Luiz Fernando S. Magnago

Defaunation affects carbon storage in tropical forests

Populations of large frugivores are declining in tropical rainforests with potential consequences for carbon storage and climate. Carbon storage is widely acknowledged as one of the most valuable forest ecosystem services. Deforestation, logging, fragmentation, fire, and climate change have significant effects on tropical carbon stocks; however, an elusive and yet undetected decrease in carbon storage may be due to defaunation of large seed dispersers. Many large tropical trees with sizeable contributions to carbon stock rely on large vertebrates for seed dispersal and regeneration, however many of these frugivores are threatened by hunting, illegal trade, and habitat loss. We used a large data set on tree species composition and abundance, seed, fruit, and carbon-related traits, and plant-animal interactions to estimate the loss of carbon storage capacity of tropical forests in defaunated scenarios. By simulating the local extinction of trees that depend on large frugivores in 31 Atlantic Forest communities, we found that defaunation has the potential to significantly erode carbon storage even when only a small proportion of large-seeded trees are extirpated. Although intergovernmental policies to reduce carbon emissions and reforestation programs have been mostly focused on deforestation, our results demonstrate that defaunation, and the loss of key ecological interactions, also poses a serious risk for the maintenance of tropical forest carbon storage.

Functional attributes change but functional richness is unchanged after fragmentation of Brazilian Atlantic forests

Summary1. Fragmentation of tropical forests is one of the greatest threats to global biodiversity. Understand-ing how biological and functional attributes of communities respond to fragmentation and, in turn,whether ecosystem functioning is impacted upon are critical steps for assessing the long-term effectsand conservation values of forest fragments. Ecosystem functioning can be inferred through func-tional diversity metrics, including functional richness, evenness and divergence, which collectivelyquantify the range, distribution and uniqueness of functional traits within a community.2. Our study was carried out in forest remnants of the Brazilian Atlantic rain forest, which is a glo-bal hotspot of threatened biodiversity that has undergone massive deforestation and fragmentation.We focus on trees, which play critical functional roles in forest structure, food provisioning and car-bon storage, to examine community organization and functional diversity across a gradient of frag-mentation, from small to large fragments and at edge versus interior habitats.3. The interiors of small fragments have marginally higher species richness, but similar communitystructures, to the interiors of bigger fragments. In contrast, fragment edges suffered significant lossesof species and changes in community structure, relative to fragment interiors.4. Despite shifts in community organization, functional richness was not impacted by fragmentation,with the same number of functions provided independent of fragment size or proximity to edge.However, functional evenness and functional divergence both increased with decreasing fragmentsize, while fragment edges had lower functional evenness than interiors did, indicating that the abun-dance and dominance of functional traits has changed, with negative implications for functionalredundancy and ecosystem resilience. At fragment edges, large-fruited trees, critical as resources forfauna, were replaced by early successional, small-seeded species. The influence of fragment sizewas smaller, with a reduction in very large-fruited trees in small fragments counterbalanced byincreased numbers of fleshy- and medium-fruited trees. Wood density was not impacted by fragmen-tation.5. Synthesis. These results suggest that the interiors of even small fragments can contain importantbiodiversity, ecosystem functions and carbon stores, offering potential opportunities for cobenefitsunder existing carbon markets. Retaining forest fragments is an important conservation strategywithin the highly threatened Brazilian Atlantic forest biome.Key-words: carbon, fauna resources, fragmented landscape, functional diversity, functional traitattributes, species richness, tableland Atlantic rain forest, wood density

Would protecting tropical forest fragments provide carbon and biodiversity cobenefits under REDD

