Cerrado deforestation threatens regional climate and water availability for agriculture and ecosystems.

The Brazilian Cerrado is one of the most biodiverse savannas in the world, yet 46% of its original cover has been cleared to make way for crops and pastures. These extensive land-use transitions (LUTs) are expected to influence regional climate by reducing evapotranspiration (ET), increasing land surface temperature (LST), and ultimately reducing precipitation. Here, we quantify the impacts of LUTs on ET and LST in the Cerrado by combining MODIS satellite data with annual land use and land cover maps from 2006 to 2019. We performed regression analyses to quantify the effects of six common LUTs on ET and LST across the entire gradient of Cerrado landscapes. Results indicate that clearing forests for cropland or pasture increased average LST by ~3.5°C and reduced mean annual ET by 44% and 39%, respectively. Transitions from woody savannas to cropland or pasture increased average LST by 1.9°C and reduced mean annual ET by 27% and 21%, respectively. Converting native grasslands to cropland or pasture increased average LST by 0.9 and 0.6°C, respectively. Conversely, grassland-to-pasture transitions increased mean annual ET by 15%. To date, land changes have caused a 10% reduction in water recycled to the atmosphere annually and a 0.9°C increase in average LST across the biome, compared to the historic baseline under native vegetation. Global climate changes from increased atmospheric greenhouse gas concentrations will only exacerbate these effects. Considering potential future scenarios, we found that abandoning deforestation control policies or allowing legal deforestation to continue (at least 28.4 Mha) would further reduce yearly ET (by -9% and -3%, respectively) and increase average LST (by +0.7 and +0.3°C, respectively) by 2050. In contrast, policies encouraging zero deforestation and restoration of the 5.2 Mha of illegally deforested areas would partially offset the warming and drying impacts of land-use change.

O Cerrado brasileiro é uma das savanas mais biodiversas do mundo. Apesar disso, 46% da sua cobertura original foi desmatada para dar lugar a cultivos agrícolas e pastos. Estas extensas transições de uso do solo (LUT) têm o potencial de influenciar o clima regional, reduzindo a evapotranspiração (ET), aumentando a temperatura da superfície terrestre (LST) e por fim reduzindo a precipitação. O objetivo deste estudo foi quantificar os impactos de LUTs sobre ET e LST no Cerrado, combinando dados do satélite MODIS com mapas anuais de uso e cobertura do solo de 2006-2019. Foram realizadas análises de regressão para quantificar os efeitos de seis LUTs usuais sobre ET e LST, ao longo de todo o gradiente de paisagens do Cerrado. Os resultados indicaram que a retirada de florestas para dar lugar à agricultura ou pastagem aumentou a LST média em ~3.5°C e reduziu a ET média anual em 44% e 39%, respectivamente. Transições de formações savânicas para agricultura ou pastagem aumentaram a LST média em 1.9°C e reduziram a ET média anual em 27% e 21%, respectivamente. A conversão de campos nativos para agricultura ou pastagem aumentou a LST média em 0.9 e 0.6°C, respectivamente. Em contrapartida, transições de formações campestres nativas para pastagens aumentaram a ET média anual em 15%. Até o momento, as mudanças de uso do solo causaram redução de 10% da água reciclada para a atmosfera anualmente e aumento de 0.9°C da LST média ao longo do bioma, em comparação com a linha de base histórica sob vegetação nativa. As mudanças climáticas globais decorrentes do aumento das concentrações atmosféricas de gases do efeito estufa irão exacerbar esses efeitos. Considerando potenciais cenários futuros, observou-se que o abandono das políticas de controle do desmatamento ou o avanço do desmatamento legal (ao menos 28.4 Mha) reduziriam a ET anual (em −9% e −3%, respectivamente) e aumentariam a LST média (em +0.7 e +0.3ºC, respectivamente) até 2050. Por outro lado, políticas que promovam desmatamento zero e restauração dos 5.2 Mha de áreas ilegalmente desmatadas compensariam parte dos impactos de aquecimento e seca causados por alterações de uso do solo.

Cerrado ecoregions: A spatial framework to assess and prioritize Brazilian savanna environmental diversity for conservation.

