Search Results (26)

Fire is an essential component of species, ecosystems, and atmospheric dynamics. However, human activity has caused changes in fire regimes over the past two decades. In many cases, the spatial patterns of vegetation change after fire at the landscape scale remain unknown. The aim of this study was to evaluate spatial vegetation trends in burned areas across the Americas (2001–2024), using non-parametric tests and analyzing Normalized Difference Vegetation Index (NDVI) remote sensing products. Over a period of 24 years, fire activity burned a total area of 429.7 million hectares in 44 countries or territories and 269 ecoregions in the Americas. Regarding fire recurrence, the data indicates that 244.7 Mha (56.9%) burned only once (≤1), while 185.0 Mha (43.1%) burned multiple times (≥2), with certain regions experiencing up to 39 fires. The NDVI trend analysis showed that burned areas with increasing trends (p < 0.05) represented a total of 149.6 Mha (34.8%), primarily in Brazil (54.6 Mha, 12.7%), Argentina (17.8 Mha, 4.2%), the United States (14.4 Mha, 3.4%). In terms of decreasing NDVI trends (p < 0.05), these represented a total of 91.8 Mha (21.37%), primarily in Brazil (29.1 Mha, 6.8%), Canada (23.4 Mha, 5.4%), and the United States (14.2 Mha, 3.3%). The ecoregions with the largest areas showing increasing NDVI trends (p < 0.05) were the Cerrado (33.8 Mha, 7.8%), the Llanos (13.3 Mha, 3.1%) and the Humid Chaco (7 Mha, 1.6%). In contrast, the ecoregions with the largest areas showing decreasing NDVI trends (p < 0.05) were the Dry Chaco (9.2 Mha, 2.1%), the Cerrado (8.6 Mha, 2.0%), and the Boreal Shield (8.3 Mha, 1.9%). In terms of land cover types, savannas (37.2%) exhibited the highest proportions of increasing NDVI trends (p < 0.05), while decreasing trends were also present in savannas (28.0%) and grasslands (22.1%). Identifying spatiotemporal trends in vegetation change after fires is a fundamental step in implementing strategies and public policies to ensure ecological restoration. Moreover, given the high costs of restoration efforts, governments must work together to prevent these ecosystems from burning repeatedly. Full article

Dry forests are increasingly threatened by degradation, which determines their structural integrity, functional capacity, and the ability to provide essential ecosystem services. Degradation is the consequence of processes that reduce the different attributes of forests. This study aimed to (i) identify remote sensing proxies for above-ground biomass (AGB) and tree regeneration in three ecoregions of dry forest localized in west Argentina; (ii) analyze the temporal dynamics between 1993 and 2023; (iii) assess the role of precipitation in their temporal variability, and (iv) map their spatial distribution. The median Tasseled Cap Transformation Wetness (TCTW) was the best-performing spectral proxy for AGB, while median Enhanced Vegetation Index (EVI) best captured tree regeneration. In the time series of TCTW, no significant breakpoint was detected; however, a pronounced decline in the median EVI occurred in 1998 in the Monte of Plains and Plateaus and Monte of Hills and Basins ecoregions, particularly near watercourses. In the Dry Chaco, tree regeneration recovered after 2013; however, a decline after a breakpoint coincided with decreased precipitation. Overall, AGB and tree regeneration exhibited contrasting temporal and spatial patterns, underscoring the heterogeneity of dry forests. A weakening relationship between precipitation, a key driver of forests, and forest attributes suggests the influence of other factors, including topography and land use change. Full article

