Journal of Arid Environments最新文献

Woody plant encroachment degrades the economic and environmental potential of drylands by altering processes such as nutrient fluxes, ecohydrology, and ecosystem services. Though past research has investigated the encroachment process, relatively little is known about post-encroachment shrub community ecology. To better quantify dynamics within post-woody encroachment shrub communities, we combined USGS lidar height data and multispectral imagery to estimate shrub density, shrub height, shrub cover, and shrub volume across the Jornada Basin Long Term Ecological Research (JRN-LTER) site in southern New Mexico, USA. Structural estimates were analyzed in search of telltale signs of community competition, specifically, the presence of thinning relationships. Results demonstrated density-dependent thinning relationships in shrub communities of creosote and mesquite, indicating a large role for competition in arid shrub communities even at relatively low shrub densities and cover (∼35% cover). In addition, shrub volume estimates better modeled the expected thinning dynamics of shrub communities than shrub canopy cover measurements. Overall, our results indicate the utility of lidar data in extending two-dimensional descriptions of woody vegetation structure (i.e., woody canopy cover) into the critical third dimension (i.e., woody plant volume), as well as the relative importance of competition and demographic bottlenecks to vegetation structure in drylands.

Understanding human impacts on drylands is crucial in a global scenario of forest degradation and biodiversity loss. This study analyzed foliar concentrations of nitrogen (N) and phosphorous (P) in the Brazilian seasonally dry tropical forests (Caatinga). Foliar patterns of N, P, and the N/P ratio were assessed both within and among botanical families. To do this, 10 plots were established in an anthropized area and 10 in a conserved area. Within each plot, leaves from all tree species and soil samples from four random points were collected. Stoichiometric analyses were performed on the leaves of 136 trees from 14 botanical families. Significant differences were observed in soil P concentrations, organic matter content, and cation exchange capacity, with the highest values found in the conserved area. Foliar N and P concentrations and N/P were also higher in the conserved area for the F+ (nitrogen-fixing Fabaceae), F- (non-nitrogen-fixing Fabaceae), and NF (non-Fabaceae) groups, indicating greater efficiency in nutrient retention and cycling. When comparing species found in both areas, Aspidosperma pyrifolium (NF), Bauhinia forficata (F-), and Mimosa ophthalmocentra (F+) showed significant differences in foliar N concentrations and foliar P (for A. pyrifolium and B. forficata only). Degradation of the Caatinga directly impacts nutrient cycling.

The Zagros region in western Iran has experienced prolonged drought, significantly impacting water resource and forest ecosystems over the past few centuries. Understanding historical prolonged drought is crucial for making precise forecasts of shifts in regional drought in the Zagros region. Due to the lack of comprehensive historical records, the use of proxy records is considered a valuable tool for reconstructing past drought variations. We aimed to construct a tree-ring chronology of Juniper (Juniperus polycarpus) in the central Zagros region to comprehend its growth response to climate variables. We cored 25 J. polycarpus trees from the Keygooran forest reserve in western Iran and developed the tree ring chronology (1802–2022) using dplR. The relationships between tree growth and climate variables of monthly mean temperature, precipitation, PDSI (Palmer Drought Severity Index), and SPEI (Standardized Precipitation Evapotranspiration Index) were examined. The analysis revealed a strong positive correlation between tree growth and SPEI _{March-September} of 1990–2018 on a 48-month timescale with a 2-year lag (r = 0.61, p < 0.05) which was included in the transfer model. Consequently, the SPEI-48 _{March-September} was reconstructed for the period 1802–2022. On this reconstruction, several extremely dry years in 1832, 1867, and 1876 and extremely wet years in 1807, 1814, 1838, 1850, 1907, and 1908 years were identified, some of them aligning with historical records in Iran. Furthermore, there was a relationship between SPEI-48 _{March-September} and teleconnection events suggesting that certain drought occurrences in the area were associated with the El Niño-Southern Oscillation (ENSO). Consequently, this reconstruction can serve as a reliable proxy for large-scale drought variability in the Zagros region of western Iran. Moreover, our research underscores the utility of SPEI in reconstructing the history of semi-arid climate conditions.

The Arabian ostrich (Struthio camelus syriacus) was an integral element in the wildlife of the Middle East until its extinction in the mid-20th century. Here we discuss the historic and archaeological record that provides baseline information on the past distribution of ostriches in the Negev Desert (Israel). Specifically, we focus on survey data of ancient petroglyph depictions of ostriches and examine their spatial distribution. Through the application of models of optimal habitat reconstruction using data on the houbara bustard as a proxy species for the ostrich, correlated with the spatial distribution of the ostrich petroglyphs and ecological data on the region, we identified the optimal areas that the Syrian ostrich could have inhabited in the past. Finally, we applied our model to examine reintroduction programs of a closely related ostrich subspecies, S. c. camelus, that have been carried out in the Negev to date.

