Globally, many lakes are drying up, leaving exposed lakebeds where wind erosion releases dust and sand rich in salt and harmful heavy metals into the atmosphere. Therefore, understanding the characteristics and spatial distribution of playa surface crusts is important to recognize the manifestation of salt dust storms. The objective of this study was to explore the playa surface crust types as well as their spatial distribution and evolution of Qehan Lake in Inner Mongolia Autonomous Region, China to understand the salt dust release potential of different types of playa surface crusts. Various crust characteristics were investigated by field sampling in Qehan Lake, and playa surface crusts were further divided into five types: vegetated areas, salt crusts, clay flats, curly crusts, and margins. It should be noted that curly crusts were distributed in clay flats and covered only a small area in Qehan Lake. The spatial distribution characteristics of playa surface crust types were obtained by supervised classification of remote sensing images, and the salt dust release potential of crusts was explored by the wind tunnel experiments. The field investigation of Qehan Lake revealed that playa surface crust types had a circum-lake band distribution from the inside to the outside of this lake, which were successively vegetated areas, clay flats, salt crusts, and margins. The spatial distribution patterns of playa surface crust types were mainly controlled by the hydrodynamics of the playa, soil texture, and groundwater. There was a significant negative correlation between crust thickness and electrical conductivity. The results of the wind tunnel experiments showed that the initial threshold of friction wind velocity for the salt dust release was higher in clay flats (0.7-0.8 m/s) than in salt crusts (0.5-0.6 m/s). Moreover, the particle leap impact processes occurring under natural conditions may reduce this threshold value. Salinity was the main factor controlling the difference in the initial threshold of friction wind velocity for the salt dust release of clay flats and salt crusts. This study provides a scientific reference for understanding how salt dust is released from a lakebed, which may be used for ecological restoration of dry salt lakes.

Ecosystem responses to climate change, particularly in arid environments, is an understudied topic. This study conducted a spatial analysis of ecosystem responses to short-term variability in temperature, precipitation, and solar radiation in the Qilian Mountains National Park, an arid mountainous region in Northwest China. We collected precipitation and temperature data from the National Science and Technology Infrastructure Platform, solar radiation data from the China Meteorological Forcing Dataset, and vegetation cover remote-sensing data from the Moderate Resolution Imaging Spectroradiometer. We used the vegetation sensitivity index to identify areas sensitive to climate change and to determine which climatic factors were significant in this regard. The findings revealed a high degree of heterogeneity and non-linearity of ecosystem responses to climate change. Four types of heterogeneity were identified: longitude, altitude, ecosystem, and climate disturbance. Furthermore, the characteristics of nonlinear ecosystem responses to climate change included: (1) inconsistency in the controlling climatic factors for the same ecosystems in different geographical settings; (2) the interaction between different climatic factors results in varying weights that affect ecosystem stability and makes them difficult to determine; and (3) the hysteresis effect of vegetation increases the uncertainty of ecosystem responses to climate change. The findings are significant because they highlight the complexity of ecosystem responses to climate change. Furthermore, the identification of areas that are particularly sensitive to climate change and the influencing factors has important implications for predicting and managing the impacts of climate change on ecosystems, which can help protect the stability of ecosystems in the Qilian Mountains National Park.

In the context of global warming, drought events occur frequently. In order to better understanding the process and mechanism of drought occurrence and evolution, scholars have dedicated much attention on drought propagation, mainly focusing on drought propagation time and propagation probability. However, there are relatively few studies on the sensitivities of drought propagation to seasons and drought levels. Therefore, we took the Heihe River Basin (HRB) of Northwest China as the case study area to quantify the propagation time and propagation probability from meteorological drought to agricultural drought during the period of 1981-2020, and subsequently explore their sensitivities to seasons (irrigation and non-irrigation seasons) and drought levels. The correlation coefficient method and Copula-based interval conditional probability model were employed to determine the drought propagation time and propagation probability. The results determined the average drought propagation time as 8 months in the whole basin, which was reduced by 2 months (i.e., 6 months) on average during the irrigation season and prolonged by 2 months (i.e., 10 months) during the non-irrigation season. Propagation probability was sensitive to both seasons and drought levels, and the sensitivities had noticeable spatial differences in the whole basin. The propagation probability of agricultural drought at different levels generally increased with the meteorological drought levels for the upstream, midstream, and southern downstream regions of the HRB. Lesser agricultural droughts were more likely to be triggered during the irrigation season, while severer agricultural droughts were occurred mostly during the non-irrigation season. The research results are helpful to understand the characteristics of drought propagation and provide a scientific basis for the prevention and control of droughts. This study is of great significance for the rational planning of local water resources and maintaining good ecological environment in the HRB.