The Brazilian Cerrado is the second largest biome in Latin America, extending over more than 200 million ha and hosts some of the most intensive agricultural activities for grain and beef production in the world. Because of the biodiversity richness and high levels of endemism, Cerrado is considered one of world's hotspot for biodiversity conservation. The objectives of this study are three-fold: to present a comprehensive division of Cerrado into different ecoregions that reflect the environmental heterogeneity within the biome; to analyze the ecoregions in terms of biophysical characteristics, protected areas, environmental liability in riparian permanent protection areas along watercourses, and priorities for biodiversity conservation; and to rank the ecoregions in terms of endangerment for biodiversity conservation and restoration. A previous study that delineated 22 ecoregions using geomorphology, vegetation, soil, geology, and plant diversity maps was revised using topography, vegetation, precipitation, and soil maps. Our new ecoregion map consists of 19 units that are unique in terms of landscape characteristics and has been adjusted to the current official boundary map of Cerrado. Some of the ecoregions consist of only one geomorphological compartment, whereas others are heterogeneous, consisting of up to eight compartments. Ferralsols comprise the dominant soil type in 14 of the ecoregions. The percentage of protected areas within ecoregions ranges from 1.7% to 51.5%. The most endangered ecoregion, where land use change critically threatens habitat integrity, is the Depressão Cárstica do São Francisco (states of Bahia, Minas Gerais, and Piauí), where environmental liability along riparian permanent protection areas amounts to 85.6% of the total area. Our proposed ecoregion map provides a spatial framework for regional and local assessments to improve decision-making processes to reconcile conservation and restoration planning, sustainable agriculture, and provision of ecosystem services. Besides de adjustment of the previous Cerrado's ecoregion map to the official biome boundary (relevant for the implementation of public policies of conservation as those regulated by the Brazilian Forest Code), the new analyses of the ecoregion map represent a substantial improvement in comparison to the ones conducted by the previous study in 2003. In addition, current web resources allow us to make all the information used or derived from this study available to other users. This opens the possibility of additional improvements of our findings by the scientific community or to be used effectively by decision makers.

Toward an integrated monitoring framework to assess the effects of tropical forest degradation and recovery on carbon stocks and biodiversity.

Tropical forests harbor a significant portion of global biodiversity and are a critical component of the climate system. Reducing deforestation and forest degradation contributes to global climate-change mitigation efforts, yet emissions and removals from forest dynamics are still poorly quantified. We reviewed the main challenges to estimate changes in carbon stocks and biodiversity due to degradation and recovery of tropical forests, focusing on three main areas: (1) the combination of field surveys and remote sensing; (2) evaluation of biodiversity and carbon values under a unified strategy; and (3) research efforts needed to understand and quantify forest degradation and recovery. The improvement of models and estimates of changes of forest carbon can foster process-oriented monitoring of forest dynamics, including different variables and using spatially explicit algorithms that account for regional and local differences, such as variation in climate, soil, nutrient content, topography, biodiversity, disturbance history, recovery pathways, and socioeconomic factors. Generating the data for these models requires affordable large-scale remote-sensing tools associated with a robust network of field plots that can generate spatially explicit information on a range of variables through time. By combining ecosystem models, multiscale remote sensing, and networks of field plots, we will be able to evaluate forest degradation and recovery and their interactions with biodiversity and carbon cycling. Improving monitoring strategies will allow a better understanding of the role of forest dynamics in climate-change mitigation, adaptation, and carbon cycle feedbacks, thereby reducing uncertainties in models of the key processes in the carbon cycle, including their impacts on biodiversity, which are fundamental to support forest governance policies, such as Reducing Emissions from Deforestation and Forest Degradation.

Seasonal effects in a lake sediment archaeal community of the Brazilian Savanna.

The Cerrado is a biome that corresponds to 24% of Brazil's territory. Only recently microbial communities of this biome have been investigated. Here we describe for the first time the diversity of archaeal communities from freshwater lake sediments of the Cerrado in the dry season and in the transition period between the dry and rainy seasons, when the first rains occur. Gene libraries were constructed, using Archaea-specific primers for the 16S rRNA and amoA genes. Analysis revealed marked differences between the archaeal communities found in the two seasons. I.1a and I.1c Thaumarchaeota were found in greater numbers in the transition period, while MCG Archaea was dominant on the dry season. Methanogens were only found in the dry season. Analysis of 16S rRNA sequences revealed lower diversity on the transition period. We detected archaeal amoA sequences in both seasons, but there were more OTUs during the dry season. These sequences were within the same cluster as Nitrosotalea devanaterra's amoA gene. The principal coordinate analysis (PCoA) test revealed significant differences between samples from different seasons. These results provide information on archaeal diversity in freshwater lake sediments of the Cerrado and indicates that rain is likely a factor that impacts these communities.

