Climate change significantly affects the arid/humid processes and patterns in China,directly impacting management decisions related to adaptive agriculture and water resources management,desertification control,and sp...Climate change significantly affects the arid/humid processes and patterns in China,directly impacting management decisions related to adaptive agriculture and water resources management,desertification control,and spatial ecological restoration.However,current studies primarily focus on changes in arid/humid climate variables,lacking quantitative characterization of the dynamic evolution of areal systems and their nonlinear responses.Based on the data of national meteorological stations from 1961 to 2020,we systematically quantified the nonlinear response of arid/humid patterns to climate change.The results revealed that 6.98%of eco-geographical arid/humid regions underwent type shifts over the past six decades,with 4.95%transitioning toward wetter conditions.Humid and semi-arid regions expanded significantly while sub-humid and arid regions contracted significantly.In the late 1990s,trends of the humid and sub-humid region shifted.Humid region contraction in northern China was driven primarily by precipitation decline,whereas the Tibetan Plateau responded to increasing potential evapotranspiration.During the same period,the retreat rate of the arid region slowed,linked to intensified aridification in the west part of northern China and a decelerating wetting trend in northwest China,both primarily driven by precipitation trends.Our study reveals the nonlinear response of the arid/humid patterns under climate change,providing a scientific basis for the improvement of regional climate resilience.展开更多
Riparian dunes in deserts exhibit unique geographic features due to aeolian-fluvial interactions.In this study,we collected 510 surface sediment samples from eight drainage basins and conducted a systematic analysis t...Riparian dunes in deserts exhibit unique geographic features due to aeolian-fluvial interactions.In this study,we collected 510 surface sediment samples from eight drainage basins and conducted a systematic analysis to examine the grain size characteristics of major riparian dunes in the typical cold and arid deserts of China.The results indicate that major riparian dunes of deserts in study area can be classified into three types based on their grain size characteristics.The Bartlett test of sphericity and the Kaiser-Meyer-Olkin(KMO)test were also performed,and their significance values were found to be 0.000 and 0.584,respectively.The results of the principal component analysis revealed that the cumulative contribution rate of the total variance reached 85.9%for the two principal components with characteristic roots greater than 1.0.The primary principal component included medium sand,whereas the secondary principal component included fine sand.We conducted a cluster analysis and classified the samples into three major types.Type I rivers include the Keriya River,Langqu River,Tora River and Heihe River,which are characterized by by fine particle size,and well-sorted.Type II includes Mu Bulag River,Kuye River,and the Xar Moron River,Compared with type I,it has a relatively coarser mean grain size and relatively poor sorting for this type.Type III includes the Maquan River,which is characterized mainly by fine sand and medium sand,accounting for more than 90%,and the sorting coefficient(0.52)suggests relatively well sorting in this pattern.Moreover,principal component analysis was applied to determine the particle sizes of samples from different watersheds.Moreover,these sediments exhibit both hydromorphic and aeolian features.At the drainage basin scale,the mode and intensity of aeolian-fluvial interactions depend on climatic conditions.In arid and semi-arid climate regions,wind is the dominant force,and the grain size exhibits significant aeolian features.Conversely,in the semi-humid region,flowing water is the dominant force,and riparian dunes in this region are formed by aeolian-fluvial interaction.The angle between the wind direction and flow direction in different reaches influences both the supply of sediment sources and the development of riparian dunes.This study will provide a new perspective for evaluating aeolian-fluvial interactions on riparian dunes in the deserts of China’s cold and arid regions.展开更多
Under arid and semi-arid bioclimates,steppes are increasingly threatened by anthropogenic disturbance and climatic variability,which strongly affects ecosystem functioning and subsequently leads to desertification.We ...Under arid and semi-arid bioclimates,steppes are increasingly threatened by anthropogenic disturbance and climatic variability,which strongly affects ecosystem functioning and subsequently leads to desertification.We investigated the morphological and physiological responses of Stipa tenacissima L.across three disturbance levels(undisturbed,slightly disturbed,and highly disturbed)in three Tunisian steppe areas(Kasserine,Sidi Bouzid,and Sfax).Morphological and physiological traits were monitored over one year,together with microclimatic variables.Result showed that disturbance was a strong driver of plant functional dynamics,with significant effects on all traits and strong interactions with site and season.Disturbance reduced photosynthetic activity and water use efficiency,particularly in Sfax,where plants adopted conservative strategies(i.e.,higher leaf dry matter content and reduced leaf area).In contrast,undisturbed populations maintained a stronger coordination between physiological and morphological traits.Seasonal analyses revealed that disturbance amplified physiological stress with limited recovery.Heatmap analyses further showed that disturbance weakened trait coordination and reshaped trade-offs between acquisitive and conservative traits.Partial least squares-path modeling showed that morphology strongly drove physiological performance(path coefficient=0.48).Disturbance(path coefficient=0.41)and tussock cover(path coefficient=0.47)influenced morphology both directly and indirectly through their effects on physiology.In conclusion,S.tenacissima adjusts physiological and morphological traits under disturbance,favoring stress tolerance,while undisturbed sites maintain high physiological efficiency and coordinated trait integration,reflecting a trade-off between survival and performance while overriding local site differences.Disturbance strongly restructures trait networks,drives site-specific adjustments,and modulates the seasonal balance between morphological stability and physiological flexibility.展开更多
This study presents a multi-physical modeling approach to analyze the dynamics of moisture potential and stress-deformation features near deep desiccation cracks in clayey soils under three consecutive years’climate ...This study presents a multi-physical modeling approach to analyze the dynamics of moisture potential and stress-deformation features near deep desiccation cracks in clayey soils under three consecutive years’climate variability in an arid region.A triple research approach of statistical analysis,analytical framework,and numerical modeling was used to investigate the complex thermo-hydro-mechanical behavior of desiccation-cracked soil,incorporating realistic climatic data of Qom,Iran.The results revealed the interplay between stress,strain,and pore water pressure over time,demonstrating that soil experiences significant swelling and shrinkage due to cyclic wetting and drying.The horizontal stress distribution shows compressive stress concentration at crack tips during wetting,transitioning to tensile stresses uniformly across the soil surface during drying paths.Similarly,vertical stress distributions exhibit localized compressive stresses along crack boundaries during wetting and tensile stresses during drying,highlighting the critical stress conditions at crack tips.The model differentiates between microstructural and macrostructural changes in porosity.Annual trends in micro-porosity revealed cyclic-dependent behavior,with significant volumetric changes occurring in the first year,stabilizing with successive cycles.The results also indicated that part of the volumetric changes are irreversible,with volumetric plastic strain increasing exponentially but at a decreasing rate over three years.Principal stress analysis indicates a shift from compressive to tensile stress states around cracks,driven by climate-induced wetting and drying cycles.These findings underscore the critical role of climate variability in shaping cracked soil behavior in arid regions,providing insights into the heterogeneous behavior of cracked soil surfFicial layers.展开更多
Arid and semi-arid ecosystems are prone to extensive fires due to specific climatic conditions,sparse vegetation cover,and high density of fine fuels.Understanding the flammability characteristics of land covers is es...Arid and semi-arid ecosystems are prone to extensive fires due to specific climatic conditions,sparse vegetation cover,and high density of fine fuels.Understanding the flammability characteristics of land covers is essential for fire management and designing land restoration programs in arid and semi-arid ecosystems.This study provided a new approach to evaluate the flammability of shrublands and woodlands using flammability indices(FIs)including time to ignition(TI),duration of combustion(DC),and flame height(FH)of plant species and their relative frequencies in the Dalfard Basin of southeastern Iran.The results showed that there was a significant difference in FIs between land covers.Shrublands had higher flammability potential compared with woodlands.Plant moisture content had a negative relationship with TI(P<0.010)and no significant relationship with DC and FH(P>0.050).Artemisia spp.,Astragalus gossypinus Fischer,Amygdalus scoparia Spach,and Cymbopogon jwarancusa(Jones)Schult.had the highest FI.Tree species such as Rhazya stricta Decne.,and Pistacia atlantica Desf.showed greater resistance to fire.Using principal component analysis,the relationship between species and FIs was examined,and TI of wet fuel was the most important FI in relation to species.Structural equation model showed that life form(P<0.001)was the most important flammability driver.Precipitation(P<0.010)and legume species(P<0.010)were significantly related to the flammability in arid land.This study emphasizes the importance of managing high-risk species and using resistant species in vegetation restoration and shows that combining species FIs with their abundance is an effective tool for assessing fire risk and fuel management at the plant community scale.展开更多
