Brazilian Tropical Dry Forest Research Articles

Effects of aluminium on antioxidative system in native species of the Brazilian Tropical Dry Forest (Caatinga)

ABSTRACT Changes in soil resulting from agricultural practices can lead to acidification and the accumulation of toxic elements, such as Al3+. In acidic soils, aluminium solubility decreases nutrient availability, causing biochemical and morphophysiological changes that impede plant growth. This study aimed to determine how native species respond to the effects of Al3+ and its impact on their persistence in the environment. Soil samples were collected in areas with and without Al3+ in a natural regeneration zone. Leaves of three herbaceous species prevalent in the rainy season underwent biochemical analysis. The results revealed that Al3+ influenced enzymatic activity in Ayenia erecta, reducing superoxide dismutase and increasing ascorbate peroxidase and catalase. Pavonia varians exhibited an accumulation of H2O2 and a reduction in ascorbate peroxidase, while Sida galheirensis demonstrated an accumulation of sucrose and a reduction in proline levels in areas affected by Al3+, without changes in enzymatic activity or the accumulation of reactive oxygen species. The presence of 0.31 cmolc/dm³ of Al3+ was insufficient to induce lipid peroxidation in the studied species. Overall, the species responded differently to aluminium, impacting oxidative stress and potentially influencing their survival in the environment. These results provide insights into conservation practices and sustainable management in arid areas.

Foliar non-structural carbohydrates and resprouting ability of woody species in a tropical dry forest

Diverse disturbances contribute to biomass loss in tropical dry forests (TDF), of which slash-and-burn agriculture (SBA) may be the most severe; it is practiced by large populations of residents. Plant species capable of resprouting in response to such disturbances often possess above-ground structures that survive and mobilize resources for resprouting, in addition to below-ground structures. In Brazilian TDF, woody species regenerating from stem pieces that persist after SBA events are common. In this study, we evaluated the foliar concentrations of non-structural carbohydrates (NSC) and mineral nutrients during the first six months after an SBA event in all species that resprouted within the experimental area. Almost all the species resprouted exclusively from the stems. The measured nutrient concentrations did not change drastically after an SBA event. Two patterns were observed with respect to NSC concentrations among the species. Half of the studied species exhibited high concentrations of NSC before the SBA event, which gradually decreased three and six months after the disturbance. In contrast, the remaining species maintained consistent NSC concentrations throughout the study period. The cost of building new leaf tissue was similar for all species before the SBA event. However, after disturbance, the species invested different amounts of carbon into the new leaves. Those species that decreased NSC leaf concentration after SBA showed the highest regrowth intensity through the number of new tillers. Our results suggest that the intense translocation of NSC from the leaves before SBA may support the increased activity of the buds present in the remaining stem piece.

Gas exchange and phenotypic plasticity in three tree species in preserved and anthropized areas in a Tropical Dry Forest

Caatinga, the Brazilian tropical dry forest and source of endemic species, suffers anthropic disturbances that are responsible for affecting plants and their functional traits. Therefore, we aimed to evaluate the plasticity woody species’ leaf traits due to abiotic conditions of preserved and anthropized areas in Caatinga. The study took place in Vale do Riacho São José, in the municipality of Caetés, Pernambuco, Brazil. The selected species were Mimosa tenuiflora, Mimosa arenosa and Senna sp., all belonging to the Fabaceae family. We measured gas exchange, water content, specific leaf area and phenotypic plasticity index of all selected species in both areas. For all species, stomatal conductance was higher in preserved areas, but photosynthesis followed this pattern only for Senna sp. which also showed lower water use efficiency among all species. Furthermore, Senna sp. presented the highest relative water content in preserved areas, and showed no differences in specific leaf area between preserved and anthropized areas. The plasticity index showed that Senna sp. were the most plastic species, mainly adjusting water content and gas exchange parameters according to the area. The less plastic species was Mimosa arenosa. A principal component analysis showed a group formation due to anthropization, for all species. However, Senna sp. showed the largest distance among species. We conclude that all analyzed species respond to environmental conditions of preserved and anthropized areas, but this pattern cannot be related to the characteristics of the botanical family due to species-specific leaf traits’ variations.

