Gradient In Brazil Research Articles

Soil Biological Properties along a Topographic Gradient in Brazil’s Atlantic Forest Biome

The Atlantic Forest exhibits remarkable floristic diversity over short distances, and when combined with altitude, it results in variations in soil biological properties and hydrological dynamics. This study aimed to quantify the distribution pattern of soil biological properties along a small topographic gradient and identify how these properties are related to soil chemical, physical, and topographical attributes in an Atlantic Forest fragment in Brazil. Plots were established along hillslope positions varying from 100 to 180 m of altitude. Soil biological characterization was performed at a depth of 0.0–0.10 m in both summer and winter seasons. The lowland showed higher microbial biomass nitrogen in summer (57.28 ± 5.57 μg g−1 soil) and higher anaerobically mineralizable nitrogen in summer and winter (42.70 ± 2.14 mg kg−1 and 41.06 ± 3.37 mg kg−1, respectively). The midland showed lower microbial biomass carbon, enzymatic activity, and soil moisture in both seasons, and higher metabolic coefficients in summer. Soil chemical properties exerted a greater influence on the variability of biological properties in both seasons. The land slope conditioned lower microbial activity and organic cycling in the midland. Soil biological properties were affected by seasonality. Even a small altitudinal gradient (up to 100 m) in the Sea of Hills regions of the Atlantic Forest can lead to significant changes in soil biological and chemical attributes.

Stocking response of Eucalyptus growth depends on site water deficit across a 2100-km gradient in Brazil

Stocking in forests strongly influence stand growth by influencing resource capture, tree survival, and competition between trees and understory vegetation. Many studies have examined these patterns for specific locations and conditions, though with limited populations of inference. The influence of stocking was examined in the TECHS experimental platform, at 16 sites, with 18 clones, across a 2100 km geographic gradient. Stocking was examined by varying spacing within columns, with constant (3-m) spacing between rows. We examined how wood production and quality related to genotypes and environmental conditions, with stocking ranging from 480 to 3300 trees ha−1. Mean annual increment (Mg ha−1 yr−1) for the entire rotation increased with stocking, asymptoting above 1500 trees ha−1. Water-stressed sites had much lower responses to stocking levels than wetter sites. The three driest sites showed only a 25% increase in MAI (7 to 9 Mg ha−1 yr−1) with stocking increases from 480 to 3300 trees ha−1, whereas the 3 most productive sites increased by 50% (20 Mg ha−1 yr−1 to 30 Mg ha−1 yr−1). A similar result occurred for the clones, where the response to the change in stocking was higher in the more productive clones. From a qualitative point of view, tree breakage declined as stocking increased, going from 0% of broken trees in the highest stocking to a maximum of 3% with the stocking of around 480 trees ha−1. Injury to trees increased with stocking, going from about 4 to 9%. Mortality showed a similar pattern, increasing from 8 to 14% with increasing stocking. The percentage of intact (surviving, undamaged) trees at the lowest stocking was 83%, reaching a peak of 94% between 700 and 1100 trees ha−1, declining again to about 85% at the densest stocking. Survival rates declined when stocking exceeded 2900 trees ha−1 on wetter sites, compared with just 900 trees ha−1 on the driest sites. Overall, an increase in stocking from 480 trees ha−1 to 3300 trees ha−1 led to 50% increase in growth. To put this in perspective, the poorest 25% of sites averaged 59% less growth than the top 25%. The poorest 25% of genotypes grew 47% less than the best 25%. The interactions of effects, such as stocking by site, had effects that were of the same magnitude as these main effects. Management decisions about optimal stocking may be substantially improved by considering the main effects and especially their interactions.

