Responses of plant diversity and soil microorganism diversity to nitrogen addition in the desert steppe,China

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.

Effects of long-term fencing on soil microbial community structure and function in the desert steppe,China

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.

Response of soil respiration to short-term changes in precipitation and nitrogen addition in a desert steppe

Changes in precipitation and nitrogen(N)addition may significantly affect the processes of soil carbon(C)cycle in terrestrial ecosystems,such as soil respiration.However,relatively few studies have investigated the effects of changes in precipitation and N addition on soil respiration in the upper soil layer in desert steppes.In this study,we conducted a control experiment that involved a field simulation from July 2020 to December 2021 in a desert steppe in Yanchi County,China.Specifically,we measured soil parameters including soil temperature,soil moisture,total nitrogen(TN),soil organic carbon(SOC),soil microbial biomass carbon(SMBC),soil microbial biomass nitrogen(SMBN),and contents of soil microorganisms including bacteria,fungi,actinomyces,and protozoa,and determined the components of soil respiration including soil respiration with litter(RS+L),soil respiration without litter(RS),and litter respiration(RL)under short-term changes in precipitation(control,increased precipitation by 30%,and decreased precipitation by 30%)and N addition(0.0 and 10.0 g/(m^(2)·a))treatments.Our results indicated that short-term changes in precipitation and N addition had substantial positive effects on the contents of TN,SOC,and SMBC,as well as the contents of soil actinomyces and protozoa.In addition,N addition significantly enhanced the rates of RS+L and RS by 4.8%and 8.0%(P<0.05),respectively.The increase in precipitation markedly increased the rates of RS+L and RS by 2.3%(P<0.05)and 5.7%(P<0.001),respectively.The decrease in precipitation significantly increased the rates of RS+L and RS by 12.9%(P<0.05)and 23.4%(P<0.001),respectively.In contrast,short-term changes in precipitation and N addition had no significant effects on RL rate(P>0.05).The mean RL/RS+L value observed under all treatments was 27.63%,which suggested that RL is an important component of soil respiration in the desert steppe ecosystems.The results also showed that short-term changes in precipitation and N addition had significant interactive effects on the rates of RS+L,RS,and RL(P<0.001).In addition,soil temperature was the most important abiotic factor that affected the rates of RS+L,RS,and RL.Results of the correlation analysis demonstrated that the rates of RS+L,RS,and RL were closely related to soil temperature,soil moisture,TN,SOC,and the contents of soil microorganisms,and the structural equation model revealed that SOC and SMBC are the key factors influencing the rates of RS+L,RS,and RL.This study provides further insights into the characteristics of soil C emissions in desert steppe ecosystems in the context of climate change,which can be used as a reference for future related studies.

Responses of vegetation yield to precipitation and reference evapotranspiration in a desert steppe in Inner Mongolia,China

Drought,which restricts the sustainable development of agriculture,ecological health,and social economy,is affected by a variety of factors.It is widely accepted that a single variable cannot fully reflect the characteristics of drought events.Studying precipitation,reference evapotranspiration(ET_(0)),and vegetation yield can derive information to help conserve water resources in grassland ecosystems in arid and semi-arid regions.In this study,the interactions of precipitation,ET_(0),and vegetation yield in Darhan Muminggan Joint Banner(DMJB),a desert steppe in Inner Mongolia Autonomous Region,China were explored using two-dimensional(2D)and three-dimensional(3D)joint distribution models.Three types of Copula functions were applied to quantitatively analyze the joint distribution probability of different combinations of precipitation,ET_(0),and vegetation yield.For the precipitation–ET_(0)dry–wet type,the 2D joint distribution probability with precipitation≤245.69 mm/a or ET_(0)≥959.20 mm/a in DMJB was approximately 0.60,while the joint distribution probability with precipitation≤245.69 mm/a and ET_(0)≥959.20 mm/a was approximately 0.20.Correspondingly,the joint return period that at least one of the two events(precipitation was dry or ET_(0)was wet)occurred was 2 a,and the co-occurrence return period that both events(precipitation was dry and ET_(0)was wet)occurred was 5 a.Under this condition,the interval between dry and wet events would be short,the water supply and demand were unbalanced,and the water demand of vegetation would not be met.In addition,when precipitation remained stable and ET_(0)increased,the 3D joint distribution probability that vegetation yield would decrease due to water shortage in the precipitation–ET_(0)dry–wet years could reach up to 0.60–0.70.In future work,irrigation activities and water allocation criteria need to be implemented to increase vegetation yield and the safety of water resources in the desert steppe of Inner Mongolia.

