Vegetation restoration and reconstruction are effective approaches to desertification control and achieving social and economic sustainability in desert areas.However,the self-succession ability of native plants durin...Vegetation restoration and reconstruction are effective approaches to desertification control and achieving social and economic sustainability in desert areas.However,the self-succession ability of native plants during the later periods of vegetation restoration remains unclear.Therefore,this study was conducted to bridge the knowledge gap by investigating the regeneration dynamics of artificial forest under natural conditions.The information of seed rain and soil seed bank was collected and quantified from an artificial Caragana korshinskii Kom.forest in the Tengger Desert,China.The germination tests were conducted in a laboratory setting.The analysis of species quantity and diversity in seed rain and soil seed bank was conducted to assess the impact of different durations of sand fixation(60,40,and 20 a)on the progress of vegetation restoration and ecological conditions in artificial C.korshinskii forest.The results showed that the top three dominant plant species in seed rain were Echinops gmelinii Turcz.,Eragrostis minor Host.,and Agropyron mongolicum Keng.,and the top three dominant plant species in soil seed bank were E.minor,Chloris virgata Sw.,and E.gmelinii.As restoration period increased,the density of seed rain and soil seed bank increased first and then decreased.While for species richness,as restoration period increased,it gradually increased in seed rain but decreased in soil seed bank.There was a positive correlation between seed rain density and soil seed bank density among all the three restoration periods.The species similarity between seed rain or soil seed bank and aboveground vegetation decreased with the extension of restoration period.The shape of the seeds,specifically those with external appendages such as spines and crown hair,clearly had an effect on their dispersal,then resulting in lower seed density in soil seed bank.In addition,precipitation was a crucial factor in promoting rapid germination,also resulting in lower seed density in soil seed bank.Our findings provide valuable insights for guiding future interventions during the later periods of artificial C.korshinskii forest,such as sowing and restoration efforts using unmanned aerial vehicles.展开更多
The latticed dunes in the Tengger Desert are widely distributed,and the sand-blocking fence placed here are highly susceptible to local failure due to complex wind-sand activities,posing a serious threat to the safe o...The latticed dunes in the Tengger Desert are widely distributed,and the sand-blocking fence placed here are highly susceptible to local failure due to complex wind-sand activities,posing a serious threat to the safe operation of the highway.To explore the local failure mechanism of sand-blocking fence in the latticed dune area,the local failure of sand-blocking fence in the latticed dune areas along the Wuhai-Maqin Highway in China was observed.Taking the first main ridge of the latticed dune as the placement location,the structure of the wind-sand flow field of sand-blocking fence placed at top,the bottom and the middle of windward slope was analyzed by Computational Fluid Dynamics(CFD).The results show that when placed at top of the first main ridge,the wind speed near the sand-blocking fence is the highest,up to 15.23 m/s.Therefore,the wind load strength on the sand barrier is correspondingly larger,up to 232.61 N∙m-2.As the strength of material continues to decrease,the nylon net is prone to breakage.The roots of the angle steel posts are susceptible to hollowing by vortex action,which can cause sand-blocking fence to fall over in strong wind conditions.When placed at the bottom of windward slope,wind speed drop near sand-blocking fence is greatest,with the decrease of 12.48-14.32 m/s compared to the original wind speed.This is highly likely to lead to large-scale deposition of sand particles and burial of the sand-blocking fence.When placed in the middle of windward slope,sand-blocking fence is subjected to less wind load strength(168.61N∙m-2)and sand particles are mostly deposited at the bottom of windward slope,with only a small amount of sand accumulating at the root of sand-blocking fence.Based on field observations and numerical modelling results,when the sand-blocking fence is placed in latticed dune area,it should be placed in the middle of the windward slope of the first main ridge as a matter of priority.Besides the sand-blocking fence should be placed at the top of the first main ridge,and sand fixing measures should be added.展开更多
One of the goals of grazing management in the desert steppe is to improve its ecosystem.However,relatively little is known about soil microbe communities in the desert steppe ecosystem under grazing management.In this...One of the goals of grazing management in the desert steppe is to improve its ecosystem.However,relatively little is known about soil microbe communities in the desert steppe ecosystem under grazing management.In this study,we investigated the diversity and aboveground biomass of Caragana korshinskii Kom.shrub communities in long-term fencing and grazing areas,combined with an analysis of soil physical-chemical properties and genomics,with the aim of understanding how fence management affects plant-soil-microbial inter-relationships in the desert steppe,China.The results showed that fence management(exclosure)increased plant diversity and aboveground biomass in C.korshinskii shrub area and effectively enhanced soil organic carbon(233.94%),available nitrogen(87.77%),and available phosphorus(53.67%)contents.As well,the Shannon indices of soil bacteria and fungi were greater in the fenced plot.Plant-soil changes profoundly affected the alpha-and beta-diversity of soil bacteria.Fence management also altered the soil microbial community structure,significantly increasing the relative abundances of Acidobacteriota(5.31%-8.99%),Chloroflexi(3.99%-5.58%),and Glomeromycota(1.37%-3.28%).The soil bacterial-fungal co-occurrence networks under fence management had higher complexity and connectivity.Based on functional predictions,fence management significantly increased the relative abundance of bacteria with nitrification and nitrate reduction functions and decreased the relative abundance of bacteria with nitrate and nitrite respiration functions.The relative abundances of ecologically functional fungi with arbuscular mycorrhizal fungi,ectomycorrhizal fungi,and saprotrophs also significantly increased under fence management.In addition,the differential functional groups of bacteria and fungi were closely related to plant-soil changes.The results of this study have significant positive implications for the ecological restoration and reconstruction of dry desert steppe and similar areas.展开更多
Neoproterozoic island arc assemblage of the Arabian–Nubian Shield(ANS)in the Eastern Desert(ED)of Egypt comprises juvenile suites of metavolcanics(MV),large amounts of meta-sedimentary rocks(MS),and voluminous metaga...Neoproterozoic island arc assemblage of the Arabian–Nubian Shield(ANS)in the Eastern Desert(ED)of Egypt comprises juvenile suites of metavolcanics(MV),large amounts of meta-sedimentary rocks(MS),and voluminous metagabbros-diorites(MGD)and syn-tectonic intrusions of older granitoids(OG).We report here the updates of these four rock units in terms of classification,distribution,chemical characteristics,geodynamic evolution,metamorphism,and ages.In addition,we discuss these integrated data to elucidate a reasonable and reliable model for crustal evolution in the ANS.The main features of these rock units indicate their relation to each other and the geodynamic environment dominated by early immature oceanic island arcs to primitive continental arcs.Integrated information of the island arc metavolcanic and plutonic rocks(gabbros,diorites,tonalites,and granodiorites)furnish evidence of the genetic relationships.These include proximity and a coeval nature in the field;all protolith magmas are subalkaline in nature following calc-alkaline series with minor tholeiitic affinities;common geochemical signature of the arc rocks and subduction-related magmatism;their similar enrichment in LREEs;and similar major element compositions with mafic melts derived from metasomatized mantle wedge.The volcano-sedimentary and the OG rocks underwent multiphase deformation events whereas the MGD complexes deformed slightly.Based on the magmatic,sedimentological,and metamorphic evolutions constrained by geochronological data as well as the progressive evolutionary trend from extensional to compressional regimes,a possible gradual decrease in the subducted slab dip angle is the most infl uential in any geodynamic model for arc assemblage in the ED of Egypt.展开更多