The role of chronic anthropogenic disturbances in plant community assembly along a water availability gradient in Brazil’s semiarid Caatinga region

The effects of anthropogenic disturbances on the structure and function of seasonally dry tropical forests (SDTFs) are mediated both by disturbance type and intensity, and the environmental conditions, including climate. In a climate change scenario, the interaction between low water availability and chronic anthropogenic disturbances may potentially have drastic consequences on SDTF dynamics and the ecosystem services it provides. We hypothesized that in these naturally stressed systems, the effects of human disturbance are strongest in the most water-stressed sites, implying a worrisome synergism between harsh abiotic conditions (lower precipitation, higher temperature) and human effects, ultimately resulting in a less developed community structure and reduced diversity. By integrating information for the adult and regenerating vegetation strata in 21 sites distributed across climatic, plant cover and disturbance gradients in the Caatinga (seasonally dry tropical) forest of Brazil, we analyzed the individual and combined effects of chronic anthropogenic disturbances, as measured through the Cattle Pressure Index and the Human Activity Index, along climate gradients, on community structure, diversity, and composition. As expected, the Cattle Pressure Index was negatively related to diameter at ground level, basal area, and diversity in the adult stratum, whereas for the regenerating stratum, litter stock had the strongest effect on vegetation structure. Climatic factors were poor predictors of the variation in the three true diversity measures (0D, 1D, and 2D) of the regenerating community. Our results revealed important cross-site differences in both vegetation strata over a small range of climatic variation. We conclude that the most stressful conditions associated with a very low precipitation regime enhance the effects on chronic disturbances, gradually driving SDTF communities into new alternative states and rendering these environments more prone to desertification.

Climate-growth relations of congeneric tree species vary across a tropical vegetation gradient in Brazil

Seasonally dry tropical forests are an important global climatic regulator, a main driver of the global carbon sink dynamics and are predicted to suffer future reductions in their productivity due to climate change. Yet, little is known about how interannual climate variability affects tree growth and how climate-growth responses vary across rainfall gradients in these forests. Here we evaluate changes in climate sensitivity of tree growth along an environmental gradient of seasonally dry tropical vegetation types (evergreen forest – savannah – dry forest) in Northeastern Brazil, using congeneric species of two common neotropical genera: Aspidosperma and Handroanthus. We built tree-ring width chronologies for each species × forest type combinations and explored how growth variability correlated with local (precipitation, temperature) and global (the El Niño Southern Oscillation - ENSO) climatic factors. We also assessed how growth sensitivity to climate and the presence of growth deviations varied along the gradient. Precipitation stimulates tree growth and was the main growth-influencing factor across vegetation types. Trees in the dry forest site showed highest growth sensitivity to interannual variation in precipitation. Temperature and ENSO phenomena correlated negatively with growth and sensitivity to both climatic factors were similar across sites. Negative growth deviations were present and found mostly in the dry-forest species. Our results reveal a dominant effect of precipitation on tree growth in seasonally dry tropical forests and suggest that along the gradient, dry forests are the most sensitivity to drought. These forests may therefore be the most vulnerable to the deleterious effects of future climatic changes. These results highlight the importance of understanding the climatic sensitivity of different tropical forests. This understanding is key to predict the carbon dynamics in tropical regions, and sensitivity differences should be considered when prioritizing conservation measures of seasonally dry topical forests.

Carbon isotopic composition of leaf wax n-alkanes in mangrove plants along a latitudinal gradient in Brazil

The carbon isotopic composition (δ13C) of selected specific biomarkers provides important information on the relationship between plant species and the environment in which they developed. Here we present baseline data of δ13C values of individual n-alkanes (δ13Cn-alkanes) from leaf waxes of mangrove species – Avicennia spp., Rhizophora mangle and Laguncularia racemosa – typical of mangrove forests collected from equatorial to sub-tropical regions in Brazil. The objective was to evaluate the influence of tree physiology, local hydrology and climatic factors upon the molecular and isotopic signature of the leaf wax n-alkanes. Total n-alkanes concentration, average chain length (ACL25-35) and carbon preference index (CPI24-36) are higher for Avicennia spp. contrasting with the lower values found for R. mangle and L. racemosa. This seems to derive from the physiological characteristics of each species with respect to the intrinsic water use efficiency under the specific tidal flooding regime of mangrove forests. For Avicennia spp. inverse correlations between δ13Cn-alkanes values (δ13C27, δ13C29, δ13C31, δ13C33 and δ13CWA) and mean annual precipitation suggests plant response to local environmental conditions. For R. mangle species, relationships between ACL25-35 and mean annual potential evapotranspiration, and between CPI24-36 and mean annual temperature were observed. These results indicate that δ13Cn-alkanes values in Avicennia spp. as well as ACL25-35 and CPI24-36 in R. mangle may be useful in tracing environmental changes and, as long as preservation of reliable record in sediments is verified, may also be applied in the reconstruction of past environmental conditions. The different molecular and isotopic footprints of the mangrove species presented here have potential in future interpretations of n-alkanes as biomarkers in biogeochemical studies in mangrove-dominated coastal regions.