Contrasting patterns of foraging behavior in neotropical stingless bees using pollen and honey metabarcoding.

Stingless bees are major flower visitors in the tropics, but their foraging preferences and behavior are still poorly understood. Studying stingless bee interactions with angiosperms is methodologically challenging due to the high tropical plant diversity and inaccessibility of upper canopy flowers in forested habitats. Pollen DNA metabarcoding offers an opportunity of assessing floral visitation efficiently and was applied here to understand stingless bee floral resources spectra and foraging behavior. We analyzed pollen and honey from nests of three distantly related stingless bee species, with different body size and social behavior: Melipona rufiventris, Scaptotrigona postica and Tetragonisca angustula. Simultaneously, we evaluate the local floristic components through seventeen rapid botanical surveys conducted at different distances from the nests. We discovered a broad set of explored floral sources, with 46.3 plant species per bee species in honey samples and 53.67 in pollen samples. Plant families Myrtaceae, Asteraceae, Euphorbiaceae, Melastomataceae and Malpighiaceae dominated the records, indicating stingless bee preferences for abundant resources that flowers of these families provide in the region. Results also reinforce the preference of stingless bees for forest trees, even if only available at long distances. Our high-resolution results encourage future bee-plant studies using pollen and honey metabarcoding in hyper-diverse tropical environments.

Alien and endangered plants in the Brazilian Cerrado exhibit contrasting relationships with vegetation biomass and N : P stoichiometry.

Although endangered and alien invasive plants are commonly assumed to persist under different environmental conditions, surprisingly few studies have investigated whether this is the case. We examined how endangered and alien species are distributed in relation to community biomass and N : P ratio in the above-ground community biomass in savanna vegetation in the Brazilian Cerrado. For 60 plots, we related the occurrence of endangered (Red List) and alien invasive species to plant species richness, vegetation biomass and N : P ratio, and soil variables. Endangered plants occurred mainly in plots with relatively low above-ground biomass and high N : P ratios, whereas alien invasive species occurred in plots with intermediate to high biomass and low N : P ratios. Occurrences of endangered or alien plants were unrelated to extractable N and P concentrations in the soil. These contrasting distributions in the Cerrado imply that alien species only pose a threat to endangered species if they are able to invade sites occupied by these species and increase the above-ground biomass and/or decrease the N : P ratio of the vegetation. We found some evidence that alien species do increase above-ground community biomass in the Cerrado, but their possible effect on N : P stoichiometry requires further study.

Characterization of soil bacterial assemblies in Brazilian savanna-like vegetation reveals acidobacteria dominance.

The Brazilian Cerrado is the second largest biome in Brazil and is considered a biodiversity hotspot. In this work, we compared the bacterial communities in Cerrado soil associated with four types of native vegetation (Cerrado Denso, Cerrado sensu stricto, Campo Sujo, and Mata de Galeria) by ribosomal RNA intergenic spacer analysis, terminal fragment restriction length polymorphism and pyrosequencing. The fingerprinting results were very similar. The bacterial communities of Cerrado Denso and Cerrado sensu stricto grouped together and were distinct from those in Campo Sujo and Mata de Galeria. Pyrosequencing generated approximately 40,000 16S rRNA gene sequences per sample and allowed the identification of 17 phyla in soil samples under Cerrado vegetation. Acidobacteria were dominant in all areas studied with a relative frequency of 40-47 %, followed closely by Proteobacteria accounting for 34-40 % of the sequences. Results from all molecular techniques used suggested that the bacterial communities of Cerrado sensu stricto and Cerrado Denso are very similar to each other, while Campo Sujo forms a separate group, and Mata de Galeria is the most distinct with higher species richness. This is the first extensive study of native Cerrado soil microbiota, an important but endangered biome.