The maintenance of sand-fixing vegetation is important for the stability of artificial sand-fixing systems in which seed dispersal plays a key role.Based on field wind tunnel experiments using 11 common plant species ...The maintenance of sand-fixing vegetation is important for the stability of artificial sand-fixing systems in which seed dispersal plays a key role.Based on field wind tunnel experiments using 11 common plant species on the southeastern edge of the Tengger Desert,China,we studied the secondary seed dispersal in the fixed and semi-fixed sand dunes as well as in the mobile dunes in order to understand the limitations of vegetation regeneration and the maintenance of its stability.Our results indicated that there were significant variations among the selected 11 plant species in the threshold of wind speed(TWS).The TWS of Caragana korshinskii was the highest among the 11 plant species,whereas that of Echinops gmelinii was the lowest.Seed morphological traits and underlying surface could generally explain the TWS.During the secondary seed dispersal processes,the proportions of seeds that did not disperse(no dispersal)and only dispersed over short distance(short-distance dispersal within the wind tunnel test section)were significantly higher than those of seeds that were buried(including lost seeds)and dispersed over long distance(long-distance dispersal beyond the wind tunnel test section).Compared with other habitats,the mobile dunes were the most difficult places for secondary seed dispersal.Buried seeds were the easiest to be found in the semi-fixed sand dunes,whereas fixed sand dunes were the best sites for seeds that dispersed over long distance.The results of linear mixed models showed that after controlling the dispersal distance,smaller and rounder seeds dispersed farther.Shape index and wind speed were the two significant influencing factors on the burial of seeds.The explanatory power of wind speed,underlying surface,and seed morphological traits on the seeds that did not disperse and dispersed over short distance was far greater than that on the seeds that were buried and dispersed over long distance,implying that the processes and mechanisms of burial and long-distance dispersal are more complex.In summary,most seeds in the study area either did not move,were buried,or dispersed over short distance,promoting local vegetation regeneration.展开更多
Nitrogen(N)deposition is a significant aspect of global change and poses a threat to terrestrial biodiversity.The impact of plant-soil microbe relationships to N deposition has recently attracted considerable attentio...Nitrogen(N)deposition is a significant aspect of global change and poses a threat to terrestrial biodiversity.The impact of plant-soil microbe relationships to N deposition has recently attracted considerable attention.Soil microorganisms have been proven to provide nutrients for specific plant growth,especially in nutrient-poor desert steppe ecosystems.However,the effects of N deposition on plant-soil microbial community interactions in such ecosystems remain poorly understood.To investigate these effects,we conducted a 6-year N-addition field experiment in a Stipa breviflora Griseb.desert steppe in Inner Mongolia Autonomous Region,China.Four N treatment levels(N0,N30,N50,and N100,corresponding to 0,30,50,and 100 kg N/(hm2•a),respectively)were applied to simulate atmospheric N deposition.The results showed that N deposition did not significantly affect the aboveground biomass of desert steppe plants.N deposition did not significantly reduce the alfa-diversity of plant and microbial communities in the desert steppe,and low and mediate N additions(N30 and N50)had a promoting effect on them.The variation pattern of plant Shannon index was consistent with that of the soil bacterial Chao1 index.N deposition significantly affected the beta-diversity of plants and soil bacteria,but did not significantly affect fungal communities.In conclusion,N deposition led to co-evolution between desert steppe plants and soil bacterial communities,while fungal communities exhibited strong stability and did not undergo significant changes.These findings help clarify atmospheric N deposition effects on the ecological health and function of the desert steppe.展开更多
The clay–sand barriers in Minqin desert area,China,represent a pioneering windbreak and sand fixation project with a venerable history of 60 a.However,studies on evaluating the long-term effectiveness of clay–sand b...The clay–sand barriers in Minqin desert area,China,represent a pioneering windbreak and sand fixation project with a venerable history of 60 a.However,studies on evaluating the long-term effectiveness of clay–sand barriers against aeolian erosion,particularly from the perspective of surface sediment grain size,are limited and thus insufficient to ascertain the protective impact of these barriers on regional aeolian activities.This study focused on the surface sediments(topsoil of 0–3 cm depth)of clay–sand barriers in Minqin desert area to explain their erosion resistance from the perspective of surface sediment grain size.In March 2023,six clay–sand barrier sampling plots with clay–sand barriers of different deployment durations(1,5,10,20,40,and 60 a)were selected as experimental plots,and one control sampling plot was set in an adjacent mobile sandy area without sand barriers.Surface sediment samples were collected from the topsoil of each sampling plot in the study area in April 2023 and sediment grain size characteristics were analyzed.Results indicated a predominance of fine and medium sands in the surface sediments of the study area.The deployment of clay–sand barriers cultivated a fine quality in grain size composition of the regional surface sediments,increasing the average contents of very fine sand,silt,and clay by 30.82%,417.38%,and 381.52%,respectively.This trend became markedly pronounced a decade after the deployment of clay–sand barriers.The effectiveness of clay–sand barriers in erosion resistance was manifested through reduced wind velocity,the interception of sand flow,and the promotion of fine surface sediment particles.Coarser particles such as medium,coarse,and very coarse sands predominantly accumulated on the external side of the barriers,while finer particles such as fine and very fine sands concentrated in the upwind(northwest)region of the barriers.By contrast,the contents of finest particles such as silt and clay were higher in the downwind(southeast)region of the sampling plots.For the study area,the deployment of clay–sand barriers remains one of the most cost-effective engineering solutions for aeolian erosion control,with sediment grain size parameters serving as quantitative indicators for the assessment of these barriers in combating desertification.The results of this study provide a theoretical foundation for the construction of windbreak and sand fixation systems and the optimization of artificial sand control projects in arid desert areas.展开更多
Precipitation infiltration serves as a significant source of groundwater in the Badain Jaran Desert.To investigate variations in precipitation infiltration within the desert,this study collected data on moisture conte...Precipitation infiltration serves as a significant source of groundwater in the Badain Jaran Desert.To investigate variations in precipitation infiltration within the desert,this study collected data on moisture content and temperature from the vadose zone through in-situ field monitoring.Utilizing these data,a numerical model is employed to explore the mechanism of groundwater recharge via precipitation.The results are as follows:(1)Moisture content and temperature in the shallow vadose zone exhibit significant seasonal variations,with moisture content diminishing with increasing depth;(2)Groundwater recharge via precipitation infiltration initially increases and then decreases with groundwater level depth(GWD).Peak groundwater recharge via precipitation occurs at a GWD of 0.75 m,decreasing to merely 0.012 cm at GWDs exceeding 2 m;(3)Groundwater is no longer susceptible to phreatic water evaporation when the GWD reaches approximately 3.7 m.Therefore,GWD plays a crucial role in governing groundwater recharge via precipitation in the Badain Jaran Desert.展开更多
New mega energy base propels the transformation of Kubuqi Desert into a source of economic growth.DALAD Banner in Ordos,Inner Mongolia Autonomous Region in north China,is characterized by a seemingly endless stretch o...New mega energy base propels the transformation of Kubuqi Desert into a source of economic growth.DALAD Banner in Ordos,Inner Mongolia Autonomous Region in north China,is characterized by a seemingly endless stretch of barren land.Kubuqi,China’s seventh-largest desert,occupies nearly one-third of the county-equivalent banner’s land area.展开更多