Ionospheric spatial decorrelation assessment for GBAS daytime operations in Brazil

<h3>Abstract</h3> Extensive ionospheric studies were conducted to support the initial phase of system design approval for the existing SLS-4000 GBAS installed at Antonio Carlos Jobim International Airport (formerly Galeão International Airport) (GIG) in Rio de Janeiro, Brazil. This paper focuses on determining the broadcast value of the standard deviation of vertical ionospheric gradients (or 𝜎_vig) that is required to bound ionospheric spatial gradients in Brazil under nominal conditions during daytime hours. The time-step method is useful for gaining sufficient samples at distances less than the physical separation distance of ground stations and was utilized to estimate ionospheric spatial gradients. A new method called “geometric similarity” was developed to estimate ionospheric temporal gradients and evaluate the temporal effect added to the bounding 𝜎_vig values. As a result, a 𝜎_vig of 13 mm/km, including a temporal gradient contribution of approximately 2 mm/km, is conservative enough to bound ionospheric spatial decorrelation for daytime GBAS operations in Brazil.

The influence of agricultural occupation and climate on the spatial distribution of Plusiinae (Lepidoptera: Noctuidae) on a latitudinal gradient in Brazil

Abstract Studies have reported the presence of certain Plusiinae species in both natural and agricultural landscapes, but their turnover in association with agricultural activities remains unexplored. Aiming to understand how the assemblages of Plusiinae are structured by agricultural occupation and climate, this study used automated light traps sampled moths in 18 sites in Brazil, across a broad latitudinal gradient. Our data has demonstrated that climate variables prevails as the most important variables influencing both the composition of Plusiinae and the abundance of its dominant species Chrysodeixis includens. On the other hand, the lack of significance found for the effect of variables representing agricultural occupation evidences that pest species are present both in agricultural and natural ecosystems, also sharing similar abundances at those locations. In other words, instead of following a gradient of agricultural occupation (e.g. crop sizes around sample sites) the composition of these extremely polyphagous insects is more clearly shaped by the latitudinal gradient, in which temperature and precipitation are better predictors. Thus, in contrary to our expectations, pest species inhabits both natural and agricultural landscapes at similar latitudinal sites, probably due to their wide polyphagy spectrum. These results can be used in management and monitoring programs of pest species in South America, since the local abundance variation and species composition can be more reliable predicted by changes in climate conditions.

Contrasting water use of two Eucalyptus clones across a precipitation and temperature gradient in Brazil