Habemus seeds but they are non-viable: The importance of assessing seed viability in seed rain

Seed rain is critical for forest recovery, especially in abandoned lands that have been converted to agriculture. However, such a critical role depends on seed viability, which has been largely overlooked in most seed rain studies. We assessed the viability of seeds in the seed rain falling into 12 plots from a Brazilian tropical dry forest: six plots exposed to slash-and-burn agriculture (‘burned plots’ = 111 seeds from 10 species) and six located in forest stands (‘control plots’ = 5267 seeds from 23 species). Using the tetrazolium test, we found that only 767 of 5378 seeds (14%) from 16 species were viable, but surprisingly, seed viability was 2.2 times higher in burned plots than in control ones. This does not imply that forest regeneration through seed rain is more effective in burned plots, as very few seeds arrived at these plots. A functional analysis revealed that the higher seed viability in burned plots may be explained by the fact that these plots were dominated by relatively large, hard-coated (orthodox), and abiotically dispersed seeds, with some type of dormancy, as seeds with these functional trait attributes showed the highest viability. To accurately assess the importance of seed rain for forest regeneration we must consider seed viability, as it can be very low in some places, especially if dominated by species with relatively small, animal-dispersed and recalcitrant seeds lacking dormancy.

Variation in the water use and gas exchange of two Brazilian tropical dry forest phytophysiognomies in response to successional stage

Water availability is the main limiting factor to plants growth in tropical dry forests, influencing vegetation ecophysiological responses throughout ecological succession. In this study, we analyzed the water potential and gas exchange in two phytophysiognomies of a Brazilian tropical dry forest, along a chronosequence and in moments of low and high VPD. We selected an area of Crystalline Caatinga (CC) and Arboreal Caatinga (AC), and in both sites delimited three plots at different successional stages (initial, intermediate, and late). At each collection site within areas at each successional stage, we sampled the four most abundant species. For CC plants, water potential and gas exchange were similar at all successional stages, regarding VPD, and higher than in AC site. Trees growing in the AC site showed more plastic responses than those in the CC area, mainly in gas exchange, whereas CC plants (mainly herbs) showed a higher variation in water potential. We established that this differential response occurred due to the structure of the plant community and soil water availability. Trees’ leaf traits tend to present long-term responses, and we observed that vegetation in the AC site showed most markedly differences among successional stages than plants in CC site.

Bioremediation potential of industrial laundry effluent by agaricomycetes from brazilian tropical dry forest

Mycotic bioremediation of effluents from industrial jeans laundries is a necessary biotechnological treatment to prevent contamination of water bodies. In phase I, the discoloration of Indigo Carmine Dye (ICD) and Textile Effluent (TE) by seven species of Agaricomycetes from the brazilian tropical dry forest (Caatinga) was evaluated. First, nutritional stress was caused by Nitrogen Limitation (NL) at three experimental times, T1 (1 day). T2 (4 days) and T3 (7 days). In phase II, microorganisms were cultivated in the initial growth times Gi1 (10 days) and Gi2 (25 days), Without Addition of Nutrients (WAN) and stress was induced by NL (T1). Subsequently, ICD and TE discoloration tests continued for 28 days. In the ecotoxic analysis, the biotreated samples in phase II were tested on nauplii of Artemia HIGH 5 without the addition of food. In phase I, the percentages of ICD and TE discoloration were greater than 55% using fungi F1, F2, F5 and F6 for 10 days without sterility. In phase II, the best percentages of discoloration were found for TE in Gi1 and for ICD in Gi2, with F1 and F5 (identified by molecular biology). The results showed that Gi1 (WAN) increased the biodegradation of TE and Gi2 (WAN) favored the biodegradation of ICD, in T1 (NL) without sterility. The best enzymatic activity of laccase and lignin peroxidase was presented in F5. The enzyme extracts had a Michaelis-Menten kinetic behavior. All samples of TE bioremediated in phase II no showed toxicity on Artemia sp. in 48 hours of experimentation.

Differential response of tree species from Brazilian tropical dry Forest (Caatinga) to phosphorus doses associated with organic matter

The availability of phosphorus (P) and organic matter in Chromic Luvisols, predominant in the Caatinga biome, is generally low and makes it difficult to reintroduce native plants in forest recovery projects. The objective was to evaluate the production of dry mass, accumulation a and use efficiency of P by three tree species native from Caatinga biome with application of doses of P and organic matter. This experiment was carried out in a greenhouse in a completely randomized design in a 2 × 3 × 5 factorial scheme, consisting of with two doses of organic matter (0 and 50 g kg−1), three species of plants (Tabebuia aurea (Silva Manso) Benth. & Hook.f. ex S Moore, Amburana cearensis, Allemão AC Smith and Caesalpinia ferrea Mart. Ex Tul.) and five doses of P (0, 50, 100, 150 and 200 mg dm−3). At 120 days after transplanting, concentrations of P available in the soil and leaf soluble P fractions increased linearly with the P doses. The availability of P in the soil and, consequently, the accumulation of soluble and total P in the plant tissues were greater with organic matter application. The studied species use different P compartmentalization strategies depending on their dry mass production capacity. Phosphate and or organic matter application is necessary in the initial growth phase of the studied species, notably T. aurea and C. ferrea. The dry mass of T. aurea was greater than that of C. ferrea and A. cearensis.