Surface water plays an essential role in the ecohydrological cycle,especially in water-scarce regions.Changes in surface water restrict social,economic,and agricultural development.However,the patterns and underlying ...Surface water plays an essential role in the ecohydrological cycle,especially in water-scarce regions.Changes in surface water restrict social,economic,and agricultural development.However,the patterns and underlying causes of surface water changes over varying frequencies in global arid regions remain unclear.Thus,this study investigated the changes in surface water and the underlying causes using the trend analysis and Spearman correlation coefficient on the basis of multi-source remote sensing and climate datasets across global arid regions during 2000–2020.The surface water was divided into temporary surface water(TSW),seasonal surface water(SSW),and permanent surface water(PSW)by calculating the surface water inundation frequency.Considering that surface water may be influenced by precipitation in the upper basins,we analyzed the response of surface water area to climatic factors at the basin scale.The area of all surface water(ASW)increased dramatically in global arid regions from 2000 to 2020,increasing from 61.88×104 to 67.40×104 km^(2);however,this increase was accompanied by a decrease in surface water inundation frequency.TSW increased by 55.46%relative to its area in 2000,with a net change rate of 3284.00 km^(2)/a.Changes in surface water were predominantly observed in the Kyzylkum Desert in Central Asia,the Thar Desert in southwestern Asia,and the deserts in Oceania.Precipitation had a significant effect on SSW and TSW at the basin scale.The correlation between precipitation and SSW area can reach 0.808 in the Indus River Basin of the Thar Desert(P<0.01).The findings provide a more comprehensive understanding of surface water variability in global arid regions,carrying significant practical implications for the scientific management of surface water at different frequencies.展开更多
High-concentration photovoltaic(HCPV)systems present significant thermal management challenges due to the intense heat fluxes generated under concentrated solar irradiation,especially in arid environments.Effective he...High-concentration photovoltaic(HCPV)systems present significant thermal management challenges due to the intense heat fluxes generated under concentrated solar irradiation,especially in arid environments.Effective heat dissipation is critical to prevent performance degradation and structural failure.This study investigates the thermal performance and design optimization of an enhanced HCPV module,integrating numerical,analytical,and experimental methods.A coupled optical-thermal-electrical model was developed to simulate ray tracing,heat transfer,and temperature-dependent electrical behaviour,with predictions validated under real-world desert conditions.Compared to a baseline commercial module operating at 106℃,the optimized design achieved a peak temperature reduction of 16℃,lowering the cell temperature to 90℃under a concentration ratio of 961×and direct normal irradiance(DNI)of 950 W/m^(2).The total thermal resistance was reduced from 0.25 to 0.15 K/W(a 40%improvement),and the electrical efficiency increased from 37.5%to 38.6%,representing a relative gain of approximately 3.1%.The system consistently maintained a fill factor exceeding 78%,underscoring stable performance under high thermal load.These findings demonstrate that targeted thermal design,informed by integrated modeling,is essential for unlocking the reliability and efficiency of high-flux solar energy systems.展开更多
Within the context of global climate change and rapid urbanization,increasing urban resilience(UR)is especially important in the arid region of Northwest China(ANC),where fragile ecosystems and an uneven water distrib...Within the context of global climate change and rapid urbanization,increasing urban resilience(UR)is especially important in the arid region of Northwest China(ANC),where fragile ecosystems and an uneven water distribution create significant sustainability challenges.In this study,a coupled UR-water ecosystem services(WESs)framework was developed on the basis of 1-km resolution remote sensing data for the 2000–2020 period obtained from the Landsat series,Defense Meteorological Satellite Program(DMSP)/Operational Linescan System(OLS),and Global Precipitation Measurement(GPM),among other sources.Within the framework,the Integrated Valuation of Ecosystem Services and Tradeoffs(InVEST)model was incorporated to provide a WES indicator system.Moreover,entropy weighting was employed to quantify both UR and WES indicators;the coupling coordination degree(CCD)model was used to measure the coupled relationship between UR and WESs;an extreme gradient boosting(XGBoost)-SHapley Additive exPlanations(SHAP)interpretation approach was adopted to identify key drivers and underlying mechanisms;and Geographically Weighted Regression(GWR)was applied to capture spatial distribution characteristics of major driving factors.The results indicated that UR steadily increased from 4.60×10^(-3) to 10.24×10^(-3),whereas WESs followed an inverted V-shaped trend,with a peak value observed in 2010(11.84×10^(-3)).The CCD remained consistently low(mean:0.0166–0.0246)and exhibited considerable spatial heterogeneity.Notably,the degree of coordination was greater in the oasis and mountain core areas but significantly lower at desert areas.XGBoost-SHAP model analysis revealed six key drivers influencing various states of the CCD between UR and WESs systems.The contributions of these factors could be ranked as follows:water yield(WY;24.30%)>farmland area per capita(FP;21.10%)>gross domestic product(GDP)per capita(GDPC;19.00%)>soil retention(SR;14.90%)>population density(PD;5.42%)>water purification(WP;4.40%).In contrast,in UR system,WP(53.66%)and SR(31.62%)served as the dominant drivers.Moreover,the dominant drivers shifted from a combination of natural and socioeconomic factors in StateⅠ(sustainable high resilience)to primarily socioeconomic factors in StateⅢ(unsustainable low resilience).SR and WP exerted positive moderating effects,whereas socioeconomic factors such as GDPC and PD exerted inhibitory effects on the coordination relationship.This research highlights that UR in the ANC region is limited mainly by water scarcity,weak feedback loops,and spatial variability,emphasizing the need for tailored intervention strategies.展开更多
Based on the data up to 1999 from hydroclimatological departments, this pape analyzes the climatic divide implications of the Qinling Mountains in regional response to the process of climate warming, due to which the ...Based on the data up to 1999 from hydroclimatological departments, this pape analyzes the climatic divide implications of the Qinling Mountains in regional response to the process of climate warming, due to which the grades of dryness/wetness (GDW) in 100 years show that the northern region has entered a drought period, while the southern is a humid period. In a course of ten years, the D-value of annual average air temperature over southern Shaanxi (the Hanjiang Valley) and the Central Shaanxi Plain (the Guanzhong Plain) has narrowed, i.e., the former with a slight change and the latter with rapid increase in temperature. Both regions were arid with the decrease in precipition D-value, namely the plain became warmer while the south was drier. The Qinling Mountains play a pronounced role in the climatic divide. The runoff coefficient (RC) of the Weihe River decreases synchronously with that of the Hanjiang due to climate warming. The RC of Weihe dropped from 0.2 in the 1950s to less than 0.1 in the 1990s. The Weihe Valley (the Guanzhong Plain) is practically an arid area due to shortage of water. The successive 0.5, 1.0°C temperature anomaly over China marks, perhaps, the improtant transition period in which the environment becomes more vulnerable than before. The study shows the obvious trend of environmental aridity, which is of help to the understanding of regional response to global climate change.展开更多
As the increases of climatic aridity and grazing intensity, shrubs play an increasingly important role in grassland ecosystem in arid and semi-arid regions, and its abundance also generally increases. However, the eff...As the increases of climatic aridity and grazing intensity, shrubs play an increasingly important role in grassland ecosystem in arid and semi-arid regions, and its abundance also generally increases. However, the effects of climatic aridity and grazing intensity on sexual reproduction of shrubs in grassland remain largely unclear. In order to understand the effects of grazing intensity and climatic drought stress, and their interaction on seed production of shrub species, we examined the seed number, seed weight and seed yield of Caragana stenophylla under three grazing intensities （fenced, mild grazing and severe grazing） across a climatic aridity gradient （semi-arid, arid, very arid and intensively arid zones） in the Inner Mongolia Steppe, northern China during 2012-2013. The seed number, seed weight and seed yield gradually increased from the semi-arid to the very arid zones, but decreased from the very arid to the intensively arid zones in fenced plots. The seed number and seed yield decreased from the semi-arid to the intensively arid zones in mild and severe grazing treatment plots, therefore, grazing enhanced the suppression effect of climatic aridity on seed production of C. stenophylla. The seed number and seed yield gradually decreased as grazing intensity increased. The seed weight was highest in severe grazing plots, followed by the mild grazing plots and then the fenced plots. Precipitation varied interannually during the study period. We observed that the seed number seed weight and seed yield were lower in the low precipitation year （2013） than in the high precipitation year （2012）. As climatic drought stress increased, the negative effects of grazing on seed production of C. stenophylla also gradually increased. Our results indicated that climatic drought stress may contribute to the encroachment of C. stenophylla shrub in arid zones by promoting its seed production. However, grazing had negative effects on sexual reproduction of C. stenophylla, and the combined effects of drought stress and grazing seriously suppressed sexual reproduction of C. stenophylla in the intensively arid zone.展开更多
