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The proposal for a method of identifying the occurrence of desertification that has a strong association with in situ data leads to more assertive results when analysing the contribution of climate and social and economic factors to advancing the process. This study aimed to develop a methodology called the RisDes_Index to evaluate the evolution of the desertification process based on satellite data. The concept of the RisDes_Index method was based on the reflectance variables of the R, B and G bands, albedo and LAI of the Landsat 5/TM and Landsat 8/OLI satellites. Principal component analysis was used to assess the biophysical basis of the RisDes_Index by associating the results with micrometeorological data, physical and chemical properties, and vegetation cover data collected from five experimental sites in the semi-arid region of Brazil. These sites included one from a seasonally dry forest (i.e., the Caatinga), an agricultural cactus plantation, an area undergoing desertification, and two irrigated sugarcane crops (wetlands), one with and one without straw cover. The RisDes_Index was applied to all pixels of the images from 5 December 1991, 14 November 2001, 20 November 2009 and 6 October 2016 of an important desertification nucleus (DN) in the semi-arid region of Brazil, i.e., the DN of Cabrobó. The proposed RisDes_Index was able to identify areas with significant processes of desertification, which mainly occur in areas of sandy, acidic, bare soils with a high β value (Bowen ratio) and high soil temperature. The results of the RisDes_Index showed that in 5 December 1991, desertified areas comprised 38% of the total area of the DN of Cabrobó, expanding to 51% in 2016. Application of the RisDes_Index confirmed the advance of desertification in the DN of Cabrobó. This was due to a consequent increase in the water deficit and intensified deforestation to increase the areas of livestock farming. The RisDes_Index proved to be a robust method, as its estimation based on simple satellite products exhibited a strong association with biophysical variables of areas with different land uses and degradation levels. Thus, it is suggested that the RisDes_Index be applied in various regions of the world, with the idea of directing action to meet the advance of desertification.

Monitoring areas susceptible to desertification contributes to the strategic development of regions located in environments of extreme hydric and social vulnerability. Therefore, the objective of this study is to evaluate the process of soil degradation in the Desertification Nucleus of Cabrobó (DNC) over the past three decades using remote sensing techniques. This study used primary climatic data from TerraClimate, geospatial data of land use and land cover (LULC), and vegetation indices (SAVI and LAI) via Google Earth Engine (GEE) from Landsat 5/TM and 8/OLI satellites, and established the aridity index (AI) from 1992 to 2022. The results indicated 10 predominant LULC classes with native vegetation suppression, particularly in agriculture and urbanization. SAVI ranged from −0.84 to 0.90, with high values influenced by La Niña episodes and increased rainfall; conversely, El Niño episodes worsened the rainfall regime in the DNC region. Based on the Standardized Precipitation Index (SPI), it was possible to correlate normal and severe drought events in the DNC with years under the influence of El Niño and La Niña phases. In summary, the AI images indicated that the DNC remained semi-arid and that the transition to an arid region is a cyclical and low-frequency phenomenon, occurring in specific periods and directly influenced by El Niño and La Niña phenomena. The Mann–Kendall analysis showed no increasing trend in AI, with a Tau of −0.01 and a p-value of 0.97. During the analyzed period, there was an increase in Non-Vegetated Areas, which showed a growing trend with a Tau of 0.42 in the Mann–Kendall analysis, representing exposed soil areas. Annual meteorological conditions remained within the climatic pattern of the region, with annual averages of precipitation and actual evapotranspiration (ETa) close to 450 mm and an average temperature of 24 °C, showing changes only during El Niño and La Niña events, and did not show significant increasing or decreasing trends in the Mann–Kendall analysis.

Supplementary irrigation can be strategic for forage cactus, aiming to guarantee higher levels of productivity and economic return. Therefore, this study aimed to evaluate the growth dynamics, productivity, evapotranspiration, and water economy indices of three forage cactus clones under different water regimes. The study was carried out in the Brazilian semi-arid region during two cycles between 2020 and 2022. Clones of forage cactus Orelha de Elefante Mexicana—OEM (Opuntia stricta (Haw.) Haw.) were evaluated; IPA Sertânia—IPA and Miúda—MIU (both species Nopalea cochenillifera (L.) Salm-Dyck) were subjected to four water regimes: rainfed and three irrigation depths (4, 8 and 12 mm). Growth dynamics and evapotranspiration were evaluated throughout the cycles, and productivity and water economy indices were based on data from the harvest time. The OEM clone showed higher dry matter productivity (21.8 Mg ha−1). The MIU clone, when intended for seed sales, presented a higher economic return (USD 20,823.33). The use of irrigation brought forward the cutting time and reduced water saving rates. With this, it can be concluded that the increase in water availability in cactus increases water consumption and reduces economic-water indices but brings important productive returns.