Eucalyptus plantation productivity has increased 4-fold across Brazil as a result of improved genetic selection and intensive silviculture. However, the rate of productivity improvements is slowing and suggests increased production will require planting in areas that have never been previously planted with Eucalyptus with uncertain impacts on local water supplies. This study compares water use and water use efficiency between a drought resistant (E. grandis × E. camaldulensis) and high productivity Eucalyptus clone (E. urophylla) across three sites (dry, mesic and wet) spanning a two-fold precipitation gradient (~600–1350 mm y−1) in Brazil. Each site included a 30% reduced rainfall treatment for each clone to investigate within site response to reduced precipitation. We found that the drought resistant clone used as much or more water than the high productivity clone at all three sites. The drought resistant clone transpired almost 20% percent more water than the high productivity clone at the dry site (3.7 vs. 3.0 m3 y−1) while water use between clones did not differ at the mesic (4.6 vs 4.0 m3 y−1) and wet site (4.0 vs 4.5 m3 y−1). The high productivity clone transpired 54, 46 and 37% of annual precipitation at the dry, mesic and wet sites respectively while the drought resistant clone consumed 67, 47 and 31% of annual precipitation from the dry to the wet site. Although the rain reduction treatments did not impact annual water use for either clone at the dry and mesic sites, there were some differences at a subannual timescale. Rain reduction treatments at the dry site lowered transpiration in the driest, hottest three months for the high productivity clone by 25–32%. Rainfall reduction led to lower water use by the drought resistant clone for only one month during the dry season (18%). The high productivity clone transpired less water (24–26%) in the rainfall reduction treatment at the mesic site during three months and the drought resistant clone transpired 18 and 20% less water in the rainfall reduction treatment during two months. Rainfall reduction reduced annual transpiration by 59% for the high productivity clone at the wet site. Average water use efficiency of the drought resistant clone was almost 70% lower than the high productivity clone at the dry and mesic sites (~5.2 vs. 1.5 kg m−3 y−1) and was due to the combination of low growth and high water use. Higher than expected growth by the drought resistant clone at the wet site resulted in similar water use efficiency between clones (6.3 vs. 5.8 kg m−3 y−1). We discuss potential implications of our findings and highlight several lines of evidence that suggest the drought resistant clone in this study allocates a greater proportion of gross primary productivity below ground allowing it to access deeper reserves of soil water during dry periods. Our results suggest that decisions to plant drought resistant clones in drought prone areas should be carefully considered and also highlight the need for more research on water use and drought tolerance strategies for Eucalyptus clones bred for more arid areas in Brazil.

Quantifying turgor loss point and leaf water potential across contrasting Eucalyptus clones and sites within the TECHS research platform

Understanding the mechanisms governing drought tolerance in highly productive clonal Eucalyptus plantations in Brazil will become increasingly important with climate change driven increases in temperature and drought events. We quantified how leaf water potential, hydraulic safety margin (mid-day – pre-dawn leaf water potential, Ψδ) and the physiological parameters obtained from standard pressure–volume curves differed between four contrasting Eucalyptus genotypes across a temperature and water availability gradient in Brazil. We hypothesized that genotypes developed in dry areas were more drought tolerant and would exhibit lower mid-day leaf water potentials and turgor loss points than clones developed in wetter regions. Recognizing that standard pressure volume curves are time consuming and may not be a suitable screening tool for forest managers, we also tested if a key physiological parameter from the pressure–volume curve (turgor loss point, πtlp) could be accurately estimated from an osmometer as has been found in other species. We found no support for our first hypothesis; physiological parameters determined (including turgor loss point) from the pressure volume curves were not associated with the supposed drought tolerance of any of the clones. Similarly, mid-day leaf water potentials were not directly correlated with drought tolerance. The lack of support for our hypothesis may be because our measurements were taken during periods of minimum water stress. However, we did find that, overall, turgor loss point tended to be lower at the dry compared to wetter sites we studied suggesting that it may be a useful tool for assessing drought tolerance of Eucalyptus plantations in the future. We also found that estimates of osmotic potential at full turgor were similar between the pressure volume curve and osmometer techniques and that turgor loss point can be accurately estimated with an osmometer in highly productive Eucalyptus genotypes (R2 = 0.79).

Impacts and uncertainties of climate change projections on Eucalyptus plantations productivity across Brazil

Eucalyptus is the world’s most planted hardwood tree. Concerns about potential impacts and uncertainties of climate change on Eucalyptus plantations productivity are arising and studies about that are still scarce. This study assesses the effects of climate change on Eucalyptus plantations productivity across a geographic gradient in Brazil by mid- and end-century and quantifies the uncertainty of climate and productivity projections. Ten global circulation models (GCM) under intermediate (RCP4.5) and high (RCP8.5) greenhouse gas emission scenarios, for the 2040–2069 and 2070–2099 periods were used for future climate projections. The APSIM Next Generation Eucalyptus model was used to simulate the Eucalyptus mean annual increment (MAI, m3 ha−1 yr−1) at seven years for eight locations in Brazil. The response of Eucalyptus productivity is expected to be site-specific and will mostly depend on the balance between the possible negative effects of increasing temperatures and the potential productivity increments caused by higher CO2 concentration. Plantations located in South and Southeast Brazil are expected to experience increases in MAI, while those located in Center-North Brazil will experience more pronounced MAI reductions. Uncertainties in projections are higher under RCP8.5 and for the end-of-century, especially for annual rainfall and MAI. Future climate projections from GCMs coupled with a Eucalyptus simulation model provide valuable information to facilitate the exploration of potential strategies and guidance of policy decision-making for forestry adaptation to climate change on a regional or national scale. However, forest companies and foresters should be cautious when using projected information for local-scale adaptation options, as the uncertainties in climate (especially in rainfall) and productivity projections are substantially large.