Wuwei City in Gansu Province in northwest China was once an impoverished area characterised by arid and barren land.After years of reform and restructuring,Wuwei saw its last impoverished residents lifted out of absol...Wuwei City in Gansu Province in northwest China was once an impoverished area characterised by arid and barren land.After years of reform and restructuring,Wuwei saw its last impoverished residents lifted out of absolute poverty in 2020,and has undergone a stunning transformation,becoming an inspiring case study of sustainable agricultural development.展开更多
Dalad Banner in Ordos,Inner Mongolia Autonomous Region in north China,is characterised by a seemingly endless stretch of barren land.Kubuqi,China’s seventh-largest desert,occupies nearly one-third of the county-equiv...Dalad Banner in Ordos,Inner Mongolia Autonomous Region in north China,is characterised by a seemingly endless stretch of barren land.Kubuqi,China’s seventh-largest desert,occupies nearly one-third of the county-equivalent banner’s land area.How to transform and utilise this barren land has been a focus of the banner’s development.展开更多
Governmental, educational, environmental and other nonprofit organizations have placed efforts on conservation action for the threatened Mojave desert tortoise (Gopherus agassizii). While federal and state institution...Governmental, educational, environmental and other nonprofit organizations have placed efforts on conservation action for the threatened Mojave desert tortoise (Gopherus agassizii). While federal and state institutions have focused on the desert tortoise in its native habitat of the southwestern United States, there are other conservation groups whose work has been dedicated to the rescue, rehabilitation, rescue, placement and adoption of the desert tortoise in civilian homes and neighborhoods as well as sanctuaries, reserves and exhibits. AWAKE Community (AWAKE), a nonprofit organization dedicated to natural wildlife habitats and endangered species, has focused its research on desert tortoises in captivity. The California Turtle and Tortoise Club (CTTC), the official adoption arm of California’s Department of Fish and Wildlife (CDFW), has provided instruction on methods of care for desert tortoises raised in captivity including housing, feeding, sexing, health and hibernation for both adults and hatchlings. AWAKE’s research has been aimed at benefiting and supplementing the guidelines provided by CTTC, specifically for coastal climates. AWAKE’s research has also aimed to provide insight to be considered for expanding adoption possibilities to other locations, specifically tropical climates, as adoption needs for desert tortoises have increased. This manuscript presents an analysis of one coastal and one tropical climate that can serve as a basis for: 1) understanding and evaluating climate in both existing and potential habitats for desert tortoise adoptions, rescues and exhibits, 2) providing insight and special instruction for desert tortoise adoptions in coastal communities, and 3) expanding awareness around desert tortoise needs in captivity.展开更多
The recent ecological improvement in the Mu Us Desert of China, largely attributed to large-scale afforestation projects, has created new opportunities for cultivation activities. However, the subsequent rapid increas...The recent ecological improvement in the Mu Us Desert of China, largely attributed to large-scale afforestation projects, has created new opportunities for cultivation activities. However, the subsequent rapid increase in reclamation on desertification land and its impact on desertification have raised concerns. In this study, we first extracted data on cultivated land and desertification land in 1975,1990, 2000, 2005, 2010, 2015, and 2020 through the human-computer interaction visual interpretation method. By overlaying the cultivated land dynamics and desertification land, we subsequently explored the effect of cultivation activities on desertification in the Mu Us Desert during the six periods from 1975 to 2020(1975–1990, 1990–2000, 2000–2005, 2005–2010, 2010–2015, and 2015–2020). The results showed that cultivated land in the Mu Us Desert showed a fluctuating and increasing trend from 3769.26 km~2 in 1975 to 4865.73 km~2 in 2020, with 2010 as the turning point for the recent rapid increase. The main contributors included the large and regular patches distributed in Yuyang District and Shenmu of Shaanxi Province, and relatively smaller patches concentrated in Inner Mongolia Autonomous Region. The increased cultivated land from the reclamation on desertification land was dominated by moderate and severe desertification lands, and the decreased cultivated land that was transferred into desertification land as abandoned cultivated land was dominated by slight and moderate desertification lands. The effect of cultivation activities on desertification reversal(average area proportion of 10.61% for reversed desertification land) was greater than that of the development of desertification(average area proportion of 5.82% for developed desertification land). Nevertheless, compared to reversed desertification land,both the significant increase of developed desertification land during the periods of 2000–2005 and 2005–2010 and the insignificant decrease during the periods of 2005–2010, 2010–2015, and 2015–2020 implied a potential remobilization risk. Therefore, this study provides a significant theoretical reference for the formulation of ecological restoration projects and regional macroeconomic development policies by considering the influence of cultivation activities, to ensure the overall environmental stability and sustainability in desertification land where reclamation and abandonment activities have taken place.展开更多
The effects of sand encroachment on composition,diversity,and functional patterns of vegetation in drylands are rarely studied,and yet addressing these aspects is important to deepen our understanding of the biodivers...The effects of sand encroachment on composition,diversity,and functional patterns of vegetation in drylands are rarely studied,and yet addressing these aspects is important to deepen our understanding of the biodiversity conservation.This study aimed to investigate the effect of sand encroachment on plant functional biodiversity of desert pavements(gravel deserts)in the Sahara Desert of Algeria.Plants were sampled and analyzed in three desert pavements with different levels of sand encroachment(LSE)and quantity of aeolian deposits(low,LLSE;medium,MLSE;and high,HLSE).Within the sample-plot area(100 m^(2)),density of every plant species was identified and total vegetation cover was determined.Plant taxonomic and functional diversity were analyzed and compared between LSE.Result showed that 19 plant species in desert pavements were classified into 18 genera and 13 families.Asteraceae and Poaceae were the most important families.The species Anabasis articulata(Forssk)Moq.characterized LLSE desert pavements with 11 species,whereas Thymelaea microphylla Coss.&Durieu ex Meisn.and Calobota saharae(C&D)Boatwr.&van Wyk were dominant species of desert pavements with MLSE(14 species)and HLSE(10 species),respectively.The highest values of species richness and biodiversity were recorded in desert pavements with MLSE,while low values of these ecological parameters were obtained in desert pavements with HLSE.Desert pavements with LLSE were characterized with the highest values of species abundances.Plant communities were dominated by chamaephytes,anemochorous,arido-active,and competitive stress-tolerant plants.The increase in LSE along the gradient from LLSE to HLSE induced significant changes in plant community variables including decreases in plant density,plant rarity,lifeform composition,morphological type,and aridity adaptation.Desert pavements with HLSE favor the degradation of vegetation and trigger biodiversity erosion.展开更多
China has vast areas of deserts,gobis,and desertified lands,with a total area of 3.96×106 km2,accounting for 41.3%of the national land area.The desert area is 6.88×105 km2,the Gobi area is 6.61×105 km2,...China has vast areas of deserts,gobis,and desertified lands,with a total area of 3.96×106 km2,accounting for 41.3%of the national land area.The desert area is 6.88×105 km2,the Gobi area is 6.61×105 km2,and the desertification land area is 2.61×106 km2,respectively(National Forestry and Grassland Administration,2018).These are mainly distributed in the northwestern and northern regions west of the“Hu Huanyong Line”(Fig.1),including Taklimakan Desert,Gurban Tungut Desert,Badain Jalan Desert,Tengger Desert,Ulan Buhe Desert,Kubuqi Desert,Qaidam Basin Desert and Kumtag Desert,Mu Us Sandy Land,Hunshandak Sandy Land,Horqin Sandy Land and Hulun Buir Sandy Land.展开更多