Successional and Intraspecific Variations in Leaf Traits, Spectral Reflectance Indices and Herbivory in a Brazilian Tropical Dry Forest

Leaf traits are good indicators of ecosystem functioning and can affect herbivory and leaf reflectance patterns, allowing a better understanding of changes in environmental conditions, such those observed during forest natural regeneration. The aim of this study was to evaluate the intraspecific variation in leaf traits and their influence on the pattern of herbivory and leaf reflectance in three species distributed along a successional gradient (early, intermediate and late stages) in a tropical dry forest (TDF) in northern Minas Gerais, Brazil. We sampled individuals of the following abundant tree species that occurred in multiple successional stages: Cenostigma pluviosum, Handroanthus ochraceus, and Tabebuia reticulata. We collected 10 leaves from each tree to determine the contents of chlorophyll a, b, and total, carotenoids and water, as well as the percentage of leaf area removed by herbivores and leaf specific mass (LSM). We also measured five spectral reflectance indices (Normalized Difference Vegetation Index-NDVI, Simple Ratio-SR, modified Normalized Difference-nND, modified SR-mSR and Water Index-WI) using a portable spectrometer. Our results showed intraspecific differences in most leaf traits along the successional gradient, suggesting that local adaptation may play an important role in plant community assembly. However, herbivory only differed for H. ochraceus in early and intermediate stages, but it was not affected by the leaf traits considered here. Spectral reflectance indices also differed among successional stage for all species together and for each species separately, except for T. reticulata in intermediate and late stages. Thus, leaf spectral signatures may be an important tool to the remote detection of different successional stages in TDFs, with implications for forest management.

Dung beetle β‐diversity across Brazilian tropical dry forests does not support the Pleistocene Arc hypothesis

AbstractTropical dry forests (TDFs) are one of the most threatened ecosystems worldwide. Two hypotheses have been proposed to explain the origin of TDFs in South America: the Amazonian TDF hypothesis and the Pleistocene Arc hypothesis (PAH). There is a need to evaluate the distribution patterns of different organisms across the TDF distribution. We tested the following hypotheses: the species composition is determined by historical‐evolutionary events, and therefore, the TDFs have a similar species composition as predicted by the PAH. Alternatively, the species composition is determined by recent ecological processes, and therefore, the TDFs have a sharing of species to their respective adjacent dominant habitat, with no support for the PAH. We expect that climatic factors drive the species richness, abundance and species dissimilarity (β‐diversity) between TDFs and adjacent habitats across the latitudinal gradient. We sampled dung beetles across six Brazilian states in TDF fragments and adjacent dominant habitats and obtained the climatic conditions across the gradient. We used the β‐diversity partition and generalised linear models to test our hypotheses. We sampled 8,625 dung beetles representing 102 species. Sorensen dissimilarity was higher among TDFs than between TDFs and adjacent habitats and was mostly due to the substitution of species. Annual mean temperature had a positive effect on abundance in TDFs but did not affect species richness. Species substitution (Podani’s approach) between TDFs and adjacent habitats decreased with mean diurnal range of temperature, while nestedness patterns (Baselga’s approach) increased with annual precipitation. Depending on the approach used (Baselga’s vs. Podani’s), we can obtain different results across the latitudinal gradient. The composition and structure of dung beetle assemblages in TDFs are mostly determined by more recent regional‐to‐local ecological processes since each TDF has a unique evolutionary history and a different dung beetle species composition. Our results do not support the Pleistocene Arc hypothesis.

Cladophialophora bromeliacearum (Herpotrichiellaceae, Chaetothyriales), a novel endophytic species from the Brazilian tropical dry forest

Two isolates of fungal endophytes were obtained from the leaves of Tillandsia catimbauensis (Bromeliaceae) in the Brazilian tropical dry forest (Caatinga), according to their morphology, they were previously identified as Phialophora-like fungi. On the basis of phylogenetic analysis using ITS and LSU rDNA sequences, along with morphological features, these isolates are here described as Cladophialophora bromeliacearum sp. nov. The new species is morphologically characterized by Phialophora-like conidiogenous cells, subspheric to ellipsoid conidia, and the production of chlamydospores in culture.

