Brazilian Savanna Research Articles

A plant-ant interaction in the Brazilian Savanna: The interesting case of Alibertia edulis (Rich.) A.Rich (Rubiaceae) and Camponotus rufipes Fabr. (Formicinae)

Plant-ant interaction in savanna ecosystems is an iconic example of species mutualism. In Cerrado, Brazilian savanna, it is common to find this type of interaction mediated by the offer of extrafloral rewards. This study described a new plant-ant interaction for the tree Alibertia edulis (Rubiaceae) and the ant species Camponotus rufipes and elucidated the main structure involved in the interaction. To do so, (i) we monitored the phenology of A. edulis, (ii) recorded the ant species visitation, and, (iii) collected fruits in different stages of development to perform anatomical and histochemical trials to characterize the structures and chemical components related to the secreted substances - which could be responsible for attracting the ants. Ants’ visitation starts at the beginning of fruit development and stops when they are completely ripe. An extrafloral nectary – pericarpical nectary - on the top of the fruits was identified and described for the first time in the Alibertia edulis, derived from the flower structure, which remains to exude (sugar components) during the fruit development. Based on these results, C. rufipes, known for being an aggressive ant, may play a role in protecting fruits against predation until they are completely ripe and the seeds are ready to be dispersed. During seed dispersal, the fruits reduce the production of nectar, signaling the end of the partnership with the ants until the next reproductive season. Here, we shed light and bring new insights into a new plant-ant interaction for a widely spread tree and ant species.

Large wood recruitment, retention and mobilization in low-order streams of the Brazilian Savanna

The delivery of wood to streams varies in space and time and may occur continuously or episodically. Once in a stream, wood may be retained or transported due to the balance between driving (water flow) and resisting forces (channel features and wood characteristics). Despite there being few studies directly measuring wood mobility, notable variations in annual transport rates and mean travelled distances have already been detected worldwide. In the tropics, due to wetter and warmer conditions and consequently higher decay rates and peak discharge, wood is believed that more readily degraded and transported downstream. However, there exists a knowledge gap regarding wood dynamics in tropical streams and even more considering tropical non-forested environments. In the present study, we aimed to document large wood (LW) recruitment, retention, and mobilization over a period of one year in eight low-order streams of the Cerrado (the South American Savanna) by tagging and tracing LW pieces. We detected high LW transport and recruitment rates in Cerrado streams, such that the total wood amounts remained constant over time. However, there were important differences between streams due to their distinct channel morphologies and the occurrence of episodic events. The LW length and diameter, original location and orientation were the most important factors in the prediction of the LW travelled distance, which ranged from zero to almost 100 m in one year. Our findings provide unprecedented information regarding wood mobility in tropical savanna streams in South America. To further advance knowledge about the dynamics of wood in Cerrado streams, future studies should characterize the great diversity of wood, especially with regard to densities that may strongly affect wood mobility. Furthermore, it is essential to perform long-term studies to document the dynamics of wood over years in these environments.

Effect of liming in plinthic and petroplinthic soils for soybean cultivation in the Brazilian Savanna

Agricultural expansion is advancing on marginal soils (Plinthic soils), but the liming recommendation for this soil, especially for soybean cultivation, remains unknown. This study aimed to evaluate soybean (Glycine max) responses to limestone doses in concretionary soils (plinthic and/or petroplinthic). The experiment was carried out in the greenhouse, in randomized blocks, with four soil types and six limestone doses (4x6 factorial scheme), with four replicates. Soils were: RYO: Red-Yellow Oxisols; CPP-29, CPP-72, CPP-82 corresponds to the Concretionary Petric Plinthosol with 29, 72, and 82% concretions, respectively. Limestone doses varied from 0 to 4 times for each soil, based on the recommendation of regional bulletins. Soil temperature, crop emergence, development, and soybean yield characteristics were evaluated. Results were evaluated by ANOVA, followed by the LSD test or polynomial regression adjustment (p ≤ 0.05). Soybean response to liming varied with soil types. Seedlings showed lower vigor in Plinthic soils with plinthite contents ≥72%. These soils showed higher thermal accumulation (°C), and this increase showed a strong negative correlation with soybean development and reproductive characteristics. Evidence of liming response was observed after crop stage V5. Limestone substantially improved soybean growth and development in Plinthic soils with high plinthite levels, although they had lower yield potential than low plinthite levels and Oxisol. In general, the maximum response of the crop occurred at doses ~2 times higher than that practiced in the Brazilian Savanna region, especially in Plinthic soils

Complexity of the Male Perfume of Eulaema nigrita from Forest and Woody Physiognomies of the Brazilian Savanna: Is There a Relationship with Body Size and Wing Wear?