Drought impacts in arid desert ecosystems can result in decreased ecosystem productivity and biodiversity.Implementation of restoration projects in arid desert environments is largely dependent on water availabi...Drought impacts in arid desert ecosystems can result in decreased ecosystem productivity and biodiversity.Implementation of restoration projects in arid desert environments is largely dependent on water availability and soil moisture condition.This study investigated the influence of induced drought stress by using polyethylene glycol(PEG-6000)solution on germination viz.Cenchrus ciliaris and Cenchrus setigerus as the important rangeland species.The water stress potential treatments were 0(control),-0.5 MPa,-1.0 MPa,-1.5 MPa,and-2.0 MPa.The extent of seed germination was severely affected by decreased water stress potential.As drought increased,the percentage of germination decreased in both Cenchrus’species.The water deficit at-0.5 MPa showed a significant(P<0.001)reduction in the final germination percentage in the case of C.setigerus and C.ciliaris by 65%and 42.5%,respectively.At-1.0 MPa to-1.5 MPa,changes in intermediate germination were observed in C.ciliaris(from 35%to 17.5%,respectively)and C.setigerus(from 22.5%to 11.25%respectively).Higher levels of water stress(-2.0 MPa)prevented the survival of both species.Understanding the germination strategies of native desert plant species associated with drought stress and identifying favorable conditions during the germination process can be useful for restoration practices and rangeland management actions to improve desert ecosystems and maintain biodiversity.展开更多
Western Desert represents a major oil and gas province in Egypt producing more than 50%of the country’s oil production.Oil and gas blend occurs in most producing fields,however,the genetic link between gas and liquid...Western Desert represents a major oil and gas province in Egypt producing more than 50%of the country’s oil production.Oil and gas blend occurs in most producing fields,however,the genetic link between gas and liquid hydrocarbon phases are not well-constrained.Obayied sub-basin in the Western Desert where oil and gas phases coexist in the Middle Jurassic sandstones of the Khatatba Formation provides an ideal place to investigate the link between oil and gas generation.Geochemical analyses on rock samples(Rock–Eval pyrolysis,vitrinite reflectance,R_(o))and gases(molecular and isotopic composition)were conducted in order to identify the genetic characteristics of the hydrocarbon phases produced.Maturity-relevant parameters(Rock–Eval T_(max),vitrinite reflectance R_(o))elucidate that only Middle Jurassic Khatatba organofacies capable of generating wet and dry hydrocarbon gases.Additionally,the enrichment of C_(7)normal alkanes,mono-branched alkanes relative to polybranched components in the Obayied gases reflect their generation via cracking of oil.Basin modelling results confirm gas generation through both primary and secondary cracking.However,secondary cracking of liquid hydrocarbon phases is volumetrically more significant.Primary cracking of the Khatatba organofacies likely predate and catalyze the secondary cracking of the liquid phases and therefore the volume of generated gas increases incrementally eastward where both processes coexist.The present study highlights the significant role of secondary cracking in the generation and accumulation of huge gas accumulations in the basins containing oil-prone source intervals.展开更多
Desert lakes are important wetland resources in the blown-sand area of western China and play a significant role in maintain-ing the regional ecological environment.However,large-scale coal mining in recent years has ...Desert lakes are important wetland resources in the blown-sand area of western China and play a significant role in maintain-ing the regional ecological environment.However,large-scale coal mining in recent years has considerably impacted the deposition condition of several lakes.Rapid and accurate extraction of lake information based on satellite images is crucial for developing protective measures against desertification.However,the spatial resolution of these images often leads to mixed pixels near water boundaries,affecting extraction precision.Traditional pixel unmixing methods mainly obtain water coverage information in a mixed pixel,making it difficult to accurately describe the spatial distribution.In this paper,the cellular automata(CA)model was adopted in order to realize lake information extraction at a sub-pixel level.A mining area in Shenmu City,Shaanxi Province,China is selected as the research region,using the image of Sentinel-2 as the data source and the high spatial resolution UAV image as the reference.First,water coverage of mixed pixels in the Sentinel-2 image was calculated with the dimidiate pixel model and the fully constrained least squares(FCLS)method.Second,the mixed pixels were subdivided to form the cellular space at a sub-pixel level and the transition rules are constructed based on the water coverage information and spatial correlation.Lastly,the process was implemented using Python and IDL,with the ArcGIS and ENVI software being used for validation.The experiments show that the CA model can improve the sub-pixel positioning accuracy for lake bodies in mixed pixel image and improve classification accuracy.The FCLS-CA model has a higher accuracy and is able to identify most water bodies in the study area,and is therefore suitable for desert lake monitor-ing in mining areas.展开更多
The tallest sand dune worldwide is located in the Badain Jaran Desert(BJD),China,and has been standing for thousands of years.Previous studies have conducted limited physical exploration and excavation on the formatio...The tallest sand dune worldwide is located in the Badain Jaran Desert(BJD),China,and has been standing for thousands of years.Previous studies have conducted limited physical exploration and excavation on the formation of sand dunes and have proposed three viewpoints,that is,bedrock control,wind dominance,and groundwater maintenance with no unified conclusion.Therefore,this study analyzed the underlying bedding structure of sand dunes in the BJD.Although the bedrock of sand dunes is uplifted and wind controls the shape of dunes,the main cause of dune formation is groundwater that maintains the deposition of calcareous sandstone and accumulation of aeolian sand.According to water transport model and vapor transports in the unsaturated zone of sand dunes,capillary water transport height is limited with film water constituting the main form of water in dunes.Chemical properties and temperature of groundwater showed that aquifers in different basins receive relatively independent recharge from deep sources in the crater.Result of dune formation mechanism is of considerable importance in understanding groundwater circulation and provides a new perspective on water management in arid desert areas.展开更多
Maintaining the stability of exotic sand-binding shrub has become a large challenge in arid and semi-arid grassland ecosystems in northern China.We investigated two kinds of shrublands with different BSCs(biological s...Maintaining the stability of exotic sand-binding shrub has become a large challenge in arid and semi-arid grassland ecosystems in northern China.We investigated two kinds of shrublands with different BSCs(biological soil crusts)cover in desert steppe in Northwest China to characterize the water sources of shrub(Caragana intermedia Kuang et H.C.Fu)and grass(Artemisia scoparia Waldst.et Kit.)by stable 18O isotopic.Our results showed that both shrublands were subject to persistent soil water deficiency from 2012 to 2017,the minimum soil depth with CV(coefficient of variation)<15% and SWC(soil water content)<6% was 1.4 m in shrubland with open areas lacking obvious BSC cover,and 0.8 m in shrubland covered by mature BSCs.For C.intermedia,a considerable proportion of water sources pointed to the surface soil.Water from BSCs contributed to averages 22.9%and 17.6%of the total for C.intermedia and A.scoparia,respectively.C.intermedia might use more water from BSCs in rainy season than dry season,in contrast to A.scoparia.The relationship between shrub(or grass)and soil water by δ^(18)O shown significant differences in months,which partly verified the potential trends and relations covered by the high variability of the water source at seasonal scale.More fine roots at 0-5 cm soil layer could be found in the surface soil layer covered by BSCs(8000 cm/m^(3))than without BSCs(3200 cm/m^(3)),which ensured the possibility of using the surface soil water by C.intermedia.The result implies that even under serious soil water deficiency,C.intermedia can use the surface soil water,leading to the coexistence between C.intermedia and A.scoparia.Different with the result from BSCs in desert areas,the natural withdrawal of artificial C.intermedia from desert steppe will be a long-term process,and the highly competitive relationship between shrubs and grasses also determines that its habitat will be maintained in serious drought state for a long time.展开更多
基金funded by the General Project of Key R&D Plan of Ningxia Hui Autonomous Region,China(2021BEG03008,2022BEG02012)the Science and Technology Innovation Leading Talent Project of Ningxia Hui Autonomous Region(2021GKLRLX13)the National Natural Science Foundation of China(31760707).
