Journal of Arid Environments最新文献

Seasonally dry tropical forests and woodlands (SDTFW) represent one of the world's most endangered biomes. Approximately 56.3% of its species are non-woody, but little is known about their functional adaptations. The reproductive phenologies of 75 SDTFW species (supplementary material A 1) were studied according to their life forms and seed dispersal syndromes in northeastern Brazil. We used circular statistics and the GLM to assess their seasonalities and relationships of their phenologies with environmental variables. The community exhibited continuous pattern of flowering and fruiting. Flowering and fruiting by most species occurred during only a short period of time and were found to be related to rainfall and photoperiod. Moderate peaks in the seasonal activities of therophytes, hemicryptophytes, and camephytes were observed during the rainy season; succulents and epiphytes flowered all year around but fruited only seasonally. Dispersal modes exhibited seasonality of fruiting in the rainy season, with autochory being predominant over zoochory and anemochory. The observed overlapping of fruiting and flowering periods ensures a consistent resource supply throughout the year and contributes to the preservation of vital ecosystem services. These data highlight the importance of conserving these unique semiarid environments and also provide insights for conservation efforts aimed at preserving SDTFW and safeguarding their biodiversity.

Drought has the most significant impact on arid grassland ecosystems. Managed grazing, including the timing and intensity of defoliation, may interact with drought to differentially affect processes related to soil organic matter decomposition. Extracellular enzyme activity (EEA) provides integrated measure of soil microbial activity which affects nutrient cycling. This study examined EEAs in response to five defoliation regimes and drought at seven grasslands across temperate grasslands of Canada. All sites were dominated by perennial grasses and forbs, but differed in plant species, climate, and soils. Soil samples were analyzed for five EEAs involved in carbon (C), nitrogen (N) and phosphorus (P) cycling. Drought reduced activity of enzymes involved in C cycling, β-glucosidase and β-cellobiosidase by 16 and 17%, respectively, P cycling (acid phosphatase) by 11%, and N cycling (N-acetyl-β-glucosaminidase) by 12%. β-xylosidase showed close association with, and was not affected by drought, suggesting a reduction in C turnover under future drought. β-glucosidase activity was reduced by intermediate defoliation relative to both control and heavy. Acid phosphatase and N-acetyl-β-glucosaminidase were affected by three-way interaction of drought, defoliation and mean growing season precipitation, highlighting the complex mechanism underlying EEA responses. Findings suggest that EEA was affected by drought, but defoliation effects were largely dependent upon drought and local climate.

Aedes aegypti is the primary vector of dengue worldwide and is able to transmit several other arboviruses of public health importance. Despite extensive research on its ecology throughout the world, limited attention has been given to arid regions. The province of San Juan is an arid region of Argentina with unique climatic characteristics commonly known as the “monte ecoregion”. It has scarce precipitation and, therefore, has a network of irrigation canals that supply water to the region. The canal system is outdated, poorly maintained and, accumulating small bodies of water of anthropic origin. Urban ditches were checked from January to December 2019, and during January to June, 771 immature specimens of A. aegypti were found. In this work, we report the presence of A. aegypti in ditches, describing for the first-time new breeding sites that, despite their extreme physical and chemical properties, were used as successful larval habitats. The remarkable adaptability of A. aegypti in this breeding sites raises concerns about the possible detection and spread of dengue cases in the province. The alarming expansion of dengue cases in the region further highlights the urgent need to take control measures against this insect.

