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
Biological soil crusts(BSCs) play an important role in surface soil hydrology. Soils dominated with moss BSCs may have higher infiltration rates than those dominated with cyanobacteria or algal BSCs. However, it is un...Biological soil crusts(BSCs) play an important role in surface soil hydrology. Soils dominated with moss BSCs may have higher infiltration rates than those dominated with cyanobacteria or algal BSCs. However, it is unnown whether improved infiltration in moss BSCs is accompanied by an increase in soil hydraulic conductivity or water retention capacity. We investigated this question in the Tengger Desert, where a 43-year-old revegetation program has promoted the formation of two distinct types of BSCs along topographic positions, i.e. the moss-dominated BSCs on the interdune land and windward slopes of the fixed sand dunes, and the algal-dominated BSCs on the crest and leeward slopes. Soil water retention capacity and hydraulic conductivity were measured using an indoor evaporation method and a field infiltration method. And the results were fitted to the van Genuchten–Mualem model. Unsaturated hydraulic conductivities under greater water pressure(<–0.01 MPa) and water retention capacities in the entire pressure head range were higher for both crust types than for bare sand. However, saturated and unsaturated hydraulic conductivities in the near-saturation range(>–0.01 MPa) showed decreasing trends from bare sand to moss crusts and to algal crusts. Our data suggested that topographic differentiation of BSCs significantly affected not only soil water retention and hydraulic conductivities, but also the overall hydrology of the fixed sand dunes at a landscape scale, as seen in the reduction and spatial variability in deep soil water storage.展开更多
In May to August of 2011, we assessed the effects of extreme rainfall (quantity and intensity) events on the carbon release from soils covered by different types of biological soil crusts (BSCs) in fixed sand dunes in...In May to August of 2011, we assessed the effects of extreme rainfall (quantity and intensity) events on the carbon release from soils covered by different types of biological soil crusts (BSCs) in fixed sand dunes in the Tengger Desert, northern China. A Li-6400-09 Soil Chamber was used to measure the respiration rates of the BSCs immediately after the rainfall stopped, and continued until the respiration rates of the BSCs returned to the pre-rainfall basal rate. Our results showed that almost immediately after extreme rainfall events the respiration rates of algae crust and mixed crust were significantly inhibited, but moss crust was not significantly affected. The respiration rates of algae crust, mixed crust, and moss crust in extreme rainfall quantity and intensity events were, respectively, 0.12 and 0.41 μmolCO 2 /(m 2 ·s), 0.10 and 0.45 μmolCO 2 /(m 2 ·s), 0.83 and 1.69 μmolCO 2 /(m 2 ·s). Our study indicated that moss crust in the advanced succession stage can well adapt to extreme rainfall events in the short term.展开更多
Antioxidant enzyme activity,photosynthetic pigment content,and free malondialdehyde(MDA),as well as flavonoid content and the key enzyme activity in the flavonoid pathway were determined in two desert shrubs,Caryopter...Antioxidant enzyme activity,photosynthetic pigment content,and free malondialdehyde(MDA),as well as flavonoid content and the key enzyme activity in the flavonoid pathway were determined in two desert shrubs,Caryopteris mongolica Bunge and Reaumuria soongorica(Pall.)Maxim.under drought stress.The free MDA content was enhanced during the experimental period,which may be an indicator of oxidative stress.Superoxide dismutase(SOD),peroxidase(POD),and ascorbate peroxidase(APX)activities in C.mongholica showed a significant increase during the experiment,but catalase(CAT)activity was slightly decreased.On the other hand,POD and APX activities showed a significant increase and SOD and CAT activity data had no significant changes in R.soongorica.APX,SOD,and CAT activities were higher in R.soongorica than in C.mongholica,but MDA content was lower,indicating that the lower values of MDA were attributed to higher activities of antioxidant enzyme in R.soongorica.Chlorophyll content decreased significantly in the two shrubs during the experiment,which indicated that there was a photopro-tection mechanism through reducing light absorbance by decreasing pigments content.Caretonoids content increased in C.mongholica and decreased in R.soongorica.The ratio of Chla/Chlb decreased significantly but caretonoids/Chl revealed a sig-nificant increase in the two shrubs,which could be explained as no decrease of peripheral light-harvesting complexes and a higher tolerance to drought.Total flavonoid content and the activities of phenylalanine ammonialyase(PAL)and chalcone isomerase(CHI)showed different changes between C.mongholica and R.soongorica after treatment.These values decreased in R.soongorica and increased in C.mongholica except for PAL activity.However,anthocyanin content increased in the two shrubs,indicating that there was a different regulation response in the flavonoid pathway in the two shrubs under drought stress,and an-thocyanin should be an important antioxidant both in the shrubs.Our results demonstrated the different responses of antioxidant defense and drought tolerance ability between the two shrubs.展开更多
In this study,seasonal variation characteristics of surface soil microbial biomass carbon(MBC)and soil microbial biomass nitrogen(MBN)of an artificial vegetation area located in Shapotou for different time periods wer...In this study,seasonal variation characteristics of surface soil microbial biomass carbon(MBC)and soil microbial biomass nitrogen(MBN)of an artificial vegetation area located in Shapotou for different time periods were studied using the chloroform fumigation method,and the results were compared with those of near-natural vegetation areas and mobile dunes.Results showed that the MBC and MBN levels in the 0–5 cm soil layer were higher in autumn than in summer and spring.As the prolongation of vegetation restoration raised the MBC and MBN levels in summer and autumn,no clear variation was found in spring.However,the MBC and MBN in 5–20 cm had no obvious seasonal variation.During summer and autumn,the variation trend of MBC and MBN in the vertical direction was shown to be0–5>5–10>10–20 cm in the vegetation area,while for mobile dunes,the MBC and MBN levels increased as the depth increased.The natural vegetation area was shown to possess the highest MBC and MBN levels,and yet mobile dunes have the lowest MBC and MBN levels.MBC and MBN levels in artificial sand-binding vegetation increased with the prolongation of vegetation restoration,indicating that the succession of sand-binding vegetation will result in the accumulation of soil carbon and nitrogen,as well as the restoration of soil fertility.展开更多
Soil water repellency (SWR) is one of the most important physical properties of soils found all over the world, and it may have significant effects on the eco-hydrological processes of land ecosystems. In this study, ...Soil water repellency (SWR) is one of the most important physical properties of soils found all over the world, and it may have significant effects on the eco-hydrological processes of land ecosystems. In this study, the Capillary Rise Method was used to measure the SWR in the artificial vegetation area in Shapotou, located in the southeast area of the Tengger Desert, Ningxia Province of western China. The variation of the soil water repellency among different minor topographies, different depths and different particle sizes was analyzed. The results of the study indicate that the SWR shows distinct changes with vegetation restoration, and it increases with an increase in the period of dune stabilization. In the same vegetation area, the SWR of soils in inter-dune depressions or windward slopes is slightly greater than that in crest or leeward slopes. The SWR of 0-3 cm topsoil is significantly greater than that in the 3-6 cm soil layer. The SWR decreases with an increase in grain size and the differences among the SWRs of different sieved soil fractions are found to be significant. There is also a significantly positive correlation between the SWR and the proportion of soils with grain sizes of 0-0.05, 0.05-0.01 and 0.01-0.15 mm, and a significantly negative correlation between the SWR and the propotion of soils with grain sizes exceeding 0.15 mm. The increase of SWR in revegetation areas may depend on the continuous depositing of atmospheric dust on the stabilized dune surface as well as the formation of biological soil crusts, especially on the formation of algal and lichen crusts. Enhanced SWR influences the effectiveness of water use of sand plants inhabiting the sand dunes.展开更多
