Body size predicts ontogenetic nitrogen stable-isotope (δ15N) variation, but has little relationship with trophic level in ectotherm vertebrate predators.

Large predators have disproportionate effects on their underlying food webs. Thus, appropriately assigning trophic positions has important conservation implications both for the predators themselves and for their prey. Large-bodied predators are often referred to as apex predators, implying that they are many trophic levels above primary producers. However, theoretical considerations predict both higher and lower trophic position with increasing body size. Nitrogen stable isotope values (δ15N) are increasingly replacing stomach contents or behavioral observations to assess trophic position and it is often assumed that ontogenetic dietary shifts result in higher trophic positions. Intraspecific studies based on δ15N values found a positive relationship between size and inferred trophic position. Here, we use datasets of predatory vertebrate ectotherms (crocodilians, turtles, lizards and fishes) to show that, although there are positive intraspecific relationships between size and δ15N values, relationships between stomach-content-based trophic level (TPdiet) and size are undetectable or negative. As there is usually no single value for 15N trophic discrimination factor (TDF) applicable to a predator species or its prey, estimates of trophic position based on δ15N in ectotherm vertebrates with large size ranges, may be inaccurate and biased. We urge a reconsideration of the sole use of δ15N values to assess trophic position and encourage the combined use of isotopes and stomach contents to assess diet and trophic level.

Stable isotopic composition of Bothrops atrox (common lancehead) in four distinct land covers in eastern Amazonia

Since consumers reflect the isotopic composition of an assimilated diet, stable isotopes can be a useful tool to address the feeding ecology of tropical snakes. This is the first study reporting carbon and nitrogen stable isotopic composition of Bothrops atrox (Linnaeus, 1758) living in different landscapes located in the lower Amazon river, encompassing four main natural landscapes of the Amazon: old-growth forests, várzeas (flooded forests), savannas, and pastures. Our null hypothesis is that the δ13C of forest specimens of B.atrox is more negative because forests are dominated by C3 plants, while C4 plants are common in the other landscapes. On the other hand, δ15N of forest specimens should be more positive, since the δ15N of old-growth forests are higher than plants of savanna, várzea, and pastures. Confirming our hypothesis, the δ13C of B. atrox scales of the Tapajós National Forest was approximate −25‰ to −24‰, increased to approximately −23.5‰ to −23.0‰ in the savanna and pasture, and to −21‰ in the várzea, showing an increased contribution of C4-derived carbon. Some specimens of B. atrox had δ15N as high as 18‰, which is much higher than the average δ15N of the snake's prey (7‰), confirming the apex position of B. atrox in the Amazon region. The δ15N values of the forest specimens were 5‰ higher than the savanna specimens, and this difference decreased to 3‰ between the forest and the pasture, and the várzea specimens. Finally, there were not large differences between δ15N values of livers and scales in any of the landscapes, suggesting a constant diet through time, and reinforcing the possibility of the use of snake's scale as a less invasive and non-lethal tissue to analyze.

Linking above and belowground carbon sequestration, soil organic matter properties, and soil health in Brazilian Atlantic Forest restoration.

Forest restoration mitigates climate change by removing CO2 and storing C in terrestrial ecosystems. However, incomplete information on C storage in restored tropical forests often fails to capture the ecosystem's holistic C dynamics. This study provides an integrated assessment of C storage in above to belowground subsystems, its consequences for greenhouse gas (GHG) fluxes, and the quantity, quality, and origin of soil organic matter (SOM) in restored Atlantic forests in Brazil. Relations between SOM properties and soil health indicators were also explored. We examined two restorations using tree planting ('active restoration'): an 8-year-old forest with green manure and native trees planted in two rounds, and a 15-year-old forest with native-planted trees in one round without green manure. Restorations were compared to reformed pasture and primary forest sites. We measured C storage in soil layers (0-10, 10-20, and 20-30 cm), litter, and plants. GHG emissions were assessed using CH4 and CO2 fluxes. SOM quantity was evaluated using C and N, quality using humification index (HLIFS), and origin using δ13C and δ15N. Nine soil health indicators were interrelated with SOM attributes. The primary forest presented the highest C stocks (107.7 Mg C ha-1), followed by 15- and 8-year-old restorations and pasture with 69.8, 55.5, and 41.8 Mg C ha-1, respectively. Soil C stocks from restorations and pasture were 20% lower than primary forest. However, 8- and 15-year-old restorations stored 12.3 and 28.3 Mg ha-1 more aboveground C than pasture. The younger forest had δ13C and δ15N values of 2.1 and 1.7‰, respectively, lower than the 15-year-old forest, indicating more C derived from C3 plants and biological N fixation. Both restorations and pasture had at least 34% higher HLIFS in deeper soil layers (10-30 cm) than primary forest, indicating a lack of labile SOM. Native and 15-year-old forests exhibited higher soil methane influx (141.1 and 61.9 µg m-2 h-1). Forests outperformed pasture in most soil health indicators, with 69% of their variance explained by SOM properties. However, SOM quantity and quality regeneration in both restorations approached the pristine forest state only in the top 10 cm layer, while deeper soil retained agricultural degradation legacies. In conclusion, active restoration of the Atlantic Forest is a superior approach compared to pasture reform for GHG mitigation. Nonetheless, the development of restoration techniques to facilitate labile C input into deeper soil layers (>10 cm) is needed to further improve soil multifunctionality and long-term C storage.