Biocrust-induced partitioning of soil water between grass and shrub in a desert steppe of Northwest China

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.

Interactive effects of wind speed,vegetation coverage and soil moisture in controlling wind erosion in a temperate desert steppe,Inner Mongolia of China

The rapid desertification of grasslands in Inner Mongolia of China poses a significant ecological threaten to northern China. The combined effects of anthropogenic disturbances （e.g., overgrazing） and biophysical processes （e.g., soil erosion） have led to vegetation degradation and the consequent acceleration of regional desertification. Thus, mitigating the accelerated wind erosion, a cause and effect of grassland desertification, is critical for the sustainable management of grasslands. Here, a combination of mobile wind tunnel experiments and wind erosion model was used to explore the effects of different levels of vegetation coverage, soil moisture and wind speed on wind erosion at different positions of a slope inside an enclosed desert steppe in the Xilamuren grassland of Inner Mongolia. The results indicated a significant spatial difference in wind erosion intensities depending on the vegetation coverage, with a strong decreasing trend from the top to the base of the slope. Increasing vegetation coverage resulted in a rapid decrease in wind erosion as explained by a power function correlation. Vegetation coverage was found to be a dominant control on wind erosion by increasing the surface roughness and by lowering the threshold wind velocity for erosion. The critical vegetation coverage required for effectively controlling wind erosion was found to be higher than 60%. Further, the wind erosion rates were negatively correlated with surface soil moisture and the mass flux in aeolian sand transport increased with increasing wind speed. We developed a mathematical model of wind erosion based on the results of an orthogonal array design. The results from the model simulation indicated that the standardized regression coefficients of the main effects of the three factors （vegetation coverage, soil moisture and wind speed） on the mass flux in aeolian sand transport were in the following order： wind speed〉vegetation coverage〉soil moisture. These three factors had different levels of interactive effects on the mass flux in aeolian sand transport. Our results will improve the understanding of the interactive effects of wind speed, vegetation coverage and soil moisture in controlling wind erosion in desert steppes, and will be helpful for the design of desertification control programs in future.

Effects of climate change on phenology and primary productivity in the desert steppe of Inner Mongolia

Variations in temperature and precipitation affect local ecosystems. Considerable spatial and temporal heterogeneity exists in arid ecosystems such as desert steppes. In this study, we analyzed the spatiotemporal dy- namics of climate and vegetation phenology in the desert steppe of Inner Mongolia, China using meteorological data （1961-2010） from 11 stations and phenology data （2004-2012） from 6 ecological observation stations. We also estimated the gross primary production for the period of 1982-2009 and found that the annual mean tem- perature increased at a rate of 0.47~C/decade during 1961-2010, with the last 10 years being consistently warmer than the 50 years as an average. The most significant warming occurred in winters. Annual precipitation slightly decreased during the 50-year period, with summer precipitation experiencing the highest drop in the last 10 years, and spring precipitation, a rise. Spatially, annual precipitation increased significantly in the northeastern and eastern central areas next to the typical steppe. From 2004 to 2012, vegetation green-up and senescence date advanced in the study area, shortening the growing season. Consequently, the primary productivity of the desert steppe de- creased along the precipitation gradient from southeast to northwest. Temporally, productivity increased during the period of 1982-1999 and significantly decreased after 2000. Overall, the Last decade witnessed the most dramatic climatic changes that were likely to negatively affect the desert steppe ecosystem. The decreased primary produc- tivity, in particular, decreases ecosystem resilience and impairs the livelihood of local farmers and herdsmen.

Grazing exclusion-induced shifts,the relative importance of environmental filtering,biotic interactions and dispersal limitation in shaping desert steppe communities,northern China