Metagenomic studies have demonstrated the existence of ammonia-oxidizing archaea(AOA) and revealed they are responsible for ammoxidation in some extreme environments. However, the changes in compositional structure an...Metagenomic studies have demonstrated the existence of ammonia-oxidizing archaea(AOA) and revealed they are responsible for ammoxidation in some extreme environments. However, the changes in compositional structure and ammonia-oxidation capacity of AOA communities in biological soil crusts(BSCs) of desert ecosystems remain poorly understood.Here, we utilized Illumina MiSeq sequencing and microbial functional gene array(GeoChip 5.0) to assess the above changes along a 51-year revegetation chronosequence in the Tengger Desert, China. The results showed a significant difference in AOA-community richness between 5-year-old BSCs and older ones. The most dominant phylum during BSC development was Crenarchaeota, and the corresponding species were ammonia-oxidizing_Crenarchaeote and environmental_samples_Crenarchaeota. Network analysis revealed that the positive correlations among dominant taxa increased, and their cooperation was reinforced in AOA communities during BSC succession. Redundancy analysis showed that the dominant factor influencing the change in AOA-community structure was soil texture. GeoChip 5.0 indicated that the amoA gene abundances of AOA and ammonia-oxidizing bacteria(AOB) were basically the same, demonstrating that AOA and AOB played an equally important role during BSCs development. Our study of the long-term succession of BSC demonstrated a persistent response of AOA communities to revegetation development in desert ecosystems.展开更多
Soil temperatures at 0, 5, 10 and 20 cm depths were monitored continuously at different microhabitats (beneath shrub canopy (BSC); bare intershrub spaces (BIS)) induced by xerophytic shrub (Caragana korshinskii Kom.) ...Soil temperatures at 0, 5, 10 and 20 cm depths were monitored continuously at different microhabitats (beneath shrub canopy (BSC); bare intershrub spaces (BIS)) induced by xerophytic shrub (Caragana korshinskii Kom.) canopy, respectively. We mainly aimed to assess the effects of shrub canopy and precipitation on the spatial-temporal variability of soil temperature. Results indicate that both precipitation and vegetation canopy significantly affect soil temperature. In clear days, soil temperatures within the BSC area were significantly lower than in the BIS at the same soil depth due to shading effects of shrub canopy. Diurnal variations of soil temperature show a unimodal sinusoidal curve. The amplitude of soil temperature tended to decrease and a hysteresis of diurnal maximum soil temperature existed at deeper soil layers. Vertical fluctuations of soil temperature displayed four typical curves. In the nighttime (approximately from sunset to sunrise), surface temperature within the BSC area was higher than in the BIS. In rainy days, however, soil temperatures were affected mainly by precipitation and the shrub canopy had a negligible effect on soil temperature, and little difference in soil temperature at the same soil depth was found between the BSC area and in the BIS. Diurnal variations in soil temperature decreased exclusively as rainfall continued and the vertical fluctuations of soil temperature show an increased tendency with increasing soil depth.展开更多
Water is the most important limiting factor in arid areas,and thus water resource management is critical for the health of dryland ecosystems.However,global climate change and anthropogenic activity make water resourc...Water is the most important limiting factor in arid areas,and thus water resource management is critical for the health of dryland ecosystems.However,global climate change and anthropogenic activity make water resource management more difficult,and this situation may be particularly crucial for dryland restoration,because of variation in water uptake patterns associated with artificial revegetation of different ages and vegetation type.However,there is lacking longterm restorations that are suitable for studying this issue.In Shapotou area,Northwest China,artificial revegetation areas were planted several times beginning in 1956,and now form a chronosequence of sand-binding landscapes that are ideal for studying variability in water uptake source by plants over succession.The stable isotopesδ18O andδ2H were employed to investigate the water uptake patterns of the typical revegetation shrubs Artemisia ordosica and Caragana korshinskii,which were planted in different years.We compared the stable isotope ratios of shrub stem water to groundwater,precipitation,and soil water pools at five layers(5−10,10−40,40−80,80−150,and 150−300 cm).The results indicate that Artemisia ordosica derived the majority of their water from the 20−150 cm soil layer,whereas Caragana korshinskii obtained water from the 40−150 cm soil layer.The main water sources of Artemisia ordosica and C.korshinskii plants changed over time,from deeper about 150 cm depth to shallow 20 cm soil layer.This study can provide insights into water uptake patterns of major desert vegetation and thus water management of artificial ecosystems,at least in Northwest China.展开更多
One-month old Zygophyllum xanthoxylon seedlings were grown under five different Ni concentrations (0, 50, 150, 450 and 900 mg/kg). Growth parameters, tissues Ni accumulation, soluble protein content, photosynthetic pi...One-month old Zygophyllum xanthoxylon seedlings were grown under five different Ni concentrations (0, 50, 150, 450 and 900 mg/kg). Growth parameters, tissues Ni accumulation, soluble protein content, photosynthetic pigment content, lipid peroxidation, antioxidative enzyme activities, and proline content were studied after one month of Ni exposure. The significant reduction in fresh biomass in the shoot and roots was detected at high Ni concentrations (≥450 mg/kg), whereas dry biomass was not significantly affected in both organs by any of the Ni doses tested. The Ni contents in the shoots and roots increased in a dose-dependent manner, and Ni contents in roots were higher than that in shoots at all treatments. The high Ni doses elevated soluble protein contents in leaves and roots. No visible symptoms of chlorosis were observed in leaves of plants grown in presence of Ni. Malondialdehyde (MDA) contents significantly increased in leaves and roots at high Ni treatments (≥450 mg/kg), indicating that Ni induces oxidative stress. Enzyme activities might play a central role in cellular protection against the Ni induced oxidative stress. Proline contents proportionally increased with the elevated Ni concentrations. Zygophyllum xanthoxylon revealed moderate Ni tolerance under tested culture conditions, and could be used as tools for revegetation for erosion control in moderate Ni contaminated sites.展开更多