Detecting variation trend in dry-wet conditions can provide information for devel- oping strategic measures to mitigate the impacts of global warming, particularly in dry regions Taking the hilly region of northern Sh...Detecting variation trend in dry-wet conditions can provide information for devel- oping strategic measures to mitigate the impacts of global warming, particularly in dry regions Taking the hilly region of northern Shaanxi on the Loess Plateau as a case area, this study analyzed the trend of aridity variation during 1981-2012, and explored the effect of vegetation restoration promoted by the Grain-for-Green （GFG） program implemented in 1999. The re- sults indicated that the aridity in the region was non-significantly increased by 0.88% per year during 1981-2012, showing a drying trend. This drying trend and amplitude were changed by the influence of vegetation restoration promoted by the GFG program, based on two findings. The first one was that the aridity variation tended to increase during 1981-1999 while it turned to decrease during 2000-2012, with the regional mean relative change rate changed from 2.45% to -1.06%. This distinction was more remarkable in the loess gully region, where the vegetation was improved more obviously. The second one was that the mean vegetation coverage as indicated by EVI increased by 0.90% to 4.32% per year at county level, while the aridity decreased by 0.14% to 2.32% per year during 2000-2012. The regression analysis using the mean county data indicated that the change rate of aridity was negatively related to that of EVI with the coefficient of determination （R2） of 0.56, illustrating that around half of the aridity decline was explained by the EVI change. The mechanism of this effect was compli- cated, but it was found that the wind speed decline induced by the vegetation improvement could be an important contributor. It is concluded that the region became drier during 1981-2012, but the eco-restoration reduced the drying speed. However, this conclusion is involved in uncertainties, and further study based on experiments is needed to confirm the effect of the GFG-promoted vegetation restoration.展开更多
Mid-western China is one of the most sensitive and fragile areas on the Earth.Evapotranspiration(ET)is a key part of hydrological cycle in these areas and is affected by both global climate change and human activities...Mid-western China is one of the most sensitive and fragile areas on the Earth.Evapotranspiration(ET)is a key part of hydrological cycle in these areas and is affected by both global climate change and human activities.The dynamic changes in ET and potential evapotranspiration(PET),which can reflect water consumption and demand,are still unclear,and there is a lack of predictive capacity on drought severity.In this study,we used global MODIS(moderate-resolution imaging spectroradiometer)terrestrial ET(MOD16)products,Morlet wavelet analysis,and simple linear regression to investigate the spatiotemporal variations of ET,PET,reference ET(ET0),and aridity index(AI)in mid-western pastoral regions of China(including Gansu Province,Qinghai Province,Ningxia Hui Autonomous Region,and part of Inner Mongolia Autonomous Region)from 2001 to 2016.The results showed that the overall ET gradually increased from east to southwest in the study area.Actual ET showed an increasing trend,whereas PET tended to decrease from 2001 to 2016.The change in ET was affected by vegetation types.During the study period,the average annual ET0 and AI tended to decrease.At the monthly scale within a year,AI value decreased from January to July and then increased.The interannual variations of ET0 and AI showed periodicity with a main period of 14 a,and two other periodicities of 11 and 5 a.This study showed that in recent years,drought in these pastoral regions of mid-western China has been alleviated.Therefore,it is foreseeable that the demand for irrigation water for agricultural production in these regions will decrease.展开更多
Rainfall and evapotranspiration are two vital elements for food production under rainfed agriculture. This study aims at investigating the combined changes in these variables in the form of aridly index in the souther...Rainfall and evapotranspiration are two vital elements for food production under rainfed agriculture. This study aims at investigating the combined changes in these variables in the form of aridly index in the southern Senegal. The temporal trends in annual and monthly (from May to October) aridity index, rainfall and evapotranspiration are examined and adaptation strategies to the vulnerability of rainfed rice cultivation to the changes are developed. The results show a significant decreasing trend in annual rainfall at all study locations for the period 1922-2015. When analyzing the trends in sub-periods, there are two clear patterns in the annual rainfall series: a decreasing trend for the period 1922-1979 and a reversal increasing trend for the period 1980-2015. An increasing trend is also observed in annual reference evapotranspiration. The results reveal that the region will be drier with a significant increase in aridity at the annual and most monthly series. Appropriate adaptation strategies should be implemented to diminish the adverse influence of the increasing aridity on rice productivity for a sustainable agriculture.展开更多
The olive species(Olea europaea L.)is an ancient traditional crop grown under rainfed conditions in the Mediterranean Basin.In response to the growing national and international demand for olive oil,the olive cultivar...The olive species(Olea europaea L.)is an ancient traditional crop grown under rainfed conditions in the Mediterranean Basin.In response to the growing national and international demand for olive oil,the olive cultivars are introduced into highly arid new bioclimatic areas.Subsequently,the morpho-physiology and phytochemistry of olive trees are potentially changing among cultivar types and geographical conditions.In the present work,we have undertaken an assessment on the impacts of geographical location and cultivar types on the leaf morpho-physiology and phytochemistry of olive trees.Thus,leaves of the two most cultivated olive tree varieties,Chemlal and Sigoise,were collected from three geographical regions(Setif,Batna,and Eloued)with increasing aridity in Algeria.Leaf samples from the geographical regions were analyzed using the standard physiological experiment,colorimetric method,and a chromatography assay.Leaves of both cultivars exhibited a significant variance in terms of the leaf shape index but not for the leaf tissue density,specific leaf weight,and specific leaf area.Photosynthetic pigment contents were affected by both cultivar type and geographical location,with the lowest pigment content recorded in the Sigoise cultivar from the Setif region.Compared with the Setif and Batna regions,dried leaves of both cultivars from the Eloued region showed the higher levels of the total polyphenol,total flavonoid,and total tannin,as well as a better antioxidant capacity.Liquid chromatography-mass spectrometry analysis of all leaf extracts identified the following phenolic acids as major compounds:oleuropein,naringin,apigenin-7-O-glucoside,kaempferol,quercetin,quercitrin,luteolin-7-O-naringenin,and quinic acid.Lower contents were found for p-Coumaric acid,trans-Ferulic acid,hyperoside,rutin,apigenin,caffeic acid,protocatechuic acid,o-Coumaric acid,and gallic acid.Also,epicatechin and catechin+were not found in the leaf extracts of the Sigoise cultivar.The leaf organic extracts in both cultivars displayed promising anti-cancer activity that was affected by geographical location and organic solvent polarity.Briefly,although increasing aridity and soil organic and mineral deficiency affected the leaf morpho-physiological parameters,both cultivars sustained a chemical richness,a good antioxidant,and an anti-tumoral capacity in leaves.Furthermore,the findings revealed that regardless the olive tree genotype,there was a significant impact of geographical location on the leaf morpho-physiology,bioactivity,and chemical composition,which may consequently modulate the growth and oil production of olive trees.展开更多
