Journal of Arid Environments最新文献

The targeted removal of a non-native species can result in secondary invasions and other unexpected shifts in plant community composition, but the persistence of these effects is less well known. We investigated how the plant community changed at three time points including before removal (pre-removal), in the years directly following removal (post-removal), and 16 years following Tamarix removal (recent) in an arid depressional wetland. Non-native species cover increased and several non-native species invaded the study area in the years between post-removal surveys and the recent time period, suggesting Tamarix removal may have been a catalyst for increases in non-native species abundance. We also found an increase in the cover of species tolerating upland conditions, and these species were largely non-native. Overall, interactions between targeted removal and shifts in the abiotic environment due to climate change are important drivers of persistent shifts in the plant community. Hydrogeomorphic restoration is likely needed in tandem with invasive removal to see improvements in riparian health, particularly when the invasive species to be removed is a passenger in addition to being a driver of change.

Animal populations that require tree cavities can be either limited or structured depending on the quality and availability of tree cavities in their ecosystems. Over the last century, the Caldén forest of Argentina has experienced severe habitat degradation due to anthropogenic activities. Here, we report the density and characteristics of cavities and their vertebrate users in areas of the Caldén forest with two different types of management: a protected area and an area with cattle ranching. The average density of cavities was 16.1 cavities/ha. However, the reserve's cavity density was four times higher than the ranch's (19.5 vs. 5.8 cavities/ha). The characteristics of the cavities and their support trees showed significant variations, but they were generally similar between sites. Forty-four vertebrate species use or may use tree cavities. The proportion of recorded species using cavities in the reserve was higher (30/41 vs. 6/32; p < 0.01). While most cavity users in the semi-arid forest are not threatened, this ecosystem has been dramatically fragmented, with only 11% of its original area remaining. If anthropogenic activities continue to alter this fragile ecosystem, it is possible that in the future, many species, including tree cavity nesters, will suffer a decline in their populations.

The impacts of anthropogenic activities have significantly contributed to recent and future climate changes worldwide. The future effects of climate change on biodiversity have been intensively studied globally over the past two decades. Currently, dry ecoregions are among the most threatened ecosystems in the world. In South America, three such seasonal dry ecoregions stand out: the Cerrado, Caatinga, and the Gran Chaco. Among these, the Chaco has experienced high deforestation rates and landscape degradation over the last decade, making it a top priority for conservation efforts. In this study, we employed ecological niche modeling to estimate the present and future distribution of snakes in the Chaco region. Our goal was to assess how snake diversity will change with projected climate changes across this geographic area. Our findings suggest that snake assemblages in the Chaco will undergo significant changes under future climatic conditions, with a clear trend toward biotic homogenization of the ecoregion and a decrease in species richness. These negative changes will likely extend to the protected areas within the Chaco, resulting in biotic homogenization and a loss of species richness.

The Siberian jerboa (Orientallactaga sibirica), a keystone species in desert ecosystems and a critical indicator for environmental change assessment. However, little is known about the spatial distribution and habitat suitability of Siberian jerboa in China, particularly under the dual impacts of climate change and human disturbance. This study employed the MaxEnt model to discern key factors affecting the Siberian jerboa's habitat suitability, predicated future habitat shifts in response to climatic and anthropogenic influences. The results reveal that the species predominantly inhabits northwestern China, centering in Gansu's Hexi Corridor and central Inner Mongolia under current climate conditions. Vegetation cover emerges as the primary determinant of its distribution, with elevation, human disturbance, temperature fluctuations, and slope also significantly influencing habitat suitability of the species. The potentially suitable habitat range of the Siberian jerboa is shrinking due to global climate change. Notably, future projections suggest an expansion of its distribution towards the Tibetan Plateau, driven by climate change. This research contributes valuable insights into the adaptive responses of desert rodents to the environmental change.

Ungulates have physiological and behavioral mechanisms to respond to seasonal variation and resource availability to meet their nutritional needs. To understand the effects of primary productivity in long-term studies, vegetation indices (e.g., enhanced vegetation index, EVI) can be used as indirect indicators of the nitrogen available to herbivores in arid and mountain environments. In this research, we explore the relationship between the variation in guanaco's local density (Lama guanicoe) and the EVI between 2008 and 2017 in a wild partially migratory population of La Payunia Reserve (Mendoza, Argentina) using a weighted linear regression. Our results indicated a significant relation between guanaco local density and EVI (R² = 0.68; p-value = 0.003), suggesting that the interannual variation in guanaco local density can be explained, at least in part, by higher aerial net primary productivity. Possibly, when nutrient availability is high, the local environment can support a higher local animal density than in years in which primary productivity is lower. When nutrients are limited, some individuals may use other areas not considered in this study. Even preliminary, these results bring new insights into the ecophysiology of this extremely plastic ungulate and contribute to understanding its energetic strategy.