Soil water repellency(WR) is an important physical characteristic of soil surface. It is capable of largely influencing the hydrological and geomorphological processes of soil, as well as affecting the ecological proc...Soil water repellency(WR) is an important physical characteristic of soil surface. It is capable of largely influencing the hydrological and geomorphological processes of soil, as well as affecting the ecological processes of plants, such as growth and seed germination, and has thus been a hot topic in recent research around the world. In this paper, the capillary rise method was used to study the soil WR characteristics of Nitraria tangutorun nebkhas. Soil water repellencies at different succession stages of Nitraria tangutorun were investigated, and the relationships between soil WR and soil organic matter, total N, and total P, soil texture, pH, and concentrations of CO3 2-, HCO3-, Cl-, SO4 2-, Na+, K+, Ca2+and Mg2+were discussed. Soil WR may be demonstrated at the following nebkhas dune evolvement stages: extremely degraded>degraded>stabilized>well developed>newly developed>quick sand. Apart from some soil at the bottom, the WR of other soils(crest and slope of dune) was found to be largest at the topsoil, and decreased as the soil depth increased. The results showed that multiple factors affected soil WR characteristics, e.g. WR increased significantly as the contents of soil organic matter and total N increased, but did not change as the total P content increased. Soil texture was a key factor affecting soil WR; soil WR increased significantly as clay content increased, and decreased significantly as sand content increased. Low pH was shown to be more suitable for the occurrence of soil WR. Four cations(Ca2+, Mg2+, K+and Na+) and two anions(Cl-and SO4 2-) enhanced soil WR, while CO3 2-decreased it. HCO3-did not show any observable effect. Finally, we established a best-fit general linear model(GLM) between soil-air-water contact angle(CA) and influencing factors(CA=5.606 sand+6.496(clay and silt)–2.353 pH+470.089 CO3 2-+11.346 Na+–407.707 Cl-–14.245 SO4 2-+0.734 total N–519.521). It was concluded that all soils contain subcritical WR(0°<CA<90°). The development and succession of Nitraria tangutorun nebkhas may improve the formation of soil subcritical WR. There exist significant relationships between soils subcritical WR and soil physical or chemical properties.展开更多
On the edge of the Tengger Desert in northern China,revegetation has changed the landscape from moving dunes to stabilized dunes covered by shrubs,which further modifies the pattern of rainfall redistribution.To study...On the edge of the Tengger Desert in northern China,revegetation has changed the landscape from moving dunes to stabilized dunes covered by shrubs,which further modifies the pattern of rainfall redistribution.To study rainfall interception loss by shrubs and its relationship to rainfall properties and crown structure,throughfalls passing through crowns of Artemisia ordosica Krash.and Caragana korshinskii Kom.were measured using nine PVC cups under the canopy of each of the two shrubs during 73 rain events over a three-year period,with total rainfall of 260.9 mm.Interception losses of gross rainfall by A.ordosica and C.korshinskii account for 15% and 27% of the total on a crown area basis,and 6% and 11% on a ground area basis,respectively.Individual throughfall(T) and interception(I) were significantly related to rainfall amount(Pg),duration(D),and intensity(R).Ratios of throughfall to rainfall(T/Pg) and interception to rainfall(I/Pg) were not only significantly related to Pg,D,and R,but also to shrub species,and interactions of species with crown volume(CV) and leaf area index(LAI).Under most rain events,interceptions by C.korshinskii with greater CV and LAI were significantly higher than those by A.ordosica,and more rainfall interception occurred at locations closer to the stems of the two shrubs.For C.korshinskii,I/Pg had a significant positive linear relation with CV and LAI,while T/Pg had a significant negative linear relation with them.CV has a greater influence on T/Pg and I/Pg than does LAI.Using a regression method,canopy water storage capacities are estimated to be 0.52 and 0.68 mm,and free throughfall coefficient to be 0.62 and 0.47 for A.ordosica and C.korshinskii,respectively.展开更多
Soil moisture is the key link between land hydrological and ecological processes which plays an important role in the terrestrial water cycle. As extreme weather events have increased in recent years, the stochastic s...Soil moisture is the key link between land hydrological and ecological processes which plays an important role in the terrestrial water cycle. As extreme weather events have increased in recent years, the stochastic simulation of soil moisture has gradually become the focus of ecohydrology research. Based on continuous monitoring of soil moisture data from 2008 to 2011, and historical precipitation data from 1991 to 2011, combined with the Rodriguez-Iturbe soil moisture dynamic stochastic model, soil moisture dynamics and its probability density function in a revegetated desert area was simulated. Results show that annual soil moisture dynamic changes of the revegetated desert area during the growing season complied with rainfall distribution; soil moisture probability presents a single-peak distribution in the plant rhizosphere layer (0-60 cm). The peak width in the 20 cm topsoil was wider than in other soils, and the distribution presented the strong fluctuations and multiple aggregates. The peak widths of 40 cm and 60 cm soil moisture probability distribution were small, which are in accordance with simulated results of the Rodriguez-Iturbe model. This confirms that the Rodriguez-Iturbe model has good applicability and can well simulate the statistical characteristics of soil moisture in an arid revegetated desert area.展开更多
Distribution of rainfall event sizes and interval lengths between events are important characteristics of arid and semi-arid climates. Understanding their importance will contribute to our ability to understand ecosys...Distribution of rainfall event sizes and interval lengths between events are important characteristics of arid and semi-arid climates. Understanding their importance will contribute to our ability to understand ecosystem dynamics in these regions. Rainfall event timing and magnitude are important drivers of ecosystem processes and are instrumental in creating landscape heterogeneity in arid and semi-arid regions. Rainfall event characteristics were analyzed using an automatic tipping-bucket rain-gauge record across the entire summer monsoon season from 2008 to 2015 at the arid desert area of Shapotou in the Tengger Desert, China. Changing the minimum inter-event time(MIT) from 30 min to 24 h alters the number of rainfall events from 64 to 25 for the event depth larger than 0.1 mm. The mean rainfall intensity declined from 0.95 mm/h to 0.53 mm/h, and the geometric mean event duration rose from 0.55 h to 4.4 h. The number of rainfall events, mean rainfall intensity, and geometric mean event duration differed under different criteria of individual rainfall depths, except that for an individual rainfall depth of 0.5, 1.0, and 5.0 mm. The aforementioned features differed only at the lowest range of the mean rainfall intensity and depth for MIT=3 and 6 h. These findings suggest that identification of event-based rainfall in this specific arid region can be better achieved by setting the MIT at six hours. The wide variation in rainfall event properties indicate the need for paying more attention to the proper selection and reporting of event criteria in studies that adopt event-based data analysis. This is especially true in quantifying effective rainfall for soil water replenishment in terms of rainfall depth and intensity with infrequent rainfall events.展开更多