Aridity index reflects the exchanges of energy and water between the land surface and the atmosphere,and its variation can be used to forecast drought and flood patterns,which makes it of great significance for agricu...Aridity index reflects the exchanges of energy and water between the land surface and the atmosphere,and its variation can be used to forecast drought and flood patterns,which makes it of great significance for agricultural production.The ratio of potential evapotranspiration and precipitation is applied to analyse the spatial and temporal distributions of the aridity index in the Belt and Road region under the 1.5℃and 2.0℃global warming scenarios on the basis of outputs from four downscaled global climate models.The results show that:(1)Under the 1.5℃warming scenario,the area-averaged aridity index will be similar to that in 1986-2005(around 1.58),but the changes vary spatially.The aridity index will increase by more than 5%in Central-Eastern Europe,north of West Asia,the monsoon region of East Asia and northwest of Southeast Asia,while it is projected to decrease obviously in the southeast of West Asia.Regarding the seasonal scale,spring and winter will be more arid in South Asia,and the monsoon region of East Asia will be slightly drier in summer compared with the reference period.While,West Asia will be wetter in all seasons,except winter.(2)Relative to 1986-2005,both areal averaged annual potential evapotranspiration and precipitation are projected to increase,and the spatial variation of aridity index will become more obvious as well at the 2.0℃warming level.Although the aridity index over the entire region will be maintained at approximately 1.57 as that in 1.5℃,the index in Central-Eastern Europe,north of West Asia and Central Asia will grow rapidly at a rate of more than 20%,while that in West Siberia,northwest of China,the southern part of South Asia and West Asia will show a declining trend.At the seasonal scale,the increase of the aridity index in Central-Eastern Europe,Central Asia,West Asia,South Asia and the northern part of Siberia in winter will be obvious,and the monsoon region in East Asia will be drier in both summer and autumn.(3)Under the scenario of an additional 0.5℃increase in global temperature from 1.5℃to 2.0℃,the aridity index will increase significantly in Central Asia and north of West Asia but decrease in Southeast Asia and Central Siberia.Seasonally,the aridity index in the Belt and Road region will slightly increase in all other seasons except spring.Central Asia will become drier annually at a rate of more than 20%.The aridity index in South Asia will increase in spring and winter,and that in East Asia will increase in autumn and winter.(4)To changes of the aridity index,the attribution of precipitation and potential evapotranspiration will vary regionally.Precipitation will be the major influencing factor over southern West Asia,southern South Asia,Central-Eastern Siberia,the non-monsoon region of East Asia and the border between West Asia and Central Asia,while potential evapotranspiration will exert greater effects over Central-Eastern Europe,West Siberia,Central Asia and the monsoon region of East Asia.展开更多
A distinct aridity trend in China in last 100 years is presented by applying a linear fitting to both the climate records and the hydrological records, which is supported by evidence of environmental changes and seems...A distinct aridity trend in China in last 100 years is presented by applying a linear fitting to both the climate records and the hydrological records, which is supported by evidence of environmental changes and seems to be associated with a global warming trend during this period.The Mann Kendall Rank statistic test reveals a very interesting feature that the climate of China entered into a dry regime abruptly in about 1920's, which synchronized with the rapid warming of the global temperature at almost the same time.According to an analysis of the meridional profile of observed global zonal mean precipitation anomalies during the peak period of global wanning (1930-1940), the drought occurred in whole middle latitude zone (25°N-55°N) of the Northern Hemisphere, where the most part of China is located in. Although this pattern is in good agreement with the latitude distribution of the difference of zonal mean rates of precipitation between 4 × CO2 and 1 × CO2 simulated by climate model (Manabe and Wetherald, 1983), more studies are required to understand the linkage between the aridity trend in China and the greenhouse effect.The EOF analysis of the Northern Hemisphere sea level pressure for the season of June to August shows an abrupt change of the time coefficient of its first eigenvector from positive to negative in mid-1920's, indicating an enhancement of the subtropical high over Southeast Asia and the western Pacific after that time. This is an atmospheric circulation pattern that is favorable to the development of dry climate in China.展开更多
Asian aridity can be traced back to the early Cenozoic(e.g.,Guo et al.,2008;Licht et al.,2016;Li et al.,2018a).Previous modelling studies focus mainly on the monsoon climate during the early Cenozoic,and studies for t...Asian aridity can be traced back to the early Cenozoic(e.g.,Guo et al.,2008;Licht et al.,2016;Li et al.,2018a).Previous modelling studies focus mainly on the monsoon climate during the early Cenozoic,and studies for the Asian aridity are still limited(e.g.,Huber and Goldner,2012;Zhang et al.,2012;Li et al.,2018b).Here Asian aridity during the early Cenozoic is investigated through climate modelling by changing atmospheric CO2 concentration,orbital parameters,and topography.展开更多
Aim to linking the variability of drought in northwest China to the oceanic influence of North Atlantic SSTs at the background of global warming and at the regional climate change shifting stages, year aridity index v...Aim to linking the variability of drought in northwest China to the oceanic influence of North Atlantic SSTs at the background of global warming and at the regional climate change shifting stages, year aridity index variations in northwest China and summer North Atlantic sea surface temperature （SST） variations are examined for the 44 a period of 1961-2004 using singular value decomposition （SVD） analysis. Results show that the SST anomalies （SSTA）in the North Atlantic in summer reflected three basic models. The first SVD mode of SST pattern shows a dipole - like variation with the positive center located at southwest and negative center at northeast of extratropical North Atlantic. And it strongly relates to the positive trend in AI variation in northwest China. The second coupled modes display the coherent positive anomalies in extratropical North Atlantic SST and the marked opposite trend of AI variability between north and south of Xinjiang. In addition, the lag correlation analysis of the first mode of SSTA and geopotential heights at 500 hPa variations also shows that the indication of the former influencing the latter configuration, which result in higher air temperature and less precipitation when the SSTA in the North Atlantic Ocean in summer motivated Eurasian circulation of EA pattern, further to influence the wet - dry variations in northwest China by the ocean-to - atmosphere forcing.展开更多
A comprehensive analysis of climate data(1958-2018)is carried out at the national scale in India to assess spatiotemporal variation in aridity.The aridity is analyzed using UNEP(United Nations Environment Programme)Ar...A comprehensive analysis of climate data(1958-2018)is carried out at the national scale in India to assess spatiotemporal variation in aridity.The aridity is analyzed using UNEP(United Nations Environment Programme)Aridity Index(AI),which is the ratio between Precipitation(P)and Potential Evapotranspiration(PET).Freely available Terra-Climate database,P and PET variables,offered an unprecedented opportunity for monitoring variations in AI and aridity index anomalies(AIA)at inter-seasonal and inter-decadal basis.The study also assesses longer term patterns of P and AI anomalies with vegetation anomalies.The results indicate that significant clustered areas with maximum dryness are located at west-central part of India,the state of Maharashtra.Overall,there is a gradual increase in the extent of arid zone during 60-year period and spatially maximum extent of percentage change in aridity area is observed.The change patterns of AI in India are largely driven by the changing patterns of precipitation.The maximum impact of decline in precipitation on AIA was observed during Kharif season frequently,for every 4-5 years during 1972-1992.The pattern repeated in the last few recent years(2013-2018),the decline in precipitation resulted increased aridity.The study also reveals that the availability and usage of irrigation sources have increased from 2014 to 2018.Thus,despite of less precipitation positive vegetation has been resulted in this period.The findings are important to understand the impacts of climate change on land use pattern,and land and water resource management.展开更多
基金National Natural Science Foundation of China,No.42377460。
文摘Climate change significantly affects the arid/humid processes and patterns in China,directly impacting management decisions related to adaptive agriculture and water resources management,desertification control,and spatial ecological restoration.However,current studies primarily focus on changes in arid/humid climate variables,lacking quantitative characterization of the dynamic evolution of areal systems and their nonlinear responses.Based on the data of national meteorological stations from 1961 to 2020,we systematically quantified the nonlinear response of arid/humid patterns to climate change.The results revealed that 6.98%of eco-geographical arid/humid regions underwent type shifts over the past six decades,with 4.95%transitioning toward wetter conditions.Humid and semi-arid regions expanded significantly while sub-humid and arid regions contracted significantly.In the late 1990s,trends of the humid and sub-humid region shifted.Humid region contraction in northern China was driven primarily by precipitation decline,whereas the Tibetan Plateau responded to increasing potential evapotranspiration.During the same period,the retreat rate of the arid region slowed,linked to intensified aridification in the west part of northern China and a decelerating wetting trend in northwest China,both primarily driven by precipitation trends.Our study reveals the nonlinear response of the arid/humid patterns under climate change,providing a scientific basis for the improvement of regional climate resilience.