Habitat fragmentation profoundly alters ecological processes such as seed predation and dispersal. Ants play a central role as seed removers and dispersers, yet the effects of fragmentation on seed-carrying ant assemblages in dry tropical forests remain insufficiently studied. In this work, we examined the influence of forest fragmentation on seed-carrying ants in the Chaco forests of central Argentina. Ants were sampled across nine forest fragments of varying sizes and two continuous forests within an agroecosystem landscape, and species richness, composition, and occurrence were analyzed. Our results revealed that species richness did not vary significantly with fragment size; however, fragmentation caused pronounced shifts in species composition, with clear distinctions between continuous forests and fragments. Large-bodied specialist harvester ants declined in fragments, whereas small- to medium-sized generalist species from genera such as Pheidole and Solenopsis persisted. These compositional changes suggest that although overall seed removal rates may remain stable, the functional quality of seed dispersal likely diminishes. This study highlights the sensitivity of seed-carrying ant assemblages to habitat fragmentation and underscores the need for further research that integrates behavioral and landscape-scale approaches to better assess impacts on seed removal, dispersal, and forest regeneration in fragmented dry forests. Full article

Although the creation of protected areas helps to protect biodiversity, it does not necessarily contribute to the reduction in some conflicts, such as livestock predation by large carnivores. We evaluated the presence of puma (Puma concolor) in a large ranch converted into a National Park and in surrounding rancher areas in the Dry Chaco of Argentina. Two years after livestock removal from the protected area, puma occupancy was associated with wild prey richness, which was greater in the park than in the neighboring ranches, and was negatively related to livestock presence. We also evaluated ranchers’ perceptions of puma presence and their tolerance to livestock predation. Ranchers showed a negative perception of puma presence and a low tolerance to livestock predation. Therefore, this study suggests that, while the creation of a protected area can improve both predator and prey densities, successful mitigation of human–predator conflict requires further strategies and interventions, like economic compensation and environmental education programs. Full article

Ruminant production in the Chaco region relies on pastures and native forest foliage, whose nutritional value is poorly characterized and may be influenced by tannins. This study evaluated the in situ digestibility and in vitro ruminal fermentation of foliage from Prosopis affinis (PA), Prosopis nigra (PN), Acacia polyphylla (AP), Phyllostylon rhamnoides (PR), and Tabebuia nodosa (TN), incubated with or without polyethylene glycol (PEG) to assess the effects of tannin on gas production and nitrogen (N) compounds degradability. Foliage contained ≥17% crude protein (CP) and ≥40% fiber-bound N. Tannin concentration was >4% dry matter (DM) in PN and PA and <1% DM in PR, AP, and TN. In situ digestibility was ≤51% in all species except PR (73%; p < 0.05). Gas production was higher in PA, PR, and TN (p < 0.05), with no PEG effect. Methane production was not affected by tree species or PEG (p ≤ 0.277). Both species and PEG affected the effective N compounds degradability (END), with PEG increasing it in PN and AP (p < 0.05). Although foliage is high in CP, its digestibility is low; N is largely fiber-bound, and tannins may further limit END, factors to consider when including them in ruminant diets. Full article

(1) Background: Changes in the spatial, temporal, and magnitude-related patterns of fires caused by humans are expected to exacerbate with climate change, significantly impacting ecosystems and societies worldwide. However, our understanding of fire regimes in many regions remains limited, largely due to the inherent complexity of fire as an ecological process. Pyrogeography, combined with unsupervised learning methods and the availability of long-term satellite data, offers a robust framework for approaching this problem. The purpose of the study is to identify the pyroregions of the Argentine Gran Chaco, the world’s largest continuous tropical dry forest region. (2) Methods: Using globally available fire occurrence datasets, we computed five fire metrics, related to the extent, frequency, intensity, size, and seasonality of fires at three spatial scales (5, 10, and 25 km). In addition, we tested two widely used cluster algorithms, the K-means algorithm and the Gaussian Mixture Model (GMM). (3) Results and Discussion: The identification of pyroregions was dependent on the clustering algorithm and scale of analysis. The GMM algorithm at a 25 km scale ultimately demonstrated more coherent ecological and spatial distributions. GMM identified six pyroregions, which were labeled based on three metrics in the following order: annual burned area (categorized in low, regular or high), interannual variability of fire (rare, occasional, frequent), and fire intensity (low, moderate, intense). The values were as follows: LRM (22% of study area), ROI (19%), ROM (14%), LOM (10%), ROL (9%), and HFL (4%). (4) Conclusions: Our study provides the most comprehensive delineation of the Argentine Gran Chaco’s Dry Forest pyroregions to date, and highlights both the importance of determining the optimal scale of analysis and the critical role of clustering algorithms in efforts to accurately characterize the diverse attributes of fire regimes. Furthermore, it emphasizes the importance of integrating fire ecology principles and fire management perspectives into pyrogeographic studies to ensure a more comprehensive and meaningful characterization of fire regimes. Full article