The colonization and development of biological soil crusts(BSCs) are rarely discussed when investigating vegetation restoration with difference arrangement and structure of anthropogenically damaged areas in semi-arid...The colonization and development of biological soil crusts(BSCs) are rarely discussed when investigating vegetation restoration with difference arrangement and structure of anthropogenically damaged areas in semi-arid regions. The present study analyzes the relationships among coverage, height and density of woody vegetation and coverage and thickness of BSCs on the surface mine dumpsite in Heidaigou, China. Results showed that PR(Prunus sibirica L.), PT(Pinus tabulaeformis Carr.) and PPr(P. tabulaeformis Carr., P. sibirica L.) types had the highest coverage of total BSCs, which were 76.8%, 75.9% and 78.9%, respectively and PR showed the thickest BSCs of 4.41 mm. There was a significant correlation between coverage and thickness of BSCs and coverage and height of woody vegetation as a unimodal curve. Our findings suggest that a single woody plant species and low level coverage and height(no more than 30% and 300 cm, respectively) of woody plants may be able to create suitable conditions for facilitating BSCs restoration on the surface of mine dumpsites. The effects of vegetation arrangement and structure on BSCs colonization and development should be considered in reconstructing and managing woody vegetation in disturbed environments, such as surface mine dumpsites in semi-arid areas.展开更多
An increasing number of studies in recent years has elucidated distinguishable effects of stemflow on hydrology and biogeochemistry within a variety of ecosystems.Nonetheless,no known studies have investigated the tem...An increasing number of studies in recent years has elucidated distinguishable effects of stemflow on hydrology and biogeochemistry within a variety of ecosystems.Nonetheless,no known studies have investigated the temporal variability of stemflow volume within discrete rainfall events for xerophytic shrubs.Here,stemflow was monitored at 5-min intervals using a tipping-bucket rain gage during the 2015 growing season for a xerophytic shrub(Caragana korshinskii)within a water-limited arid desert ecosystem of northern China.We characterized the stemflow temporal variability,along with rainfall,and found the temporal heterogeneity of rainfall clearly affected the timing of stemflow inputs into basal soil within discrete rainfall events.The rainfall threshold value for stemflow generation is not a constant value but a range(0.6~2.1 mm,with an average of 1.1 mm)across rainfall events and is closely associated with the antecedent dry period.Time lags existed between the onset of rainfall and the onset of stemflow,and between rainfall peaks and stemflow peaks.Our findings are expected to be helpful for an improved process-based understanding of the temporal stemflow yield of xerophytic shrubs within water-limited arid desert ecosystems.展开更多
The main prevention and control area for wind-blown sand hazards in northern China is about 320000 km2 in size and includes sandlands to the east of the Helan Mountain and sandy deserts and desert-steppe transitional ...The main prevention and control area for wind-blown sand hazards in northern China is about 320000 km2 in size and includes sandlands to the east of the Helan Mountain and sandy deserts and desert-steppe transitional regions to the west of the Helan Mountain.Vegetation recovery and restoration is an important and effective approach for constraining wind-blown sand hazards in these areas.After more than 50 years of long-term ecological studies in the Shapotou region of the Tengger Desert,we found that revegetation changed the hydrological processes of the original sand dune system through the utilization and space-time redistribution of soil water.The spatiotemporal dynamics of soil water was significantly related to the dynamics of the replanted vegetation for a given regional precipitation condition.The long-term changes in hydrological processes in desert areas also drive replanted vegetation succession.The soil water carrying capacity of vegetation and the model for sand fixation by revegetation in aeolian desert areas where precipitation levels are less than 200 mm are also discussed.展开更多
Shrub species are considered the dominant plants in arid desert ecosystems,unlike in semiarid steppe zones or in grassland ecosystems.On the Alxa Plateau,northern China,sparse vegetation with cover ranging from 15% to...Shrub species are considered the dominant plants in arid desert ecosystems,unlike in semiarid steppe zones or in grassland ecosystems.On the Alxa Plateau,northern China,sparse vegetation with cover ranging from 15% to 30% is characterized mainly by multifarious shrubs because herbaceous species are strongly restricted by the extreme drought climate,wind erosion,overgrazing and sand burial.Patterns in shrub species richness and species abundance in relation to environmental conditions were examined by DCA(detrended correspondence analysis) and interpreted by a biplot.The rela-tionships between species diversity and environmental factors were examined using regression analyses.Our results show that the distributions of the shrub species in response to environmental conditions can be grouped into four ecological types,corresponding with the biological traits of the shrubs and their responses to the gradients of soil texture and soil water content.Patterns in species richness and species abundance were mainly determined by the deeper soil water content,instead of the soil texture as hypothesized by numerous studies in semiarid grasslands.With exception of the deeper soil water content,soil organic matter and total N content were positively correlated with species abundance,while pH was negatively correlated with it.These findings imply that it is vital for cur-rent shrub diversity conservation to reduce agricultural water use in the middle reaches of the Heihe River,which supplies water for the lower reaches in the western parts of the plateau,and to reduce the amount of groundwater exploitation and urban and oasis water use,to increase the water supply from Helan Mountain to the eastern desert of the Alxa Plateau.展开更多
Electric discharge phenomenon is often observed during the passage of sandstorms over desert regions and sometimes does great damage to human beings. Based on previous researches on the electrification of sandstorms b...Electric discharge phenomenon is often observed during the passage of sandstorms over desert regions and sometimes does great damage to human beings. Based on previous researches on the electrification of sandstorms by the scholars both at home and aboard,the authors conducted the simulation experiments on the electric fields of sandstorm-triggered creeping-saltating sand, suspending sand and watered suspending sand in the large-scale wind tunnel. According to the experimental results the electric field structure and its formation mechanism were analysed and discussed, the quantity of electric charges and electric field strengthwere measured and calculated, and finally several conclusions were drawn.展开更多
We produced and analyzed oasis structure information, and evaluated oasis functional stability using the multiple indicators based on Remote Sensing(RS) and Geographical Information System(GIS) in the arid region of C...We produced and analyzed oasis structure information, and evaluated oasis functional stability using the multiple indicators based on Remote Sensing(RS) and Geographical Information System(GIS) in the arid region of China in 2015. The results showed that the oases area was 193,734 km^2, accounting for 8.17% of the arid region of China. The spatial difference in the functional stability of oases was obvious. The Beijiang zone had the highest functional stability and was relatively stable state, and the Hexi Corridor-Alashan Plateau zone had the lowest functional stability and was relatively unstable. The functional stability is dominated by production and ecological functions, which have regional differences. Increasing oasis agricultural output, strengthening highway infrastructure construction and paying attention to education will become important ways to improve oasis functional stability. Water resources determine the ecological function, thus affecting the oasis functional stability. The results provide references for the formulation of related policies according to local conditions.展开更多
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.