Grazing exclusion is one of the most efficient approaches to restore degraded grassland but may negatively affects the recovery of species diversity. Changes in plant species diversity should be a consequence of the ecological assembly process. Local community assembly is influenced by environmental filtering, biotic interactions, and dispersal. However, how these factors potentially contribute to changes to species diversity is poorly understood, especially in harsh environments. In this study, two management sites within a Stipa breviflora desert steppe community（typical natural steppe） were selected in northern China. In one of the two management sites, grazing has been excluded since 2010 and in the other with open grazing by sheep. In August 2016, three plots were established and 100 sampling units were created within each plot in a 5 m×5 m area at the two management sites. To assess the effects of grazing exclusion on S. breviflora steppe, we analyzed the vegetation biomass, species diversity,soil organic carbon, and soil particle size distribution using paired T-tests. In addition, variation partitioning was applied to determine the relative importance of environmental filtering and dispersal limitation. Null mode analysis was used to quantify the influence of biotic interactions in conjunction with Eco Sim niche overlap and co-occurrence values. Our results demonstrated that（1） species diversity significantly decreased and the main improvements in soil quality occurred in the topsoil 0–10 cm after the grazing exclusion;（2） environmental filtering was important for community assembly between grazed and fenced grassland and this appears particularly true for soil particle size distribution, which may be well correlated with soil hydrological processes; and（3） however, competitive exclusion may play a significant role within the exclusion. The multiple pathways of assembly may collectively determine negative effects on the restoration of species diversity. Therefore, designers should be aware of the risk of reducing grazing exclusion-induced species diversity and account for manipulating processes. This in turn will reduce dominant species and promote environmental heterogeneity to maximize species diversity in semi-arid regions.

Analysis of the Variability of Canopy Resistance over a Desert Steppe Site in Inner Mongolia, China

ABSTRACT Canopy resistance substantially affects the partitioning of available energy over vegetated surfaces. This study analyzed the variability of canopy resistance and associated driving environmental factors over a desert steppe site in Inner Mongolia, China, through the use of eddy-flux and meteorological data collected from 2008 to 2010. Distinct seasonal and interannual variabilities in canopy resistance were identified within those three years, and these variabilities were controlled primarily by precipitation. Strong interannual variability was found in vapor pressure deficit （VPD）, similar to that of air temperature. Based on the principal component regression method, the analysis of the relative contribution of five major environmental factors [soil-water content （SWC）, leaf-area index （LAI）, photosynthetically active radiation （Kp）, VPD, and air temperature] to canopy resistance showed that the canopy-resistance variation was most responsive to SWC （with 〉 35% contribution）, followed by LAI, especially for water-stressed soil conditions （〉 20% influence）, and VPD （consistently with an influence of approximately 20%）. Canopy-resistance variations did not respond to Kp due to the small interannual variability in Kp during the three years. These analyses were used to develop a new exponential function of water stress for the widely used Jarvis scheme, which substantially improved the calculation of canopy resistance and latent heat fluxes, especially for moist and wet soils, and effectively reduced the high bias in evaporation estimated by the original Jarvis scheme. This study highlighted the important control of canopy resistance on plant evaporation and growth for the investigated desert steppe site with a relatively low LA1.

The aboveground biomass of desert steppe and its spatiotemporal variation in western Inner Mongolia

A precise understanding of the aboveground biomass of desert steppe and its spatio-temporal variation is important to understand how arid ecosystems respond to climate change and to ensure that scarce grassland resources are used rationally. On the basis of 756 ground survey quadrats sampled in western Inner Mongolia steppe in 2005-2011 and remote sensing data from the Moderate Resolu- tion Imaging Spectroradiometer （MODIS）--the normalized difference vegetation index （NDVI） dataset for the period of 2001-2011--we developed a statistical model to estimate the aboveground biomass of the desert steppe and further explored the rela- tionships between aboveground biomass and climate factors. The conclusions are as follows： （1） the aboveground biomass of the steppe in the research area was 5.27 Tg （1 Tg=1012 g） on average over 11 years; between 2001 and 2011, the aboveground biomass of the western Inner Mongolia steppe exhibited fluctuations, with no significant trend over time; （2） the aboveground biomass of the steppe in the research area exhibits distinct spatial variation and generally decreases gradually from southeast to northwest; and （3） the important factor causing intemnnual variations in aboveground biomass is precipitation during the period from January to July, but we did not find a significant relationship between the aboveground biomass and the corresponding temperature changes. The precipitation in this period is also an important factor influencing the spatial distribution of aboveground biomass （R2=0.39, P〈0.001）, while the temperature might be a minor factor （R2=0.12, P〈0.01 ）. The uncertainties in our estimate are primarily due to uncertainty in converting the fresh grass yield estimates to dry weight, underestimates of the biomass of shrubs, and error in remote sensing dataset.

