RESUMEN
The dynamics of fluvial erosion responds to soil erosion and surface runoff on hillslopes due to land use and environmental fragility, conditioned by the soil, geology, relief, and rainfall rate. Despite the increasing problems associated with fluvial erosion in Brazil, little information is available on bedload transport in headwater catchments under intense agricultural activity. Therefore, this study sought to characterize the fluvial erosion processes and bedload dynamics in an experimental catchment in southern Brazil located at the edge of the Brazilian Meridional plateau, which is representative of a large area of high environmental fragility and intense agricultural activity in Southern Brazil. The Guarda Mor River drains a headwater catchment (18.5 km2) with undulating and hilly terrain with fragile soils and intense agricultural activity controlling fine and coarse sediment supply downstream. During 11 major rainfall-runoff events, monitoring was conducted to measure streamflow, bedload transport rates, sediment size, and hydraulic parameters, such as Manning's n values and viscous layer thicknesses. A rating curve was established based on 40 streamflow and bedload discharge measurements taken at different water levels and stages along the hydrograph. In addition, a river portion (gravel bed) was characterized as well as the granulometric characteristics of its surface and subsurface layers. The results showed that the transport pattern is influenced by factors other than hydraulic parameters alone, including the interdependence between successive events, armoring effects, and hysteresis. These factors are strongly related to the surface runoff and erosion observed on the hillslopes, which define the streamflow energy and the supply of sand fraction, respectively. A discussion is held on the bedload transport dynamics under non-equilibrium conditions in the modeling of fluvial erosion processes.
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Agricultura , Monitoreo del Ambiente , Ríos , Erosión del Suelo , Movimientos del Agua , Brasil , Ríos/química , Lluvia , Sedimentos Geológicos/química , Suelo/químicaRESUMEN
Large-scale epidemics of arboviruses, such as dengue, have heightened societal awareness regarding the necessity of combating the primary transmission vectors. Equally critical is the identification of environmental conditions and variables that influence vector population dynamics. Aedes aegypti, the primary vector of arboviruses such as dengue and Zika in Brazil, is closely associated with the climatic and geographical conditions of urban environments. This study examines the relationship between precipitation and confirmed dengue cases in Recife (Brazil), employing regression and quantile analyses to evaluate the influence of meteorological conditions on the disease's spread. The findings reveal a direct correlation between monthly averages of precipitation and confirmed cases, although this is apparent only when excluding years of epidemic peaks. The highest number of cases generally aligns with the rainy season, and the lowest with the dry season, with weak, moderate and strong precipitation events being closely linked to increased dengue incidence. However, notable discrepancies were identified: four out of six major outbreaks occurred in drier months, challenging the assumption of a straightforward relationship between rainfall and dengue incidence. These findings underscore the multifaceted nature of dengue dynamics, suggesting that while precipitation plays a significant role, other factors, including serotype circulation and broader climatic phenomena, are equally critical in driving outbreaks. This complexity highlights the need for a more comprehensive understanding of the mechanisms influencing dengue epidemics.
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Aedes , Clima , Dengue , Mosquitos Vectores , Lluvia , Dengue/epidemiología , Brasil/epidemiología , Humanos , Aedes/virología , Animales , Salud Pública , Incidencia , Ciudades/epidemiología , Brotes de Enfermedades/estadística & datos numéricos , Estaciones del AñoRESUMEN
Identified as a potential reference pathogen by the WHO Guidelines for Drinking-Water Quality, Rotavirus (RV) is among the main enteric viruses that cause waterborne diseases. The aim of this study was to identify and correlate the presence of RV in collective and individual water sources of rural communities in the state of Goiás, within the seasons in which the collections were made (rainy and dry seasons). For this, 86 water samples in the dry period and 160 samples in the rainy period were collected. Concentration of water samples, extraction of viral genetic material and molecular tests were performed. When analyzing the presence of RV in the samples, taking into consideration the period studied, RV was found to be more prevalent in the dry season (54.7%) than in the rainy season (20%), showing a strong statistical association with the dry season (p-value < 0.001). The presence of pathogenic microorganisms in water is a public risk issue, enabling the emergence of outbreaks, endemics and epidemics. In the present research, there was an association between the presence of Rotavirus and the dry period of the year when compared to the rainy period.