Relationships among net primary productivity, nutrients and climate in tropical rain forest: a pan-tropical analysis.

Tropical rain forests play a dominant role in global biosphere-atmosphere CO(2) exchange. Although climate and nutrient availability regulate net primary production (NPP) and decomposition in all terrestrial ecosystems, the nature and extent of such controls in tropical forests remain poorly resolved. We conducted a meta-analysis of carbon-nutrient-climate relationships in 113 sites across the tropical forest biome. Our analyses showed that mean annual temperature was the strongest predictor of aboveground NPP (ANPP) across all tropical forests, but this relationship was driven by distinct temperature differences between upland and lowland forests. Within lowland forests (< 1000 m), a regression tree analysis revealed that foliar and soil-based measurements of phosphorus (P) were the only variables that explained a significant proportion of the variation in ANPP, although the relationships were weak. However, foliar P, foliar nitrogen (N), litter decomposition rate (k), soil N and soil respiration were all directly related with total surface (0-10 cm) soil P concentrations. Our analysis provides some evidence that P availability regulates NPP and other ecosystem processes in lowland tropical forests, but more importantly, underscores the need for a series of large-scale nutrient manipulations - especially in lowland forests - to elucidate the most important nutrient interactions and controls.

The climatic sensitivity of the forest, savanna and forest-savanna transition in tropical South America.

*We used a climate-vegetation-natural fire (CVNF) conceptual model to evaluate the sensitivity and vulnerability of forest, savanna, and the forest-savanna transition to environmental changes in tropical South America. *Initially, under current environmental conditions, CVNF model results suggested that, in the absence of fires, tropical forests would extend c. 200 km into the presently observed savanna domain. *Environmental changes were then imposed upon the model in temperature, precipitation and lightning strikes. These changes ranged from 2 to 6 degrees C warming, +10 to -20% precipitation change and 0 to 15% increase in lightning frequency, which, in aggregate form, represent expected future climatic changes in response to global warming and deforestation. *The most critical vegetation changes are projected to take place over the easternmost portions of the basin, with a widening of the forest-savanna transition. The transition width would increase from 150 to c. 300 km, with tree cover losses ranging from 20 to 85%. This means that c. 6% of the areas currently covered by forests could potentially turn into grass-dominated savanna landscapes. The mechanism driving tree cover reduction consists of the combination of less favorable climate conditions for trees and more fire activity. In addition, this sensitivity analysis predicts that the current dry shrubland vegetation of northeast Brazil could potentially turn into a bare soil landscape.

Species richness both impedes and promotes alien plant invasions in the Brazilian Cerrado.

Worldwide, alien plant invasions have been intensively studied in the past decades, but mechanisms controlling the invasibility of native communities are not fully understood yet. The stochastic niche hypothesis predicts that species-rich plant communities are less prone to alien plant invasions than species-poor communities, which is supported by some but not all field studies, with some very species-rich communities such as the Brazilian Cerrado becoming heavily invaded. However, species-rich communities potentially contain a greater variety of facilitative interactions in resource exploitation than species-poor communities, from which invasive plants might benefit. This alternative hypothetical mechanism might explain why nutrient-poor, species-rich ecosystems are prone to invasion. Here we show that a high species richness both impedes and promotes invasive plants in the Brazilian Cerrado, using structural equation modelling and data from 38 field sites. We found support for the stochastic niche hypothesis through an observed direct negative influence of species richness on abundance of alien invasive species, but an indirect positive effect of species richness on invasive alien plants through soil phosphatase activity that enhances P availability was also found. These field observations were supported with results from a mesocosm experiment. Root phosphatase activity of plants increased with species richness in the mesocosms, which was associated with greater community P and N uptake. The most prominent alien grass species of the region, Melinis minutiflora, benefited most from the higher N and P availability in the species mixtures. Hence, this study provides a novel explanation of why species-richness may sometimes promote rather than impede invasion, and highlights the need to perform facilitation experiments in multi-species communities.

Molecular phylogenetic diversity of bacteria associated with soil of the savanna-like Cerrado vegetation.