Forest restoration rehabilitates soil multifunctionality in riparian zones of sugarcane production landscapes.

Brazilian sugarcane plays a vital role in the production of both sugar and renewable energy. However, land use change and long-term conventional sugarcane cultivation have degraded entire watersheds, including a substantial loss of soil multifunctionality. In our study, riparian zones have been reforested to mitigate these impacts, protect aquatic ecosystems, and restore ecological corridors within the sugarcane production landscapes. We examined (i) how forest restoration enables rehabilitation of the soil's multifunctionality after long-term sugarcane cultivation and (ii) how long it takes to regain ecosystem functions comparable to those of a primary forest. We investigated a time series of riparian forests at 6, 15, and 30 years after starting restoration by planting trees (named 'active restoration') and determined soil C stocks, δ13C (indicative of C origin), as well as measures indicative of soil health. A primary forest and a long-term sugarcane field were used as references. Eleven soil physical, chemical, and biological indicators were used for a structured soil health assessment, calculating index scores based on soil functions. Forest-to-cane conversion reduced 30.6 Mg ha-1 of soil C stocks, causing soil compaction and loss of cation exchange capacity, thus degrading soil's physical, chemical, and biological functions. Forest restoration for 6-30 years recovered 16-20 Mg C ha-1 stored in soils. In all restored sites, soil functions such as supporting root growth, aerating the soil, nutrient storage capacity, and providing C energy for microbial activity were gradually recovered. Thirty years of active restoration was sufficient to reach the primary forest state in overall soil health index, multifunctional performance, and C sequestration. We conclude that active forest restoration in sugarcane-dominated landscapes is an effective way to restore soil multifunctionality approaching the level of the native forest in approximately three decades. Moreover, the C sequestration in the restored forest soils will help to mediate global warming.

Basin-wide variation in tree hydraulic safety margins predicts the carbon balance of Amazon forests.

Tropical forests face increasing climate risk1,2, yet our ability to predict their response to climate change is limited by poor understanding of their resistance to water stress. Although xylem embolism resistance thresholds (for example, [Formula: see text]50) and hydraulic safety margins (for example, HSM50) are important predictors of drought-induced mortality risk3-5, little is known about how these vary across Earth's largest tropical forest. Here, we present a pan-Amazon, fully standardized hydraulic traits dataset and use it to assess regional variation in drought sensitivity and hydraulic trait ability to predict species distributions and long-term forest biomass accumulation. Parameters [Formula: see text]50 and HSM50 vary markedly across the Amazon and are related to average long-term rainfall characteristics. Both [Formula: see text]50 and HSM50 influence the biogeographical distribution of Amazon tree species. However, HSM50 was the only significant predictor of observed decadal-scale changes in forest biomass. Old-growth forests with wide HSM50 are gaining more biomass than are low HSM50 forests. We propose that this may be associated with a growth-mortality trade-off whereby trees in forests consisting of fast-growing species take greater hydraulic risks and face greater mortality risk. Moreover, in regions of more pronounced climatic change, we find evidence that forests are losing biomass, suggesting that species in these regions may be operating beyond their hydraulic limits. Continued climate change is likely to further reduce HSM50 in the Amazon6,7, with strong implications for the Amazon carbon sink.