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Rotavirus , Población Rural , Estaciones del Año , Brasil/epidemiología , Rotavirus/aislamiento & purificación , Rotavirus/genética , Microbiología del Agua , Infecciones por Rotavirus/epidemiología , Infecciones por Rotavirus/virología , Lluvia , Agua Potable/virología , HumanosRESUMEN
Outcrops play an important role in groundwater recharge. Understanding groundwater origins, dynamics and its correlation with different water sources is essential for effective water resources management and planning in terms of quantity and quality. In the case of the Guarani Aquifer System (GAS) outcrop areas are particularly vulnerable to groundwater pollution due to direct recharge processes. This study focuses on the Alto Jacaré-Pepira sub-basin, a watershed near Brotas, a city in the central region of the state of São Paulo, Brazil, where groundwater is vital for supporting tourism, agriculture, urban water supply, creeks, river and wetlands. The area has a humid tropical climate with periods of both intense rainfall and drought, and the rivers remain perennial throughout the year. Therefore, the aim of this study is to investigate the interconnections between a spring and its potential sources of contribution, namely rain and groundwater, in order to elucidate the relationships between the different water sources. To achieve this, on-site monitoring of groundwater depth, rainfall amount, and stable isotope ratios (deuterium (2H) and oxygen-18 (18O)) from rain, spring discharge, and a monitoring well was carried out from 2013 to 2021. The results indicate that the mean and standard deviations for δ18O in rainwater exhibit higher variability, resulting in -4.49 ± 3.18 VSMOW, while δ18O values from the well show minor variations, similar to those of the spring, recording -7.25 ± 0.32 and -6.94 ± 0.28 VSMOW, respectively. The mixing model's outcomes reveal seasonal variations in water sources contribution and indicate that groundwater accounts for approximately 80 % of spring discharge throughout the year. Incorporating stable isotopes into hydrological monitoring provides valuable data for complementing watershed analysis. The values obtained support the significance of the aquifer as a primary source, thereby offering critical insights into stream dynamics of the region.
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Deuterio , Monitoreo del Ambiente , Agua Subterránea , Isótopos de Oxígeno , Lluvia , Agua Subterránea/química , Agua Subterránea/análisis , Lluvia/química , Isótopos de Oxígeno/análisis , Monitoreo del Ambiente/métodos , Brasil , Deuterio/análisis , Estaciones del Año , Modelos Teóricos , Movimientos del AguaRESUMEN
Fire occurrence, intensity, and spread are highly influenced by climatic variables. This study investigates the correlation between burned area, precipitation, and temperature in Rondônia, an agricultural frontier in the southwestern Brazilian Legal Amazon, from 2001 to 2022. The analysis utilized climatological data from the Climate Hazards Group InfraRed Precipitation with Station (CHIRPS) and MODIS product MOD11A1.061 for temperature, along with MODIS product MCD64A1 for burned area. The study was conducted on a monthly scale, employing the cross-correlation function to determine the lagged effects of temperature and precipitation on burned areas. Trend analysis was performed using the Mann-Kendall test, with the magnitude of trends estimated by Sen's Slope. Results indicated a significant negative correlation between burned areas and precipitation, with a 2-month lag and an R2 of - 0.51. In contrast, temperature exhibited a significant positive correlation with burned areas, showing a 1-month lag and an R2 of 0.55. Trend analysis revealed a decrease in precipitation by - 0.0542 mm.month-1, temperature increased by 0.006 °C.month-1, while burned areas decreased by - 111.13 km2.month-1. These findings underscore the intricate relationship between climate variables and fire occurrences, highlighting the urgent need for policies addressing climate change and environmental degradation in the Amazon.