Tropical forests store vast amounts of carbon and are the most biodiverse terrestrial habitats, yet they are being converted and degraded at alarming rates. Given global shortfalls in the budgets required to prevent carbon and biodiversity loss, we need to seek solutions that simultaneously address both issues. Of particular interest are carbon-based payments under the Reducing Emissions from Deforestation and Forest Degradation (REDD+) mechanism to also conserve biodiversity at no additional cost. One potential is for REDD+ to protect forest fragments, especially within biomes where contiguous forest cover has diminished dramatically, but we require empirical tests of the strength of any carbon and biodiversity cobenefits in such fragmented systems. Using the globally threatened Atlantic Forest landscape, we measured above-ground carbon stocks within forest fragments spanning 13 to 23 442 ha in area and with different degrees of isolation. We related these stocks to tree community structure and to the richness and abundance of endemic and IUCN Red-listed species. We found that increasing fragment size has a positive relationship with above-ground carbon stock and with abundance of IUCN Red-listed species and tree community structure. We also found negative relationships between distance from large forest block and tree community structure, endemic species richness and abundance, and IUCN Red-listed species abundance. These resulted in positive congruence between carbon stocks and Red-listed species, and the abundance and richness of endemic species, demonstrating vital cobenefits. As such, protecting forest fragments in hotspots of biodiversity, particularly larger fragments and those closest to sources, offers important carbon and biodiversity cobenefits. More generally, our results suggest that macroscale models of cobenefits under REDD+ have likely overlooked key benefits at small scales, indicating the necessity to apply models that include finer-grained assessments in fragmented landscapes rather than using averaged coarse-grained cells.

Do fragment size and edge effects predict carbon stocks in trees and lianas in tropical forests

Summary Tropical forests are critical for protecting global biodiversity and carbon stores. While forest degradation and fragmentation cause negative impacts on trees, many woody lianas benefit, with associated negative effects on carbon storage. Here, we focus on the key question of how abiotic environmental changes resulting from tropical forest fragmentation mediate the allocation of carbon into trees and lianas. We focus on the globally threatened Brazilian Atlantic Forest, in forest fragments spanning 13–23 442 ha in area and at fragment edges and interiors. Within each fragment, we established two transects: one at the edge and one in the interior. Each transect consisted of ten 10 × 10 m plots spaced at 20 m intervals. Within each plot, we sampled living trees with diameter ≥4·8 cm at 1·3 m above ground, living lianas with diameter ≥1·6 cm at 10 cm above ground, and several microclimatic and soil variables. Fragmentation changed a broad suite of abiotic environmental conditions recognized as being associated with forest carbon stocks: edges and smaller fragments were hotter, windier, and less humid, with more fertile and less acid soils at edges. Tree carbon stocks were thus higher in forest interiors than at edges, and were positively related to fragment size in interiors, but were not impacted by fragment size at edges. Trees and lianas showed different responses to fragmentation: in interiors of small fragments, tree carbon stocks declined whereas liana carbon stocks increased; and at edges, tree carbon stocks were not affected by fragment size, whereas liana carbon stocks were highest in smaller fragments. These patterns were strongly related to changes in abiotic environmental conditions. We conclude that the abiotic changes across the fragmentation gradient, rather than liana proliferation, were more likely to reduce tree carbon stocks. Cutting of lianas is frequently promoted for restoring forest carbon in human-modified tropical forests. However, this approach may not be effective for restoring forest carbon stocks in fragmented forests.

Soil and altitude drive diversity and functioning of Brazilian Páramos (campo de altitude)