基金funded by the National Basic Research Program of China (2013CB429901)the National Natural Science Foundation of China (41471434, 31170385)the Foundation for Excellent Youth Scholars of CAREERI, Chinese Academy of Sciences
文摘Biological soil crusts(BSCs) play an important role in surface soil hydrology. Soils dominated with moss BSCs may have higher infiltration rates than those dominated with cyanobacteria or algal BSCs. However, it is unnown whether improved infiltration in moss BSCs is accompanied by an increase in soil hydraulic conductivity or water retention capacity. We investigated this question in the Tengger Desert, where a 43-year-old revegetation program has promoted the formation of two distinct types of BSCs along topographic positions, i.e. the moss-dominated BSCs on the interdune land and windward slopes of the fixed sand dunes, and the algal-dominated BSCs on the crest and leeward slopes. Soil water retention capacity and hydraulic conductivity were measured using an indoor evaporation method and a field infiltration method. And the results were fitted to the van Genuchten–Mualem model. Unsaturated hydraulic conductivities under greater water pressure(<–0.01 MPa) and water retention capacities in the entire pressure head range were higher for both crust types than for bare sand. However, saturated and unsaturated hydraulic conductivities in the near-saturation range(>–0.01 MPa) showed decreasing trends from bare sand to moss crusts and to algal crusts. Our data suggested that topographic differentiation of BSCs significantly affected not only soil water retention and hydraulic conductivities, but also the overall hydrology of the fixed sand dunes at a landscape scale, as seen in the reduction and spatial variability in deep soil water storage.
基金supported by the Innovation Project of the Chinese Academy of Sciences(Grant No.KZCX2-EW-301-3)the National Natural Science Foundation of China(Grant Nos.41271061,41101081and40971033)
文摘In May to August of 2011, we assessed the effects of extreme rainfall (quantity and intensity) events on the carbon release from soils covered by different types of biological soil crusts (BSCs) in fixed sand dunes in the Tengger Desert, northern China. A Li-6400-09 Soil Chamber was used to measure the respiration rates of the BSCs immediately after the rainfall stopped, and continued until the respiration rates of the BSCs returned to the pre-rainfall basal rate. Our results showed that almost immediately after extreme rainfall events the respiration rates of algae crust and mixed crust were significantly inhibited, but moss crust was not significantly affected. The respiration rates of algae crust, mixed crust, and moss crust in extreme rainfall quantity and intensity events were, respectively, 0.12 and 0.41 μmolCO 2 /(m 2 ·s), 0.10 and 0.45 μmolCO 2 /(m 2 ·s), 0.83 and 1.69 μmolCO 2 /(m 2 ·s). Our study indicated that moss crust in the advanced succession stage can well adapt to extreme rainfall events in the short term.
基金supported by the National Natural Science Foundation of China (No.30800122,31070358 and 30960065)the West Light Foundation of the Chinese Academy of Sciences
文摘Antioxidant enzyme activity,photosynthetic pigment content,and free malondialdehyde(MDA),as well as flavonoid content and the key enzyme activity in the flavonoid pathway were determined in two desert shrubs,Caryopteris mongolica Bunge and Reaumuria soongorica(Pall.)Maxim.under drought stress.The free MDA content was enhanced during the experimental period,which may be an indicator of oxidative stress.Superoxide dismutase(SOD),peroxidase(POD),and ascorbate peroxidase(APX)activities in C.mongholica showed a significant increase during the experiment,but catalase(CAT)activity was slightly decreased.On the other hand,POD and APX activities showed a significant increase and SOD and CAT activity data had no significant changes in R.soongorica.APX,SOD,and CAT activities were higher in R.soongorica than in C.mongholica,but MDA content was lower,indicating that the lower values of MDA were attributed to higher activities of antioxidant enzyme in R.soongorica.Chlorophyll content decreased significantly in the two shrubs during the experiment,which indicated that there was a photopro-tection mechanism through reducing light absorbance by decreasing pigments content.Caretonoids content increased in C.mongholica and decreased in R.soongorica.The ratio of Chla/Chlb decreased significantly but caretonoids/Chl revealed a sig-nificant increase in the two shrubs,which could be explained as no decrease of peripheral light-harvesting complexes and a higher tolerance to drought.Total flavonoid content and the activities of phenylalanine ammonialyase(PAL)and chalcone isomerase(CHI)showed different changes between C.mongholica and R.soongorica after treatment.These values decreased in R.soongorica and increased in C.mongholica except for PAL activity.However,anthocyanin content increased in the two shrubs,indicating that there was a different regulation response in the flavonoid pathway in the two shrubs under drought stress,and an-thocyanin should be an important antioxidant both in the shrubs.Our results demonstrated the different responses of antioxidant defense and drought tolerance ability between the two shrubs.
基金supported by the Chinese National Natu-ral Scientific Foundation(41171077,40801002,40971031)
文摘In this study,seasonal variation characteristics of surface soil microbial biomass carbon(MBC)and soil microbial biomass nitrogen(MBN)of an artificial vegetation area located in Shapotou for different time periods were studied using the chloroform fumigation method,and the results were compared with those of near-natural vegetation areas and mobile dunes.Results showed that the MBC and MBN levels in the 0–5 cm soil layer were higher in autumn than in summer and spring.As the prolongation of vegetation restoration raised the MBC and MBN levels in summer and autumn,no clear variation was found in spring.However,the MBC and MBN in 5–20 cm had no obvious seasonal variation.During summer and autumn,the variation trend of MBC and MBN in the vertical direction was shown to be0–5>5–10>10–20 cm in the vegetation area,while for mobile dunes,the MBC and MBN levels increased as the depth increased.The natural vegetation area was shown to possess the highest MBC and MBN levels,and yet mobile dunes have the lowest MBC and MBN levels.MBC and MBN levels in artificial sand-binding vegetation increased with the prolongation of vegetation restoration,indicating that the succession of sand-binding vegetation will result in the accumulation of soil carbon and nitrogen,as well as the restoration of soil fertility.