Selective sorption and desorption of DOM in Podzol horizons - DOC and aluminium contents of leachates from a column experiment.

Complexation of dissolved organic matter (DOM) with cations and minerals contributes to the stabilization of carbon in soils, and can enable the transport of metals in the environment. Hence, a proper understanding of mechanisms that control DOM binding properties in the soil is important for major environmental challenges, such as climate change and stream pollution. However, the role of DOM source in those mechanisms remains understudied. Here, we consider poorly drained tropical Podzols as a model environment to isolate effects of aluminium and DOM on sorption and desorption processes in podzolisation. We collected E- and Bh-horizons from a Brazilian coastal Podzol under tropical rainforest to conduct a column experiment, and percolated the columns with DOM collected from a stream (Stream), peat water (Peat), litter (Litter) and charred litter (Char). To quantify sorption and desorption from the columns, leachates were analysed for DOC content, aluminium content, pH, and the amount of fulvic acid relative to humic acid. The results showed large differences in DOC retention between DOM-types, which were consistent over all columns. Retention of DOC in the column varied between 25 % and 92 % for DOM-type Stream, between 33 % and 63 % for DOM-type Peat, between 22 % and 47 % for DOM-type Litter, and between 8 % and 49 % for DOM-type Char. Similarly, desorption from columns with B-horizon material highly differed between DOM-types. Percolation with DOM-types Stream and Peat caused a release of native DOC from B columns that was higher than in those percolated with water only. On the other hand, percolation of B columns with DOM-types Litter and Char caused a net DOC retention. These differences reflect that certain DOM-types hindered desorption, while other DOM-types caused active desorption. The large differences in sorption/desorption between DOM-types implies that changes in environmental conditions may highly influence the fate of soil carbon in Podzols.

Linking land-use and land-cover transitions to their ecological impact in the Amazon.

Human activities pose a major threat to tropical forest biodiversity and ecosystem services. Although the impacts of deforestation are well studied, multiple land-use and land-cover transitions (LULCTs) occur in tropical landscapes, and we do not know how LULCTs differ in their rates or impacts on key ecosystem components. Here, we quantified the impacts of 18 LULCTs on three ecosystem components (biodiversity, carbon, and soil), based on 18 variables collected from 310 sites in the Brazilian Amazon. Across all LULCTs, biodiversity was the most affected ecosystem component, followed by carbon stocks, but the magnitude of change differed widely among LULCTs and individual variables. Forest clearance for pasture was the most prevalent and high-impact transition, but we also identified other LULCTs with high impact but lower prevalence (e.g., forest to agriculture). Our study demonstrates the importance of considering multiple ecosystem components and LULCTs to understand the consequences of human activities in tropical landscapes.

Stemflow generation as influenced by sugarcane canopy development.

Rainfall is generally partitioned into throughfall, stemflow, and interception in ecosystems. Stemflow variability can affect the hydrology, ecology, and soil chemistry patterns. However, the influence of canopy structure and rainfall characteristics on stemflow production in sugarcane plantations which are important for renewable energy production remain poorly understood. By using funnels attached to the sugarcane stems, the present study determined the stemflow amount during the period of sugarcane growth and its relationship with plant development. Approximately, 14% of gross rainfall reached the soil as stemflow, and the funneling ratios was 60. In general, it was observed a positive relationship between stemflow rates with both leaf area index and plant height. This was attributed to an increasing number of acute branching angles of the sugarcane leaves as well as high stem tillering and density. However, at the end of growth cycle, stemflow rate was lower than in previous periods which can be attributed to changes in sugarcane canopy such as stems inclination and lodging, reducing the effectiveness of water conveyance along the stem. Our study showed the need to include stemflow to better understand the hydrology of sugarcane plantations.

Asymbiotic nitrogen fixation in the phyllosphere of the Amazon forest: Changing nitrogen cycle paradigms.