Exploring the relationship between stand growth, structure and growth dominance in Eucalyptus monoclonal plantations across a continent-wide environmental gradient in Brazil

Stand structure can have a considerable influence on forest growth and productivity. A stand’s response to factors like temperature, precipitation, vapor pressure deficit and different soil characteristics may result not only from the mean change in tree responses (e.g. growth decrease or increase), but may also depend on how individual tree responses vary in relation to their size and how they cope with competition. There may be a large growth imbalance among trees as a function of their size, which is referred to as growth dominance. That is, a change in a factor may have different impacts on stand growth depending on stand structure and how growth is distributed. Thus, using an experimental platform spanning tropical Brazil, we explored the relationship between growth dominance and stand growth, and whether this relationship changes across a wide climatic gradient, represented by soil water deficit. We found a predominance of negative growth dominance during the early phase of stand development which increased until dominance became positive, after about 30 months, and kept increasing afterwards. Increasing soil water deficit slowed the increase in growth dominance throughout time. The intensification of growth dominance (either positive or negative) was associated with decreasing stand growth. Increasing soil water deficit decreased the negative effect of growth dominance on increment in absolute terms, but we showed that, at the end of a 5-year rotation, increasing growth dominance at a site with more intense water deficit led to a greater growth loss in relative terms than at a site with milder water deficit. For example, the estimated difference in increment between a stand with a low growth dominance of 0.05 and a stand with a high growth dominance of 0.20 at the end of a 60–month rotation at a site with an accumulated water deficit of −200 mm was about 28 m3 ha−1 year−1, which is equivalent to a 39% decrease in relative terms. This same GDC difference under a water stress of −4000 mm resulted in a decrease in increment of approximately 18 m3 ha−1 year−1, or 48% in relative terms.

Land use change drives the spatio-temporal variation of ecosystem services and their interactions along an altitudinal gradient in Brazil

ContextLand use and land cover (LULC) changes may affect the provision of ecosystem services. However, little is known how LULC changes influence the spatio-temporal variation in ecosystem service and their interactions along altitudinal gradients.ObjectivesHere we assessed the spatio-temporal variation of eight ecosystem services in an altitudinal gradient between the year of 1986 and 2015, and quantified the effect of LULC transitions on the provision and interactions of ecosystems services.MethodsWe modelled and mapped eight ecosystem services in an altitudinal gradient characterized by low (< 600 m), middle (600–1200) and high altitudes (> 1200) in Zona da Mata, Minas Gerais state, Brazil. We quantified changes in ecosystem services by contrasting ecosystem service maps between 1986 and 2015, and explored how four common LULC transitions affected the variation and the interactions between the eight ecosystem services.ResultsThe spatio-temporal analysis indicated that six out of eight ecosystem services increased from 1986 to 2015, while soil erosion control and water flow regulation decreased. In areas above 1200 m, regulating services dominated, while in areas below 1200 m provisioning service were most evidenced. LULC transitions from forest to agricultural areas, and vice versa, resulted in trade-offs between provisioning and regulating ecosystem services.ConclusionsLULC changes drive the spatio-temporal variation of ecosystem services along an altitudinal gradient with contrasting biophysical conditions. Future management of ecosystem services in the landscapes should take into the account the biophysical conditions and the consequences of specific LULC transitions.