Soil organic carbon (SOC) stocks play an important role in ecosystem functioning and climate regulation. These stocks are declining in many tropical dry forests due to land-use change and degradation. Data on topsoil (0–300 mm) organic C stocks from six experiments conducted in the Dry Chaco region, the world’s largest dry tropical forest, were used to test the predictive performance of the Rothamsted Carbon Model (RothC) after its implementation in an object-oriented graphical programming language. RothC provided promising predictions (i.e., precise and accurate) of the SOC stocks under two representative land covers in the region, native forest and Rhodes grass [relative prediction error (RPE) < 10%, concordance correlation coefficient (CCC) > 0.9, modelling efficiency (MEF) > 0.7]. Comparatively, model predictions of the SOC stocks under degraded Rhodes grass swards were suboptimal. The predictions were sensitive to C inputs; under native forests and Rhodes grass, a high C input improved the predictive performance of the model by reducing the mean bias and increasing the MEF values, compared with mean and low C inputs. Larger datasets and revisiting some of the underlying assumptions in the SOC modelling will be required to improve the model’s performance, particularly under the degraded Rhodes grass land cover. Full article

Anthropogenic alteration of tropical and subtropical forests is a major driver of biodiversity loss; notably, the Chaco Forest, which is the largest dry forest in the Americas, is among the most impacted regions. Sustainable forest management, a key objective of the UN’s 15th Sustainable Development Goal (SDG), underscores the need for advanced monitoring tools. This study integrates Sentinel-2 remote sensing (RS) spectral indices with field data to analyze forests under varying management regimes and levels of alteration in a representative area of the Chaco region (Chancaní Provincial Reserve and surrounding areas of the West Arid Chaco). Forest structure types and conservation levels were linked to monthly spectral index behavior using linear mixed models. Spectral indices such as the BI (Brightness Index), NDWI_Gao (Normalized Difference Water Index), and MCARI_Sent (Modified Chlorophyll Absorption in Reflectance Index) effectively differentiated forest stands by conservation status and structural alteration. This combined RS and field data approach proved highly effective for detecting and characterizing forests with diverse conservation and sustainability conditions. The methodology demonstrates significant potential as a reliable RS-based tool for monitoring forest health and supporting progress toward SDG targets, particularly in regions like the Chaco Forest, which face extensive anthropogenic pressures. Full article

In the hostile and challenging environment of the Paraguayan Chaco, the wild carob pods (Neltuma spp.) are a valuable vegetable resource that provides nutrition and significant economic opportunities for the local populations by means of carob flour production. However, the microbiological quality of the carob flour is limited due to the manual gathering. The main objective of this investigation is to find an efficient disinfectant and its minimum application level to obtain microbial stability in carob flour. The microbial load (total mesophilic aerobes, moulds, and yeasts, Escherichia coli, Staphylococcus aureus, and Salmonella spp.) of the flour obtained by disinfection with citric acid (1 and 3%) and sodium hypochlorite (1 and 3%) was compared. Drying tests were carried out at time intervals of 2, 4, 6, and 7 h on whole carob pods to obtain flour in a hot air circulating tray type dryer, and humidity was used as a response variable in a thermobalance (desirable humidity < 5%). A combined process of disinfection with 3% citric acid and hot air circulating tray-type drying for 7 h at 60 °C is proposed to obtain an innocuous carob flour of high microbiological quality. Full article