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Agricultura , Cambio Climático , Monitoreo del Ambiente , Lluvia , Temperatura , Brasil , Animales , Bovinos , IncendiosRESUMEN
BACKGROUND: Global dengue cases are rising, notably in Brazil. METHODS: By using monthly data, we estimated linear regressions with ARIMA errors to measure the influence of temperature and precipitation on dengue incidence in the city of Campinas, São Paulo State, Brazil. RESULTS: Findings suggest that a 1°C increase in mean temperature can lead to a cumulative increase of up to 40% in dengue incidence within 2 months. Precipitation shows no significant impact. CONCLUSIONS: Results highlight the importance of temperature on the spread of dengue and potentially other mosquito-borne diseases.
Asunto(s)
Dengue , Temperatura , Brasil/epidemiología , Dengue/epidemiología , Incidencia , Humanos , Lluvia , Estaciones del AñoRESUMEN
As a pest, the gall wasp Ophelimus migdanorum poses a risk to several Eucalyptus species in Colombia. In the tropical Andes, its biological development and the damage it causes can be influenced by climate, particularly rainfall. In this regard, we examined gall phenology, population fluctuation, and leaf damage caused by O. migdanorum, and its parasitoid Closterocerus chamaeleon, over 5 months at two sites with contrasting rainfall in peri-urban areas of Bogotá, Colombia. Gall phenology and foliar damage were assessed on 10 trees per site. We characterized gall phenology by assessing their size and color, wasps' developmental stages, as well as affected leaf area and gall density on the leaf blade. Additionally, the individuals found in five attraction traps at each site were quantified biweekly to record population fluctuations. The effect of rainfall on wasp frequency and gall density between sampling sites and dates was compared using the chi-square test, while the relationship with rainfall was evaluated using the Kruskal-Wallis test. Only females of the gall wasp and its parasitoid were observed during the study, displaying multivoltine behavior. Six developmental stages of the galls were differentiated, each characterized by distinct coloration. Drier microclimates favored gall size, wasps' development stage frequency, population trend, and foliar damage. The general trend indicated a greater abundance of the parasitoid C. chamaeleon compared to O. migdanorum. Our study suggests that O. migdanorum has a less damaging effect on E. globulus in areas with rainy microclimates.
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Eucalyptus , Tumores de Planta , Lluvia , Avispas , Animales , Colombia , Avispas/fisiología , Eucalyptus/parasitología , Tumores de Planta/parasitología , Femenino , Hojas de la Planta , Dinámica PoblacionalRESUMEN
The inverse problem method can be applied to determine the properties of hydrological phenomena and estimate the parameters, which cannot be measured directly. This type of inverse focus can facilitate the implementation of the kinematic wave model (direct model-DM), to fill gaps for lateral inflow rate and runoff depth in watersheds. Thus, the goal of the study was the application of the inverse problem method (IP). The lateral inflow rate was generally obtained as a Fourier transform to represent any watersheds. The study was developed using a small catchment in the Amazon where intense rainfall events occur, producing runoff and sediments, which affect rural populations. Lateral inflow rate and runoff depth were derived using precipitation data and parameters estimated through the KINEROS2 (K2)/direct model (DM) model and the ensuing solution methods with MCMC (Markov chains Monte Carlo)/Fourier transform. The developed method was applied to four rainfall-runoff events, leading to a good fit between the observed and predicted data (Nash-Sutcliffe coefficients between 0.76 and 0.85 and RMSE values between 1.80 mm and 6.72 mm).