Adaptability and stability of eucalypt clones at different ages across environmental gradients in Brazil

The genetic gains from eucalypt breeding programs have decreased compared to previous decades while productivity reduced in recent years. This decrease is mainly attributed to climate change that, according to studies, has been limiting productivity and changing the adaptation of forest species. But other aspects can be listed, as pests and diseases and decreasing gains with the advance of breeding programs. The objective of this work is to investigate the genotype × site × age interaction in a multi-environment trial with eucalypt clones to verify the adaptability and stability of the genotypes and, finally, to identify mega-environments over time, as well as the influence of climate variables on the genotype performances. The trait diameter at breast height (DBH) of 11 Eucalyptus commercial clones at 11 sites (range from −0.84 to −24.23 latitude and from −39.60 to −52.59 longitude) and three evaluated ages (Age 1 – ranging from 13 to 17 months after planting; Age 2 – from 31 to 34 months; Age 3 – from 48 to 53 months old) was measured and analyzed by factor analytic multiplicative mixed (FAMM) model associated with the GGE biplot and multivariate regression tree using climate variables. A significant G × E interaction and genotypes with different performance across environments and ages were observed. There are clones with high adaptability to specific sites while others show good stability. The results clustered the sites into three mega-environments according to a latitude gradient, over time. The performance of Eucalyptus clones over time indicate precisely either roughly similar or extremely contrasting environments. Temperature affected the most the clustering of the studied sites followed by the latitudinal gradient, impacting productivity negatively, regardless of age. These results may help future studies on the development of selection strategies in tropical regions to address climate change and assist forest breeding programs to deal with the effect of climate change on eucalypt productivity.

Where and when? How phenological patterns of armyworm moths (Lepidoptera: Noctuidae) change along a latitudinal gradient in Brazil.

The phenological patterns exhibited by different organisms are known as adaptive responses to the cyclical environmental conditions. However, only a limited number of researches explore which factors are responsible for these phenological patterns in pest species. In the current study, abundance patterns were studied in the phenology of three Spodoptera Guenée, 1852 species, along the 29° latitudinal gradient in South America. The goal was to test whether widely distributed and abundant crop pest species would exhibit different phenological responses to seasonal meteorological variables and host plant availability. To test this, 13 light traps were set up in Brazil to collect adult Spodoptera samples at the time of the new moon, every month, from June 2015 to May 2016. The time of occurrence and intensity of the phenology were determined for each species, employing circular statistics. Both metrics revealed significant variations among the different species, as well as the factors associated with them. Latitude was found to affect the period of occurrence in Spodoptera cosmioides (Walker, 1858) and Spodoptera albula (Walker, 1857), whereas in Spodoptera frugiperda (J. E. Smith, 1797) its effect was evident only in the intensity of its phenology. Further, both meteorological variables and host plant availability in the sampling sites produced predictive models to account for the phenological patterns expressed. These findings suggest that different species of Spodoptera exhibit different adaptive strategies in their life cycles in response to environmental conditions, thus necessitating specific management practices regarding their seasonal population fluctuation.

Seed germination of a South American forest tree described by linear thermal time models

Thermal time models may describe and compare seed germination, providing information useful to explain species distribution. However, the capacity of such threshold models to describe germination of tropical native species has been less studied. We evaluated seed germination of a legume tree species (Peltophorum dubium), typical from South American seasonal forests, as described by two linear thermal time models: probit model and graphic model. Seeds were provided from four different provenances in a latitudinal gradient in Brazil, and their physical dormancy mechanically released before the trials. Graphic model and probit regression were used to determine thermal parameters (cardinal temperatures and thermal time requirement) on sub- and supra-optimal ranges for the different seed provenances. Germination rate mainly followed linear relationship with temperature, and regression lines of different germination fractions converged base temperature in the x-axis. Therefore, probit model assumed a single-value of base temperature in the sub-optimal range and a normal distribution of thermal time. Base temperature tended to be higher in the Northern provenance, Porto Velho, showing slower germination under cooler temperatures. Supra-optimal temperatures have shown similar thermal time requirements and different values for ceiling temperature, according to model predictions. No clear patterns have been found between seed provenances and thermal time requirement. Both probit and graphic models have provided reasonable predictions of germination times (t10 and t50), except under the coolest temperatures. Probit regression always described at least 70% of seed germination. Thermal time assumptions, linear models applicability and their limitations are discussed.