The skill, assumptions, and uncertainty of machine learning techniques (MLTs) for downscaling global climate model’s precipitation to the local level in Bolivia were assessed. For that, an ensemble of 20 global climate models (GCMs) from CMIP6, with random forest (RF) and support vector machine (SVM) techniques, was used on four zones (highlands, Andean slopes, Amazon lowlands, and Chaco lowlands). The downscaled series’ skill was evaluated in terms of relative errors. The uncertainty was analyzed through variance decomposition. In most cases, MLTs’ skill was adequate, with relative errors less than 50%. Moreover, RF tended to outperform SVM. Robust (weak) stationary (perfect prognosis) assumptions were found in the highlands and Andean slopes. The weakness was attributed to topographical complexity. The downscaling methods were shown to be the dominant source of uncertainties. This analysis allowed the derivation of robust future projections, showing higher annual rainfall, shorter dry spell duration, and more frequent but less intense high rainfall events in the highlands. Apart from the dry spell’s duration, a similar pattern was found for the Andean slopes. A decrease in annual rainfall was projected in the Amazon lowlands and an increase in the Chaco lowlands. Full article

This study analyzed the fire regime in the highly diverse Paraguayan Chaco, focusing on different aspects of fire patterns, including spatial (area burned) and temporal (frequency) aspects and magnitude (severity). We focused on fire as it is a natural phenomenon that drives ecosystem change and has significant economic, ecological and social impacts of particular concern in vulnerable ecosystems. Using the K-means clustering technique, we identified four distinct fire regimes in the study region: High (H), Moderately High (MH), Moderately Low (ML) and Low (L). On the one hand, the Dry Chaco predominantly featured Low and Moderately High regimes, characterized by a low fire frequency due to arid conditions. On the other hand, the Humid Chaco was particularly affected by agricultural burning, driven by extensive livestock activity and higher biomass productivity. Finally, in the Pantanal, the variations in fire intensity were influenced by flood pulses and rainfall patterns. Our findings highlight the distinct fire regimes across the Paraguayan Chaco and detail the differences in the regimes. The study’s findings are valuable for developing efficient management strategies that account for fire behaviour during agricultural burning in this poorly studied region. Full article

The eastern region of Bolivia is of high conservation interest due to the presence of the Chiquitano Dry Forest, Dry Chaco, Pantanal and Cerrado ecoregions. However, this region is under high pressure from various anthropogenic threats, which requires continuous monitoring. An alternative for this monitoring is the use of mobile applications designed under the concept of citizen science, in which local stakeholders are part of the process of obtaining information and finding solutions to environmental problems in their territories. The main objective of this study was to evaluate the information obtained during environmental monitoring with a citizen science approach in the eastern region of Bolivia. We developed a public electronic form for the ArcGIS Survey123 mobile application to capture spatial data of nine thematic variables. Between 2021 and 2023, we conducted 16 training courses in 12 population centers, with attendees from 98 communities in 6 municipalities in the region. A total of 360 volunteers from different sectors participated in the training, including technicians from public and private institutions, park rangers, community representatives and citizens. We obtained a total of 379 records, of which 70.4% were recorded near communities and the rest within protected areas. The results were reclassified and grouped into three clusters: human activities, water resources and biodiversity. In the human activities cluster, the categories with the highest number of records were wildfires and deforestation. In the water resources cluster, the categories with the most records were cattle waterholes and streams, but one of the most notable records was the reduction of wetlands in a sector of the Bolivian Pantanal. In the biodiversity cluster, the main reports were for mammals, and among the most notable records obtained were the footprints of the jaguar (Panthera onca). This monitoring tool made it possible to generate and use high-quality information in different sites in the eastern region in almost real time, which could help strengthen the interactions and relationship with users in environmental dialogue and governance processes. Full article