Aims the vegetation on Brazilian Páramos consists of assemblages that are driven mainly by the influence of strong environmental filtering. It is very important to understand the effect of environmental variation on taxonomic diversity and on functional diversity. considering the lack of information about the functional diversity in Brazilian Páramos, we analyzed for the first time the effects of altitude and edaphic attributes on functional traits, as well as on taxonomic and functional diversity. We also wanted to answer the questions: Which ecological strategies are favorable in high-altitude grassland? Does soil attributes determine distributions of traits in high-altitude grassland? considering the studied altitudinal gradient is altitude an important variable in the community assembly? Methods the study was conducted on three mountains: Mammoth (1850 m), Elephant (1790 m) and totem (1690 m) in Serra do Brigadeiro State Park, Minas Gerais State, Brazil. those mountains represent the ‘Serra das cabeças’, a smaller ridge that is surrounded by the Atlantic Forest, one of the 25 hotspot of biodiversity. the samples were taken using 100 plots of 1 m2 per mountain that were randomly distributed. All plants except mosses were sampled. the taxonomic diversity was evaluated using richness, Shannon diversity, effective number of species and Pielou evenness. For the functional diversity, we considered the functional richness, functional evenness and functional divergence. Generalized linear models (GLM/Poisson and quasi-Poisson) were used to evaluate the effect of abiotic variables (altitude, soil depth and soil chemical attributes) on biotic variables (number of species and individuals, life form, dispersal and fruit type) and ordinary least squares regression to evaluate the effect of abiotic variables on the functional and taxonomic diversity. Important Findings the soil variables presented a considerable edaphic gradient associated with altitude. the soil in Serra das cabeças plays an important role for the plant diversity: richness and diversity index were positively related with fertility. With regard to the life form, nanophanerophytes tended to increase with altitude and soil depth, while therophytes tended to decrease with altitude. the dispersal type was also associated with the abiotic variables: autochory decreases with altitude, while zoochory increases. Functional richness increases with fertility and the functional evenness with altitude. the studied gradient showed that altitude is working as a filter for functional traits and indices and is, together with soil attributes, an important determinant for the distribution of plants on Brazilian Páramos.

Water Availability Drives Gradients of Tree Diversity, Structure and Functional Traits in the Atlantic-Cerrado-Caatinga Transition, Brazil

Aims Climate and soil are among the most important factors determining variation in tree communities, but their effects have not been thoroughly elucidated to date for many vegetation features. In this study, we evaluate how climate and soil gradients affect gradients of vegetation composition, species diversity and dominance, structure and functional traits (seed mass and wood density) using over 327 000 trees in 158 sites distributed along environmental gradients in the transitions among the Atlantic forest, Cerrado and Caatinga in Minas Gerais State (MG), Brazil (nearly 600 000 km 2). Methods Gradients in species, genus and family abundance in addition to basal area, stem density, species diversity (Fishers alpha), dominance percentage, seed mass and wood density were correlated using multiple regressions with environmental variables, as summarized in four principal component analysis axes (two climatic - precipitation seasonality and temperature range - and two edaphic - soil fertility and soil moisture). Additionally, ordinary kriging maps were used to better illustrate the gradients. Important Findings Multiple regression models indicate that all variables but dominance percentage were affected by one or more of the environmental gradients, but the average R 2 was low (26.25%). Kriging maps reinforced the patterns observed in the regression models. Precipitation seasonality and soil moisture gradients were the most important gradients affecting vegetation features. This finding suggests that water availability is an important determinant of vegetation features in these vegetation transitions.

Loss of biodiversity and shifts in aboveground biomass drivers in tropical rainforests with different disturbance histories

Tropical forests account for more than half of the global carbon forest stock and much of the biological diversity on Earth. However, disturbances such as deforestation and forest degradation threaten the maintenance of these ecosystem services. This study aimed to understand how different disturbance histories affect the forest stand biomass, as well as species and functional diversity, and to what extent these differences can change the relationships between biomass and their drivers. We used data from forests with clear-cut and selectively logged disturbance histories, and from old-growth forests, situated in the Brazilian Atlantic forest. Forests with logging disturbances showed significant losses in their aboveground biomass compared to those of old-growth forests (50% loss in selectively logged forests and 80% loss in clear-cut forests). Interestingly, only clear-cut secondary forests showed differences in species and functional diversity, and were dominated by species with acquisitive trait values, commonly found early in succession. Shifts in stand biomass drivers were observed in selectively logged forests. The mass-ratio hypothesis (mainly through the functional trait of maximum height) was the most important biomass driver in clear-cut secondary and old-growth forests, whereas the importance of the niche complementarity hypothesis (through functional richness and dispersion) was higher in selectively logged forests. Our study highlights that disturbance histories can affect forest aboveground biomass and its drivers. Moreover, our results reinforce the need for conservation of intact forests but highlight the importance of including degraded forests in conservation mechanisms based in carbon stocks, as these forests retain high values of species and functional diversities that are crucial to biomass and consequently carbon stock acquisition.