Genotype-environment interaction, genetic trends, and performance dissimilarity of Nellore herds raised in three different environmental gradients

The objectives of this work were to evaluate the genotype-environment interaction, and estimate genetic parameters, genetic trends, and performance dissimilarity-weight gain from birth to weaning (WGBW), adjusted weight to 205 days (W205), weight gain from weaning to 18 months of age (WG18), and adjusted weight to 550 days (W550)-in Nellore animals born between 1986 and 2012, and raised in pasture-based system in three different environmental gradients in Brazil. Data of 62,001 animals-11,729 raised in the Alto Taquari/Bolsão region (ATBR), 21,143 raised in the Campo Grande/Dourados region (CGDR) and 29,129 raised in the western São Paulo/Paraná region (SPPR) in Brazil-were used. The contemporary groups were defined by sex, location, and birth year and season, with at least nine individuals, two different environments, and breeding bulls with at least five progenies. The statistical model contained the direct additive and residual genetic effects (random effects), and environmental and contemporary group effects (fixed effects). Genetic parameters, genotype-environment interaction and genetic trends were estimates using animal model (uni- and/or bi- traits). The level of similarity between regions was evaluated using principal components. The animals raised in the CGDR had superior performance regarding the traits evaluated. The direct heritability estimates ranged from 0.39 to 0.44 (WGBW), 0.41 to 0.45 (W205), 0.42 to 0.55 (WG18) and 0.60 to 0.62 (W550). The maternal heritability of the traits ranged from 0.20 (WGBW), 0.12 to 0.18 (W205), 0.00 to 0.06 (WG18) and 0.02 to 0.22 (W550). According to the Spearman correlation, the ranking of the breeding bulls in the regions evaluated were different. The mean of Euclidean distance indicated low similarity between ATBR and CGDR (43.20), and ATBR and SPPR (29.24). CGDR and SPPR presented similarity of 17.84. The breed values increased over the years in the traits evaluated. The cumulative variance percentage of the first two main components explained 99.99% variation among the regions, and the weight gains of the animals were the most important to differentiate the regions. A genotype-environment interaction was found for the traits evaluated, thus, the breeding bull selected with superior genetic merit for one region might not be the best for others.

Examining variation in the leaf mass per area of dominant species across two contrasting tropical gradients in light of community assembly.

Understanding variation in key functional traits across gradients in high diversity systems and the ecology of community changes along gradients in these systems is crucial in light of conservation and climate change. We examined inter‐ and intraspecific variation in leaf mass per area (LMA) of sun and shade leaves along a 3330‐m elevation gradient in Peru, and in sun leaves across a forest–savanna vegetation gradient in Brazil. We also compared LMA variance ratios (T‐statistics metrics) to null models to explore internal (i.e., abiotic) and environmental filtering on community structure along the gradients. Community‐weighted LMA increased with decreasing forest cover in Brazil, likely due to increased light availability and water stress, and increased with elevation in Peru, consistent with the leaf economic spectrum strategy expected in colder, less productive environments. A very high species turnover was observed along both environmental gradients, and consequently, the first source of variation in LMA was species turnover. Variation in LMA at the genus or family levels was greater in Peru than in Brazil. Using dominant trees to examine possible filters on community assembly, we found that in Brazil, internal filtering was strongest in the forest, while environmental filtering was observed in the dry savanna. In Peru, internal filtering was observed along 80% of the gradient, perhaps due to variation in taxa or interspecific competition. Environmental filtering was observed at cloud zone edges and in lowlands, possibly due to water and nutrient availability, respectively. These results related to variation in LMA indicate that biodiversity in species rich tropical assemblages may be structured by differential niche‐based processes. In the future, specific mechanisms generating these patterns of variation in leaf functional traits across tropical environmental gradients should be explored.