基金supported by the National Basic Research Program of China(Grant No.2009CB421303)the National Natural Sciences Foundation(Grant Nos.40971031,40701002)
文摘Soil water repellency (SWR) is one of the most important physical properties of soils found all over the world, and it may have significant effects on the eco-hydrological processes of land ecosystems. In this study, the Capillary Rise Method was used to measure the SWR in the artificial vegetation area in Shapotou, located in the southeast area of the Tengger Desert, Ningxia Province of western China. The variation of the soil water repellency among different minor topographies, different depths and different particle sizes was analyzed. The results of the study indicate that the SWR shows distinct changes with vegetation restoration, and it increases with an increase in the period of dune stabilization. In the same vegetation area, the SWR of soils in inter-dune depressions or windward slopes is slightly greater than that in crest or leeward slopes. The SWR of 0-3 cm topsoil is significantly greater than that in the 3-6 cm soil layer. The SWR decreases with an increase in grain size and the differences among the SWRs of different sieved soil fractions are found to be significant. There is also a significantly positive correlation between the SWR and the proportion of soils with grain sizes of 0-0.05, 0.05-0.01 and 0.01-0.15 mm, and a significantly negative correlation between the SWR and the propotion of soils with grain sizes exceeding 0.15 mm. The increase of SWR in revegetation areas may depend on the continuous depositing of atmospheric dust on the stabilized dune surface as well as the formation of biological soil crusts, especially on the formation of algal and lichen crusts. Enhanced SWR influences the effectiveness of water use of sand plants inhabiting the sand dunes.
基金supported financially by the Strategic Priority Research Program of Chinese Academy of Sciences (Grant No. XDA2003010301)the National Natural Science Foundation of China (Grant No. 41621001)
文摘Metagenomic studies have demonstrated the existence of ammonia-oxidizing archaea(AOA) and revealed they are responsible for ammoxidation in some extreme environments. However, the changes in compositional structure and ammonia-oxidation capacity of AOA communities in biological soil crusts(BSCs) of desert ecosystems remain poorly understood.Here, we utilized Illumina MiSeq sequencing and microbial functional gene array(GeoChip 5.0) to assess the above changes along a 51-year revegetation chronosequence in the Tengger Desert, China. The results showed a significant difference in AOA-community richness between 5-year-old BSCs and older ones. The most dominant phylum during BSC development was Crenarchaeota, and the corresponding species were ammonia-oxidizing_Crenarchaeote and environmental_samples_Crenarchaeota. Network analysis revealed that the positive correlations among dominant taxa increased, and their cooperation was reinforced in AOA communities during BSC succession. Redundancy analysis showed that the dominant factor influencing the change in AOA-community structure was soil texture. GeoChip 5.0 indicated that the amoA gene abundances of AOA and ammonia-oxidizing bacteria(AOB) were basically the same, demonstrating that AOA and AOB played an equally important role during BSCs development. Our study of the long-term succession of BSC demonstrated a persistent response of AOA communities to revegetation development in desert ecosystems.
基金supported by the 100-Talents Program of the Chinese Academy of Sciences
文摘Soil temperatures at 0, 5, 10 and 20 cm depths were monitored continuously at different microhabitats (beneath shrub canopy (BSC); bare intershrub spaces (BIS)) induced by xerophytic shrub (Caragana korshinskii Kom.) canopy, respectively. We mainly aimed to assess the effects of shrub canopy and precipitation on the spatial-temporal variability of soil temperature. Results indicate that both precipitation and vegetation canopy significantly affect soil temperature. In clear days, soil temperatures within the BSC area were significantly lower than in the BIS at the same soil depth due to shading effects of shrub canopy. Diurnal variations of soil temperature show a unimodal sinusoidal curve. The amplitude of soil temperature tended to decrease and a hysteresis of diurnal maximum soil temperature existed at deeper soil layers. Vertical fluctuations of soil temperature displayed four typical curves. In the nighttime (approximately from sunset to sunrise), surface temperature within the BSC area was higher than in the BIS. In rainy days, however, soil temperatures were affected mainly by precipitation and the shrub canopy had a negligible effect on soil temperature, and little difference in soil temperature at the same soil depth was found between the BSC area and in the BIS. Diurnal variations in soil temperature decreased exclusively as rainfall continued and the vertical fluctuations of soil temperature show an increased tendency with increasing soil depth.
基金the Strategic Priority Research Program of the Chinese Academy of Sciences(XDA23060202)the Chinese National Natural Sciences Foundation(Grant Nos.41530750,41771101).
文摘Water is the most important limiting factor in arid areas,and thus water resource management is critical for the health of dryland ecosystems.However,global climate change and anthropogenic activity make water resource management more difficult,and this situation may be particularly crucial for dryland restoration,because of variation in water uptake patterns associated with artificial revegetation of different ages and vegetation type.However,there is lacking longterm restorations that are suitable for studying this issue.In Shapotou area,Northwest China,artificial revegetation areas were planted several times beginning in 1956,and now form a chronosequence of sand-binding landscapes that are ideal for studying variability in water uptake source by plants over succession.The stable isotopesδ18O andδ2H were employed to investigate the water uptake patterns of the typical revegetation shrubs Artemisia ordosica and Caragana korshinskii,which were planted in different years.We compared the stable isotope ratios of shrub stem water to groundwater,precipitation,and soil water pools at five layers(5−10,10−40,40−80,80−150,and 150−300 cm).The results indicate that Artemisia ordosica derived the majority of their water from the 20−150 cm soil layer,whereas Caragana korshinskii obtained water from the 40−150 cm soil layer.The main water sources of Artemisia ordosica and C.korshinskii plants changed over time,from deeper about 150 cm depth to shallow 20 cm soil layer.This study can provide insights into water uptake patterns of major desert vegetation and thus water management of artificial ecosystems,at least in Northwest China.
基金supported by the China National Funds for Distinguished Young Scientists (No. 40825001)the Talent Training Program for Young Scientist in West China of Chinese Academy of Sciences
文摘One-month old Zygophyllum xanthoxylon seedlings were grown under five different Ni concentrations (0, 50, 150, 450 and 900 mg/kg). Growth parameters, tissues Ni accumulation, soluble protein content, photosynthetic pigment content, lipid peroxidation, antioxidative enzyme activities, and proline content were studied after one month of Ni exposure. The significant reduction in fresh biomass in the shoot and roots was detected at high Ni concentrations (≥450 mg/kg), whereas dry biomass was not significantly affected in both organs by any of the Ni doses tested. The Ni contents in the shoots and roots increased in a dose-dependent manner, and Ni contents in roots were higher than that in shoots at all treatments. The high Ni doses elevated soluble protein contents in leaves and roots. No visible symptoms of chlorosis were observed in leaves of plants grown in presence of Ni. Malondialdehyde (MDA) contents significantly increased in leaves and roots at high Ni treatments (≥450 mg/kg), indicating that Ni induces oxidative stress. Enzyme activities might play a central role in cellular protection against the Ni induced oxidative stress. Proline contents proportionally increased with the elevated Ni concentrations. Zygophyllum xanthoxylon revealed moderate Ni tolerance under tested culture conditions, and could be used as tools for revegetation for erosion control in moderate Ni contaminated sites.