Modelling the impact of climate change on cropping systems is crucial to support policy-making for farmers and stakeholders. Nevertheless, there exists inherent uncertainty in such cases. General Circulation Models (GCMs) and future climate change scenarios (different Representative Concentration Pathways (RCPs) in different future time periods) are among the major sources of uncertainty in projecting the impact of climate change on crop grain yield. This study quantified the different sources of uncertainty associated with future climate change impact on wheat grain yield in dryland environments (Shiraz, Hamedan, Sanandaj, Kermanshah and Khorramabad) in eastern and southern Iran. These five representative locations can be categorized into three climate classes: arid cold (Shiraz), semi-arid cold (Hamedan and Sanandaj) and semi-arid cool (Kermanshah and Khorramabad). Accordingly, the downscaled daily outputs of 29 GCMs under two RCPs (RCP4.5 and RCP8.5) in the near future (2030s), middle future (2050s) and far future (2080s) were used as inputs for the Agricultural Production Systems sIMulator (APSIM)-wheat model. Analysis of variance (ANOVA) was employed to quantify the sources of uncertainty in projecting the impact of climate change on wheat grain yield. Years from 1980 to 2009 were regarded as the baseline period. The projection results indicated that wheat grain yield was expected to increase by 12.30%, 17.10%, and 17.70% in the near future (2030s), middle future (2050s) and far future (2080s), respectively. The increases differed under different RCPs in different future time periods, ranging from 11.70% (under RCP4.5 in the 2030s) to 20.20% (under RCP8.5 in the 2080s) by averaging all GCMs and locations, implying that future wheat grain yield depended largely upon the rising CO₂ concentrations. ANOVA results revealed that more than 97.22% of the variance in future wheat grain yield was explained by locations, followed by scenarios, GCMs, and their interactions. Specifically, at the semi-arid climate locations (Hamedan, Sanandaj, Kermanshah and Khorramabad), most of the variations arose from the scenarios (77.25%), while at the arid climate location (Shiraz), GCMs (54.00%) accounted for the greatest variation. Overall, the ensemble use of a wide range of GCMs should be given priority to narrow the uncertainty when projecting wheat grain yield under changing climate conditions, particularly in dryland environments characterized by large fluctuations in rainfall and temperature. Moreover, the current research suggested some GCMs (e.g., the IPSL-CM5B-LR, CCSM4, and BNU-ESM) that made moderate effects in projecting the impact of climate change on wheat grain yield to be used to project future climate conditions in similar environments worldwide.

The greatest failure rate of reforestation programs is basically related to water deficit, especially at the seedling stage. Therefore, the main objective of this work is to investigate the responses of three accessions of carob trees (Ceratonia siliqua L.) with 2-year-old from different climate regions to drought generated by four water treatments: Tc (250 mm), T1 (180 mm), T2 (100 mm), and T3 (50 mm). The first accession (A1) comes from the protected national park of Ichkeul in northern Tunisia. This zone belongs to the bioclimatic sub-humid stage. The second accession (A2) comes from Melloulech, located in the center-east of Tunisia, belonging to the bioclimatic semi-arid stage. The third accession (A3) comes from the mountain of Matmata, located in the south of Tunisia, belonging to the bioclimatic hyper-arid stage. The experiment was undertaken in a greenhouse. Gaz exchange indices (net photosynthesis (A), stomatal conductance (g_s), transpiration rate (E), and internal CO₂ concentration (C_i)) were determined. Predawn (Ψ_pd) and midday (Ψ_md) leaf water potentials, relative soil water content (SWC), and morphological parameters (plant height (H), number of leaves (NL), number of leaflets (Nl), and number of branches (NB)) were estimated. The results showed that significant differences (P<0.001) were found between physiological and morphological parameters of each accession. The highest growth potential was recorded for Tc treatment in both accessions A1 and A2. Significant decreases in g_s, E, C_i, and SWC were recorded with the increases in water stress applied from treatment T1 to T3. Positive and significant correlations were found between SWC and Ψ_pd for all studied accessions. Ψ_pd and Ψ_md decreased as water stress increased, ranging from -0.96 to -1.50 MPa at sunrise and from -1.94 to -2.83 MPa at midday, respectively, under control and T3 treatments. C. siliqua accessions responded to drought through exhibiting significant changes in their physiological and morphological behavior. Both accessions A1 and A2 showed greater drought tolerance than accession A3. These seedlings exhibit different adaptive mechanisms such as stress avoidance, which are aimed at reducing transpiration, limiting leaf growth, and increasing root growth to exploit more soil water. Therefore, C. siliqua can be recommended for the ecological restoration in Mediterranean ecosystems.