Male orchid bees collect volatile and semi-volatile compounds from the environment for storage and accumulation in specialized hind legs. Later, these compounds form a perfume blend used during courtship to lure conspecific females for mating. Male orchid bees perfume has been suggested to play an important role as a sexual signaling trait involved in pre-mating isolation of species, functioning as an indicator of male genetic quality. Eulaema nigrita Lepeletier (Apidae: Euglossini) is a common species in both forested and woody savanna (Cerrado stricto sensu) physiognomies of the Brazilian savanna biome. By identifying the chemical composition of male E. nigrita perfume, we tested for differences in the bouquet chemical profile in populations from remnants of seasonal semideciduous forest and woody savanna. In addition, we assessed the relation between perfume complexity and morphological traits associated with size and age of males. Our analysis showed a low effect of physiognomies on differences in the perfume chemical profile of sampled males. Nevertheless, we observed significant differences in the chemical profile of individuals from two seasonal semideciduous forest remnants, which suggests an environmental effect in individual bouquet. Wing wear measurements were positively related to perfume complexity, consistent with the premise that perfumes from older individuals are indicators of survival capacity in male orchid bees.

Stem wound healing is dependent upon bark and trunk growth rates in Brazilian savanna

Stem wound healing is dependent upon bark and trunk growth rates in Brazilian savanna

Diversity of Ants (Hymenoptera: Formicidae) Captured by Myrmeleon (Neuroptera: Myrmeleontidae) Larvae in a Ecosystem of the Brazilian Cerrado Biome

This study aimed to investigate the diversity of ants captured in Myrmeleon pits in a Cerrado environment (Brazilian savanna) and assess the relationship between pit size and capture success. Field expeditions were performed in the Inhamum Municipal Environmental Protection Area, Caxias, Maranhão State, Brazil. Pits of Myrmeleon larvae were observed, and captured ants were collected and identified. Our results showed that Myrmeleon larvae inhabiting this Cerrado site rely on ants as their main natural prey. Seven ant species were identified. There was a positive relationship between pit diameter and capture success. This is the first investigation of the diversity of ants naturally predated by antlions.

The effect of urbanization on species composition and trophic guilds of bats (Mammalia, Chiroptera) in the Brazilian Savanna.

Urban environments present less environmental heterogeneity in relation to the natural ones, affecting the biodiversity of bats and the ecological processes in which they participate. In this way, we will identify how urbanization influences the structure of bat communities in the municipality of Goiânia, Goiás, Brazil. We compared species composition, guilds and bat richness in a gradient that crossed urban, semi-urban and natural areas in the municipality of Goiânia, contained in the Cerrado biome. We captured a total of 775 bats of 16 species distributed in three families. Urban areas had a higher species abundance, while semi-urban areas had a higher species richness. The three types of environments have different compositions, the urban one being more homogeneous, the fauna in these areas is composed of generalist species, which benefit from this process. The diversity present in semi-urban areas is a consequence of the intersection between urban and natural fauna, which is why urban expansion needs to occur in a planned manner to minimize the impacts of this process and ensure the maintenance of biodiversity.