Water utilization of typical plant communities in desert steppe,China

Water is a limiting factor in the restoration and construction of desert steppe.Exploring plant water sources is necessary to understand soil-plant interactions and species coexistence;however,water sources of major plant communities within the desert steppe of Ningxia Hui Autonomous Region,China remain poorly understood.In this study,we analyzed the water uptake of plants in four typical communities:Agropyron mongolicum Keng.;Sophora alopecuroids Linn.;Stipa breviflora Griseb.,and Achnatherum splendens(Trin.)Nevski communities.Stable isotopesδD andδ^(18)O in the xylem of plant and soil water at different soil depths were analyzed.An IsoSource model was used to determine the soil depths from which plants obtained water.Results showed that A.mongolicum community obtained water predominantly from 0–20 and 40–80 cm depth,S.alopecuroids community from 0–20 cm depth,S.breviflora community from 0–40 cm depth,and A.splendens community from 0–20 and 80–140 cm depths.S.alopecuroides had a wider range of soil depths for water extraction,i.e.,utilizing different water sources depending on habitat,and the plasticity of its water uptake pattern determined its role in different communities.Water source of plants relayed heavily on the distribution of their roots.Competition for soil water exists between different plant life forms in the sierozem habitat(A.mongolicum,S.alopecuroids,and S.breviflora communities),and in the sandy soil habitat(A.splendens community).The use of soil water by A.splendens community is more spatially differentiated,and shrubs and herbs can coexist stably.Under the pattern of extended drought period in the future,sierozem habitat may be more favorable for the formation of a dominant monoculture community type of perennial fibrous plants.In aeolian sandy soil habitat,A.splendens had a strong competitive advantage,and the growth of shallow-rooted plants was easily suppressed.

Effects of fertilization on population density and productivity of herbaceous plants in desert steppe

In order to investigate the impacts of fertilization on population density and productivity on herbaceous plants in desert steppe, nitrogen （N）, phosphorus （P）, and N-P addition experiments were performed. Each fertilizer treatment included four addition levels, i.e., 0, 5, 10, and 20 g/m2. The results indicated that population density decreased as fertilization levels increased regardless of the sort of fertilizer. More specifically, total density as well as density ofArtemisia capillaris, Allium polyrhizum, and Enneapogon brachystachyus decreased significantly in 20 g/m2 treated plots, as compared with the control plots. Fertilization effects on aboveground and root biomasses were extremely similar to that found in population density; that is, both total aboveground biomass and aboveground biomasses for A. capillaris, A. polyrhizum, and E. brachystachyus were negatively correlated with increasing fertilization levels, with all determination coefficients （R2） greater than 0.80. Therefore, in the case of desert regions （annual precipitation 〈180 mm）, fertilization would inhibit population density and productivity of herbaceous plants.

Effects of the grazing systems on germinable soil seed bank of desert steppe

We studied a soil seed bank in the Stipa breviflora desert steppe under three grassland management systems, namely continuous grazing, rotational grazing, and no grazing, from 1999 until 2007. The germinable seed bank species in rotational, continuous and no gazing were 11, 9 and 8 species, respectively. Rotational grazing increased the number of seed bank plant species and perenni- al grasses. The density of germinal soil seed bank was significantly higher in the enclosed area （19,533.33 seeds/m2） than those in rotational （3,233.33 seeds/mz） and continuous grazing areas （2,553.60 seeds/m2）. The vertical distribution of the soil seed bank had a similar trend： 75.06%-83.19% of the seeds are distributed in the top 0-5 cm soil layer, 14.16%-21.68% in the 5-10 cm lay- er, and 2.65%-4.95% in the 10-15 cm layer, which varied between the grazing treatments. Density of the soil seed bank was sig- nificantly higher in the enclosed area, and there was no significant difference between rotational and continuous grazing. The Margalef and Shannon-Wiener indices for the soil seed bank were higher for rotational grazing treatment than for continuous grazing. The Sorensen＇s similarity index for the soil seed bank between the enclosed and rotational grazing areas reached 0.857.

Vegetation characteristics and soil properties in grazing exclusion areas of the Inner Mongolia desert steppe

In arid and semi-arid desert steppe areas,grazing exclusion with fencing is widely regarded as an effective strategy for restoring degraded vegetation and enhancing the quality of degraded soil.In this study,we hypothesized that grazing exclusion caused by fencing enhances both vegetation and soil properties,and that the longer an area is fenced,the more considerable the improvement.We conducted an observational study wherein random sampling was utilized to select 9 plots fenced for ten or more years,25 plots fenced for four to nine years,25 plots fenced for one to three years and 29 free-grazing plots within an area of approximately 63,000 km^(2)of Inner Mongolia desert steppe.A one-way ANOVA revealed no significant differences in the characteristics of grassland vegetation or soil properties between grasslands fenced for one to three years and free-grazing grassland.After 4 years of fencing,noticeable increases in above-ground biomass,litter content,Simpson index,soil organic carbon,and available nitrogen were observed.Significant positive differences in vegetation coverage,height,species richness,soil available phosphorus,and available potassium were associated with plots with a minimum of 10 years of fencing.The soil layer with the greatest difference in the fenced-in areas for soil organic carbon was at 0-25 cm.For available nitrogen and available phosphorus,fencing produced the most significant differences in the 0-20 cm soil layer,while for available potassium,fencing produced the most significant differences in the 0-30 cm soil layer.However,the fencing did not indicate any statistically significant differences in terms of clay,silt,and sand content in any soil layer.The data support our hypothesis that grazing exclusion improves both vegetation and soil properties,and that longer periods of grazing exclusion result in greater degrees of improvement.This research offers technical guidance for the reasonable choice of fencing time across a vast area of the Inner Mongolian desert steppe.