Calotropis procera (Aiton) W. T. Aiton, belonging to the family Apocynaceae, is C₃ evergreen plant species in arid and semi-arid areas of the Punjab Province, Pakistan. It grows in a variety of habitats like salt affected and waterlogged area, desert/semi-desert, roadside, wasteland, graveyard, forest, crop field, coastline, and river/canal bank. A total of 12 populations growing in different ecological regions were sampled to evaluate their growth, physio-biochemical, and anatomical responses to specific environmental condition. Population adapted to desert/semi-desert showed vigorous growth (plant height, shoot length, and number of leaves), enhanced photosynthetic level (chlorophyll a, chlorophyll b, carotenoids, and total chlorophyll), and apparent anatomical modifications such as increased stem radius, cuticle thickness, storage parenchyma tissues (cortex and pith), and vascular bundles in stems, while the maximum of midrib and lamina thickness, epidermal cells, cuticle thickness, cortical proportion, abaxial stomatal density, and its area in leaves. There was high plasticity in structural and functional features of these populations, which enable them to survive and tolerate under such hot and dry desert environment. Population of saline areas exhibited very critical modifications to sustain under salt prone environment. At physiological level, it possesses the maximum amount of organic osmolytes (glycine betaine and proline) and antioxidants (superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD)), while at anatomical level, it showed intensive sclerification, large phloem region (inner and outer), pith parenchyma cells, and metaxylem vessels in stems and leaves. The population of dry mountains showed very distinctive features, such as increased shoot ionic contents (K⁺ and Ca²⁺), collenchyma and sclerenchyma thickness in stems, trichomes size, and numerous small stomata on abaxial surface of leaves. It is concluded that no definite or precise single character can be taken as a yardstick for adjudging the biomass production in this rubber bush weed population.

Variations of precipitation have great impacts on soil carbon cycle and decomposition of soil organic matter. Soil bacteria are crucial participants in regulating these ecological processes and vulnerable to altered precipitation. Studying the impacts of altered precipitation on soil bacterial community structure can provide a novel insight into the potential impacts of altered precipitation on soil carbon cycle and carbon storage of grassland. Therefore, soil bacterial community structure under a precipitation manipulation experiment was researched in a semi-arid desert grassland in Chinese Loess Plateau. Five precipitation levels, i.e., control, reduced and increased precipitation by 40% and 20%, respectively (referred here as CK, DP40, DP20, IP40, and IP20) were set. The results showed that soil bacterial alpha diversity and rare bacteria significantly changed with altered precipitation, but the dominant bacteria and soil bacterial beta diversity did not change, which may be ascribed to the ecological strategy of soil bacteria. The linear discriminate analysis (LDA) effect size (LEfSe) method found that major response patterns of soil bacteria to altered precipitation were resource-limited and drought-tolerant populations. In addition, increasing precipitation greatly promoted inter-species competition, while decreasing precipitation highly facilitated inter-species cooperation. These changes in species interaction can promote different distribution ratios of bacterial populations under different precipitation conditions. In structural equation model (SEM) analysis, with changes in precipitation, plant growth characteristics were found to be drivers of soil bacterial community composition, while soil properties were not. In conclusion, our results indicated that in desert grassland ecosystem, the sensitive of soil rare bacteria to altered precipitation was stronger than that of dominant taxa, which may be related to the ecological strategy of bacteria, species interaction, and precipitation-induced variations of plant growth characteristics.

Soil faunas account for 23% of known animal species and play a crucial role in ecosystem processes such as mineralizing nutrients, regulating microbial community composition, forming soil aggregates, and enhancing primary productivity. However, due to global climate change, population density, community composition, and distribution patterns of soil fauna vary. Understanding the responses of soil fauna to major environmental change facilitate the conservation of biodiversity. Therefore, a review work of recent researches for analysing the effects of key environmental factors on soil fauna, such as warming, drought, food quality, and soil physical-chemical properties was studied. For most species, warming may exert a positive effect on their abundance and population development, however, it can inhibit the survival and reproduction of hibernating species. Drought leads to low soil porosity and water holding capacity, which reduces soil fauna population and changes their community composition. Drought also can reduce the coverage of flora and alter microclimate of the soil surface, which in turn indirectly reduces fauna abundance. Climate warming and elevated atmospheric carbon dioxide can reduce litter quality, which will force soil fauna to change their dietary choices (from higher-quality foods to poor quality foods) and reduce reproduction for survival. However, it is still predicted that enhanced species richness of plant (or litter) mixtures will positively affect soil fauna diversity. Habitat loss caused by the deterioration of soil physical-chemical property is primary factor affecting soil fauna. We mainly discuss the threats of increased salinity (a major factor in arid land) to soil fauna and their potential responses to anthropogenic disturbance in saline soils. The increase in soil salinity can override other factors that favour habitat specialists, leading to negative effects on soil fauna. Moreover, we find that more studies are needed to explore the responses of soil fauna in saline soils to human activities. And the relationship of important ecological processes with soil fauna density, community structure, and diversity needs to be redefined.