文摘Vegetation restoration and reconstruction are effective approaches to desertification control and achieving social and economic sustainability in desert areas.However,the self-succession ability of native plants during the later periods of vegetation restoration remains unclear.Therefore,this study was conducted to bridge the knowledge gap by investigating the regeneration dynamics of artificial forest under natural conditions.The information of seed rain and soil seed bank was collected and quantified from an artificial Caragana korshinskii Kom.forest in the Tengger Desert,China.The germination tests were conducted in a laboratory setting.The analysis of species quantity and diversity in seed rain and soil seed bank was conducted to assess the impact of different durations of sand fixation(60,40,and 20 a)on the progress of vegetation restoration and ecological conditions in artificial C.korshinskii forest.The results showed that the top three dominant plant species in seed rain were Echinops gmelinii Turcz.,Eragrostis minor Host.,and Agropyron mongolicum Keng.,and the top three dominant plant species in soil seed bank were E.minor,Chloris virgata Sw.,and E.gmelinii.As restoration period increased,the density of seed rain and soil seed bank increased first and then decreased.While for species richness,as restoration period increased,it gradually increased in seed rain but decreased in soil seed bank.There was a positive correlation between seed rain density and soil seed bank density among all the three restoration periods.The species similarity between seed rain or soil seed bank and aboveground vegetation decreased with the extension of restoration period.The shape of the seeds,specifically those with external appendages such as spines and crown hair,clearly had an effect on their dispersal,then resulting in lower seed density in soil seed bank.In addition,precipitation was a crucial factor in promoting rapid germination,also resulting in lower seed density in soil seed bank.Our findings provide valuable insights for guiding future interventions during the later periods of artificial C.korshinskii forest,such as sowing and restoration efforts using unmanned aerial vehicles.
文摘The latticed dunes in the Tengger Desert are widely distributed,and the sand-blocking fence placed here are highly susceptible to local failure due to complex wind-sand activities,posing a serious threat to the safe operation of the highway.To explore the local failure mechanism of sand-blocking fence in the latticed dune area,the local failure of sand-blocking fence in the latticed dune areas along the Wuhai-Maqin Highway in China was observed.Taking the first main ridge of the latticed dune as the placement location,the structure of the wind-sand flow field of sand-blocking fence placed at top,the bottom and the middle of windward slope was analyzed by Computational Fluid Dynamics(CFD).The results show that when placed at top of the first main ridge,the wind speed near the sand-blocking fence is the highest,up to 15.23 m/s.Therefore,the wind load strength on the sand barrier is correspondingly larger,up to 232.61 N∙m-2.As the strength of material continues to decrease,the nylon net is prone to breakage.The roots of the angle steel posts are susceptible to hollowing by vortex action,which can cause sand-blocking fence to fall over in strong wind conditions.When placed at the bottom of windward slope,wind speed drop near sand-blocking fence is greatest,with the decrease of 12.48-14.32 m/s compared to the original wind speed.This is highly likely to lead to large-scale deposition of sand particles and burial of the sand-blocking fence.When placed in the middle of windward slope,sand-blocking fence is subjected to less wind load strength(168.61N∙m-2)and sand particles are mostly deposited at the bottom of windward slope,with only a small amount of sand accumulating at the root of sand-blocking fence.Based on field observations and numerical modelling results,when the sand-blocking fence is placed in latticed dune area,it should be placed in the middle of the windward slope of the first main ridge as a matter of priority.Besides the sand-blocking fence should be placed at the top of the first main ridge,and sand fixing measures should be added.
基金funded by the National Natural Science Foundation of China(32061123006,32360426).
文摘One of the goals of grazing management in the desert steppe is to improve its ecosystem.However,relatively little is known about soil microbe communities in the desert steppe ecosystem under grazing management.In this study,we investigated the diversity and aboveground biomass of Caragana korshinskii Kom.shrub communities in long-term fencing and grazing areas,combined with an analysis of soil physical-chemical properties and genomics,with the aim of understanding how fence management affects plant-soil-microbial inter-relationships in the desert steppe,China.The results showed that fence management(exclosure)increased plant diversity and aboveground biomass in C.korshinskii shrub area and effectively enhanced soil organic carbon(233.94%),available nitrogen(87.77%),and available phosphorus(53.67%)contents.As well,the Shannon indices of soil bacteria and fungi were greater in the fenced plot.Plant-soil changes profoundly affected the alpha-and beta-diversity of soil bacteria.Fence management also altered the soil microbial community structure,significantly increasing the relative abundances of Acidobacteriota(5.31%-8.99%),Chloroflexi(3.99%-5.58%),and Glomeromycota(1.37%-3.28%).The soil bacterial-fungal co-occurrence networks under fence management had higher complexity and connectivity.Based on functional predictions,fence management significantly increased the relative abundance of bacteria with nitrification and nitrate reduction functions and decreased the relative abundance of bacteria with nitrate and nitrite respiration functions.The relative abundances of ecologically functional fungi with arbuscular mycorrhizal fungi,ectomycorrhizal fungi,and saprotrophs also significantly increased under fence management.In addition,the differential functional groups of bacteria and fungi were closely related to plant-soil changes.The results of this study have significant positive implications for the ecological restoration and reconstruction of dry desert steppe and similar areas.