Seed hydration memory is an adaptive strategy for plants in semiarid environments where water availability is irregular and unpredictable. Species native to these environments that have memory benefit from discontinuous hydration during their germination process and acquire tolerance to environmental stresses. The guiding question of this study is "does an alien species that invades a semiarid ecosystem also have seed hydration memory and benefit from discontinuous hydration?" To answer this question, we collected seeds of Leucaena leucocephala (Lam.) de Wit, an alien species that invades a Brazilian Tropical Dry Forest. We subjected the seeds to 0, 1, 2 and 3 hydration/dehydration cycles (HD cycles) at three different time intervals and, subsequently, to water, saline and thermal stresses. In addition, we used modeling to define the osmotic and thermal limits for occurrence of L. leucocephala and evaluated whether these limits increase after discontinuous hydration of seeds. The cycles of HD positively influenced the germination of seeds submitted to all stresses evaluated, increasing seed tolerance to treatments of water, saline, and thermal stresses. Discontinuous hydration increased the osmotic limits of salinity and thermal tolerance, although not increasing the osmotic limit of water deficit. Our results show that HD cycles also change the patterns of germinative responses of an invasive species to the environmental stresses of the invaded ecosystem.

This study aimed to assess subterranean termite nests in residential and open crop fields in Central Ethiopia: knowledge and perception of farmers on causes and effects. A descriptive research design was used for primary data collection from the selected district of central Ethiopia. Termite nests were counted from each kebele after clustered into local division called Gox. A total of 72 sampling frames with a 1 km² were used for termite nests count. In addition, 190 household heads were selected at random from each kebele for questionnaires survey. Termite nests were abundant in Warabo (7.251.71 per 1000 m²), but scarce in Warke Walensu Kebele (2.250.50 per 1000 m²). Teff (49.5%) and wheat (32.6%) were the crops most severely affected by termites. The mean annual hectares of land and quintals of teff and wheat damaged per household were higher in Warabo Kebele (p = 0.000) and lowest in Warke Walensu Kebele. The annual economic loss from crops loss due to termite's effect was greater in Warabo Kebele (4722.23 ± 869.67 ETB and 4396.43 ± 852.65 ETB from teff and wheat per household, respectively). Agroecology, deforestation, grazing, and crop type were the factors that determine termite abundance and its impact on farmers' livelihoods. Mound opening and smoking were the traditional management methods used, but there was no government support. Therefore, integrated and effective termite pest management is critical for long-term food security in the study area.

Ecosystems around the world face a variety of threats from anthropogenic activities and drylands are among the most affected due to their unique environmental characteristics. To maintain phylogenetic history and ecological functionality in these areas, it is imperative to preserve community structure and composition by identifying and protecting key conservation areas. Various methods have been used to define these areas in need of protection; in this study, we used patterns of taxonomic and phylogenetic diversity in the arid lands of the Altiplano-Puna Bioregion of South America, using non-volant small mammal communities as a model system. Based on detailed records of species presence in the study area we estimated indices of species richness and phylogenetic redundancy. The geographic distribution of these indices was then compared to the distribution of protected areas in the region. These analyses identified areas around Lake Titicaca as being of exceptional conservation importance and in need of protection efforts. We propose a network of interconnected areas that together would provide high conservation value while allowing genetic exchange and facilitating ecological processes across landscapes.

Here, we explored how variations in the allopatric speciation scenario, specifically ecological vs. vicariant allopatry, relate to climatic niche change in sister species. We selected two sister species pairs of North American hummingbirds (Calypte anna, C. costae, Basilinna leucotis, B. xantusii) that diverged 2.5 and 3.6 million years ago, under ecological (arid climate tendency during Pliocene) and vicariant (Baja California peninsula separation) allopatric processes, respectively. We constructed the climatic niche of each species using occurrence records and estimated the distance, similarity, and unique fraction of climatic niche between sister species. Calypte species showed moderate niche divergence (Euclidean distance between centroids = 1.94, Sørensen index of similarity = 0.080, unique fraction of hypervolume in C. costae = 0.57, and C. anna = 0.95). However, contrary to expectations, Basilinna species, which diverged under a vicariant scenario, displayed clear niche divergence (Euclidean distance between centroids = 3.78, Sørensen index of similarity = 0.0001, and unique fraction of hypervolume in B. xantusii = 0.98, and B. leucotis = 0.99). We explained dissimilarity in climatic niches between Basilinna species by the ecological divergence between habitats of disjunct populations, which would have also been associated with increased aridity during the Pliocene.

Dust storms are linked to large scale accidents and fatalities in the Central Sonoran Desert, specifically in the central Gila River Valley of the United States during the North American Monsoon. This study analyzes three events where the underlying topography impacts large summertime dust storms and their movement. All three examples demonstrate the shielding or, conversely, funneling effects associated the underlying terrain. The funneling between isolated mountain complexes, such as White Tank Mountains, the Sierra Estrella, the Sacaton Mountains, the San Tan Mountains, and the South Mountain Complex can combine to create substantially higher dust concentrations. Conversely, dust flow into these isolated mountain complexes can also lead to shielding, or blocking, of the dust such that area behind the topographic features experiences less dust while the windward side of the barriers have accented dust concentrations. These dust storm/topography studies provide a first opportunity to identify topographic influences on central Arizona dust storms.

Significance statement

The purpose of this study is to identify Topographic elements of the central Sonoran Desert located in the Arizona region of the Southwestern United States that impact the movement of dust storms. Using IDW interpolation to analyze PM10 concentration levels and wind speeds, we find that stand-alone mountain complexes can provide significant dust shielding and funneling that effect the overall trajectory of a dust storm in this region.