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Modelos Teóricos , Lluvia , Movimientos del Agua , Brasil , Monitoreo del Ambiente/métodos , Ríos , Hidrología/métodosRESUMEN
Parasitism is a strong selective pressure, and its study is crucial for predicting the persistence of host species. Mantled howler monkeys are infected by the larvae of the bot fly Cuterebra baeri. This parasitosis produces myiasis and may have negative impacts on host health, although systematic information on the dynamics of this host-parasite relationship is very limited. Currently, all available information on infection patterns of C. baeri comes from a single mantled howler monkey population (Barro Colorado Island, Panama). Therefore, in this study we describe temporal variation in infection patterns for a newly mantled howler monkey population and analyze the relationship between climate and infection likelihood. We assessed the presence of C. baeri nodules in 17 adult individuals in Los Tuxtlas for 10 months through direct observation and compiled data on ambient temperature and rainfall. Most subjects had nodules during the study and there were no differences between sexes in the number of nodules. Nodules were usually located in the neck. Prevalence and abundance of nodules peaked thrice during the study (February, April, and September), a pattern that was very similar to that of parasitism intensity (February, April, and August). Incidence closely tracked these peaks, increasing before and decreasing after them. The likelihood of nodule appearance increased when both mean and minimum temperature decreased in the 24-21 prior days to nodule appearance. It also increased with decreased rainfall in the 5-2 prior days to nodule appearance. Although only three of the eight analyzed climate variables had a significant effect on parasitosis, these results suggest that climate may affect pupal development and the access of larvae to hosts. Besides contributing data on C. baeri parasitism for a new mantled howler monkey population, our study provides novel information on the influence of environmental factors on the dynamics of host-parasite systems.
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Alouatta , Clima , Dípteros , Interacciones Huésped-Parásitos , Enfermedades de los Monos , Miasis , Animales , Alouatta/fisiología , Alouatta/parasitología , Miasis/veterinaria , Miasis/epidemiología , Miasis/parasitología , Enfermedades de los Monos/parasitología , Enfermedades de los Monos/epidemiología , Masculino , Femenino , Dípteros/fisiología , Panamá/epidemiología , Larva/fisiología , Prevalencia , Estaciones del Año , Lluvia , TemperaturaRESUMEN
Among the set of phenological traits featuring mangrove ecosystems, litterfall production stands out with marked intra-annual and longer-term variation. Furthermore, mangrove forests resilience is one of the most important ecological attribute, reconciling the juxtaposed terrestrial and marine environment such transitional systems occupy. However, world's mangroves are nowadays facing recurrent climatic events, reflected in anomalies depicted by major drivers, including temperature and precipitation. This physical-environmental setting may either constrain or favor overall forest productivity. A combination of time series analysis (spectral density and cross-correlation techniques) and statistical model fitting (General additive model) was implemented to explore trends in total litterfall of a well-developed mangrove forest in southeastern Gulf of Mexico (Celestun Lagoon, SE Mexico) and potential association with the varying behavior of temperature (°C) and precipitation (mm month-1), highlighting their anomalies. The results are consistent with a synchronous response between litterfall production and climatic variables (mean monthly temperature and total monthly precipitation). Concurrent peak litterfall production in Celestun lagoon with high temperatures and precipitation occurred during June and October, featuring a two-month time lag for the response time. More than half of the litterfall anomalies (53.5%) could be reflecting either multiple sources of climatic anomalies (maximum, minimum, and monthly average temperature and monthly total precipitation) or single point events (cyclone landfall). This relationship dynamics showed an interannual persistence (1999-2010). The structure portrayed by the litterfall time-series was not unequivocally related to climatic anomalies. Arguably, climatic anomalies behave with different intensities and even may exhibit complex interactions among them. The study of anomalies provides a baseline for a better grasp of: i) mangrove anomalies responses and ii) their vulnerability to these extremes.