文摘Neoproterozoic island arc assemblage of the Arabian–Nubian Shield(ANS)in the Eastern Desert(ED)of Egypt comprises juvenile suites of metavolcanics(MV),large amounts of meta-sedimentary rocks(MS),and voluminous metagabbros-diorites(MGD)and syn-tectonic intrusions of older granitoids(OG).We report here the updates of these four rock units in terms of classification,distribution,chemical characteristics,geodynamic evolution,metamorphism,and ages.In addition,we discuss these integrated data to elucidate a reasonable and reliable model for crustal evolution in the ANS.The main features of these rock units indicate their relation to each other and the geodynamic environment dominated by early immature oceanic island arcs to primitive continental arcs.Integrated information of the island arc metavolcanic and plutonic rocks(gabbros,diorites,tonalites,and granodiorites)furnish evidence of the genetic relationships.These include proximity and a coeval nature in the field;all protolith magmas are subalkaline in nature following calc-alkaline series with minor tholeiitic affinities;common geochemical signature of the arc rocks and subduction-related magmatism;their similar enrichment in LREEs;and similar major element compositions with mafic melts derived from metasomatized mantle wedge.The volcano-sedimentary and the OG rocks underwent multiphase deformation events whereas the MGD complexes deformed slightly.Based on the magmatic,sedimentological,and metamorphic evolutions constrained by geochronological data as well as the progressive evolutionary trend from extensional to compressional regimes,a possible gradual decrease in the subducted slab dip angle is the most infl uential in any geodynamic model for arc assemblage in the ED of Egypt.
基金supported by the Key R&D Program of Ningxia Hui Autonomous Region,China(2021BEG03008)the Natural Science Foundation of Ningxia Hui Autonomous Region,China(2021AAC03083).
文摘The maintenance of sand-fixing vegetation is important for the stability of artificial sand-fixing systems in which seed dispersal plays a key role.Based on field wind tunnel experiments using 11 common plant species on the southeastern edge of the Tengger Desert,China,we studied the secondary seed dispersal in the fixed and semi-fixed sand dunes as well as in the mobile dunes in order to understand the limitations of vegetation regeneration and the maintenance of its stability.Our results indicated that there were significant variations among the selected 11 plant species in the threshold of wind speed(TWS).The TWS of Caragana korshinskii was the highest among the 11 plant species,whereas that of Echinops gmelinii was the lowest.Seed morphological traits and underlying surface could generally explain the TWS.During the secondary seed dispersal processes,the proportions of seeds that did not disperse(no dispersal)and only dispersed over short distance(short-distance dispersal within the wind tunnel test section)were significantly higher than those of seeds that were buried(including lost seeds)and dispersed over long distance(long-distance dispersal beyond the wind tunnel test section).Compared with other habitats,the mobile dunes were the most difficult places for secondary seed dispersal.Buried seeds were the easiest to be found in the semi-fixed sand dunes,whereas fixed sand dunes were the best sites for seeds that dispersed over long distance.The results of linear mixed models showed that after controlling the dispersal distance,smaller and rounder seeds dispersed farther.Shape index and wind speed were the two significant influencing factors on the burial of seeds.The explanatory power of wind speed,underlying surface,and seed morphological traits on the seeds that did not disperse and dispersed over short distance was far greater than that on the seeds that were buried and dispersed over long distance,implying that the processes and mechanisms of burial and long-distance dispersal are more complex.In summary,most seeds in the study area either did not move,were buried,or dispersed over short distance,promoting local vegetation regeneration.
基金the National Natural Science Foundation of China(31860136,31560156)the Basic Scientific Research Service Fee Project of Colleges and Universities of Inner Mongolia Autonomous Regionthe Graduate Scientific Research Innovation Project of Inner Mongolia Autonomous Region(B20210158Z).
文摘Nitrogen(N)deposition is a significant aspect of global change and poses a threat to terrestrial biodiversity.The impact of plant-soil microbe relationships to N deposition has recently attracted considerable attention.Soil microorganisms have been proven to provide nutrients for specific plant growth,especially in nutrient-poor desert steppe ecosystems.However,the effects of N deposition on plant-soil microbial community interactions in such ecosystems remain poorly understood.To investigate these effects,we conducted a 6-year N-addition field experiment in a Stipa breviflora Griseb.desert steppe in Inner Mongolia Autonomous Region,China.Four N treatment levels(N0,N30,N50,and N100,corresponding to 0,30,50,and 100 kg N/(hm2•a),respectively)were applied to simulate atmospheric N deposition.The results showed that N deposition did not significantly affect the aboveground biomass of desert steppe plants.N deposition did not significantly reduce the alfa-diversity of plant and microbial communities in the desert steppe,and low and mediate N additions(N30 and N50)had a promoting effect on them.The variation pattern of plant Shannon index was consistent with that of the soil bacterial Chao1 index.N deposition significantly affected the beta-diversity of plants and soil bacteria,but did not significantly affect fungal communities.In conclusion,N deposition led to co-evolution between desert steppe plants and soil bacterial communities,while fungal communities exhibited strong stability and did not undergo significant changes.These findings help clarify atmospheric N deposition effects on the ecological health and function of the desert steppe.
基金the National Natural Science Foundation of China(42230720,32160410,42167069)the Gansu Key Research and Development Program(22YF7FA078,GZTZ20240415)Gansu Province Forestry and Grassland Science and Technology Innovation Project(LCCX202303).
文摘The clay–sand barriers in Minqin desert area,China,represent a pioneering windbreak and sand fixation project with a venerable history of 60 a.However,studies on evaluating the long-term effectiveness of clay–sand barriers against aeolian erosion,particularly from the perspective of surface sediment grain size,are limited and thus insufficient to ascertain the protective impact of these barriers on regional aeolian activities.This study focused on the surface sediments(topsoil of 0–3 cm depth)of clay–sand barriers in Minqin desert area to explain their erosion resistance from the perspective of surface sediment grain size.In March 2023,six clay–sand barrier sampling plots with clay–sand barriers of different deployment durations(1,5,10,20,40,and 60 a)were selected as experimental plots,and one control sampling plot was set in an adjacent mobile sandy area without sand barriers.Surface sediment samples were collected from the topsoil of each sampling plot in the study area in April 2023 and sediment grain size characteristics were analyzed.Results indicated a predominance of fine and medium sands in the surface sediments of the study area.The deployment of clay–sand barriers cultivated a fine quality in grain size composition of the regional surface sediments,increasing the average contents of very fine sand,silt,and clay by 30.82%,417.38%,and 381.52%,respectively.This trend became markedly pronounced a decade after the deployment of clay–sand barriers.The effectiveness of clay–sand barriers in erosion resistance was manifested through reduced wind velocity,the interception of sand flow,and the promotion of fine surface sediment particles.Coarser particles such as medium,coarse,and very coarse sands predominantly accumulated on the external side of the barriers,while finer particles such as fine and very fine sands concentrated in the upwind(northwest)region of the barriers.By contrast,the contents of finest particles such as silt and clay were higher in the downwind(southeast)region of the sampling plots.For the study area,the deployment of clay–sand barriers remains one of the most cost-effective engineering solutions for aeolian erosion control,with sediment grain size parameters serving as quantitative indicators for the assessment of these barriers in combating desertification.The results of this study provide a theoretical foundation for the construction of windbreak and sand fixation systems and the optimization of artificial sand control projects in arid desert areas.
基金funded by China Geological Survey Program(121201106000150093).