基金supported by the National Basic Research Program of China (2009CB421303)the Strategic Priority Re- search Program–Climate Change: Carbon Budget and Relevant Issues of the Chinese Academy of Sciences (XDA05050406-1)the National Natural Science Foundation of China (40930636, 41240003, 41271061)
文摘Soil water repellency(WR) is an important physical characteristic of soil surface. It is capable of largely influencing the hydrological and geomorphological processes of soil, as well as affecting the ecological processes of plants, such as growth and seed germination, and has thus been a hot topic in recent research around the world. In this paper, the capillary rise method was used to study the soil WR characteristics of Nitraria tangutorun nebkhas. Soil water repellencies at different succession stages of Nitraria tangutorun were investigated, and the relationships between soil WR and soil organic matter, total N, and total P, soil texture, pH, and concentrations of CO3 2-, HCO3-, Cl-, SO4 2-, Na+, K+, Ca2+and Mg2+were discussed. Soil WR may be demonstrated at the following nebkhas dune evolvement stages: extremely degraded>degraded>stabilized>well developed>newly developed>quick sand. Apart from some soil at the bottom, the WR of other soils(crest and slope of dune) was found to be largest at the topsoil, and decreased as the soil depth increased. The results showed that multiple factors affected soil WR characteristics, e.g. WR increased significantly as the contents of soil organic matter and total N increased, but did not change as the total P content increased. Soil texture was a key factor affecting soil WR; soil WR increased significantly as clay content increased, and decreased significantly as sand content increased. Low pH was shown to be more suitable for the occurrence of soil WR. Four cations(Ca2+, Mg2+, K+and Na+) and two anions(Cl-and SO4 2-) enhanced soil WR, while CO3 2-decreased it. HCO3-did not show any observable effect. Finally, we established a best-fit general linear model(GLM) between soil-air-water contact angle(CA) and influencing factors(CA=5.606 sand+6.496(clay and silt)–2.353 pH+470.089 CO3 2-+11.346 Na+–407.707 Cl-–14.245 SO4 2-+0.734 total N–519.521). It was concluded that all soils contain subcritical WR(0°<CA<90°). The development and succession of Nitraria tangutorun nebkhas may improve the formation of soil subcritical WR. There exist significant relationships between soils subcritical WR and soil physical or chemical properties.
基金supported by the National Natural Scientific Foundation of China (40825001 and 30870401)
文摘On the edge of the Tengger Desert in northern China,revegetation has changed the landscape from moving dunes to stabilized dunes covered by shrubs,which further modifies the pattern of rainfall redistribution.To study rainfall interception loss by shrubs and its relationship to rainfall properties and crown structure,throughfalls passing through crowns of Artemisia ordosica Krash.and Caragana korshinskii Kom.were measured using nine PVC cups under the canopy of each of the two shrubs during 73 rain events over a three-year period,with total rainfall of 260.9 mm.Interception losses of gross rainfall by A.ordosica and C.korshinskii account for 15% and 27% of the total on a crown area basis,and 6% and 11% on a ground area basis,respectively.Individual throughfall(T) and interception(I) were significantly related to rainfall amount(Pg),duration(D),and intensity(R).Ratios of throughfall to rainfall(T/Pg) and interception to rainfall(I/Pg) were not only significantly related to Pg,D,and R,but also to shrub species,and interactions of species with crown volume(CV) and leaf area index(LAI).Under most rain events,interceptions by C.korshinskii with greater CV and LAI were significantly higher than those by A.ordosica,and more rainfall interception occurred at locations closer to the stems of the two shrubs.For C.korshinskii,I/Pg had a significant positive linear relation with CV and LAI,while T/Pg had a significant negative linear relation with them.CV has a greater influence on T/Pg and I/Pg than does LAI.Using a regression method,canopy water storage capacities are estimated to be 0.52 and 0.68 mm,and free throughfall coefficient to be 0.62 and 0.47 for A.ordosica and C.korshinskii,respectively.
基金supported by the Key Orientation Project of Chinese Academy of Sciences(KZCX2-EW-301-3)Talented Young Scientist Fund of the Cold and Arid Regions Environmental and Engineering Research Institute,CAS(51Y251971)National Natural Scientific Foundation of China(41101054,41201084)
文摘Soil moisture is the key link between land hydrological and ecological processes which plays an important role in the terrestrial water cycle. As extreme weather events have increased in recent years, the stochastic simulation of soil moisture has gradually become the focus of ecohydrology research. Based on continuous monitoring of soil moisture data from 2008 to 2011, and historical precipitation data from 1991 to 2011, combined with the Rodriguez-Iturbe soil moisture dynamic stochastic model, soil moisture dynamics and its probability density function in a revegetated desert area was simulated. Results show that annual soil moisture dynamic changes of the revegetated desert area during the growing season complied with rainfall distribution; soil moisture probability presents a single-peak distribution in the plant rhizosphere layer (0-60 cm). The peak width in the 20 cm topsoil was wider than in other soils, and the distribution presented the strong fluctuations and multiple aggregates. The peak widths of 40 cm and 60 cm soil moisture probability distribution were small, which are in accordance with simulated results of the Rodriguez-Iturbe model. This confirms that the Rodriguez-Iturbe model has good applicability and can well simulate the statistical characteristics of soil moisture in an arid revegetated desert area.
基金funded by the National Natural Science Foundation of China (Grant Nos. 41530750, 41501108 and 41371101)
文摘Distribution of rainfall event sizes and interval lengths between events are important characteristics of arid and semi-arid climates. Understanding their importance will contribute to our ability to understand ecosystem dynamics in these regions. Rainfall event timing and magnitude are important drivers of ecosystem processes and are instrumental in creating landscape heterogeneity in arid and semi-arid regions. Rainfall event characteristics were analyzed using an automatic tipping-bucket rain-gauge record across the entire summer monsoon season from 2008 to 2015 at the arid desert area of Shapotou in the Tengger Desert, China. Changing the minimum inter-event time(MIT) from 30 min to 24 h alters the number of rainfall events from 64 to 25 for the event depth larger than 0.1 mm. The mean rainfall intensity declined from 0.95 mm/h to 0.53 mm/h, and the geometric mean event duration rose from 0.55 h to 4.4 h. The number of rainfall events, mean rainfall intensity, and geometric mean event duration differed under different criteria of individual rainfall depths, except that for an individual rainfall depth of 0.5, 1.0, and 5.0 mm. The aforementioned features differed only at the lowest range of the mean rainfall intensity and depth for MIT=3 and 6 h. These findings suggest that identification of event-based rainfall in this specific arid region can be better achieved by setting the MIT at six hours. The wide variation in rainfall event properties indicate the need for paying more attention to the proper selection and reporting of event criteria in studies that adopt event-based data analysis. This is especially true in quantifying effective rainfall for soil water replenishment in terms of rainfall depth and intensity with infrequent rainfall events.