Paraburkholderia spp. are the main rhizobial microsymbionts of Mimosa tenuiflora (Willd.) Poir. in soils of the Brazilian tropical dry forests (Caatinga biome)

Mimosa tenuiflora (Willd.) Poir. is widespread in southern and central American drylands, but little information is available concerning its associated rhizobia. Therefore, this study aimed to characterize M. tenuiflora rhizobia from soils of the tropical dry forests (Caatinga) in Pernambuco State, Brazil, at the molecular and symbiotic levels. Soil samples of pristine Caatinga areas in four municipalities were used to grow M. tenuiflora. First, the bacteria from root nodules were subjected to nodC/nifH gene amplification, and the bacteria positive for both genes had the 16S rRNA gene sequenced. Then, ten strains were evaluated using recA, gyrB, and nodC gene sequences, and seven of them had their symbiotic efficiency assessed. Thirty-two strains were obtained and 22 of them were nodC/nifH positive. Twenty strains clustered within Paraburkholderia and two within Rhizobium by 16S rRNA gene sequencing. The beta-rhizobia were similar to P. phenoliruptrix (12) and P. diazotrophica (8). Both alpha-rhizobia were closely related to R. miluonense. The recA + gyrB phylogenetic analysis clustered four and five strains within the P. phenoliruptrix and P. diazotrophica branches, respectively, but they were somewhat divergent to the 16S rRNA phylogeny. For Rhizobium sp. ESA 637, the recA + gyrB phylogeny clustered the strain with R. jaguaris. The nodC phylogeny indicated that ESA 626, ESA 629, and ESA 630 probably represented a new symbiovar branch. The inoculation assay showed high symbiotic efficiency for all tested strains. The results indicated high genetic diversity and efficiency of M. tenuiflora rhizobia in Brazilian drylands and included P. phenoliruptrix-like bacteria in the list of efficient beta-rhizobia in the Caatinga biome.

Intra- and interspecific variations on plant functional traits along a successional gradient in a Brazilian tropical dry forest

The present study aimed to determine how plant functional traits change both at the intra- and interspecific levels along three successional stages (early, intermediate and late) in a Brazilian tropical dry forest (TDF). Plants in early-successional plots are expected to exhibit conservative traits to increase photoprotection and water conservation, whereas late successional plants would invest on acquisitive traits. Sampling was conducted in three plots of 50 × 20 m per successional stage, where plant species composition and structural parameters were previously determined for individuals with DBH ≥ 5 cm. From each of three plots, the five tree species with the highest importance values were selected. This resulted in a total of 13 species from seven families selected for this study. We quantified specific leaf area (SLA), leaf slenderness, polyphenols and chlorophyll contents, and leaf lifespan. Based on leaf traits, we detected two major tree functional species groups: the early-intermediate and the late successional groups. Confirming our expectations, the former was positively associated with drought tolerance traits (polyphenols and slenderness) related to conservative resource use; and the latter was positively associated with acquisitive traits (SLA). This pattern was partially corroborated at the intraspecific level for species that occurred in more than one successional stage. We found a weak phylogenetic signal for the functional grouping (only for polyphenols). The analysis of variance structure across scales indicated that a very small proportion (up to 2.8%) of the general variance in leaf traits occurred at intraspecific level suggesting that, compared to interspecific variations, trait differences among individuals due to phenotypic plasticity are low. Although further studies with a larger number of species are needed, our findings suggest a decoupling between functional and structural/species composition regeneration, contradicting several studies on secondary succession where species composition is regarded as the main indicator of the regeneration of ecological functions.

Hydropriming changes temperature thresholds for seed germination of tree species from the Caatinga, a Brazilian tropical dry forest

Abstract: This study evaluates the effects of hydration and dehydration cycles (HD cycles) on seed germination of four Caatinga tree species (Anadenanthera colubrina var. cebil, Enterolobium contortisiliquum, Pityrocarpa moniliformis and Pterogyne nitens) subjected to different temperatures and determine the thermal upper and lower limits of germination. For this, seeds were subjected to 0, 1, 2 and 3 HD cycles and set to germinate at temperatures of 5, 10, 15, 25, 35, 40 and 45 °C. Germinability and t50 were calculated and the differences of these parameters were compared by two-way ANOVA. In addition, germination rate (GR = 1/t50), as well as ceiling (Tc), optimum (To) and base (Tb) temperatures were calculated to estimate the limits below or above which the seeds fail to germinate. We observed that the more HD cycles, the better the seed responds, especially at extreme temperatures. Seeds of all studied species showed To between 25 and 35 °C, Tb < 10 °C, and Tc > 40 °C. The slope of regression curves for germination rate showed that submitting seeds to HD cycles expands its thermal tolerance range, revealing that this seed pre-treatment can be efficient for species as it increases their tolerance to thermal stress.