Estimation of Adaptability and Stability of Nellore Sires, based on the Productive Progeny Performance Raised in Brazilian Savanna

Estimation of Adaptability and Stability of Nellore Sires, based on the Productive Progeny Performance Raised in Brazilian Savanna

Estimativas de parâmetros genéticos em genótipos de cevada irrigada no cerrado brasileiro do Distrito Federal

ABSTRACT Barley is an important crop for Brazil and an advantageous alternative for irrigated cultivation in the Brazilian Savanna. The present study aimed to characterize and estimate genetic, phenotypic, and environmental parameters and select genotypes from the Embrapa Cerrados irrigated barley working collection. The experiment was established in Randomized Blocks with four replications under irrigation in Embrapa Cerrados, Planaltina-DF. The traits evaluated were grain yield, commercial classification of first grains, 1000-seed weight, plant height, lodging, and cycle. The genetic parameters and correlations between the traits evaluated were obtained. High values of heritability, in a broad sense, were verified. The high coefficients of genotypic variance and the high selective accuracy obtained corroborate the favorable environmental condition for the selection of genotypes. It was verified that the genotypic correlations were higher than the phenotypic correlation coefficients, showing a greater contribution of genetic factors in the expression of the traits. Earlier genotypes had higher grain yields, first-class commercial classification, 1000-seed weight, and height. There was a strong positive correlation between the commercial classification of first grains and 1000-seed weight. Genotypes PFC 2005143, PFC 2006134, and PFC 2004212 were selected for use in crossbreeding blocks within the Brazilian irrigated barley breeding program.

Reduced gene flow and bottleneck in the threatened giant armadillo (Priodontes maximus): implications for its conservation.

The progressive fragmentation and loss of habitats represent the main threats for endangered species, causing genetic consequences that may have potential implications for a population's long-term persistence. Large mammals are the most affected species among vertebrates. The giant armadillo Priodontes maximus is a large South American mammal threatened species, showing nocturnal, solitary and fossorial behavior, occurring at low population densities, and its population dynamics are still poorly known. In this study, we carried out the first assessment of genetic variability and population genetic structure of the species, using a panel of 15 polymorphic microsatellites developed by high-throughput genome sequencing. The spatial Bayesian clustering, Fst and Dest results indicated the presence of two genetic clusters (K = 2) in the study area. These results suggest a reduction in gene flow between individuals inhabiting the Brazilian savanna (Cerrado) and the Pantanal wetlands, with the increased human-driven habitat modifications possibly contributing for this scenario. A bottleneck signal was detected in both populations, and a subpopulation structuring in the Cerrado may also be reflecting consequences of the extensive habitat modifications. Findings from this study provide important and useful information for the future maintenance of genetic diversity and long-term conservation of this flagship species.

Diet and between-tissue isotope comparisons reveal different foraging strategies for age and sex of a Saffron Finch (Sicalis flaveola Linnaeus, 1766) population.

Measuring stable isotopes in different tissues offers the opportunity to provide insight into the foraging ecology of a species. This study aimed to assess how diet varies between yellow females, yellow males, and dull individuals of a Saffron Finch (Sicalis flaveola) population. We measured δ13C and δ15N in blood over a year, and in different feathers, to estimate seasonal consistency of resource use for each category. We conducted this study in a private farm in the Central Brazilian savannas. We sampled 195 individuals in seven field samplings between January 2017 and March 2018. The mean blood δ13C values were similar among yellow females, yellow males and dull individuals, indicating that this population of Saffron Finch predominantly accesses similar resources throughout the year, with a predominant C4 signal. Although Saffron Finch is considered a granivorous species, the mean δ15N values found indicate that both adults and juveniles also incorporate in their tissues some invertebrate. The slight isotope-tissue difference between feathers and blood is similar to the reported in previous studies and may reflect tissue-to-tissue discrimination. The isotopic space of yellow males was greater than that of yellow females and dull individuals, indicating greater dietary diversity due to greater inter-individual variation in diet. In Saffron Finch, which delays plumage maturation, competition-driven partitioning of food resources seems essential in driving carotenoid-based plumage coloration between age classes and sexes.

Is leaf fluctuating asymmetry related to plant and leaf size in Miconia albicans, a common Melastomataceae species?