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Humedales , México , Temperatura , Clima , Estaciones del Año , Ecosistema , Cambio Climático , LluviaRESUMEN
Tropical forests account for over 50% of the global terrestrial carbon sink, but climate change threatens to alter the carbon balance of these ecosystems. We show that warming and drying of tropical forest soils may increase soil carbon vulnerability, by increasing degradation of older carbon. In situ whole-profile heating by 4 °C and 50% throughfall exclusion each increased the average radiocarbon age of soil CO2 efflux by ~2-3 years, but the mechanisms underlying this shift differed. Warming accelerated decomposition of older carbon as increased CO2 emissions depleted newer carbon. Drying suppressed decomposition of newer carbon inputs and decreased soil CO2 emissions, thereby increasing contributions of older carbon to CO2 efflux. These findings imply that both warming and drying, by accelerating the loss of older soil carbon or reducing the incorporation of fresh carbon inputs, will exacerbate soil carbon losses and negatively impact carbon storage in tropical forests under climate change.
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Carbono , Bosques , Suelo , Clima Tropical , Calor , Carbono/química , Carbono/metabolismo , Panamá , Dióxido de Carbono/química , Dióxido de Carbono/metabolismo , Suelo/química , Agua , Estaciones del Año , Lluvia , AltitudRESUMEN
Ecological theory predicts that species that can utilise a greater diversity of resources and, therefore, have wider niche breadths should also occupy larger geographic areas (the 'niche breadth-range size hypothesis'). Here, we tested this hypothesis for a blood-sucking group of insects of medical significance: the Triatominae (aka 'kissing bugs') (Hemiptera: Reduviidae). Given that niches can be viewed from different perspectives, we tested this hypothesis based on both dietary and climatic niches. We assembled the most complete dataset of triatomine feeding patterns to date by reviewing 143 studies from the literature up to 2021 and tested whether the niche breadth-range size hypothesis held for this group for both dietary and climatic components of the niche. Temperature and precipitation niche breadths were estimated from macro-environmental variables, while diet breadth was calculated based on literature data that used PCR and/or ELISA to identify different types of hosts as blood sources per triatomine species. Our results showed that temperature and precipitation niche breadths, but not dietary breadth, were positively correlated with range sizes, independent of evolutionary history among species. These findings support the predictions from the range size-niche breadth hypothesis concerning climate but not diet, in Triatominae. It also shows that support for the niche breadth-range size hypothesis is dependent upon the niche axis under consideration, which can explain the mixed support for this hypothesis in the ecological literature.
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Enfermedad de Chagas , Conducta Alimentaria , Insectos Vectores , Temperatura , Triatominae , Animales , Enfermedad de Chagas/transmisión , Insectos Vectores/fisiología , Triatominae/fisiología , Triatominae/parasitología , Ecosistema , Lluvia , Dieta , ClimaRESUMEN
Soybean molasses (SBMO) is a byproduct derived from the production of soy protein concentrate, obtained through solubilization in water and alcohol. The utilization of SBMO as an animal feed ingredient shows promising potential, primarily due to its low cost and as a potential energy concentrate. This study aimed to assess the intake, digestibility, ruminal parameters (pH and ruminal ammonia - NH3), nitrogen retention (NR) and microbial protein synthesis in grazing beef cattle supplemented with SBMO as a substitute for corn during the rainy season. Five Nellore (10-month-old) bulls with an average initial weight of 246 ± 11.2 kg were utilized in a 5 × 5 Latin square design. The animals were housed in five paddocks, each consisting of 0.34 ha of Marandu grass (Urochloa brizantha). Five isonitrogenous protein-energy supplements (300 g crude protein [CP]/kg supplement) were formulated, with SBMO replacing corn at varying levels (0, 0.25, 0.50, 0.75, or 1.00 g-1 g). The supplements were provided daily at a quantity of 2.0 kg-1 animal. The inclusion of SBMO at any level of corn substitution did not significantly affect the intake of pasture dry matter or total dry matter (P > 0.10). Likewise, the intake of CP and, consequently, the ruminal concentration of NH3 did not differ among the SBMO levels. Increasing the inclusion of SBMO did not have a significant impact on NR (P > 0.10), indicating that animals receiving supplements containing 100% SBMO as a substitute for corn may perform similarly to animals receiving supplements with 100% corn (0% SBMO). Soybean molasses represents a viable alternative energy source for grazing beef cattle during the rainy season and can entirely replace corn without adversely affecting animal nutritional performance.