Biophysical and Socioeconomic Factors Associated to Deforestation and Forest Recovery in Brazilian Tropical Dry Forests

The determination of land cover changes (LCCs) and their association to biophysical and socioeconomic factors is vital to support government policies toward the sustainable use of natural resources. The present study aimed to quantify deforestation, forest recovery and net cover change in tropical dry forests (TDFs) in Brazil from 2007 to 2016, and investigate how they are associated to biophysical and socioeconomic factors. We also assessed the effects of LCC variables in human welfare indicators. For this purpose, we used MODIS imagery to calculate TDF gross loss (deforestation), gross gain (forest recovery) and net cover change (the balance between deforestation and forest recovery) for 294 counties in three Brazilian states (Minas Gerais, Bahia, and Piauí). We obtained seven factors potentially associated to LCC at the county level: total county area, road density, humidity index, slope, elevation, and % change in human population and in cattle density. From 2007 to 2016, TDF cover increased from 76,693 to 80,964 km2 (+5.6%). This positive net change resulted from a remarkable forest recovery of 19,018 km2 (24.8%), offsetting a large deforested area (14,748 km2; 19.2%). Practically all these cover changes were a consequence of transitions from TDF to pastures and vice-versa, highlighting the importance of developing sustainable policies for cattle raising in TDF regions. Each LCC variable was associated to different set of factors, but two biophysical variables were significantly associated both to TDF area gained and lost per county: county area (positively) and slope (negatively), indicating that large and flat counties have very dynamic LCCs. The TDF net area change was only associated (negatively) to the humidity index, reflecting an increase in TDF cover in more arid counties. The net increase in Brazilian TDF area is likely a result from an interplay of biophysical and socioeconomic factors that reduced deforestation and caused pasture abandonment. Although the ecological integrity and permanence of secondary TDFs need further investigation, the recovery of this semi-arid ecosystem must be valued and accounted for in the national forest restoration programs, as it would significantly help achieving the goals established in the Bonn agreement and the Atlantic Rain Forest pact.

Diversity of endophytic fungi in the leaflets and branches of Poincianella pyramidalis, an endemic species of Brazilian tropical dry forest

ABSTRACT Plants harbour diverse communities of fungal species in their internal compartments. Endophytic fungi help their hosts to establish, survive, and adapt to different environments. Here, we examined the diversity of endophytic fungi in the leaflets and branches of Poincianella pyramidalis, a plant species endemic to the Brazilian tropical dry forest (Caatinga). A total of 360 fragments of leaflets and branches were analysed and 189 endophytic fungi were isolated and distributed among 21 ascomycetous genera based on their ITS and LSU rDNA sequences. Diaporthe was the most frequently identified genus, followed by Didymella and Rhytidhysteron. The colonisation rate of plant fragments was higher in the branches (74 %) than in leaflets (14 %). The richness of the genera of endophytic fungi was also higher in the branches than in leaflets, whereas no difference was observed in endophyte diversity between the plant parts, based on Shannon-Wiener and Fisher alpha diversity indices. Our results indicate that endemic plant species from Brazilian dry forest, such as P. pyramidalis, are predominantly colonised by ascomycetous fungi, especially members of the class Dothideomycetes.

Don’t stay out too long! Thermal tolerance of the stingless bees Melipona subnitida decreases with increasing exposure time to elevated temperatures

In hot climates, foraging bees risk overheating during food collection. Here, we investigated influence of ambient temperature on the foraging activity in Melipona subnitida, a stingless bee species that naturally occurs in the hottest and driest regions of the Brazilian tropical dry forest. We observed a decrease in round-trip duration of pollen foragers with increasing ambient temperature. Foraging duration of nectar collectors, however, was not affected by the thermal conditions of the environment. When exposed to heat stress in incubators, the upper thermal limits of foragers decreased with increasing exposure time. Moreover, individuals with previous access to liquid food showed higher critical and lethal temperatures than unfed bees. Our study revealed plastic changes in the upper thermal limit of M. subnitida, which help to understand the foraging activity pattern of this stingless bee species.