Fluctuating asymmetry, defined as random differences between the two sides of a symmetrical structure, has been often related to development stress in both plants and animals. In plants, leaf fluctuating asymmetry has been related to stresses such as pollution and fire and may also be related to leaf growth and herbivory rates. We assessed whether leaf fluctuating asymmetry is related to plant and leaf size in Miconia albicans (Sw.) Triana (Melastomataceae), a common multi-stem Neotropical shrub, in a Brazilian savanna area. We collected 15 leaves from each of 70 individuals, and measured fluctuating asymmetry as the difference in area between the right and left sides of the leaves using the central vein as reference. To avoid spurious results due to measurement error, the division along the central vein was performed independently by three researchers. We also measured the basal area and height of each stem of the plant individuals. We used linear models to assess the relations between leaf fluctuating asymmetry, plant size and leaf size. No consistent relations were observed between leaf fluctuating asymmetry and plant size, as the analyses performed on the fluctuating asymmetry values obtained by the different researchers showed different results. However, relative fluctuating asymmetry values, obtained by dividing the fluctuating asymmetry by the total leaf area, tended to be smaller in larger leaves. It thus appears that, in the study species, fluctuating asymmetry is related to the developmental conditions faced by the individual leaves and not by the plant as a whole.

Long-term effects of nitrogen enrichment in pollen chemistry of a plant species from Brazilian savannas, Pavonia rosa campestris

Human activities have substantially increased soil nutrient availability during the past decades, affecting plant community composition and plants' nutritional content. Several amino acids found in pollen, the main source of larval diet for bees, affect the development, health, and behaviour of this important group of pollinators. A better understanding of the consequences of global changes on pollen amino acid content can help explain and predict future impacts on bee populations and diversity. This is particularly relevant in regions that are highly exposed to fertilizers due to their importance for global food production, such as the Brazilian savannas (Cerrado), where soils are mostly dystrophic. Here, we use a long-term controlled fertilization experiment conducted in Cerrado and demonstrate that even after 10 years since the last fertilization addition, effects were still detectable on leaf and pollen chemical content. More specifically, pollen amino acid content of Pavonia rosa-campestris (Malvaceae), a species known to be important for the diet of several native bee species, changed because of nitrogen (N) addition. Not only did the overall amino acid content increase with N addition, but its profile was also affected, with the proportion of some amino acids increasing (e.g. isoleucine, leucine, serine, threonine), while decreasing for others (e.g. cysteine). These amino acids can have important effects on larval development and flower visitor behaviour. Further studies evaluating the effects on a diverse set of plant species and the consequent impacts on flower visitation and bee fitness are essential to better understand the full consequences of increased nitrogen availability in nutrient-limited ecosystems such as Cerrado.

Frequency analysis of extreme air temperature events in an urban center in the Brazilian savanna

The increase in the planet's average air temperature in recent years has influenced the pattern of natural climatic phenomenons, with levels outside the normal range, the occurrence of prolonged dry periods, torrential rains and heat waves. Due to the climate crisis, extreme events have become increasingly frequent and more intense. With that in view, the aim of this article was to analyze the frequency of occurrence of extreme air temperature events between 2003 and 2023 in Cuiabá-MT-Brazil, as well as to understand the relationship between these extreme heat wave events and the occurrence and intensity of ENOS events. To this purpose, extreme events were analyzed using daily maximum air temperature data for the period from January 1, 2003 to October 31, 2023 obtained from the automated station of the National Meteorological Institute (INMET) located in Cuiabá - MT (CÓDA907), and ONI (Oceanic Niño Index) data. The results showed a significant increase of 86% in the occurrence of extreme events in 2020, compared to 2007, the year with the lowest number of occurrences. Therefore, it is extremely important that issues such as climate emergency, climate change and climate resilience are discussed as a means of public policy, preventing these increases from becoming even worse in frequency and/or intensity.

Optimal Time for Haymaking and Potential Production of Grass Hay on Soybean Overseeding in Brazilian Savanna