Biological nitrogen fixation is a key process for the maintenance of natural ecosystems productivity. In tropical forests, the contribution of asymbiotic nitrogen fixation (ANF) to the nitrogen (N) input has been underestimated, even though few studies have shown that ANF may be as important as symbiotic nitrogen fixation in such environments. The inputs and abiotic modulators of ANF in the Amazon forest are not completely understood. Here, we determined ANF rates and estimated the N inputs from ANF in the phyllosphere, litter and rhizospheric soil of nine tree species in the Amazon forest over time, including an extreme drought period induced by the El Niño-Southern Oscillation. Our data showed that ANF rates in the phyllosphere were 2.8- and 17.6-fold higher than in the litter and rhizospheric soil, respectively, and was highly dependent on tree taxon. Sampling time was the major factor modulating ANF in all forest compartments. At the driest period, ANF rates were approximately 1.8-fold and 13.1-fold higher than at periods with higher rainfall, before and after the extreme drought period, respectively. Tree species was a key modulator of ANF in the phyllosphere, as well as N and Vanadium concentrations. Carbon, molybdenum and vanadium concentrations were significant modulators of ANF in the litter. Based on ANF rates at the three sampling times, we estimated that the N input in the Amazon forest through ANF in the phyllosphere, litter and rhizospheric soil, was between 0.459 and 0.714 kg N ha-1 yr-1. Our results highlight the importance of ANF in the phyllosphere for the N input in the Amazon forest, and suggest that changes in the patterns of ANF driven by large scale climatic events may impact total N inputs and likely alter forest productivity.

Rainforest-to-pasture conversion stimulates soil methanogenesis across the Brazilian Amazon.

The Amazon rainforest is a biodiversity hotspot and large terrestrial carbon sink threatened by agricultural conversion. Rainforest-to-pasture conversion stimulates the release of methane, a potent greenhouse gas. The biotic methane cycle is driven by microorganisms; therefore, this study focused on active methane-cycling microorganisms and their functions across land-use types. We collected intact soil cores from three land use types (primary rainforest, pasture, and secondary rainforest) of two geographically distinct areas of the Brazilian Amazon (Santarém, Pará and Ariquemes, Rondônia) and performed DNA stable-isotope probing coupled with metagenomics to identify the active methanotrophs and methanogens. At both locations, we observed a significant change in the composition of the isotope-labeled methane-cycling microbial community across land use types, specifically an increase in the abundance and diversity of active methanogens in pastures. We conclude that a significant increase in the abundance and activity of methanogens in pasture soils could drive increased soil methane emissions. Furthermore, we found that secondary rainforests had decreased methanogenic activity similar to primary rainforests, and thus a potential to recover as methane sinks, making it conceivable for forest restoration to offset greenhouse gas emissions in the tropics. These findings are critical for informing land management practices and global tropical rainforest conservation.

Tree mode of death and mortality risk factors across Amazon forests.

The carbon sink capacity of tropical forests is substantially affected by tree mortality. However, the main drivers of tropical tree death remain largely unknown. Here we present a pan-Amazonian assessment of how and why trees die, analysing over 120,000 trees representing > 3800 species from 189 long-term RAINFOR forest plots. While tree mortality rates vary greatly Amazon-wide, on average trees are as likely to die standing as they are broken or uprooted-modes of death with different ecological consequences. Species-level growth rate is the single most important predictor of tree death in Amazonia, with faster-growing species being at higher risk. Within species, however, the slowest-growing trees are at greatest risk while the effect of tree size varies across the basin. In the driest Amazonian region species-level bioclimatic distributional patterns also predict the risk of death, suggesting that these forests are experiencing climatic conditions beyond their adaptative limits. These results provide not only a holistic pan-Amazonian picture of tree death but large-scale evidence for the overarching importance of the growth-survival trade-off in driving tropical tree mortality.

What do stable isotopes tell us about the trophic ecology of Thamnodynastes hypoconia (Serpentes: Dipsadidae) in southern Brazil?

Snakes are a useful model for ecological studies because they are gape-limited predators that may undergo ontogenetic changes in diet. We analyzed carbon and nitrogen stable isotope ratios to estimate percent contributions of different prey to snake biomass, trophic positions and isotopic niche width of juveniles and adults of the snake Thamnodynastes hypoconia. We also estimated the isotopic niche overlap between the two age categories. During eight intervals over a two-year period, we collected samples of whole blood and scales at a site in southern Brazil. Isotopic ratios of carbon and nitrogen did not differ between juveniles and adults for either tissue type, nor did mean trophic positions of juveniles and adults differ. The percent contribution of prey categories to snake biomass differed to a limited extent between the two years, with Hylidae being the most important anuran group assimilated during the first year and Leptodactylidae during the second year, for both ages. The isotopic niche occupied by adult snakes was slightly larger than that of juveniles when the analysis was based on data from whole blood samples, as expected because snakes are gape-limited. We found a reverse pattern when the analysis was based on scales, which may indicate that adult snakes have a smaller niche over the long term as they become selective foragers in certain prey. Isotopic overlap between juveniles and adults occurred during the two years, but it was bigger during the second year. We infer that, despite differences in gape size, juvenile and adult snakes in the study area exploit similar prey, with the degree of trophic similarity varying interannually.