文摘Precipitation infiltration serves as a significant source of groundwater in the Badain Jaran Desert.To investigate variations in precipitation infiltration within the desert,this study collected data on moisture content and temperature from the vadose zone through in-situ field monitoring.Utilizing these data,a numerical model is employed to explore the mechanism of groundwater recharge via precipitation.The results are as follows:(1)Moisture content and temperature in the shallow vadose zone exhibit significant seasonal variations,with moisture content diminishing with increasing depth;(2)Groundwater recharge via precipitation infiltration initially increases and then decreases with groundwater level depth(GWD).Peak groundwater recharge via precipitation occurs at a GWD of 0.75 m,decreasing to merely 0.012 cm at GWDs exceeding 2 m;(3)Groundwater is no longer susceptible to phreatic water evaporation when the GWD reaches approximately 3.7 m.Therefore,GWD plays a crucial role in governing groundwater recharge via precipitation in the Badain Jaran Desert.
文摘New mega energy base propels the transformation of Kubuqi Desert into a source of economic growth.DALAD Banner in Ordos,Inner Mongolia Autonomous Region in north China,is characterized by a seemingly endless stretch of barren land.Kubuqi,China’s seventh-largest desert,occupies nearly one-third of the county-equivalent banner’s land area.
文摘Wuwei City in Gansu Province in northwest China was once an impoverished area characterised by arid and barren land.After years of reform and restructuring,Wuwei saw its last impoverished residents lifted out of absolute poverty in 2020,and has undergone a stunning transformation,becoming an inspiring case study of sustainable agricultural development.
文摘Dalad Banner in Ordos,Inner Mongolia Autonomous Region in north China,is characterised by a seemingly endless stretch of barren land.Kubuqi,China’s seventh-largest desert,occupies nearly one-third of the county-equivalent banner’s land area.How to transform and utilise this barren land has been a focus of the banner’s development.
文摘Governmental, educational, environmental and other nonprofit organizations have placed efforts on conservation action for the threatened Mojave desert tortoise (Gopherus agassizii). While federal and state institutions have focused on the desert tortoise in its native habitat of the southwestern United States, there are other conservation groups whose work has been dedicated to the rescue, rehabilitation, rescue, placement and adoption of the desert tortoise in civilian homes and neighborhoods as well as sanctuaries, reserves and exhibits. AWAKE Community (AWAKE), a nonprofit organization dedicated to natural wildlife habitats and endangered species, has focused its research on desert tortoises in captivity. The California Turtle and Tortoise Club (CTTC), the official adoption arm of California’s Department of Fish and Wildlife (CDFW), has provided instruction on methods of care for desert tortoises raised in captivity including housing, feeding, sexing, health and hibernation for both adults and hatchlings. AWAKE’s research has been aimed at benefiting and supplementing the guidelines provided by CTTC, specifically for coastal climates. AWAKE’s research has also aimed to provide insight to be considered for expanding adoption possibilities to other locations, specifically tropical climates, as adoption needs for desert tortoises have increased. This manuscript presents an analysis of one coastal and one tropical climate that can serve as a basis for: 1) understanding and evaluating climate in both existing and potential habitats for desert tortoise adoptions, rescues and exhibits, 2) providing insight and special instruction for desert tortoise adoptions in coastal communities, and 3) expanding awareness around desert tortoise needs in captivity.
基金supported by the National Natural Science Foundation of China (41971277, 41730752)。
文摘The recent ecological improvement in the Mu Us Desert of China, largely attributed to large-scale afforestation projects, has created new opportunities for cultivation activities. However, the subsequent rapid increase in reclamation on desertification land and its impact on desertification have raised concerns. In this study, we first extracted data on cultivated land and desertification land in 1975,1990, 2000, 2005, 2010, 2015, and 2020 through the human-computer interaction visual interpretation method. By overlaying the cultivated land dynamics and desertification land, we subsequently explored the effect of cultivation activities on desertification in the Mu Us Desert during the six periods from 1975 to 2020(1975–1990, 1990–2000, 2000–2005, 2005–2010, 2010–2015, and 2015–2020). The results showed that cultivated land in the Mu Us Desert showed a fluctuating and increasing trend from 3769.26 km~2 in 1975 to 4865.73 km~2 in 2020, with 2010 as the turning point for the recent rapid increase. The main contributors included the large and regular patches distributed in Yuyang District and Shenmu of Shaanxi Province, and relatively smaller patches concentrated in Inner Mongolia Autonomous Region. The increased cultivated land from the reclamation on desertification land was dominated by moderate and severe desertification lands, and the decreased cultivated land that was transferred into desertification land as abandoned cultivated land was dominated by slight and moderate desertification lands. The effect of cultivation activities on desertification reversal(average area proportion of 10.61% for reversed desertification land) was greater than that of the development of desertification(average area proportion of 5.82% for developed desertification land). Nevertheless, compared to reversed desertification land,both the significant increase of developed desertification land during the periods of 2000–2005 and 2005–2010 and the insignificant decrease during the periods of 2005–2010, 2010–2015, and 2015–2020 implied a potential remobilization risk. Therefore, this study provides a significant theoretical reference for the formulation of ecological restoration projects and regional macroeconomic development policies by considering the influence of cultivation activities, to ensure the overall environmental stability and sustainability in desertification land where reclamation and abandonment activities have taken place.
文摘The effects of sand encroachment on composition,diversity,and functional patterns of vegetation in drylands are rarely studied,and yet addressing these aspects is important to deepen our understanding of the biodiversity conservation.This study aimed to investigate the effect of sand encroachment on plant functional biodiversity of desert pavements(gravel deserts)in the Sahara Desert of Algeria.Plants were sampled and analyzed in three desert pavements with different levels of sand encroachment(LSE)and quantity of aeolian deposits(low,LLSE;medium,MLSE;and high,HLSE).Within the sample-plot area(100 m^(2)),density of every plant species was identified and total vegetation cover was determined.Plant taxonomic and functional diversity were analyzed and compared between LSE.Result showed that 19 plant species in desert pavements were classified into 18 genera and 13 families.Asteraceae and Poaceae were the most important families.The species Anabasis articulata(Forssk)Moq.characterized LLSE desert pavements with 11 species,whereas Thymelaea microphylla Coss.&Durieu ex Meisn.and Calobota saharae(C&D)Boatwr.&van Wyk were dominant species of desert pavements with MLSE(14 species)and HLSE(10 species),respectively.The highest values of species richness and biodiversity were recorded in desert pavements with MLSE,while low values of these ecological parameters were obtained in desert pavements with HLSE.Desert pavements with LLSE were characterized with the highest values of species abundances.Plant communities were dominated by chamaephytes,anemochorous,arido-active,and competitive stress-tolerant plants.The increase in LSE along the gradient from LLSE to HLSE induced significant changes in plant community variables including decreases in plant density,plant rarity,lifeform composition,morphological type,and aridity adaptation.Desert pavements with HLSE favor the degradation of vegetation and trigger biodiversity erosion.
文摘China has vast areas of deserts,gobis,and desertified lands,with a total area of 3.96×106 km2,accounting for 41.3%of the national land area.The desert area is 6.88×105 km2,the Gobi area is 6.61×105 km2,and the desertification land area is 2.61×106 km2,respectively(National Forestry and Grassland Administration,2018).These are mainly distributed in the northwestern and northern regions west of the“Hu Huanyong Line”(Fig.1),including Taklimakan Desert,Gurban Tungut Desert,Badain Jalan Desert,Tengger Desert,Ulan Buhe Desert,Kubuqi Desert,Qaidam Basin Desert and Kumtag Desert,Mu Us Sandy Land,Hunshandak Sandy Land,Horqin Sandy Land and Hulun Buir Sandy Land.