基金Under the auspices of the General Project of Science and Technology Department of Shaanxi Province(No.2023-JCYB-264)General Program of National Natural Science Foundation of China(No.41801004,42371008,42471012)。
文摘Riparian dunes in deserts exhibit unique geographic features due to aeolian-fluvial interactions.In this study,we collected 510 surface sediment samples from eight drainage basins and conducted a systematic analysis to examine the grain size characteristics of major riparian dunes in the typical cold and arid deserts of China.The results indicate that major riparian dunes of deserts in study area can be classified into three types based on their grain size characteristics.The Bartlett test of sphericity and the Kaiser-Meyer-Olkin(KMO)test were also performed,and their significance values were found to be 0.000 and 0.584,respectively.The results of the principal component analysis revealed that the cumulative contribution rate of the total variance reached 85.9%for the two principal components with characteristic roots greater than 1.0.The primary principal component included medium sand,whereas the secondary principal component included fine sand.We conducted a cluster analysis and classified the samples into three major types.Type I rivers include the Keriya River,Langqu River,Tora River and Heihe River,which are characterized by by fine particle size,and well-sorted.Type II includes Mu Bulag River,Kuye River,and the Xar Moron River,Compared with type I,it has a relatively coarser mean grain size and relatively poor sorting for this type.Type III includes the Maquan River,which is characterized mainly by fine sand and medium sand,accounting for more than 90%,and the sorting coefficient(0.52)suggests relatively well sorting in this pattern.Moreover,principal component analysis was applied to determine the particle sizes of samples from different watersheds.Moreover,these sediments exhibit both hydromorphic and aeolian features.At the drainage basin scale,the mode and intensity of aeolian-fluvial interactions depend on climatic conditions.In arid and semi-arid climate regions,wind is the dominant force,and the grain size exhibits significant aeolian features.Conversely,in the semi-humid region,flowing water is the dominant force,and riparian dunes in this region are formed by aeolian-fluvial interaction.The angle between the wind direction and flow direction in different reaches influences both the supply of sediment sources and the development of riparian dunes.This study will provide a new perspective for evaluating aeolian-fluvial interactions on riparian dunes in the deserts of China’s cold and arid regions.
基金supported by the Tunisian Ministry of Higher Education and Scientific Research,Research General Direction,Excellence Project(21P2ES-D1P3)the International Foundation for Science(IFS)(I1-D-6596-1).
文摘Under arid and semi-arid bioclimates,steppes are increasingly threatened by anthropogenic disturbance and climatic variability,which strongly affects ecosystem functioning and subsequently leads to desertification.We investigated the morphological and physiological responses of Stipa tenacissima L.across three disturbance levels(undisturbed,slightly disturbed,and highly disturbed)in three Tunisian steppe areas(Kasserine,Sidi Bouzid,and Sfax).Morphological and physiological traits were monitored over one year,together with microclimatic variables.Result showed that disturbance was a strong driver of plant functional dynamics,with significant effects on all traits and strong interactions with site and season.Disturbance reduced photosynthetic activity and water use efficiency,particularly in Sfax,where plants adopted conservative strategies(i.e.,higher leaf dry matter content and reduced leaf area).In contrast,undisturbed populations maintained a stronger coordination between physiological and morphological traits.Seasonal analyses revealed that disturbance amplified physiological stress with limited recovery.Heatmap analyses further showed that disturbance weakened trait coordination and reshaped trade-offs between acquisitive and conservative traits.Partial least squares-path modeling showed that morphology strongly drove physiological performance(path coefficient=0.48).Disturbance(path coefficient=0.41)and tussock cover(path coefficient=0.47)influenced morphology both directly and indirectly through their effects on physiology.In conclusion,S.tenacissima adjusts physiological and morphological traits under disturbance,favoring stress tolerance,while undisturbed sites maintain high physiological efficiency and coordinated trait integration,reflecting a trade-off between survival and performance while overriding local site differences.Disturbance strongly restructures trait networks,drives site-specific adjustments,and modulates the seasonal balance between morphological stability and physiological flexibility.
基金support provided by the Research Grant Office at Sharif University Technology by way of grants G4010902 and QB020105 is gratefully acknowledged.
文摘This study presents a multi-physical modeling approach to analyze the dynamics of moisture potential and stress-deformation features near deep desiccation cracks in clayey soils under three consecutive years’climate variability in an arid region.A triple research approach of statistical analysis,analytical framework,and numerical modeling was used to investigate the complex thermo-hydro-mechanical behavior of desiccation-cracked soil,incorporating realistic climatic data of Qom,Iran.The results revealed the interplay between stress,strain,and pore water pressure over time,demonstrating that soil experiences significant swelling and shrinkage due to cyclic wetting and drying.The horizontal stress distribution shows compressive stress concentration at crack tips during wetting,transitioning to tensile stresses uniformly across the soil surface during drying paths.Similarly,vertical stress distributions exhibit localized compressive stresses along crack boundaries during wetting and tensile stresses during drying,highlighting the critical stress conditions at crack tips.The model differentiates between microstructural and macrostructural changes in porosity.Annual trends in micro-porosity revealed cyclic-dependent behavior,with significant volumetric changes occurring in the first year,stabilizing with successive cycles.The results also indicated that part of the volumetric changes are irreversible,with volumetric plastic strain increasing exponentially but at a decreasing rate over three years.Principal stress analysis indicates a shift from compressive to tensile stress states around cracks,driven by climate-induced wetting and drying cycles.These findings underscore the critical role of climate variability in shaping cracked soil behavior in arid regions,providing insights into the heterogeneous behavior of cracked soil surfFicial layers.