The objective of this research was to determine the potential for hay production of Quenia guinea grass (Megathyrsus maximus cv. BRS Quenia), Congo grass (Urochloa ruziziensis), and Xaraes palisade grass (Urochloa brizantha cv. Xaraes) following soybean cultivation (Glycine max) in the Brazilian Cerrado. The experimental field was divided into 12 plots, with 4 replicates of each grass species. Chemical composition, forage mass (FM), and the potential for milk and carcass production were determined for the three grasses. Principal component analysis showed that the total digestible nutrients (TDN) had the most significant influence on milk and carcass potential. Quenia guinea grass reached maximum forage accumulation at 134 days after soybean harvest, representing 4191.51 kg ha−1 of FM. Congo grass and Xaraes palisade grass produced 4033.51 kg ha−1 and 4437.22 kg ha−1, respectively, in cuts made at 154 and 138 days. Quenia guinea grass had 20.71% soluble protein in its composition when harvested at 115 days. Regarding milk production potential, Congo grass, on the other hand, showed a linear reduction in milk production as the number of days after soybean harvest increased. As for carcass production potential, Congo grass demonstrated the highest carcass production potential (110.65 kg Mg−1 FM) at 107 cutting days. Xaraes palisade grass had the highest FM production, while Quenia guinea grass stood out in soluble protein. Conversely, Congo grass showed greater potential for hay production when overseeding in soybeans, as it excelled in carcass production potential. Therefore, for this grass, the ideal point for haymaking should occur within up to 107 days after sowing.

Combining Digital Imaging and Artificial Neural Networks for Individual Volumetric Estimation of Non-Straight Trees

Tree volume models have become an important decision-making tool in forest resources management. The objective of this work was to create Artificial Neural Networks (ANN) to fit individual tree models from the Brazilian Savanna (the Cerrado biome), characterized by non-straight and very bifurcated tree stems. Data were collected in two different areas and through different methods: i) individual tree volume by digital photographs, and also by tree climbing measurements (both obtained in a non-destructive way); ii) tree volumes measured destructively by the traditional rigorous cubing procedure after thinning. Data obtained from climbing measurements were compared with the corresponding tree obtained from digital photographs, resulting in a reasonable operational linear relation of 0.80. Ten ANN structures were created with different combinations of forestry variables. Five ANN structures depicted predictive ability results above 0.80. Then, the results obtained by ANN were compared with those obtained by classic tree volumetric models, once again showing the predictive superiority of ANN. The present study indicates that tree volume obtained from digital photographs, achieved by popular mobiles, can be safely used for the estimation of very-crooked trees from the Brazilian Savanna and demonstrated the greater predictive ability of ANN in relation to the classic regression-based volumetric models in terms of lower modeling bias.

Analysis of the correlation between land use and surface runoff in a Brazilian savanna basin

– Since the 1980s, the Brazilian savanna (Cerrado) has been suppressed to make space for agricultural production, mainly soybean, corn, and cotton. This savanna strategically contains important South American river sources – Paraná, Paraguai, São Francisco, Araguaia, Tocantins, and tributaries of the Amazon River. Land use and cover are conditioning factors in generating the hydrological cycle components, notably surface runoff. Thus, this study aimed to evaluate spatial and temporal land use changes and their correlations with surface runoff in the Grande River basin. The study area is a relevant São Francisco River sub-basin, covering part of the Urucuia Aquifer System, encompassing the dry forest and savanna biomes. The inputs included landscape ecology metrics, land use time series from 1990 to 2020, and water flow values near the basin outlet. The landscape metrics were modeled with the R software landscapemetrics package. Aside from the time series trend, the correlation between land use, land cover, and flow variations was also evaluated through statistical tests – Mann-Kendall, Sen's slope, Pittitt, and rho Spearman. Changes were observed in areas covered by forest, savanna, and grassland formations. The areas presented reduction from 22,121 km2, 27,889 km2, and 15,366 km2 to 9916 km2, 27,870 km2, and 5666 km2, respectively. On the other hand, there was an increase, especially in rainfed agriculture (from 5241 km2 to 20,856 km2) and, more recently (2005), in irrigated agriculture (from 94 km2 to 1362 km2). Results show a reduction in the fragments of native vegetation (from 2,235 km2 to 1794 km2) and an increase in the fragments of agricultural activities (from 678 km2 to 1081 km2). For most classes, the change point was identified as the year 2005. A strong direct correlation was observed between the average and minimum flows (Q90) with forest and grassland formations. In comparison, an inverse correlation was noticed between pasture, urban infrastructure, rainfed agriculture, and irrigated agriculture classes.

Soil water repellency in the Brazilian neotropical savanna: first detection, seasonal effect, and influence on infiltrability.