基金sponsored by the National Natural Scientific Foundation of China (41501270 and 41530746)Foundation for Excellent Youth Scholars of Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences
文摘The colonization and development of biological soil crusts(BSCs) are rarely discussed when investigating vegetation restoration with difference arrangement and structure of anthropogenically damaged areas in semi-arid regions. The present study analyzes the relationships among coverage, height and density of woody vegetation and coverage and thickness of BSCs on the surface mine dumpsite in Heidaigou, China. Results showed that PR(Prunus sibirica L.), PT(Pinus tabulaeformis Carr.) and PPr(P. tabulaeformis Carr., P. sibirica L.) types had the highest coverage of total BSCs, which were 76.8%, 75.9% and 78.9%, respectively and PR showed the thickest BSCs of 4.41 mm. There was a significant correlation between coverage and thickness of BSCs and coverage and height of woody vegetation as a unimodal curve. Our findings suggest that a single woody plant species and low level coverage and height(no more than 30% and 300 cm, respectively) of woody plants may be able to create suitable conditions for facilitating BSCs restoration on the surface of mine dumpsites. The effects of vegetation arrangement and structure on BSCs colonization and development should be considered in reconstructing and managing woody vegetation in disturbed environments, such as surface mine dumpsites in semi-arid areas.
基金supported by the National Natural Science Foundation of China (41530750, 41501108, 41371101)the CAS "Light of West China" Program
文摘An increasing number of studies in recent years has elucidated distinguishable effects of stemflow on hydrology and biogeochemistry within a variety of ecosystems.Nonetheless,no known studies have investigated the temporal variability of stemflow volume within discrete rainfall events for xerophytic shrubs.Here,stemflow was monitored at 5-min intervals using a tipping-bucket rain gage during the 2015 growing season for a xerophytic shrub(Caragana korshinskii)within a water-limited arid desert ecosystem of northern China.We characterized the stemflow temporal variability,along with rainfall,and found the temporal heterogeneity of rainfall clearly affected the timing of stemflow inputs into basal soil within discrete rainfall events.The rainfall threshold value for stemflow generation is not a constant value but a range(0.6~2.1 mm,with an average of 1.1 mm)across rainfall events and is closely associated with the antecedent dry period.Time lags existed between the onset of rainfall and the onset of stemflow,and between rainfall peaks and stemflow peaks.Our findings are expected to be helpful for an improved process-based understanding of the temporal stemflow yield of xerophytic shrubs within water-limited arid desert ecosystems.
基金supported by the National Basic Research Program of China(2013CB429906)
文摘The main prevention and control area for wind-blown sand hazards in northern China is about 320000 km2 in size and includes sandlands to the east of the Helan Mountain and sandy deserts and desert-steppe transitional regions to the west of the Helan Mountain.Vegetation recovery and restoration is an important and effective approach for constraining wind-blown sand hazards in these areas.After more than 50 years of long-term ecological studies in the Shapotou region of the Tengger Desert,we found that revegetation changed the hydrological processes of the original sand dune system through the utilization and space-time redistribution of soil water.The spatiotemporal dynamics of soil water was significantly related to the dynamics of the replanted vegetation for a given regional precipitation condition.The long-term changes in hydrological processes in desert areas also drive replanted vegetation succession.The soil water carrying capacity of vegetation and the model for sand fixation by revegetation in aeolian desert areas where precipitation levels are less than 200 mm are also discussed.
基金Supported by National Key Technology R & D Program (Grant Nos. 2007BAD46B03, 2006BAD26B0201)National Natural Science Foundation of China (Gant No. 40825001)
文摘Shrub species are considered the dominant plants in arid desert ecosystems,unlike in semiarid steppe zones or in grassland ecosystems.On the Alxa Plateau,northern China,sparse vegetation with cover ranging from 15% to 30% is characterized mainly by multifarious shrubs because herbaceous species are strongly restricted by the extreme drought climate,wind erosion,overgrazing and sand burial.Patterns in shrub species richness and species abundance in relation to environmental conditions were examined by DCA(detrended correspondence analysis) and interpreted by a biplot.The rela-tionships between species diversity and environmental factors were examined using regression analyses.Our results show that the distributions of the shrub species in response to environmental conditions can be grouped into four ecological types,corresponding with the biological traits of the shrubs and their responses to the gradients of soil texture and soil water content.Patterns in species richness and species abundance were mainly determined by the deeper soil water content,instead of the soil texture as hypothesized by numerous studies in semiarid grasslands.With exception of the deeper soil water content,soil organic matter and total N content were positively correlated with species abundance,while pH was negatively correlated with it.These findings imply that it is vital for cur-rent shrub diversity conservation to reduce agricultural water use in the middle reaches of the Heihe River,which supplies water for the lower reaches in the western parts of the plateau,and to reduce the amount of groundwater exploitation and urban and oasis water use,to increase the water supply from Helan Mountain to the eastern desert of the Alxa Plateau.
基金This project was supported by the InnovationProject of the Chinese Academy of Sciences (Grant No. 210027) the Knowledge Innovation Project of Chinese Academy of Sciences (GrantNo. KZCX2-304)+1 种基金the National Natural Science Foundation of China(Grant No.39971013) the State Key Basic Research Development Planning (Grnat No.20000487).
文摘Electric discharge phenomenon is often observed during the passage of sandstorms over desert regions and sometimes does great damage to human beings. Based on previous researches on the electrification of sandstorms by the scholars both at home and aboard,the authors conducted the simulation experiments on the electric fields of sandstorm-triggered creeping-saltating sand, suspending sand and watered suspending sand in the large-scale wind tunnel. According to the experimental results the electric field structure and its formation mechanism were analysed and discussed, the quantity of electric charges and electric field strengthwere measured and calculated, and finally several conclusions were drawn.
基金This work was supported by the National Key Research and Development Program of China (2017YFC0504301)the Strategic Priority Research Program of Chinese Academy of Sciences,Pan-Third Pole Environment Study for a Green Silk Road (Pan-TPE)
文摘We produced and analyzed oasis structure information, and evaluated oasis functional stability using the multiple indicators based on Remote Sensing(RS) and Geographical Information System(GIS) in the arid region of China in 2015. The results showed that the oases area was 193,734 km^2, accounting for 8.17% of the arid region of China. The spatial difference in the functional stability of oases was obvious. The Beijiang zone had the highest functional stability and was relatively stable state, and the Hexi Corridor-Alashan Plateau zone had the lowest functional stability and was relatively unstable. The functional stability is dominated by production and ecological functions, which have regional differences. Increasing oasis agricultural output, strengthening highway infrastructure construction and paying attention to education will become important ways to improve oasis functional stability. Water resources determine the ecological function, thus affecting the oasis functional stability. The results provide references for the formulation of related policies according to local conditions.