文摘Arid and semi-arid ecosystems are prone to extensive fires due to specific climatic conditions,sparse vegetation cover,and high density of fine fuels.Understanding the flammability characteristics of land covers is essential for fire management and designing land restoration programs in arid and semi-arid ecosystems.This study provided a new approach to evaluate the flammability of shrublands and woodlands using flammability indices(FIs)including time to ignition(TI),duration of combustion(DC),and flame height(FH)of plant species and their relative frequencies in the Dalfard Basin of southeastern Iran.The results showed that there was a significant difference in FIs between land covers.Shrublands had higher flammability potential compared with woodlands.Plant moisture content had a negative relationship with TI(P<0.010)and no significant relationship with DC and FH(P>0.050).Artemisia spp.,Astragalus gossypinus Fischer,Amygdalus scoparia Spach,and Cymbopogon jwarancusa(Jones)Schult.had the highest FI.Tree species such as Rhazya stricta Decne.,and Pistacia atlantica Desf.showed greater resistance to fire.Using principal component analysis,the relationship between species and FIs was examined,and TI of wet fuel was the most important FI in relation to species.Structural equation model showed that life form(P<0.001)was the most important flammability driver.Precipitation(P<0.010)and legume species(P<0.010)were significantly related to the flammability in arid land.This study emphasizes the importance of managing high-risk species and using resistant species in vegetation restoration and shows that combining species FIs with their abundance is an effective tool for assessing fire risk and fuel management at the plant community scale.
基金supported by the National Key Research and Development Program of China(2023YFC3208701)the Fundamental Research Funds for the Central Universities(B210201035).
文摘Surface water plays an essential role in the ecohydrological cycle,especially in water-scarce regions.Changes in surface water restrict social,economic,and agricultural development.However,the patterns and underlying causes of surface water changes over varying frequencies in global arid regions remain unclear.Thus,this study investigated the changes in surface water and the underlying causes using the trend analysis and Spearman correlation coefficient on the basis of multi-source remote sensing and climate datasets across global arid regions during 2000–2020.The surface water was divided into temporary surface water(TSW),seasonal surface water(SSW),and permanent surface water(PSW)by calculating the surface water inundation frequency.Considering that surface water may be influenced by precipitation in the upper basins,we analyzed the response of surface water area to climatic factors at the basin scale.The area of all surface water(ASW)increased dramatically in global arid regions from 2000 to 2020,increasing from 61.88×104 to 67.40×104 km^(2);however,this increase was accompanied by a decrease in surface water inundation frequency.TSW increased by 55.46%relative to its area in 2000,with a net change rate of 3284.00 km^(2)/a.Changes in surface water were predominantly observed in the Kyzylkum Desert in Central Asia,the Thar Desert in southwestern Asia,and the deserts in Oceania.Precipitation had a significant effect on SSW and TSW at the basin scale.The correlation between precipitation and SSW area can reach 0.808 in the Indus River Basin of the Thar Desert(P<0.01).The findings provide a more comprehensive understanding of surface water variability in global arid regions,carrying significant practical implications for the scientific management of surface water at different frequencies.
基金funded by King Abdullah City for Atomic and Renewable Energy(KACARE),grant number“PC-2020-1”.
文摘High-concentration photovoltaic(HCPV)systems present significant thermal management challenges due to the intense heat fluxes generated under concentrated solar irradiation,especially in arid environments.Effective heat dissipation is critical to prevent performance degradation and structural failure.This study investigates the thermal performance and design optimization of an enhanced HCPV module,integrating numerical,analytical,and experimental methods.A coupled optical-thermal-electrical model was developed to simulate ray tracing,heat transfer,and temperature-dependent electrical behaviour,with predictions validated under real-world desert conditions.Compared to a baseline commercial module operating at 106℃,the optimized design achieved a peak temperature reduction of 16℃,lowering the cell temperature to 90℃under a concentration ratio of 961×and direct normal irradiance(DNI)of 950 W/m^(2).The total thermal resistance was reduced from 0.25 to 0.15 K/W(a 40%improvement),and the electrical efficiency increased from 37.5%to 38.6%,representing a relative gain of approximately 3.1%.The system consistently maintained a fill factor exceeding 78%,underscoring stable performance under high thermal load.These findings demonstrate that targeted thermal design,informed by integrated modeling,is essential for unlocking the reliability and efficiency of high-flux solar energy systems.
基金supported by the Natural Science Foundation of Xinjiang Uygur Autonomous Region(2022D01B109)the Tianchi Doctoral Program of Xinjiang Uygur Autonomous Region(BS2021007).
文摘Within the context of global climate change and rapid urbanization,increasing urban resilience(UR)is especially important in the arid region of Northwest China(ANC),where fragile ecosystems and an uneven water distribution create significant sustainability challenges.In this study,a coupled UR-water ecosystem services(WESs)framework was developed on the basis of 1-km resolution remote sensing data for the 2000–2020 period obtained from the Landsat series,Defense Meteorological Satellite Program(DMSP)/Operational Linescan System(OLS),and Global Precipitation Measurement(GPM),among other sources.Within the framework,the Integrated Valuation of Ecosystem Services and Tradeoffs(InVEST)model was incorporated to provide a WES indicator system.Moreover,entropy weighting was employed to quantify both UR and WES indicators;the coupling coordination degree(CCD)model was used to measure the coupled relationship between UR and WESs;an extreme gradient boosting(XGBoost)-SHapley Additive exPlanations(SHAP)interpretation approach was adopted to identify key drivers and underlying mechanisms;and Geographically Weighted Regression(GWR)was applied to capture spatial distribution characteristics of major driving factors.The results indicated that UR steadily increased from 4.60×10^(-3) to 10.24×10^(-3),whereas WESs followed an inverted V-shaped trend,with a peak value observed in 2010(11.84×10^(-3)).The CCD remained consistently low(mean:0.0166–0.0246)and exhibited considerable spatial heterogeneity.Notably,the degree of coordination was greater in the oasis and mountain core areas but significantly lower at desert areas.XGBoost-SHAP model analysis revealed six key drivers influencing various states of the CCD between UR and WESs systems.The contributions of these factors could be ranked as follows:water yield(WY;24.30%)>farmland area per capita(FP;21.10%)>gross domestic product(GDP)per capita(GDPC;19.00%)>soil retention(SR;14.90%)>population density(PD;5.42%)>water purification(WP;4.40%).In contrast,in UR system,WP(53.66%)and SR(31.62%)served as the dominant drivers.Moreover,the dominant drivers shifted from a combination of natural and socioeconomic factors in StateⅠ(sustainable high resilience)to primarily socioeconomic factors in StateⅢ(unsustainable low resilience).SR and WP exerted positive moderating effects,whereas socioeconomic factors such as GDPC and PD exerted inhibitory effects on the coordination relationship.This research highlights that UR in the ANC region is limited mainly by water scarcity,weak feedback loops,and spatial variability,emphasizing the need for tailored intervention strategies.
基金Knowledge Innovation Project of Chinese Academy of Sciences, KZCX2-310-05 National Natural Science Foundation of China, No.4007
文摘Based on the data up to 1999 from hydroclimatological departments, this pape analyzes the climatic divide implications of the Qinling Mountains in regional response to the process of climate warming, due to which the grades of dryness/wetness (GDW) in 100 years show that the northern region has entered a drought period, while the southern is a humid period. In a course of ten years, the D-value of annual average air temperature over southern Shaanxi (the Hanjiang Valley) and the Central Shaanxi Plain (the Guanzhong Plain) has narrowed, i.e., the former with a slight change and the latter with rapid increase in temperature. Both regions were arid with the decrease in precipition D-value, namely the plain became warmer while the south was drier. The Qinling Mountains play a pronounced role in the climatic divide. The runoff coefficient (RC) of the Weihe River decreases synchronously with that of the Hanjiang due to climate warming. The RC of Weihe dropped from 0.2 in the 1950s to less than 0.1 in the 1990s. The Weihe Valley (the Guanzhong Plain) is practically an arid area due to shortage of water. The successive 0.5, 1.0°C temperature anomaly over China marks, perhaps, the improtant transition period in which the environment becomes more vulnerable than before. The study shows the obvious trend of environmental aridity, which is of help to the understanding of regional response to global climate change.