Soil water repellency (SWR) has been detected worldwide in various biomes and climates. However, this phenomenon has not been shown yet in the Brazilian neotropical savanna. The present study addressed the following questions: (a) Does SWR occur in the Brazilian neotropical savanna? If so, (b) does it exhibit seasonality? (c) Does it influence infiltration? To do that, we selected two similar study areas covered by similar soils (oxisol) and vegetation (netropical savanna). We performed water repellency and infiltration tests in both areas during the transition from dry to wet season. Our results indicate that SWR occurs in soils of the Brazilian neotropical savanna only during the dry season and influence water infiltration in the dry season. The likely cause of SWR might be related to the chemical composition of soil organic matter since neotropical savanna plants produce hydrophobic substances as a survival strategy, especially during the dry season.

Landscape heterogeneity can partially offset negative effects of habitat loss on mammalian biodiversity in agroecosystems

Abstract Intensive, large‐scale agriculture promotes the conversion of natural habitats and diversified crops into monocultures, decreasing both native vegetation cover and landscape heterogeneity, leading to landscape simplification. Yet, a key knowledge gap persists on the relative impacts of the loss of native vegetation and landscape heterogeneity on biodiversity. Addressing this gap is pressing to support policies that conciliate agricultural production and biodiversity conservation and to move forward some scientific controversies, as the ‘land sharing versus land sparing’ and ‘habitat loss versus fragmentation’ debates. Through a hierarchical sampling design that maximised variation, while minimising correlation, between landscape heterogeneity and native vegetation cover, we recorded the occurrence of medium and large‐bodied mammals in native vegetation and agricultural areas of 55 landscapes in a global conservation hotspot and a key commodity production area—the Brazilian Savanna, Cerrado. We compared simple, additive and interactive models to investigate the effects of landscape heterogeneity and native vegetation cover on richness and composition of native and invasive mammals. Native and invasive mammal communities were affected by both native vegetation cover and landscape heterogeneity, although the effects of the first was stronger than the later. Both aspects had positive effects on native species richness and negative effects on invasive species richness, indicating that the loss of native vegetation and the reduction in landscape heterogeneity lead to biotic homogenisation. Yet, while landscape heterogeneity benefited most native species, the direction of its effect varied among invasive species and depended on native vegetation cover. Synthesis and applications. Besides reducing habitat loss, avoiding landscape homogenisation is key for conciliating agricultural production and biodiversity conservation, pointing to the relevance of policies encouraging crop diversification. As increasing landscape heterogeneity can in part compensate the negative effects of losing native habitat on biodiversity in agroecosystems, policies can gain feasibility by adjusting the balance between native vegetation cover and landscape heterogeneity according to what best suits local restraints and demands.

Spatiotemporal Dengue Fever Incidence Associated with Climate in a Brazilian Tropical Region

Dengue is a serious infectious disease worldwide and a climate-sensitive disease. Thus, our goals were to (i) evaluate the relationship between dengue incidence and meteorological variables (rainfall and air temperature); (ii) identify the spatiotemporal pattern of dengue incidence in the municipalities of Mato Grosso from 2001 to 2020; and (iii) verify the spatial dependence of dengue incidence in the dry and wet seasons. We used dengue data from 2001 to 2020, monthly rainfall estimates from GPM, and daily air temperature estimates from ERA-5. The municipalities of the Mato Grosso state are included in 16 healthcare territories. The seasonal rainfall pattern indicates that the peak of the dengue endemic occurred in the wet season. However, drier and/or warmer places had a lower incidence of dengue in the dry season. Furthermore, a lagged effect of meteorological variables on dengue incidence has been identified, ranging from 0 to 7 months. Hotspot areas were identified which might have the potential for an intense spreading of dengue in Mato Grosso. They were mainly concentrated in the healthcare territory of Teles Pires (ID 14) in the dry season, while they were concentrated in the healthcare territories of Garças Araguaia (ID 5), Oeste (ID 11), and Teles Pires (ID 14) in the wet season. In addition, they are located in the Am climate and in the Amazon Forest and Brazilian savanna biomes, which have higher dengue incidence values. These results help to highlight which municipalities decision-makers must intervene in the public health system to prevent and control future epidemics.