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Alimentación Animal , Suplementos Dietéticos , Digestión , Glycine max , Melaza , Rumen , Estaciones del Año , Animales , Bovinos/fisiología , Alimentación Animal/análisis , Melaza/análisis , Masculino , Glycine max/química , Suplementos Dietéticos/análisis , Rumen/metabolismo , Zea mays/química , Dieta/veterinaria , Fenómenos Fisiológicos Nutricionales de los Animales , Lluvia , Nitrógeno/metabolismoRESUMEN
Future climate presents conflicting implications for forest biomass. We evaluate how plant hydraulic traits, elevated CO2 levels, warming, and changes in precipitation affect forest primary productivity, evapotranspiration, and the risk of hydraulic failure. We used a dynamic vegetation model with plant hydrodynamics (FATES-HYDRO) to simulate the stand-level responses to future climate changes in a wet tropical forest in Barro Colorado Island, Panama. We calibrated the model by selecting plant trait assemblages that performed well against observations. These assemblages were run with temperature and precipitation changes for two greenhouse gas emission scenarios (2086-2100: SSP2-45, SSP5-85) and two CO2 levels (contemporary, anticipated). The risk of hydraulic failure is projected to increase from a contemporary rate of 5.7% to 10.1-11.3% under future climate scenarios, and, crucially, elevated CO2 provided only slight amelioration. By contrast, elevated CO2 mitigated GPP reductions. We attribute a greater variation in hydraulic failure risk to trait assemblages than to either CO2 or climate. Our results project forests with both faster growth (through productivity increases) and higher mortality rates (through increasing rates of hydraulic failure) in the neo-tropics accompanied by certain trait plant assemblages becoming nonviable.
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Dióxido de Carbono , Cambio Climático , Bosques , Clima Tropical , Dióxido de Carbono/metabolismo , Panamá , Agua , Modelos Biológicos , Transpiración de Plantas/fisiología , Biomasa , LluviaRESUMEN
The monthly fluctuation of adult Ixodes keiransi in dogs from two cattle farms in southeastern Mexico was determined. In ranch 1 (R1), 6-7 mixed breed dogs from six months to five years of age; while in ranch 2 (R2), 7-8 mixed breed dogs from one to four years of age, were followed. All dogs were monthly inspected for tick infestation through one year. The abundance of dogs infested with ticks was estimated for each month. Tick specimens were taxonomically identified as I. keiransi using morphological features. In R1 the dogs were inspected 60 times and in R2 90 times. The overall proportion of dogs infested by ticks through the year was 75% (60/80) in R1 and 67% (67/90) in R2. The higher abundance of adult I. keiransi parasitizing dogs was from July to December with maximum peaks from September to November. In April, May and June, no ticks were observed on dogs from both ranches. Tick abundance fluctuation showed a concordant pattern with rainfall but with a delay because de maximum peak of I. keiransi abundance was almost two months after the greatest rainfall peak. It is concluded that, in some conditions, the adult I. keiransi in southeastern Mexico presents high-infested rates on dogs and a maximum abundance from September to November. The I. keiransi abundance fluctuation showed a concordant pattern with rainfall.