基金supported by the National Natural Science Foundation of China(31570453,31170381,31270502,31300386)the PhD Candidate Research Innovation Fund of Nankai Universitythe Doctoral Fund of Tianjin Normal University(52XB1208)
文摘As the increases of climatic aridity and grazing intensity, shrubs play an increasingly important role in grassland ecosystem in arid and semi-arid regions, and its abundance also generally increases. However, the effects of climatic aridity and grazing intensity on sexual reproduction of shrubs in grassland remain largely unclear. In order to understand the effects of grazing intensity and climatic drought stress, and their interaction on seed production of shrub species, we examined the seed number, seed weight and seed yield of Caragana stenophylla under three grazing intensities （fenced, mild grazing and severe grazing） across a climatic aridity gradient （semi-arid, arid, very arid and intensively arid zones） in the Inner Mongolia Steppe, northern China during 2012-2013. The seed number, seed weight and seed yield gradually increased from the semi-arid to the very arid zones, but decreased from the very arid to the intensively arid zones in fenced plots. The seed number and seed yield decreased from the semi-arid to the intensively arid zones in mild and severe grazing treatment plots, therefore, grazing enhanced the suppression effect of climatic aridity on seed production of C. stenophylla. The seed number and seed yield gradually decreased as grazing intensity increased. The seed weight was highest in severe grazing plots, followed by the mild grazing plots and then the fenced plots. Precipitation varied interannually during the study period. We observed that the seed number seed weight and seed yield were lower in the low precipitation year （2013） than in the high precipitation year （2012）. As climatic drought stress increased, the negative effects of grazing on seed production of C. stenophylla also gradually increased. Our results indicated that climatic drought stress may contribute to the encroachment of C. stenophylla shrub in arid zones by promoting its seed production. However, grazing had negative effects on sexual reproduction of C. stenophylla, and the combined effects of drought stress and grazing seriously suppressed sexual reproduction of C. stenophylla in the intensively arid zone.
基金National Basic Research Program of China,No.2012CB955304
文摘Detecting variation trend in dry-wet conditions can provide information for devel- oping strategic measures to mitigate the impacts of global warming, particularly in dry regions Taking the hilly region of northern Shaanxi on the Loess Plateau as a case area, this study analyzed the trend of aridity variation during 1981-2012, and explored the effect of vegetation restoration promoted by the Grain-for-Green （GFG） program implemented in 1999. The re- sults indicated that the aridity in the region was non-significantly increased by 0.88% per year during 1981-2012, showing a drying trend. This drying trend and amplitude were changed by the influence of vegetation restoration promoted by the GFG program, based on two findings. The first one was that the aridity variation tended to increase during 1981-1999 while it turned to decrease during 2000-2012, with the regional mean relative change rate changed from 2.45% to -1.06%. This distinction was more remarkable in the loess gully region, where the vegetation was improved more obviously. The second one was that the mean vegetation coverage as indicated by EVI increased by 0.90% to 4.32% per year at county level, while the aridity decreased by 0.14% to 2.32% per year during 2000-2012. The regression analysis using the mean county data indicated that the change rate of aridity was negatively related to that of EVI with the coefficient of determination （R2） of 0.56, illustrating that around half of the aridity decline was explained by the EVI change. The mechanism of this effect was compli- cated, but it was found that the wind speed decline induced by the vegetation improvement could be an important contributor. It is concluded that the region became drier during 1981-2012, but the eco-restoration reduced the drying speed. However, this conclusion is involved in uncertainties, and further study based on experiments is needed to confirm the effect of the GFG-promoted vegetation restoration.
基金This work was supported by the earmarked fund for China Agriculture Research System of Ministry of Finance and Ministry of Agriculture and Rural Affairs(CARS-34)the National Key Research and Development Program of China(2016YFC0400302).
文摘Mid-western China is one of the most sensitive and fragile areas on the Earth.Evapotranspiration(ET)is a key part of hydrological cycle in these areas and is affected by both global climate change and human activities.The dynamic changes in ET and potential evapotranspiration(PET),which can reflect water consumption and demand,are still unclear,and there is a lack of predictive capacity on drought severity.In this study,we used global MODIS(moderate-resolution imaging spectroradiometer)terrestrial ET(MOD16)products,Morlet wavelet analysis,and simple linear regression to investigate the spatiotemporal variations of ET,PET,reference ET(ET0),and aridity index(AI)in mid-western pastoral regions of China(including Gansu Province,Qinghai Province,Ningxia Hui Autonomous Region,and part of Inner Mongolia Autonomous Region)from 2001 to 2016.The results showed that the overall ET gradually increased from east to southwest in the study area.Actual ET showed an increasing trend,whereas PET tended to decrease from 2001 to 2016.The change in ET was affected by vegetation types.During the study period,the average annual ET0 and AI tended to decrease.At the monthly scale within a year,AI value decreased from January to July and then increased.The interannual variations of ET0 and AI showed periodicity with a main period of 14 a,and two other periodicities of 11 and 5 a.This study showed that in recent years,drought in these pastoral regions of mid-western China has been alleviated.Therefore,it is foreseeable that the demand for irrigation water for agricultural production in these regions will decrease.
文摘Rainfall and evapotranspiration are two vital elements for food production under rainfed agriculture. This study aims at investigating the combined changes in these variables in the form of aridly index in the southern Senegal. The temporal trends in annual and monthly (from May to October) aridity index, rainfall and evapotranspiration are examined and adaptation strategies to the vulnerability of rainfed rice cultivation to the changes are developed. The results show a significant decreasing trend in annual rainfall at all study locations for the period 1922-2015. When analyzing the trends in sub-periods, there are two clear patterns in the annual rainfall series: a decreasing trend for the period 1922-1979 and a reversal increasing trend for the period 1980-2015. An increasing trend is also observed in annual reference evapotranspiration. The results reveal that the region will be drier with a significant increase in aridity at the annual and most monthly series. Appropriate adaptation strategies should be implemented to diminish the adverse influence of the increasing aridity on rice productivity for a sustainable agriculture.
文摘The olive species(Olea europaea L.)is an ancient traditional crop grown under rainfed conditions in the Mediterranean Basin.In response to the growing national and international demand for olive oil,the olive cultivars are introduced into highly arid new bioclimatic areas.Subsequently,the morpho-physiology and phytochemistry of olive trees are potentially changing among cultivar types and geographical conditions.In the present work,we have undertaken an assessment on the impacts of geographical location and cultivar types on the leaf morpho-physiology and phytochemistry of olive trees.Thus,leaves of the two most cultivated olive tree varieties,Chemlal and Sigoise,were collected from three geographical regions(Setif,Batna,and Eloued)with increasing aridity in Algeria.Leaf samples from the geographical regions were analyzed using the standard physiological experiment,colorimetric method,and a chromatography assay.Leaves of both cultivars exhibited a significant variance in terms of the leaf shape index but not for the leaf tissue density,specific leaf weight,and specific leaf area.Photosynthetic pigment contents were affected by both cultivar type and geographical location,with the lowest pigment content recorded in the Sigoise cultivar from the Setif region.Compared with the Setif and Batna regions,dried leaves of both cultivars from the Eloued region showed the higher levels of the total polyphenol,total flavonoid,and total tannin,as well as a better antioxidant capacity.Liquid chromatography-mass spectrometry analysis of all leaf extracts identified the following phenolic acids as major compounds:oleuropein,naringin,apigenin-7-O-glucoside,kaempferol,quercetin,quercitrin,luteolin-7-O-naringenin,and quinic acid.Lower contents were found for p-Coumaric acid,trans-Ferulic acid,hyperoside,rutin,apigenin,caffeic acid,protocatechuic acid,o-Coumaric acid,and gallic acid.Also,epicatechin and catechin+were not found in the leaf extracts of the Sigoise cultivar.The leaf organic extracts in both cultivars displayed promising anti-cancer activity that was affected by geographical location and organic solvent polarity.Briefly,although increasing aridity and soil organic and mineral deficiency affected the leaf morpho-physiological parameters,both cultivars sustained a chemical richness,a good antioxidant,and an anti-tumoral capacity in leaves.Furthermore,the findings revealed that regardless the olive tree genotype,there was a significant impact of geographical location on the leaf morpho-physiology,bioactivity,and chemical composition,which may consequently modulate the growth and oil production of olive trees.