基金This study was made possible by generous support of the Kuwait Institute for Scientific Research(KISR).
文摘Drought impacts in arid desert ecosystems can result in decreased ecosystem productivity and biodiversity.Implementation of restoration projects in arid desert environments is largely dependent on water availability and soil moisture condition.This study investigated the influence of induced drought stress by using polyethylene glycol(PEG-6000)solution on germination viz.Cenchrus ciliaris and Cenchrus setigerus as the important rangeland species.The water stress potential treatments were 0(control),-0.5 MPa,-1.0 MPa,-1.5 MPa,and-2.0 MPa.The extent of seed germination was severely affected by decreased water stress potential.As drought increased,the percentage of germination decreased in both Cenchrus’species.The water deficit at-0.5 MPa showed a significant(P<0.001)reduction in the final germination percentage in the case of C.setigerus and C.ciliaris by 65%and 42.5%,respectively.At-1.0 MPa to-1.5 MPa,changes in intermediate germination were observed in C.ciliaris(from 35%to 17.5%,respectively)and C.setigerus(from 22.5%to 11.25%respectively).Higher levels of water stress(-2.0 MPa)prevented the survival of both species.Understanding the germination strategies of native desert plant species associated with drought stress and identifying favorable conditions during the germination process can be useful for restoration practices and rangeland management actions to improve desert ecosystems and maintain biodiversity.
文摘Western Desert represents a major oil and gas province in Egypt producing more than 50%of the country’s oil production.Oil and gas blend occurs in most producing fields,however,the genetic link between gas and liquid hydrocarbon phases are not well-constrained.Obayied sub-basin in the Western Desert where oil and gas phases coexist in the Middle Jurassic sandstones of the Khatatba Formation provides an ideal place to investigate the link between oil and gas generation.Geochemical analyses on rock samples(Rock–Eval pyrolysis,vitrinite reflectance,R_(o))and gases(molecular and isotopic composition)were conducted in order to identify the genetic characteristics of the hydrocarbon phases produced.Maturity-relevant parameters(Rock–Eval T_(max),vitrinite reflectance R_(o))elucidate that only Middle Jurassic Khatatba organofacies capable of generating wet and dry hydrocarbon gases.Additionally,the enrichment of C_(7)normal alkanes,mono-branched alkanes relative to polybranched components in the Obayied gases reflect their generation via cracking of oil.Basin modelling results confirm gas generation through both primary and secondary cracking.However,secondary cracking of liquid hydrocarbon phases is volumetrically more significant.Primary cracking of the Khatatba organofacies likely predate and catalyze the secondary cracking of the liquid phases and therefore the volume of generated gas increases incrementally eastward where both processes coexist.The present study highlights the significant role of secondary cracking in the generation and accumulation of huge gas accumulations in the basins containing oil-prone source intervals.
基金supported by the Shaanxi Province Soft Science Research Program (2022KRM034).
文摘Desert lakes are important wetland resources in the blown-sand area of western China and play a significant role in maintain-ing the regional ecological environment.However,large-scale coal mining in recent years has considerably impacted the deposition condition of several lakes.Rapid and accurate extraction of lake information based on satellite images is crucial for developing protective measures against desertification.However,the spatial resolution of these images often leads to mixed pixels near water boundaries,affecting extraction precision.Traditional pixel unmixing methods mainly obtain water coverage information in a mixed pixel,making it difficult to accurately describe the spatial distribution.In this paper,the cellular automata(CA)model was adopted in order to realize lake information extraction at a sub-pixel level.A mining area in Shenmu City,Shaanxi Province,China is selected as the research region,using the image of Sentinel-2 as the data source and the high spatial resolution UAV image as the reference.First,water coverage of mixed pixels in the Sentinel-2 image was calculated with the dimidiate pixel model and the fully constrained least squares(FCLS)method.Second,the mixed pixels were subdivided to form the cellular space at a sub-pixel level and the transition rules are constructed based on the water coverage information and spatial correlation.Lastly,the process was implemented using Python and IDL,with the ArcGIS and ENVI software being used for validation.The experiments show that the CA model can improve the sub-pixel positioning accuracy for lake bodies in mixed pixel image and improve classification accuracy.The FCLS-CA model has a higher accuracy and is able to identify most water bodies in the study area,and is therefore suitable for desert lake monitor-ing in mining areas.
基金This work was funded by the National Natural Science Foundation of China(61771183).
文摘The tallest sand dune worldwide is located in the Badain Jaran Desert(BJD),China,and has been standing for thousands of years.Previous studies have conducted limited physical exploration and excavation on the formation of sand dunes and have proposed three viewpoints,that is,bedrock control,wind dominance,and groundwater maintenance with no unified conclusion.Therefore,this study analyzed the underlying bedding structure of sand dunes in the BJD.Although the bedrock of sand dunes is uplifted and wind controls the shape of dunes,the main cause of dune formation is groundwater that maintains the deposition of calcareous sandstone and accumulation of aeolian sand.According to water transport model and vapor transports in the unsaturated zone of sand dunes,capillary water transport height is limited with film water constituting the main form of water in dunes.Chemical properties and temperature of groundwater showed that aquifers in different basins receive relatively independent recharge from deep sources in the crater.Result of dune formation mechanism is of considerable importance in understanding groundwater circulation and provides a new perspective on water management in arid desert areas.
基金This research was funded by the National Natural Science Foundation of China(32060313,31760707).
文摘Maintaining the stability of exotic sand-binding shrub has become a large challenge in arid and semi-arid grassland ecosystems in northern China.We investigated two kinds of shrublands with different BSCs(biological soil crusts)cover in desert steppe in Northwest China to characterize the water sources of shrub(Caragana intermedia Kuang et H.C.Fu)and grass(Artemisia scoparia Waldst.et Kit.)by stable 18O isotopic.Our results showed that both shrublands were subject to persistent soil water deficiency from 2012 to 2017,the minimum soil depth with CV(coefficient of variation)<15% and SWC(soil water content)<6% was 1.4 m in shrubland with open areas lacking obvious BSC cover,and 0.8 m in shrubland covered by mature BSCs.For C.intermedia,a considerable proportion of water sources pointed to the surface soil.Water from BSCs contributed to averages 22.9%and 17.6%of the total for C.intermedia and A.scoparia,respectively.C.intermedia might use more water from BSCs in rainy season than dry season,in contrast to A.scoparia.The relationship between shrub(or grass)and soil water by δ^(18)O shown significant differences in months,which partly verified the potential trends and relations covered by the high variability of the water source at seasonal scale.More fine roots at 0-5 cm soil layer could be found in the surface soil layer covered by BSCs(8000 cm/m^(3))than without BSCs(3200 cm/m^(3)),which ensured the possibility of using the surface soil water by C.intermedia.The result implies that even under serious soil water deficiency,C.intermedia can use the surface soil water,leading to the coexistence between C.intermedia and A.scoparia.Different with the result from BSCs in desert areas,the natural withdrawal of artificial C.intermedia from desert steppe will be a long-term process,and the highly competitive relationship between shrubs and grasses also determines that its habitat will be maintained in serious drought state for a long time.