Climate-induced distribution dynamics of Plebeia flavocincta, a stingless bee from Brazilian tropical dry forests.

AimThe objective of this study is to estimate the current potential geographic distribution of Plebeia flavocincta and to evaluate the influence of climate on the dynamics of suitable habitat availability in the past and in the future.LocationNortheast region of Brazil and dry forest areas.MethodsThe habitat suitability modeling was based on two algorithms, two global circulation models, and six different scenarios. We used this tool to estimate the areas of occurrence in the past (Last Interglacial and Last Glacial Maximum), in the present, and in the future (years 2050 and 2070).ResultsAccording to the models, P. flavocincta had great dynamics in the availability of suitable habitats with periods of retraction and expansion of these areas in the past. Our results suggest that this taxon may benefit in terms of climate suitability gain in Northeast Brazil in the future. In addition, we identified high‐altitude areas and the eastern coast as climatically stable.ConclusionThe information provided can be used by decision makers to support actions toward protecting and sustainably managing this taxon. Protection measures for this taxon are particularly important because this insect contributes to the local flora and, although our results indicate that the climate may favor this taxon, other factors can negatively affect it, such as high levels of habitat loss due to anthropogenic activities.

Brazilian tropical dry forest (Caatinga) in the spotlight: an overview of species of Aspergillus, Penicillium and Talaromyces (Eurotiales) and the description of P. vascosobrinhous sp. nov.

ABSTRACT A literature-based checklist of species of Aspergillus, Penicillium, and Talaromyces recorded in the Brazilian tropical dry forest (Caatinga), the largest tropical dry forest region in South America, is provided. A total of 130 species (60 Aspergillus, 57 Penicillium, and 13 Talaromyces) are reported. Soil was the most common substrate, with 122 species records. Various reported species are well known in biotechnological processes. This checklist reflects the limited knowledge of fungal species in tropical dry environments. These data provide a good starting point for biogeographical studies on species of Aspergillus, Penicillium, and Talaromyces in dry environments worldwide. In addition, the new species Penicillium vascosobrinhous is introduced, an endophytic fungus isolated from cactus of the Caatinga forest in Brazil.

Increasing thermal stress with flight distance in stingless bees (Melipona subnitida) in the Brazilian tropical dry forest: Implications for constraint on foraging range

The thoracic temperature (TTX) of foraging bees usually exceeds ambient air temperatures (TAIR) by several degrees. In hot tropical climate zones, therefore, individuals may reach body temperatures close to their critical thermal maxima, which might constrain their activity. In the present study, we tested the hypothesis that thermal stress increases with flight distance in nectar foragers of M. subnitida, a stingless bee species native to the hottest regions of the Brazilian tropical dry forest. Using infrared thermography, we recorded the body surface temperature of individuals foraging at distances of 15, 50, and 100 m. Closest to the nests, foragers stabilized TTX at 40 °C when collecting sugar solution at TAIR > 30 °C. The simultaneous decrease of the temperature excess ratio of head and abdomen suggests evaporative cooling at these body parts. With increasing foraging distance, foragers increased heat dissipation to the head and abdomen. Thus, despite more intensive heating of the thorax due to faster and longer flights, the bees maintained similar TTX as foragers at close feeding sites. However, at TAIR > 30 °C, bees could no longer compensate the elevated heat gain at the head (50 m) and abdomen (50, 100 m), which caused an increasing temperature excess in these body parts. Thus, foragers of M. subnitida suffer overheating of the head and abdomen instead of the thorax when foraging in high temperatures at far feeding sites. Consequently, to avoid heat stress in the Brazilian tropical dry forest, the bees should forage close to the nest.

Estimates of deforestation avoided by protected areas: a case study in Brazilian tropical dry forests and Cerrado

ABSTRACTThe aim of this study was to evaluate the impact of the creation of protected areas (PAs) to avoid deforestation using Matching methods, focusing on the north of the Minas Gerais state, Brazil. Using GIS (Geographic Information System) techniques, we randomly distributed several 3 ha plots across the study region. The deforestation rates in plots inside and outside PAs were compared using Matching analysis. Our results indicate that the PAs created in the north of Minas Gerais in the 1990s were effective in reducing deforestation, though avoided deforestation rates have been relatively low (1.62% from 1996 to 2009). Geographical location was a key factor for PAs effectiveness and plots inside PAs in flat regions or close to large cities and roads had a greater impact on avoided deforestation. The results of this study corroborate a global trend of establishment of PAs in remote areas under low deforestation pressure.