Long-term thermal sensitivity of Earth's tropical forests.

The sensitivity of tropical forest carbon to climate is a key uncertainty in predicting global climate change. Although short-term drying and warming are known to affect forests, it is unknown if such effects translate into long-term responses. Here, we analyze 590 permanent plots measured across the tropics to derive the equilibrium climate controls on forest carbon. Maximum temperature is the most important predictor of aboveground biomass (-9.1 megagrams of carbon per hectare per degree Celsius), primarily by reducing woody productivity, and has a greater impact per °C in the hottest forests (>32.2°C). Our results nevertheless reveal greater thermal resilience than observations of short-term variation imply. To realize the long-term climate adaptation potential of tropical forests requires both protecting them and stabilizing Earth's climate.

Does food partitioning vary in leaf-eating crabs in response to source quality?

Mangroves have a relevant ecosystem function due to their efficiency in blue carbon sequestration. Autotrophic carbon conservation in mangroves remains controversial. In this sense, autotrophic nutrient assimilation by crabs can highlight their ecosystem function. This study aims to identify the relationship between quality sources and food partitioning in two leaf-eating crabs, Ucides cordatus and Goniopsis cruentata. Quantification of the litterfall biomass, analysis of the soil, the C/N ratio and stable isotopes (δ13C and δ15N) were used to evaluate food sources and crab tissues in two mangrove forests. The litterfall and soil C contents and C/N ratios of the Pacoti River (PR) were higher than those of the Jaguaribe River. The higher C/N ratios of the litterfall of the PR led to higher nitrogen ingestion from complementary food sources (soil and omnivorous invertebrates). The nutritional requirements and food partitioning behavior of both species emphasize the ecosystem functions of leaf-eating crabs concerning the assimilation and conservation of autotrophic carbon and nitrogen in mangroves.

Compositional response of Amazon forests to climate change.

Most of the planet's diversity is concentrated in the tropics, which includes many regions undergoing rapid climate change. Yet, while climate-induced biodiversity changes are widely documented elsewhere, few studies have addressed this issue for lowland tropical ecosystems. Here we investigate whether the floristic and functional composition of intact lowland Amazonian forests have been changing by evaluating records from 106 long-term inventory plots spanning 30 years. We analyse three traits that have been hypothesized to respond to different environmental drivers (increase in moisture stress and atmospheric CO2 concentrations): maximum tree size, biogeographic water-deficit affiliation and wood density. Tree communities have become increasingly dominated by large-statured taxa, but to date there has been no detectable change in mean wood density or water deficit affiliation at the community level, despite most forest plots having experienced an intensification of the dry season. However, among newly recruited trees, dry-affiliated genera have become more abundant, while the mortality of wet-affiliated genera has increased in those plots where the dry season has intensified most. Thus, a slow shift to a more dry-affiliated Amazonia is underway, with changes in compositional dynamics (recruits and mortality) consistent with climate-change drivers, but yet to significantly impact whole-community composition. The Amazon observational record suggests that the increase in atmospheric CO2 is driving a shift within tree communities to large-statured species and that climate changes to date will impact forest composition, but long generation times of tropical trees mean that biodiversity change is lagging behind climate change.

Biogeochemical diversity, O2-supersaturation and hot moments of GHG emissions from shallow alkaline lakes in the Pantanal of Nhecolândia, Brazil.