The fruit of Sarcomphalus mistol (Griseb.) is from the Great American Chaco, an important wild food resource. However, its composition and potential uses are unknown to a large part of the population. In this work, two mistol and peanuts-based products were prepared (a toasted mistol product “mistol coffee” and a mistol-peanuts-based vegan beverage), and its nutritional value and antioxidant potential was investigated. The chemical composition, total phenolics compounds (TPCs), and total antioxidant capacity (TAC) of the two products were analyzed on a dry basis with AOAC, Folin–Ciocalteu, and ABTS+ radical inhibition methods, respectively. The toasted mistol product was high in dietary fiber (51.89 ± 0.65 g/100 g) and TPC (2729 ± 362 mgGAE/100 g), which was consistent with the observed high TAC (307 ± 14 mM TEAC/g). Minerals found in the toasted mistol product were mainly calcium and magnesium. The mistol-peanut-based vegan beverage presented 12.67 g/100 g of dry extract, and its main nutritional contributions are carbohydrates (8.16 ± 1.05 g/100 g db), lipids (2.33 ± 0.29 g/100 g db), magnesium (10.34 ± 1.40 mg/100 g db), and polyphenols (345 ± 4.58 mg GAE/100 g db) in agreement with their TAC in the lyophilized product (17.6 ± 5.25 mM/TEAC/g db). These products can be used according to their observed nutritional value and antioxidant potential as foods with healthy properties, especially for vegan populations. Full article

Transporting water to supply livestock is one of the great challenges of the drylands. Ranchers usually make impoundments, filled by runoff, to access freshwater for cattle supply in flat rangelands. The aim of this study was to understand rainfall-runoff generation and water storage temporal dynamics of impoundments in the Dry Chaco rangelands (Argentina). Thus, we instrumented six impoundments over three consecutive years and analyzed water storage data by developing a probabilistic model. For all impoundments, the rainfall event size thresholds to generate runoff presented values between 15 and 33 mm. Once they reached this threshold, the water gain response slopes presented values between 19 and 99 m³ mm⁻¹. Loss patterns of water storage were described by exponential or linear functions. The predicted water storage dynamics presented high accuracy with the observed time series for all impoundments (RMSD between 380 and 1320 m³). The model only needs daily rainfall and air temperature to be run, making it easy to be used by scientists, ranchers, or local decision makers. It may be used to explore the hydrological functioning of small and seasonal water bodies of different sites of the world exposed to drought episodes caused by high climate variability and/or climate change. Full article

The persistence of subtropical seasonally dry forests urgently requires the implementation of ex situ conservation and restoration programs. We studied variation in seed traits and dormancy of six native species growing in seasonally dry Chaco forests of Argentina. We documented high intra- and interspecific variability in seed traits and dormancy. Fresh seeds of Geoffroea decorticans and Parasenegalia visco (Fabaceae) were water-permeable and nondormant (ND), while those of Parkinsonia praecox and Vachellia aroma (Fabaceae) were water-impermeable and had physical dormancy (PY). Seeds of Schnopsis lorentzii (Anacardiaceae) and Sarcomphalus mistol (Rhamnaceae) were water-permeable and had physiological dormancy (PD). Mechanical and chemical scarification were the most effective methods to break PY, and dry storage for 3 months was effective in breaking PD. Seeds of large-seeded species were ND or had PD, and those of small-seeded species had PY. Species inhabiting moist habitats had ND seeds, whereas those from seasonally dry habitats had seeds with PY or PD. These results suggest that seed traits and dormancy are species-specific and that intraspecific variation in seed traits is likely associated with high phenotypic plasticity of species in response to local environmental heterogeneity. These findings should be considered at the time of implementation of conservation techniques and for seed sourcing decisions for restoration. Full article