The Brazilian savanna-like vegetation of Cerrado is rapidly being converted to pasture and agricultural fields. A 16S rDNA-based approach was taken to study the bacterial community associated with the soil of a native cerrado area (sensu stricto) and an area that has been converted to pasture. The bacterial group most abundantly identified in cerrado sensu stricto soil was the alpha-Proteobacteria while in cerrado converted to pasture the Actinobacteria were the most abundant. Rarefaction curves indicate that the species richness of cerrado sensu stricto is greater than that of cerrado converted to pasture. Furthermore, lineage-through-time plots show that the expected richness of species present in cerrado sensu stricto soil is approximately 10 times greater than that of cerrado converted to pasture.

Crop fertilization affects pollination service provision - Common bean as a case study.

The demand for insect-pollinated crops is increasing. Conventional agricultural intensification heavily relies on increased input of fertilizers, which can have negative effects on local biodiversity. Such effects may be particularly accentuated in biodiversity hotspots that are naturally nutrient-poor. Ecological intensification of farming, i.e. practices that increase production through the increase of ecosystem services, emerges as an alternative to conventional intensification. For example, practices that boost abundance and diversity of crop pollinators can lead to substantial increases in cropland productivity. However, little is known about the synergisms and trade-offs between fertilizer input and such ecological intensification practices. Here we investigate interactive effects between fertilization practices and the provision of ecosystem services in a biodiversity hotspot where conventional agriculture is rapidly expanding (Brazilian savannas). We focus on a highly nitrogen-demanding crop species that benefits from pollinators (the common bean, Phaseolus vulgaris L.), for which nitrogen input greatly varies in the study region. Our findings show that positive effects of native pollinators on crop yield are most accentuated under low inputs of nitrogen (e.g. equal to or below 72kg ha-1). This interactive effect could be due to changes in flower visitor community composition or behaviour. Our study also suggests that landscape management practices that minimize isolation from patches of natural vegetation and maximize its cover nearby (within 500 meters) of production areas can increase pollinator and biocontrol agent abundance and richness. Overall, these results suggest that ecological intensification is a valuable alternative for common bean production in Brazil, and potentially other regions of the world. Land productivity can be enhanced if an adequate balance of chemical inputs and landscape management is achieved.

Optimizing biomass estimates of savanna woodland at different spatial scales in the Brazilian Cerrado: Re-evaluating allometric equations and environmental influences.

Cerrado is the second largest biome in South America and accounted for the second largest contribution to carbon emissions in Brazil for the last 10 years, mainly due to land-use changes. It comprises approximately 2 million km2 and is divided into 22 ecoregions, based on environmental conditions and vegetation. The most dominant vegetation type is cerrado sensu stricto (cerrado ss), a savanna woodland. Quantifying variation of biomass density of this vegetation is crucial for climate change mitigation policies. Integrating remote sensing data with adequate allometric equations and field-based data sets can provide large-scale estimates of biomass. We developed individual-tree aboveground biomass (AGB) allometric models to compare different regression techniques and explanatory variables. We applied the model with the strongest fit to a comprehensive ground-based data set (77 sites, 893 plots, and 95,484 trees) to describe AGB density variation of cerrado ss. We also investigated the influence of physiographic and climatological variables on AGB density; this analysis was restricted to 68 sites because eight sites could not be classified into a specific ecoregion, and one site had no soil texture data. In addition, we developed two models to estimate plot AGB density based on plot basal area. Our data show that for individual-tree AGB models a) log-log linear models provided better estimates than nonlinear power models; b) including species as a random effect improved model fit; c) diameter at 30 cm above ground was a reliable predictor for individual-tree AGB, and although height significantly improved model fit, species wood density did not. Mean tree AGB density in cerrado ss was 22.9 tons ha-1 (95% confidence interval = ± 2.2) and varied widely between ecoregions (8.8 to 42.2 tons ha-1), within ecoregions (e.g. 4.8 to 39.5 tons ha-1), and even within sites (24.3 to 69.9 tons ha-1). Biomass density tended to be higher in sites close to the Amazon. Ecoregion explained 42% of biomass variation between the 68 sites (P < 0.01) and shows strong potential as a parameter for classifying regional biomass variation in the Cerrado.

Controls over foliar N:P ratios in tropical rain forests.