Green water is primarily associated with the appearance of annual plants and plays a significant role in biomass production in both arid and semi-arid ecosystems. Herein, we aim to estimate the optimal threshold for determining the presence or absence of annual plants and use them as an ecological indicator to assess potential green water areas in Kuwait as a case study. We integrate remote sensing techniques and MaxEnt modeling. The AUC for the annual plant distribution with all examined factors is 0.847, and the standard deviation is 0.050. The results demonstrated that potential locations with high levels of green water cover <20% of the country. The annual plant distribution was significantly correlated with several types of perennial plants, maximum temperature, precipitation, and sandy soils. It was also found that annual plants are controlled by the spring and winter temperature decline and the timing of precipitation occurrence, especially the pattern and amount of rainfall received in November. Sandy loam and loam soils were found to be ideal for annual plants, although land depressions and soil types are crucial factors in determining annual plant distribution. Additionally, annual plants enhanced the growth of several perennial communities. To reiterate, our study's model helped to comprehend the significance of annual plants as an ecological indicator in sustaining soil moisture over a prolonged period, as well as factors controlling the distribution of annual plants. The developed model and indicators could support decision-makers in determining appropriate locations with adequate levels of green water for revegetation planning in arid landscapes.

Shrubs play a pivotal role in shaping the growth and dynamics of biological soil crusts (biocrusts) in arid and semi-arid regions through various biotic and abiotic mechanisms. Biocrusts, in turn, significantly influence soil microbiomes. However, the precise effects of shrubs on soil microbial communities within biocrusts remain poorly understood. Here, we investigated the bacterial and fungal communities within moss biocrusts situated beneath and between two predominant shrub species (Artemisia ordosica and Salix psammophila) in the Mu Us Sandland, China, using high-throughput sequencing and random matrix theory (RMT) through a network-based approach. Our findings revealed that shrub species and their canopy affect moss biocrust growth, soil properties, and microbial communities. Shrub species significantly affected moss biocrust thickness, soil water content (SWC), total phosphorus (TP), fungal community composition (e.g., Ascomycota) and structure, and microbial network structure. Moss biocrusts beneath and between shrubs differed in coverage, SWC, soil nutrients (e.g., TP, soil organic carbon (SOC), and total nitrogen (TN)), and microbial community composition (e.g., Actinobacteria), structure, and network attributes. Structural equation modeling (SEM) further validated that the canopy-induced changes in microbial community composition primarily stemmed from negative effects on the soil nutrient index (path coefficient = −0.709) and positive effects on SWC (path coefficient = 0.996). Overall, our findings suggest that shrub encroachment initiates a feedback loop favoring shrub establishment and growth at the expense of biocrusts, potentially reducing the capacity of biocrust ecosystems to sequester carbon, with far-reaching implications for ecosystem functionality and sustainability in water-limited regions. While shrub canopy strongly affects microbial community composition within biocrusts, its indirect effects are mediated predominantly through changes in soil properties, offering valuable insights into the intricate associations between soil microbes and shrublands within semi-arid ecosystems.

Bijlia dilatata (Prince Albert Vygie) is a red-listed succulent (Aizoaceae) endemic to a single valley in the Western Cape and restricted to disjunct sites in quartzite pavements. Populations of this species were surveyed in 2002 during above-average rainfall and again in 2020 and 2021 during drought, and in June 2023 following drought-breaking rains. We found that populations declined over the two low-rainfall decades, that declines differed significantly among sites, that mortality was greater among smaller plants and that recruitment had failed. Our hypothesis that elevation provides a refuge from heat-induced mortality was supported by data that showed decreasing population decline along a 300 m elevation gradient. Factors significantly influencing population structure included landuse (grazing intensity), microsites and initial population density. Shaded microsites beneath living shrubs and adjacent to large rocks were significantly cooler and stayed moister longer after rain and B. dilatata plants in such microsites were larger than those in open sites or beneath dead shrubs. Grazing and climate change, including reduced winter rainfall, and increased ambient and soil surface temperatures, appear to be contributing to declines in endemic, habitat specialist dwarf succulents already threatened by land transformation and poaching in the biodiverse, Succulent Karoo region of South Africa.

Consumption of seawater is rare among mammals. Following a local report of Arabian tahr drinking seawater, we collected camera trapping data to confirm and measure the frequency of seawater consumption by Arabian tahr. Based on herbivores’ seasonal deficiencies in sodium and other minerals and the infrequency of seawater consumption by Arabian tahr, we postulate the species uses seawater as a mineral supplement, similar to a terrestrial salt lick. As some countries protect salt licks as critical habitat features, we believe these areas where Arabian tahr can access the seashore should be similarly protected to help maintain behaviours that may contribute towards the fitness of this Endangered species.