文摘Aridity index reflects the exchanges of energy and water between the land surface and the atmosphere,and its variation can be used to forecast drought and flood patterns,which makes it of great significance for agricultural production.The ratio of potential evapotranspiration and precipitation is applied to analyse the spatial and temporal distributions of the aridity index in the Belt and Road region under the 1.5℃and 2.0℃global warming scenarios on the basis of outputs from four downscaled global climate models.The results show that:(1)Under the 1.5℃warming scenario,the area-averaged aridity index will be similar to that in 1986-2005(around 1.58),but the changes vary spatially.The aridity index will increase by more than 5%in Central-Eastern Europe,north of West Asia,the monsoon region of East Asia and northwest of Southeast Asia,while it is projected to decrease obviously in the southeast of West Asia.Regarding the seasonal scale,spring and winter will be more arid in South Asia,and the monsoon region of East Asia will be slightly drier in summer compared with the reference period.While,West Asia will be wetter in all seasons,except winter.(2)Relative to 1986-2005,both areal averaged annual potential evapotranspiration and precipitation are projected to increase,and the spatial variation of aridity index will become more obvious as well at the 2.0℃warming level.Although the aridity index over the entire region will be maintained at approximately 1.57 as that in 1.5℃,the index in Central-Eastern Europe,north of West Asia and Central Asia will grow rapidly at a rate of more than 20%,while that in West Siberia,northwest of China,the southern part of South Asia and West Asia will show a declining trend.At the seasonal scale,the increase of the aridity index in Central-Eastern Europe,Central Asia,West Asia,South Asia and the northern part of Siberia in winter will be obvious,and the monsoon region in East Asia will be drier in both summer and autumn.(3)Under the scenario of an additional 0.5℃increase in global temperature from 1.5℃to 2.0℃,the aridity index will increase significantly in Central Asia and north of West Asia but decrease in Southeast Asia and Central Siberia.Seasonally,the aridity index in the Belt and Road region will slightly increase in all other seasons except spring.Central Asia will become drier annually at a rate of more than 20%.The aridity index in South Asia will increase in spring and winter,and that in East Asia will increase in autumn and winter.(4)To changes of the aridity index,the attribution of precipitation and potential evapotranspiration will vary regionally.Precipitation will be the major influencing factor over southern West Asia,southern South Asia,Central-Eastern Siberia,the non-monsoon region of East Asia and the border between West Asia and Central Asia,while potential evapotranspiration will exert greater effects over Central-Eastern Europe,West Siberia,Central Asia and the monsoon region of East Asia.
文摘A distinct aridity trend in China in last 100 years is presented by applying a linear fitting to both the climate records and the hydrological records, which is supported by evidence of environmental changes and seems to be associated with a global warming trend during this period.The Mann Kendall Rank statistic test reveals a very interesting feature that the climate of China entered into a dry regime abruptly in about 1920's, which synchronized with the rapid warming of the global temperature at almost the same time.According to an analysis of the meridional profile of observed global zonal mean precipitation anomalies during the peak period of global wanning (1930-1940), the drought occurred in whole middle latitude zone (25°N-55°N) of the Northern Hemisphere, where the most part of China is located in. Although this pattern is in good agreement with the latitude distribution of the difference of zonal mean rates of precipitation between 4 × CO2 and 1 × CO2 simulated by climate model (Manabe and Wetherald, 1983), more studies are required to understand the linkage between the aridity trend in China and the greenhouse effect.The EOF analysis of the Northern Hemisphere sea level pressure for the season of June to August shows an abrupt change of the time coefficient of its first eigenvector from positive to negative in mid-1920's, indicating an enhancement of the subtropical high over Southeast Asia and the western Pacific after that time. This is an atmospheric circulation pattern that is favorable to the development of dry climate in China.
基金granted by the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDA20070103)the National Natural Science Foundation of China(Grant Nos.41775088 and 41625018).
文摘Asian aridity can be traced back to the early Cenozoic(e.g.,Guo et al.,2008;Licht et al.,2016;Li et al.,2018a).Previous modelling studies focus mainly on the monsoon climate during the early Cenozoic,and studies for the Asian aridity are still limited(e.g.,Huber and Goldner,2012;Zhang et al.,2012;Li et al.,2018b).Here Asian aridity during the early Cenozoic is investigated through climate modelling by changing atmospheric CO2 concentration,orbital parameters,and topography.
基金The National Natural Science Foundation of China under contract No.904110017
文摘Aim to linking the variability of drought in northwest China to the oceanic influence of North Atlantic SSTs at the background of global warming and at the regional climate change shifting stages, year aridity index variations in northwest China and summer North Atlantic sea surface temperature （SST） variations are examined for the 44 a period of 1961-2004 using singular value decomposition （SVD） analysis. Results show that the SST anomalies （SSTA）in the North Atlantic in summer reflected three basic models. The first SVD mode of SST pattern shows a dipole - like variation with the positive center located at southwest and negative center at northeast of extratropical North Atlantic. And it strongly relates to the positive trend in AI variation in northwest China. The second coupled modes display the coherent positive anomalies in extratropical North Atlantic SST and the marked opposite trend of AI variability between north and south of Xinjiang. In addition, the lag correlation analysis of the first mode of SSTA and geopotential heights at 500 hPa variations also shows that the indication of the former influencing the latter configuration, which result in higher air temperature and less precipitation when the SSTA in the North Atlantic Ocean in summer motivated Eurasian circulation of EA pattern, further to influence the wet - dry variations in northwest China by the ocean-to - atmosphere forcing.
文摘A comprehensive analysis of climate data(1958-2018)is carried out at the national scale in India to assess spatiotemporal variation in aridity.The aridity is analyzed using UNEP(United Nations Environment Programme)Aridity Index(AI),which is the ratio between Precipitation(P)and Potential Evapotranspiration(PET).Freely available Terra-Climate database,P and PET variables,offered an unprecedented opportunity for monitoring variations in AI and aridity index anomalies(AIA)at inter-seasonal and inter-decadal basis.The study also assesses longer term patterns of P and AI anomalies with vegetation anomalies.The results indicate that significant clustered areas with maximum dryness are located at west-central part of India,the state of Maharashtra.Overall,there is a gradual increase in the extent of arid zone during 60-year period and spatially maximum extent of percentage change in aridity area is observed.The change patterns of AI in India are largely driven by the changing patterns of precipitation.The maximum impact of decline in precipitation on AIA was observed during Kharif season frequently,for every 4-5 years during 1972-1992.The pattern repeated in the last few recent years(2013-2018),the decline in precipitation resulted increased aridity.The study also reveals that the availability and usage of irrigation sources have increased from 2014 to 2018.Thus,despite of less precipitation positive vegetation has been resulted in this period.The findings are important to understand the impacts of climate change on land use pattern,and land and water resource management.