Nhecolândia is a vast sub-region of the Pantanal wetland in Brazil with great diversity in surface water chemistry evolving in a sodic alkaline pathway under the influence of evaporation. In this region, >15,000 shallow lakes are likely to contribute an enormous quantity of greenhouse gas to the atmosphere, but the diversity of the biogeochemical scenarios and their variability in time and space is a major challenge to estimate the regional contribution. From 4 selected alkaline lakes, we compiled measurements of the physico-chemical characteristics of water and sediments, gas fluxes in floating chambers, and sedimentation rates to illustrate this diversity. Although these lakes have a similar chemical composition, the results confirm a difference between the black-water and green-water alkaline lakes, corresponding to distinct biogeochemical functioning. This difference does not appear to affect lake sedimentation rates, but is reflected in gas emissions. Black-water lakes are CO2 and CH4 sources, with fairly constant emissions throughout the seasons. Annual carbon dioxide and methane emissions approach 0.86molm-2y-1 and 0.07molm-2y-1, respectively, and no clear trend towards N2O capture or emission was observed. By contrast, green-water lakes are CO2 and N2O sinks but important CH4 sources with fluxes varying significantly throughout the seasons, depending on the magnitude of the phytoplankton bloom. The results highlight important daily and seasonal variations in gas fluxes, and in particular a hot moments for methane emissions, when the O2-supersaturation is reached during the afternoon under extreme bloom and sunny weather conditions, provoking an abrupt O2 purging of the lakes. Taking into account the seasonal variability, annual methane emissions are around 10.2molm-2y-1, i.e., much higher than reported in previous studies for alkaline lakes in Nhecolândia. Carbon dioxide and nitrous oxide consumption is estimated about 1.9molm-2y-1 and 0.73mmolm-2y-1, respectively. However, these balances must be better constrained with systematic and targeted measurements throughout the seasons.

Age-dependent leaf physiology and consequences for crown-scale carbon uptake during the dry season in an Amazon evergreen forest.

Satellite and tower-based metrics of forest-scale photosynthesis generally increase with dry season progression across central Amazônia, but the underlying mechanisms lack consensus. We conducted demographic surveys of leaf age composition, and measured the age dependence of leaf physiology in broadleaf canopy trees of abundant species at a central eastern Amazon site. Using a novel leaf-to-branch scaling approach, we used these data to independently test the much-debated hypothesis - arising from satellite and tower-based observations - that leaf phenology could explain the forest-scale pattern of dry season photosynthesis. Stomatal conductance and biochemical parameters of photosynthesis were higher for recently mature leaves than for old leaves. Most branches had multiple leaf age categories simultaneously present, and the number of recently mature leaves increased as the dry season progressed because old leaves were exchanged for new leaves. These findings provide the first direct field evidence that branch-scale photosynthetic capacity increases during the dry season, with a magnitude consistent with increases in ecosystem-scale photosynthetic capacity derived from flux towers. Interactions between leaf age-dependent physiology and shifting leaf age-demographic composition are sufficient to explain the dry season photosynthetic capacity pattern at this site, and should be considered in vegetation models of tropical evergreen forests.

Human-modified landscape acts as refuge for mammals in Atlantic Forest / Paisagem antropicamente modificada atua como refúgio para mamíferos na Mata Atlântica

Abstract: Human-modified landscapes (HMLs) are composed by small, isolated and defaunated forest fragments, which are surrounded by agricultural and urban areas. Information on species that thrives in these HMLs is essential to direct conservation strategies in local and regional scales. Since HMLs are dominant in the Atlantic Forest, we aimed to assess the mammalian diversity in a HML in southeastern Brazil and to propose conservation strategies. We collected data of terrestrial (small-, medium- and large-sized) and volant mammals in three small forest fragments (10, 14 and 26 ha) and adjacent areas, between 2003 and 2016, using complementary methods: active search, camera trapping, live-traps, mist nets and occasional records (i.e., roadkills). In addition, we used secondary data to complement our species list. We recorded 35 native mammal species (6 small-sized, 16 medium- and large-sized, and 13 bats) and seven exotic species in the HML. The recorded mammal assemblage (non-volant and volant), although mainly composed of common and generalist species, includes three medium- and large-sized species nationally threatened (Leopardus guttulus, Puma concolor and Puma yagouaroundi) and two data deficient species (Galictis cuja and Histiotus velatus), highlighting the importance of this HML for the maintenance and conservation of mammal populations. Despite highly impacted by anthropogenic disturbances, the study area harbors a significant richness of medium- and large-sized mammals, being an important biodiversity refuge in the region. However, this biodiversity is threatened by the low quality of the habitats, roadkills and abundant populations of domestic cats and dogs. Therefore, we stress the need of conservation strategies focusing on the medium- and large-sized mammals as an umbrella group, which could benefit all biodiversity in the landscape. We recommend actions that promotes biological restoration, aiming to increase structural composition and connectivity of the forest fragments, reducing roadkills and controlling the domestic cats and dogs' populations, in order to maintain and improve the diversity of mammals in long-term.