Locomotion is a fundamental aspect in the life cycle of any organism, and plays a crucial role in survival, feeding, escaping from predators, territoriality, and reproduction. Locomotion in amphibian anurans includes swimming, walking, jumping, climbing, and gliding. Amphibians living in arid regions face a constant compromise between hydration balance and locomotor performance. We studied the effects of water stress on the locomotion of the frog Pleurodema nebulosum, a specialist from the Monte Desert. Locomotor performance was measured through different physical variables during the jump. The locomotor performance of P. nebulosum showed a significant decrease in the magnitudes associated with a decrease in body hydration. Our study demonstrated how a desert-adapted frog (P. nebulosum) showed changes in locomotion related to the loss of body water. Additionally, we observed an abrupt drop in locomotion with 15% desiccation, followed by a plateau where the evaluated parameters remained stable. Pleuroderma nebulosum showed a clear adaptation to extreme desiccation. The frogs are rarely found in optimal hydration conditions as the environment in which they develop is extremely stressful from a water perspective. The data evaluated here are the beginning of a deeper exploration of the desert adaptations of South American desert frogs.

Belowground biomass represents a significant carbon reserve with a crucial role in terms of ecosystem functioning, but very little is known about root systems across tropical dry forests. Here we investigate patterns of root biomass, nutrient concentration/stocks, and the effect of aboveground biomass, chronic anthropogenic disturbance, precipitation, and soil depth as their potential drivers in a Caatinga dry forest, northeastern Brazil. Belowground biomass was obtained by a destructive method from July 2020 to March 2021 across forest stands in three 0.49-m² and 1-m deep trenches per stand. Root biomass ranged from 3.23 Mg ha⁻¹ to 29.6 Mg ha⁻¹, accounting for less than 1/3 of total forest biomass. Belowground biomass greatly varied across forest stands mainly represented by large roots concentrated in the superficial soil layer. In general, nutrient concentrations and stocks did not vary significantly across forest stands regarding both root size class and soil depth, although fine roots support a higher concentration of P than large-sized roots. Finally, chronic disturbance, aboveground biomass, precipitation, and soil depth were important predictors affecting root biomass and nutrients. Our results suggest that a combination of natural and human-related drivers modulate root biomass and nutrients in Caatinga dry forests immersed in human-modified landscapes.

Remote sensing techniques offer practical benefits, particularly in sensitive ecosystems or areas with limited accessibility. However, field surveys allow for more accurate and detailed information about soil properties and productivity. Therefore, it is often recommended to combine remote sensing techniques with field surveys in order to obtain comprehensive and reliable results. The underlying basis of this study involves analyzing vegetation indices, such as the Normalized Difference Vegetation Index (NDVI), Enhanced Vegetation Index (EVI), and Soil Adjusted Vegetation Index (SAVI), as indicators of soil productivity. By utilizing biomass density as an additional indicator, the study aims to provide valuable insights into the productivity potential of agricultural areas. The results demonstrate a positive association between the Soil Productivity Rating (SPR) and wheat yield values for the year 2022, as evidenced by a coefficient of determination (r²) value of 0.8214. This value indicates a moderately strong correlation between the SPR classes and wheat yields. Throughout the Ripening period, the NDVI and EVI indices exhibited a relatively strong correlation coefficient (r² = 0.987 and 0.873, respectively). On the other hand, the SAVI index displayed moderate to strong accuracy in estimating crop yield, with a coefficient of determination (r²) ranging from 0.819 to 0.908. These results suggest that the NDVI index serves as the most dependable predictor of yield during all vegetation periods. This study provides a comprehensive understanding of soil productivity, but further research using controlled trial patterns with differential reference plants is needed for validation and improvement.