared rainforest land in eastern Australia under different styles of reforestation

Rainforests in eastern Australia have been extensively cleared over the past two centuries. In recent decades, there have been increasing efforts to reforest some of these cleared lands, using a variety of methods, to meet a range of economic and environmental objectives. However, the extent to which the various styles of reforestation restore structure, composition and ecological function to cleared land is not presently understood. In this study, we develop and apply a method for quantifying the structural attributes of reforestation sites in tropical and subtropical Australia. The types of reforestation studied were plantation monocultures, mixed-species cabinet timber plots, diverse restoration plantings and unmanaged regrowth. Two age classes of reforestation were examined: 'young' (5-22 years), incorporating sites from all categories, and 'old' (30-70 years), in which only monoculture plantations and regrowth were represented. A total of 104 sites were surveyed including reference sites in intact rainforest and pasture. Intact rainforest was characterised by a suite of complex structural features including abundant special life forms (vines, epiphytes, hemi-epiphytes and strangler figs), a dense stand of trees in a range of size classes, a closed canopy, a shrubby understorey and a well-developed ground layer of leaf litter and woody debris. These features were lost on conversion to pasture. While all types of reforestation returned some elements of structural complexity to cleared land, young plantation monocultures, cabinet timber plots and young regrowth had a relatively simple structure. These sites typically had a low density of woody stems, a relatively open canopy and grassy ground cover, and lacked large trees, coarse woody debris and most special life forms. Restoration plantings and old regrowth were more complex, with a high density of woody stems, a relatively closed canopy and shrubby understorey. Old monoculture plantations in the tropics had acquired many of the structural attributes of intact forest, however this was not the case in the subtropics, where plantations were subject to more intensive management. The marked differences in structural complexity between sites suggest that the different types of reforestation practiced in eastern Australia are likely to vary considerably in their value as habitat for rainforest biota. (C) 2003 Elsevier Science B.V. All rights reserved.

Modeling the age of tropical moist forest fragments in heavily-cleared lowland landscapes of Colombia

Increasingly, large areas of native tropical forests are being transformed into a mosaic of human dominated land uses with scattered mature remnants and secondary forests. In general, at the end of the land clearing process, the landscape will have two forest components: a stable component of surviving mature forests, and a dynamic component of secondary forests of different ages. As the proportion of mature forests continues to decline, secondary forests play an increasing role in the conservation and restoration of biodiversity. This paper aims to predict and explain spatial and temporal patterns in the age of remnant mature and secondary forests in lowland Colombian landscapes. We analyse the age distributions of forest fragments, using detailed temporal land cover data derived from aerial photographs. Ordinal logistic regression analysis was applied to model the spatial dynamics of mature and secondary forest patches. In particular, the effect of soil fertility, accessibility and auto-correlated neighbourhood terms on forest age and time of isolation of remnant patches was assessed. In heavily transformed landscapes, forests account for approximately 8% of the total landscape area, of which three quarters are comprised of secondary forests. Secondary forest growth adjacent to mature forest patches increases mean patch size and core area, and therefore plays an important ecological role in maintaining landscape structure. The regression models show that forest age is positively associated with the amount of neighbouring forest, and negatively associated with the amount of neighbouring secondary vegetation, so the older the forest is the less secondary vegetation there is adjacent to it. Accessibility and soil fertility also have a negative but variable influence on the age of forest remnants. The probability of future clearing if current conditions hold is higher for regenerated than mature forests. The challenge of biodiversity conservation and restoration in dynamic and spatially heterogeneous landscape mosaics composed of mature and secondary forests is discussed. (c) 2004 Elsevier B.V. All rights reserved.