Fertilization Response, Light Use, and Growth Efficiency in Eucalyptus Plantations across Soil and Climate Gradients in Brazil

Fertilization increases productivity in Eucalyptus plantations, but losses in productivity associated with soil fertility continue at operational scales. In this study, we evaluated the fertilization response (FR), light use efficiency (LUE) and growth efficiency (GE), i.e., the amount of wood biomass accumulated per unit of light absorbed (LUE) and per unit of leaf area index of Eucalyptus plantations. We used a “twin plot” approach, with 161 blocks representing 52,700 ha of planted forests that spanned a broad range of edaphoclimatic conditions in southeastern Brazil. The normal plots (NP) were part of a permanent inventory network, whereas the twin plots (TP) received extra high levels of fertilization and extra weed control after fertilization. The intensive management (twin plots) led to a large increase of 5.3 Mg·ha−1·year−1 of wood increment. The region without dry periods and with soils with high clay content was most responsive to fertilization, with a 15% increment in the LUE and 10% increase in the GE of the TPs compared with those of the NPs. Our results suggested that water availability was the primary element affecting productivity and potential response to fertilization. With this information, decisions can be made on which regions should receive priority fertilization investments. However, more research is required to determine the most limiting nutrient in each type of environment.

ALTITUDINAL GRADIENTS: CONCEPTS AND IMPLICATIONS ON THE BIOLOGY, THE DISTRIBUTION AND CONSERVATION OF ANURANS

The understanding of the patterns of species richness along environmental gradients has been the focus of many studies of ecology and biogeography in the last decades. Among these, most of the cases of distribution of species richness along altitudinal gradients show a trend for species richness to peak at intermediate altitudes or for a linear decline in richness with increasing elevation. Due to their high diversity of species and the fact that they occupy a wide altitudinal range in the areas where they occur, amphibians have a high potential as model organisms for this type of study. Thus, this study aimed to examine the current state of knowledge on the biology, distribution and conservation of amphibians along altitudinal gradients based on research conducted using the databases of Web of Science, Scielo, and Google Scholar , as well as the reference lists of articles found. The implications of some environmental variables (ex. availability of water bodies, temperature, oxygen) on the biology of amphibians were discussed. We recorded a total of 30 articles on the distribution of species of anuran amphibians along altitudinal gradients. Most studies on the altitudinal distribution of anurans showed that there is a decrease in the number of species at higher altitudes, with some showing a peak of diversity at intermediate altitudes. Most studies which tested the Rapoport effect showed that anurans do not tend to follow that pattern. In Brazil, only two studies considered the effect of altitude on the distribution of amphibians. The restricted altitudinal range in those studies associated with the effect of distant areas and different years of sampling still limits the understanding of the distribution of anuran species along altitudinal gradients in Brazil. In fact, there is currently no published study with an experimental design designed to evaluate this type of question for anurans in Brazil, despite the great potential of the country both in terms of anuran diversity and in the availability of localities with relatively wide altitudinal range.

Portuguese

The understanding of the patterns of species richness along environmental gradients has been the focus of many studies of ecology and biogeography in the last decades. Among these, most of the cases of distribution of species richness along altitudinal gradients show a trend for species richness to peak at intermediate altitudes or for a linear decline in richness with increasing elevation. Due to their high diversity of species and the fact that they occupy a wide altitudinal range in the areas where they occur, amphibians have a high potential as model organisms for this type of study. Thus, this study aimed to examine the current state of knowledge on the biology, distribution and conservation of amphibians along altitudinal gradients based on research conducted using the databases of Web of Science, Scielo, and Google Scholar , as well as the reference lists of articles found. The implications of some environmental variables (ex. availability of water bodies, temperature, oxygen) on the biology of amphibians were discussed. We recorded a total of 30 articles on the distribution of species of anuran amphibians along altitudinal gradients. Most studies on the altitudinal distribution of anurans showed that there is a decrease in the number of species at higher altitudes, with some showing a peak of diversity at intermediate altitudes. Most studies which tested the Rapoport effect showed that anurans do not tend to follow that pattern. In Brazil, only two studies considered the effect of altitude on the distribution of amphibians. The restricted altitudinal range in those studies associated with the effect of distant areas and different years of sampling still limits the understanding of the distribution of anuran species along altitudinal gradients in Brazil. In fact, there is currently no published study with an experimental design designed to evaluate this type of question for anurans in Brazil, despite the great potential of the country both in terms of anuran diversity and in the availability of localities with relatively wide altitudinal range.