Asunto(s)
Perros , Ixodes , Infestaciones por Garrapatas , México/epidemiología , Infestaciones por Garrapatas/epidemiología , Animales , Masculino , Femenino , Lluvia , Estaciones del AñoRESUMEN
Detecting changes in the phenological responses of herbaceous species as a function of predicted climate change is important for forecasting future scenarios for the functioning of dry tropical forests, especially when predicting an increase in the frequency and intensity of extreme droughts. Because of the sensitivity of plants to water availability, our study hypothesizes that if years become drier or wetter, herbaceous plants will synchronously change the onset, duration, and intensity of their vegetative phenophases. We used a historical series of 60 years of precipitation observations for the Caatinga vegetation to define daily average of precipitation for rainy (Twet), median (Tcontrol), and dry (Tdry) years. We simulated past average daily rainfall (Twet, Tcontrol, and Tdry) while growing two herbaceous perennials and two herbaceous annuals. We monitored plant growth and measured the activity (absence or presence) and intensity of vegetative phenophases. We used circular statistical analysis to assess differences between treatments. Our results revealed that leaf production was seasonal but relatively uniform for perennial species and highly seasonal (wet season) for annual species. Simulated dry years induced lower leaf emergence concentrated over a few months in annual species, but this effect was more strongly significant in one of the two perennial species. Both annual and perennial species can experience delayed and less intense leaf abscission during the rainy season in years with below-average precipitation. In contrast, large voluminous rains in years with above-average precipitation can accelerate and intensify the process of leaf renewal. If future precipitation reductions occur, the changes in phenological response indicate that the cover of annual and perennial herbaceous species in this study will likely decrease, altering the landscape and functioning of dry tropical forests. However, the potential trade-offs observed may help populations of these species to persist during years of severe drought in the Caatinga.
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Bosques , Lluvia , Estaciones del Año , Brasil , Cambio Climático , Hojas de la Planta/fisiología , Hojas de la Planta/crecimiento & desarrollo , SequíasRESUMEN
Several remote sensing indices have been used to monitor droughts, mainly in semi-arid regions with limited coverage by meteorological stations. The objective of this study was to estimate and monitor agricultural drought conditions in the Jequitinhonha Valley region, located in the Brazilian biomes of the Cerrado and Atlantic Forest, from 2001 to 2021, using vegetation indices and the meteorological drought index from remote sensing data. Linear regression was applied to analyze drought trends and Pearson's correlation coefficient was applied to evaluate the relationship between vegetation indices and climatic conditions in agricultural areas using the Standardized Precipitation Index. The results revealed divergences in the occurrences of regional droughts, predominantly covering mild to moderate drought conditions. Analysis spatial of drought trends revealed a decreasing pattern, indicating an increase in drought in the Middle and Low Jequitinhonha sub-regions. On the other hand, a reduction in drought was observed in the High Jequitinhonha region. Notably, the Vegetation Condition Index demonstrated the most robust correlation with the Standardized Precipitation Index, with R values ââgreater than 0.5 in all subregions of the study area. This index showed a strong association with precipitation, proving its suitability for monitoring agricultural drought in heterogeneous areas and with different climatic attributes. The use of remote sensing technology made it possible to detect regional variations in the spatio-temporal patterns of drought in the Jequitinhonha Valley. This vision helps in the implementation of personalized strategies and public policies, taking into account the particularities of each area, in order to mitigate the negative impacts of drought on agricultural activities in the region.
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Agricultura , Sequías , Bosques , Tecnología de Sensores Remotos , Brasil , Lluvia , Monitoreo del Ambiente/métodosRESUMEN
Soil structural degradation and water erosion processes were observed even in no-tillage schemes in the Pampas region. Within these conservation systems, agrochemical application per hectare is one of the highest globally. Thus, this entails a serious risk of water contamination. The objectives of this study were to (1) test the hypothesis that the hydrological dynamics and sediment concentration related to surface runoff were conditioned by soil structure regardless of the presence of maize (Zea mays L.) crop residue and (2) assess the incidence of maize crop residue on glyphosate and aminomethylphosphonic acid (AMPA) concentration in runoff. The soil under study corresponded to Arroyo Dulce Series (Typic Argiudoll silty loam soil). Rain simulations were performed in the laboratory on undisturbed soil samples. Total runoff and infiltration rate were similar between treatments with C(+) and without C(-) maize crop residues (C(+) 1381.40 mL and 14.27 mm h-1, C(-): 1529.70 mL and 21.67 mm h-1). The C(-) treatments showed a higher sediment concentration than C(+) (1.58 and 0.42 g 100 mL-1, respectively). Glyphosate and AMPA average values in runoff were 15.9 and 33.9 µg L-1. High variability of the hydro-physical properties and occurrence of soil structure, particularly platy ones, were detected. The hydrological variables were conditioned mainly by the occurrence of platy structures regardless of crop residue presence. Glyphosate concentration was increased in the first runoff event by the presence of corn residues, while AMPA concentrations were higher in the second runoff event in both residue treatments. In this study, maize residue on the soil surface protected the soil from sediment detachment but did not change runoff or infiltration. Thus, the implementation of agricultural management practices that promote vegetative residue cover has shown positive results to erosion.