Correlations between foliar nutrient concentrations and soil nutrient availability have been found in multiple ecosystems. These relationships have led to the use of foliar nutrients as an index of nutrient status and to the prediction of broadscale patterns in ecosystem processes. More recently, a growing interest in ecological stoichiometry has fueled multiple analyses of foliar nitrogen:phosphorus (N:P) ratios within and across ecosystems. These studies have observed that N:P values are generally elevated in tropical forests when compared to higher latitude ecosystems, adding weight to a common belief that tropical forests are generally N rich and P poor. However, while these broad generalizations may have merit, their simplicity masks the enormous environmental heterogeneity that exists within the tropics; such variation includes large ranges in soil fertility and climate, as well as the highest plant species diversity of any biome. Here we present original data on foliar N and P concentrations from 150 mature canopy tree species in Costa Rica and Brazil, and combine those data with a comprehensive new literature synthesis to explore the major sources of variation in foliar N:P values within the tropics. We found no relationship between N:P ratios and either latitude or mean annual precipitation within the tropics alone. There is, however, evidence of seasonal controls; in our Costa Rica sites, foliar N:P values differed by 25% between wet and dry seasons. The N:P ratios do vary with soil P availability and/or soil order, but there is substantial overlap across coarse divisions in soil type, and perhaps the most striking feature of the data set is variation at the species level. Taken as a whole, our results imply that the dominant influence on foliar N:P ratios in the tropics is species variability and that, unlike marine systems and perhaps many other terrestrial biomes, the N:P stoichiometry of tropical forests is not well constrained. Thus any use of N:P ratios in the tropics to infer larger-scale ecosystem processes must comprehensively account for the diversity of any given site and recognize the broad range in nutrient requirements, even at the local scale.

Soil Acidobacterial 16S rRNA Gene Sequences Reveal Subgroup Level Differences between Savanna-Like Cerrado and Atlantic Forest Brazilian Biomes.

16S rRNA sequences from the phylum Acidobacteria have been commonly reported from soil microbial communities, including those from the Brazilian Savanna (Cerrado) and the Atlantic Forest biomes, two biomes that present contrasting characteristics of soil and vegetation. Using 16S rRNA sequences, the present work aimed to study acidobacterial diversity and distribution in soils of Cerrado savanna and two Atlantic forest sites. PCA and phylogenetic reconstruction showed that the acidobacterial communities found in "Mata de galeria" forest soil samples from the Cerrado biome have a tendency to separate from the other Cerrado vegetation microbial communities in the direction of those found in the Atlantic Forest, which is correlated with a high abundance of Acidobacteria subgroup 2 (GP2). Environmental conditions seem to promote a negative correlation between GP2 and subgroup 1 (GP1) abundance. Also GP2 is negatively correlated to pH, but positively correlated to high Al(3+) concentrations. The Cerrado soil showed the lowest Acidobacteria richness and diversity indexes of OTUs at the species and subgroups levels when compared to Atlantic Forest soils. These results suggest specificity of acidobacterial subgroups to soils of different biomes and are a starting point to understand their ecological roles, a topic that needs to be further explored.

Testing the Amazon savannization hypothesis: fire effects on invasion of a neotropical forest by native cerrado and exotic pasture grasses.

Changes in climate and land use that interact synergistically to increase fire frequencies and intensities in tropical regions are predicted to drive forests to new grass-dominated stable states. To reveal the mechanisms for such a transition, we established 50 ha plots in a transitional forest in the southwestern Brazilian Amazon to different fire treatments (unburned, burned annually (B1yr) or at 3-year intervals (B3yr)). Over an 8-year period since the commencement of these treatments, we documented: (i) the annual rate of pasture and native grass invasion in response to increasing fire frequency; (ii) the establishment of Brachiaria decumbens (an African C4 grass) as a function of decreasing canopy cover and (iii) the effects of grass fine fuel on fire intensity. Grasses invaded approximately 200 m from the edge into the interiors of burned plots (B1yr: 4.31 ha; B3yr: 4.96 ha) but invaded less than 10 m into the unburned plot (0.33 ha). The probability of B. decumbens establishment increased with seed availability and decreased with leaf area index. Fine fuel loads along the forest edge were more than three times higher in grass-dominated areas, which resulted in especially intense fires. Our results indicate that synergies between fires and invasive C4 grasses jeopardize the future of tropical forests.