The in-situ quantification of turbulent flux and evapotranspiration (ET) is necessary to monitor crop performance in stressful environments. Although cacti can withstand stressful conditions, plant responses and plant–environment interactions remain unclear. Hence, the objective of our study was to investigate the interannual and seasonal behaviour of components of the surface energy balance, environmental conditions, morphophysiological parameters, biomass yield and water relations in a crop of Nopalea cochenillifera in the semi-arid region of Brazil. The data were collected from a micrometeorological tower between 2015 and 2017. The results demonstrate that net radiation was significantly higher during the wet season. Latent heat flux was not significant between the wet season and dry season. During the dry-wet transition season in particular, sensible heat flux was higher than during the other seasons. We observed a large decline in soil heat flux during the wet season. There was no difference in ET during the wet or dry seasons; however, there was a 40% reduction during the dry-wet transition. The wet seasons and wet-dry transition showed the lowest Evaporative Stress Index. The plants showed high cladode water content and biomass during the evaluation period. In conclusion, these findings indicate high rates of growth, high biomass and a high cladode water content and explain the response of the cactus regarding energy partitioning and ET.

O sorgo é uma cultura que apresenta elevada capacidade de adaptação a condições edafoclimáticas adversas, mantendo um alto desempenho produtivo, servindo como fonte alimentar para humanos e animais, assim como matéria prima para a produção de etanol. Na região do semiárido, esta cultura tem uma importância ainda maior, sobretudo como alternativa na complementação da dieta alimentar, principalmente animal, trazendo redução de custos no setor pecuário, além de contribuir favoravelmente para o equilíbrio dos estoques reguladores de grãos e promovendo equilíbrio na produção de volumosos, contribuindo assim para o crescimento sustentável da pecuária nessa região. No entanto, evidencias indicam uma redução na área plantada nas últimas safras devido a uma diminuição do desempenho produtivo da cultura do sorgo nas condições edafoclimáticas da região, desestimulando a sua produção em grande escala. Nesse contexto, a superação destes obstáculos tem sido a utilização de cultivares adaptadas às condições edafoclimáticas dessas regiões, bem como algumas modificações no planejamento do cultivo e no manejo da cultura. Esta revisão objetivou explorar as características gerais, classificação dos tipos de sorgo, importância socioeconômica, ecofisiologia, edafologia, agentes fitossanitários e potencial produtivo de cultivares de sorgo atualmente disponível para cultivo na região Semiárida brasileira. A cultura do sorgo no Brasil vem mostrando um alto potencial produtivo, não só pela sua habilidade adaptativa em diferentes condições ambientais, mas pela sua facilidade de mecanização desde semeadura a colheita.

Abstract The vegetation structure is a good indicator of the conservation condition of an ecosystem, since it reflects alterations caused by anthropic action. This study proposes to analyze the phytosociological aspects of the Caatinga domain under anthropic disturbance and their correlations with hydrological variables. Twenty-five 400 m 2 plots were sampled in the municipality of Floresta - PE, Brazil. Phytosociological parameters such as density, frequency and dominance were calculated. The seasonality of plant area index was analyzed for six species. The association between structural characteristics and hydrological variables (throughfall, stemflow and interception loss) in the species was evaluated by multivariate analysis. A total of 930 individuals, six families and 10 species were recorded. The abundance of the species Cenostigma pyramidale in the area may be an indicator of the degree of change in the vegetation. The structural characteristics of the species revealed little association with rainfall partitioning.

A água é um dos recursos determinante para o funcionamento e crescimento pleno das plantas, ao mesmo tempo que é considerado o mais limitante. Nesse sentido, um dos principais fatores causador de estresse nas plantas é a disponibilidade hídrica. O conhecimento do desempenho das plantas forrageiras em condições de estresse hídrico é de grande valia para entendimento do efeito do período “seco” na produção de forragem, permitindo assim o uso de práticas de manejo viáveis para melhorar o cultivo durante esse período. Desta forma, objetivou-se com esta revisão discorrer sobre as respostas das plantas forrageiras submetidas ao estresse hídrico, destacando os efeitos causados e mecanismos de adaptação dessas plantas, assim como práticas para a convivência com o déficit hídrico.

Caatinga biome, located in the Brazilian semi-arid region, is the most populous semi-arid region in the world, causing intensification in land degradation and loss of biodiversity over time. The main objective of this paper is to determine and analyze the changes in land cover and use, over time, on the biophysical parameters in the Caatinga biome in the semi-arid region of Brazil using remote sensing. Landsat-8 images were used, along with the Surface Energy Balance Algorithm for Land (SEBAL) in the Google Earth Engine platform, from 2013 to 2019, through spatiotemporal modeling of vegetation indices, i.e., leaf area index (LAI) and vegetation cover (VC). Moreover, land surface temperature (LST) and actual evapotranspiration (ETa) in Petrolina, the semi-arid region of Brazil, was used. The principal component analysis was used to select descriptive variables and multiple regression analysis to predict ETa. The results indicated significant effects of land use and land cover changes on energy balances over time. In 2013, 70.2% of the study area was composed of Caatinga, while the lowest percentages were identified in 2015 (67.8%) and 2017 (68.7%). Rainfall records in 2013 ranged from 270 to 480 mm, with values higher than 410 mm in 46.5% of the study area, concentrated in the northern part of the municipality. On the other hand, in 2017 the lowest annual rainfall values (from 200 to 340 mm) occurred. Low vegetation cover rate was observed by LAI and VC values, with a range of 0 to 25% vegetation cover in 52.3% of the area, which exposes the effects of the dry season on vegetation. The highest LST was mainly found in urban areas and/or exposed soil. In 2013, 40.5% of the region’s area had LST between 48.0 and 52.0 °C, raising ETa rates (~4.7 mm day−1). Our model has shown good outcomes in terms of accuracy and concordance (coefficient of determination = 0.98, root mean square error = 0.498, and Lin’s concordance correlation coefficient = 0.907). The significant increase in agricultural areas has resulted in the progressive reduction of the Caatinga biome. Therefore, mitigation and sustainable planning is vital to decrease the impacts of anthropic actions.