Grasslands restoration is crucial to prevent degradation, with direct seeding being the most effective method. Understanding the species environmental requirements is essential for successful establishment. Our objective was to investigate the effect of water stress and temperature on seed germination of five native forage grass species used in semi-arid Pampas restoration projects. Perennial cool-season grasses (Poa ligularis, Nassella tenuis, Piptochaetium napostaense and Nassella longiglumis) and a warm-season grass (Pappophorum vaginatum) were subjected to different water potentials and temperatures. The hydrotime model was used to describe germination patterns. Results showed a decreasing germination percentage with decreasing water potential, being P. ligularis the most drought sensitive, and P. vaginatum and N. tenuis the least. Warm-season species had the shortest germination time under water stress. Temperature affected germination, with higher values observed at 20, 25 and 15/20 °C. Pappophorum vaginatum was more affected by low temperatures than the cool-season grasses. Poa ligularis, with low water stress tolerance and temperature specificity, may not be recommended for restoration strategies.

Various techniques were used to illuminate domestic structures at EBII Arad (3000-2880 BCE) and its enclaves and outposts in southern Sinai. The dwellings were constructed in a manner that required some form of illumination on overcast days and at night. The residents had three options for lighting the interior of their dwellings: first, sunlight streaming through an open door was the most efficient means of illumination as it did not require the expenditure of fuel; second, the flint “stoves” that were used for cooking provided a certain amount of light; third, lamp-bowls fueled with olive oil were used to illuminate many broadroom dwellings at Arad, but not those in southern Sinai. Lamp-bowls were not used in the latter region because the fuel had to be imported and the amount of light cast by these devices was equivalent to a candle. In this context, hearths were a more appropriate form of illumination as there was a ready supply of firewood in southern Sinai. Lastly, burning olive oil in intact vessels to provide artificial illumination was an act of conspicuous consumption practiced by elites.

Phenological studies with species of cactus have grown in recent decades but the number of species studied remains very low, considering the high species richness of this group. In addition, temporal patterns of flowering and fruiting are important to understanding the processes that govern these crucial events of plant demography and ecology. Based on a five-year study of the reproductive phenology of C. minensis we asked if there is seasonality of flowering and fruiting. Secondly, we tested which climatic variables trigger C. minensis reproductive events in the Espinhaço region. We found that not all individuals produced flowers and fruits each year and a few individuals contributed with most flowers. Flower and immature fruit production is higher during the dry months, with fruits maturing during the rainy season or just before. In general, phenological events were seasonal, except for mature fruit production in 2010 and flower production in 2011. Some phenological traits such as flower timing, frequency, duration, and timing of immature fruit production had not been reported for the genus Cipocereus and were detected only because of the long-term phenological observations. Phenological heterogeneity in cactus might be a response to annual climatic fluctuations, mainly rainfall.

Efficient nitrogen (N) acquisition by plants and microbes and internal reallocation of plant N are crucial for improving ecosystem N retention. However, little is known about shifts in N use strategy between plants and microbes under N addition. We used a¹⁵N tracer to investigate effect of N addition (0–25 g N m⁻² yr⁻¹) on the N use and retention of plant–microbe–soil system in a temperate Chinese steppe. Adding 2–5 g N m⁻² yr⁻¹ increased the ecosystem's ability to retain ¹⁵N (65–76%) after 1 year. Plant N demand during the peak growth period depended strongly on rapid N immobilization by microbes during 7 days (immobilized 45% of ¹⁵N within 24 h). When root biomass exceeded 0.36 kg m⁻², plants competed more strongly for N than the microbes. N addition increased N reallocation from roots to support new shoot growth (79–88% of N), because increased shoot N demand triggered root N transfer when external N was supplied. Thus, the temporal coupling between plant and microbial N use and in N reallocation within plants significantly altered the semi-arid grassland N cycle, and better predicting impacts of future N deposition scenarios.

In the Central Semiarid Region of Argentina, the native woody species Geoffroea decorticans has increased in range and density, probably due to overgrazing. The aim of this work was to evaluate the floristic and functional composition of the herbaceous vegetation along time in grazed sites, within thickets of G. decorticans, and compared to grasslands. We registered the cover of each herbaceous species in different locations within thickets and in the natural grassland, at each season for two years, from autumn 2021 to summer 2023. Indicator species of grasslands were found to be mostly palatable native perennials, resulting more homogeneous than those of thickets. Moreover, the mean cover of palatable species was higher in grasslands than in thickets. Consequently, grasslands confer stability and food resource for livestock. Woody thickets would exhibit a decreased stratification from the center to the edge, that would give rise to niche opportunities and biodiversity reservoirs. Temporal variability in floristic composition indicated differences between grasslands and thickets over time, which decreased in spring, probably by homogenization by grazing in winter. The temporal variability of functional composition showed a cyclical variability in all locations that decreased in spring in all cases.