Resumo: Paisagens antropicamente modificadas (HMLs) são compostas por fragmentos florestais pequenos, isolados e defaunados, imersos em áreas agrícolas e/ou urbanas. Informações sobre as espécies que habitam essas paisagens são importantes para o direcionamento de estratégias de conservação em escalas local e regional. Uma vez que as HMLs são as paisagens dominantes na Mata Atlântica, o objetivo deste trabalho foi avaliar a diversidade de mamíferos em uma HML do sudeste do Brasil e propor estratégias para sua conservação. Foram coletados dados de mamíferos terrestres (pequenos, médios e grandes) e voadores em três fragmentos florestais (10, 14 e 26 ha) e áreas adjacentes, entre 2003 e 2016, usando métodos complementares: busca ativa, armadilhamento fotográfico, armadilhas de captura e redes de neblina. Adicionalmente, foram utilizados dados de literatura para complementar a lista de espécies. Foram registradas 35 espécies de mamíferos nativos (6 de pequenos, 16 de médios e grandes e 13 de morcegos) e sete espécies exóticas. A assembleia de mamíferos registrada (terrestres e voadores), embora composta por espécies generalistas, apresentou três espécies de médio e grande porte ameaçadas de extinção nacionalmente (Leopardus guttulus, Puma concolor and Puma yagouaroundi) e duas deficientes em dados (Galictis cuja and Histiotus velatus), destacando a importância dessa HML para conservação e manutenção das populações de mamíferos. Embora inserida em uma paisagem extremamente modificada, a área de estudo abriga uma riqueza significativa de mamíferos de médio e grande porte, sendo um importante refúgio para a biodiversidade na região. Entretanto, essa biodiversidade está ameaçada pela baixa qualidade dos habitats, por atropelamentos e por abundantes populações de cães e gatos domésticos. Portanto, enfatizamos a necessidade de estratégias de conservação focadas nos mamíferos de médio e grande porte como grupo "guarda-chuva", o que pode beneficiar as demais espécies na paisagem. Recomendamos ações de conservação visando a restauração biológica, para melhorar a composição estrutural e conectividade dos fragmentos florestais, reduzir o número de atropelamentos e controlar as populações de cães e gatos domésticos, afim de manter e aumentar a diversidade local de mamíferos em longo prazo.

Impacts of converting low-intensity pastureland to high-intensity bioenergy cropland on the water quality of tropical streams in Brazil.

In Brazil, the cultivation of bioenergy crops is expanding at an accelerated rate. Most of this expansion has occurred over low-intensity pasture and is considered sustainable because it does not involve deforestation of natural vegetation. However, the impacts on the water quality of headwater streams are poorly understood, especially with regard to the influence of land use patterns in the watershed. In this study, we investigated the effects of land-use conversion on the water quality of streams draining sugarcane fields and examined whether the preservation of forested areas at the top of the headwaters would help mitigate the negative impacts of intensive agriculture. Water samples were collected in two paired catchments in southeastern Brazil, which is one of the largest sugarcane production regions in the world. Our results show significant differences in the water quality of streams predominantly draining the pasture or the sugarcane field. Several parameters commonly used to indicate water quality, such as the concentrations of nitrate and suspended solids, were significantly higher in the sugarcane than in the pasture stream. Differences in water quality between the streams draining predominantly pasture or sugarcane fields were accentuated during the wet season. The preservation of forests surrounding the headwater streams was associated with overall better water quality conditions, such as lower nitrate concentrations and temperature of the stream water. We concluded that forest conservation in the headwater agricultural catchments is an important factor preventing water quality degradation in tropical streams. Therefore, we strongly recommend the preservation of robust riparian forests in the headwaters of tropical watersheds with intensive agriculture. More studies on the effects of best agricultural practices in bioenergy crops can greatly improve our capacity to prevent the degradation of water quality in the tropical waterways as intensive agriculture continues to expand in this region of the world.