A escolha de uma espécie forrageira é um dos fatores mais importantes quando se visa à criação de ruminantes como fonte de renda. Objetivou-se analisar o crescimento e desenvolvimento de mudas de maniçoba em função de diferentes diâmetros e comprimentos de maniva submetidas à irrigação, no município de Serra Talhada-PE, região do Semiárido brasileiro. O material vegetal utilizado para análise propagativa foi à espécie forrageira maniçoba (Manihot glaziovii Müll. Arg.). O delineamento experimental utilizado foi inteiramente casualizado, em arranjado fatorial 3x3, sendo três diâmetros de maniva (2,0; 3,0 e 4,0 cm) e três comprimentos de maniva (10; 15 e 20 cm), com oito repetições. As características analisadas foram: número de brotações, comprimento das brotações e número de folhas. Mudas de maniçoba podem ser produzidas por propagação assexuada, utilizando-se manivas com diâmetro de 3,0 cm e comprimento entre 15 e 20 cm. A utilização de propagação vegetativa apresenta boa taxa de brotação, auxiliando assim na propagação da espécie.

A vegetação nativa da caatinga constitui um importante recurso alimentar para os rebanhos da região semiárida brasileira. Neste tipo de vegetação, a Família Euphorbiaceae é representada por um grande número de espécies, caracterizadas por um alto potencial produtivo e nutricional de sua forragem. No entanto, a falta de informações sobre o manejo acarretam problemas de desperdício de forragem na época das chuvas e intoxicação dos animais por substâncias presentes nas plantas, sendo necessário estudos que minimizem tais problemas. Desse modo, objetivou-se com esta revisão discorrer sobre a família botânica Euphorbiaceae, destacando a sua importância econômica e a utilização de algumas espécies nativas da caatinga na alimentação animal, mostrando as formas de utilização e caracterizando aspectos produtivos, químicos e nutricionais das forragens, assim como compostos tóxicos presentes nessas plantas.

A degradação das pastagens brasileiras tem sido um problema crescente, principalmente em regiões de fronteira agrícola, onde as práticas de manejo adotadas são inadequadas, causando um desequilíbrio neste ecossistema. Práticas de manejo que favorecem a ciclagem de nutrientes aparecem neste cenário como uma alternativa para a recuperação de pastagens degradadas. Se tratando de pastagens, os maiores reservatórios de nitrogênio (N) e carbono (C) são a atmosfera, o solo, as espécies vegetais e os animais em pastejo, sendo que a dinâmica desses nutrientes é controlada por fatores bióticos e abióticos. A serapilheira e os excrementos animais representam as principais vias de retorno dos nutrientes ao ecossistema através da decomposição por microrganismos. A utilização de espécies leguminosas consorciadas com pastagens é uma boa estratégia para incrementar o conteúdo de nitrogênio no solo, minimizando custos com adubação nitrogenada, além de melhorar a qualidade da serapilheira.

ABSTRACT Despite belonging to the same photosynthetic group (CAM - Crassulacean Acid Metabolism), evapotranspiration of distinct species of forage cactus may respond differently to meteorological variables and depends on its growth dynamics. The objective of this work was to analyze the contribution of meteorological variables and morphological characteristics of cladodes and the plants on the evapotranspiration of forage cactus species of the genus Nopalea and Opuntia. The experiment was conducted in Serra Talhada, State of Pernambuco, where the species ‘IPA Sertânia’ (Nopalea sp.), ‘Miúda’ (Nopalea sp.) and ‘Orelha de Elefante Mexicana’ (Opuntia sp.) were submitted to different irrigation depths (2.5, 5.0 and 7.5 mm) and intervals (7, 14 and 28 days). Actual evapotranspiration and biometric data of forage cactus species and meteorological variables were obtained between March 2012 and August 2013. Pearson correlation matrix and canonical and path analysis were applied to the data. It was verified that the global solar radiation stood out as the variable that most influenced the reduction of the actual evapotranspiration (ET) of the three species, and the wind velocity as the one that affected the response of ET to the atmospheric demand variation (ET/ETo) of the species ‘Orelha de Elefante Mexicana’ and ‘IPA Sertânia’. The increase in the cladode area index implied in the reduction of ET of the latter two species, while the effects of the number of 1st and 2nd order cladodes were the most important for the ‘Miúda'. Hence, forage cactus evapotranspiration depends on the seasonality of the meteorological conditions and the morphological characteristics of its species.