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Monitoreo del Ambiente , Glicina , Glifosato , Herbicidas , Lluvia , Suelo , Zea mays , Glicina/análogos & derivados , Glicina/análisis , Suelo/química , Herbicidas/análisis , Agricultura , Contaminantes del Suelo/análisis , Isoxazoles/análisis , Contaminantes Químicos del Agua/análisis , Productos Agrícolas , Movimientos del Agua , Tetrazoles/análisisRESUMEN
Understanding the Amazon Rainforest's response to shifts in precipitation is paramount with regard to its sensitivity to climate change and deforestation. Studies using Dynamic Global Vegetation Models (DGVMs) typically only explore a range of socio-economically plausible pathways. In this study, we applied the state-of-the-art DGVM LPJmL to simulate the Amazon forest's response under idealized scenarios where precipitation is linearly decreased and subsequently increased between current levels and zero. Our results indicate a nonlinear but reversible relationship between vegetation Above Ground Biomass (AGB) and Mean Annual Precipitation (MAP), suggesting a threshold at a critical MAP value, below which vegetation biomass decline accelerates with decreasing MAP. We find that approaching this critical threshold is accompanied by critical slowing down, which can hence be expected to warn of accelerating biomass decline with decreasing rainfall. The critical precipitation threshold is lowest in the northwestern Amazon, whereas the eastern and southern regions may already be below their critical MAP thresholds. Overall, we identify the seasonality of precipitation and the potential evapotranspiration (PET) as the most important parameters determining the threshold value. While vegetation fires show little effect on the critical threshold and the biomass pattern in general, the ability of trees to adapt to water stress by investing in deep roots leads to increased biomass and a lower critical threshold in some areas in the eastern and southern Amazon where seasonality and PET are high. Our findings underscore the risk of Amazon forest degradation due to changes in the water cycle, and imply that regions that are currently characterized by higher water availability may exhibit heightened vulnerability to future drying.
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Cambio Climático , Lluvia , Bosque Lluvioso , Estaciones del Año , Biomasa , Árboles , Brasil , Modelos Teóricos , Conservación de los Recursos NaturalesRESUMEN
Increasing forest structural complexity is becoming a common goal in forestry worldwide. However, the lack of empirical quantification clouds its implementation. Here we quantified the long-term effects (> 30 y) of partial harvest on stand structural complexity and net primary productivity using the east-west precipitation gradient (318-2508 mm, mean annual precipitation-MAP) of western Patagonian as a study system. In this gradient, pairs of 1-ha plots on 20 sites (20 plots harvested and 20 plots unharvested) were installed. In each plot terrestrial laser scanning was used to quantify the stand structural complexity index (SSCI), and Sentinel satellite images to obtain the Enhanced Vegetation Index (EVI: proxy of net primary productivity). Generalized linear mixed-effect models were used to relate SSCI to MAP and EVI to SSCI, with harvesting as indicator variable, and site as random variable (two plots nested to same precipitation). Results showed that harvested plots on mesic-to-humid sites (but not on dry sites) had higher SSCI and EVI values compared to unharvested plots, likely due to a greater vertical canopy packing. These results show the influence of precipitation on SSCI, which resulted in a more diversified stand structure and higher EVI. Such insights support site-specific management aimed to increase forest structural complexity.