Analysis of Parameter Sensitivity on Surface Heat Exchange in the Noah Land Surface Model at a Temperate Desert Steppe Site in China

The dominant parameters in the Noah land surface model （LSM） are identified, and the effects of parameter optimization on the surface heat exchange are investigated at a temperate desert steppe site during growing season in Inner Mongolia, China. The relative impacts of parameters on surface heat flux are examined by the distributed evaluation of local sensitivity analysis （DELSA）, and the Noah LSM is calibrated by the global shuffled complex evolution （SCE） against the corresponding observations during May-September of 2008 and 2009. The differences in flux sim- ulations are assessed between the Noah LSM calibrated by the SCE with 27 parameters and 12 dominant parameters. The systematic error, unsystematic error, root mean squared error, and mean squared error decompositions are used to evaluate the model performance. Compared to the control experiment, parameter optimization by the SCE using net radiation, sensible heat flux, latent heat flux, and ground heat flux as the objective criterion, respectively, can ob- viously reduce the errors of the Noah LSM. The calibrated Noah LSM is further validated against flux observations of growing season in 2010, and it is found that the calibrated Noah LSM can be applied in the longer term at this site. The Noah LSM with 12 dominant parameters calibrated performs similar to that with 27 parameters calibrated.

Analysis on the relationship between winter precipitation and the annual variation of horse stomach fly community in arid desert steppe, Northwest China (2007–2019)

Gasterophilus spp.have been found to be widespread in reintroduced Przewalski’s horses in the Kalamaili Nature Reserve(Northwest China).However,data on the annual variation in Gasterophilus infections are lacking.To analyze the epidemiological features and determine the cause of the annual variation in Gasterophilus infections,we treated 110 Przewalski’s horses with ivermectin and collected Gasterophilus larvae from fecal samples each winter from 2007 to 2019.All 110 Przewalski’s horses studied were found to be infected by Gasterophilus spp.,and a total of 141379 larvae were collected.Six species of Gasterophilus were identified with the following prevalence:G.pecorum(100%),G.nasalis(96.36%),G.nigricornis(94.55%),G.haemorrhoidalis(56.36%),G.intestinalis(59.09%),and G.inermis(3.64%).The mean infection intensity of Gasterophilus spp.larvae in Przewalski’s horses was 1285±653.G.pecorum(92.96%±6.71%)was the most abundant species.The intensity of Gasterophilus spp.(r=–0.561,P<0.046)was significantly correlated with winter precipitation.Our findings confirmed that,in the Kalamaili Nature Reserve,gasterophilosis is a severe parasitic disease in Przewalski’s horses.Winter precipitation at the beginning of the year can indirectly affect the intensity and composition of Gasterophilus spp.in Przewalski’s horses at the end of the year.Therefore,the water-related ecological regulation should be carried out to help reduce the parasite infection of Przewalski’s horses.

Seasonal dynamic changes in bacterial compositions in the Inner Mongolia desert steppe

Polymerase chain reaction-denaturing gradient gel electrophoresis(PCR-DGGE)technique was employed to examine the seasonal dynamic changes in bacterial community composition in the Inner Mongolia desert steppe using specific primers F954 and R1369.Bright and reproducible bands were sequenced,and the phylogenic tree was constructed.The results show that the bacterial community composition changed between different seasons.The specific bands were different between the sampling sites with light and heavy levels of degraded grassland.Three main types of bacteria constituting the microbial community in the Inner Mongolia desert steppe belonged to the α,γ and δ-sub phyla of Proteobacteria,Bacteroidetes and Acidobacteria.The unculturable bacteria accounted for 69%of the whole bacterial community of the Inner Mongolia desert steppe.

Relative Ecological Value of Major Plants in Minqin Desert Area

This paper analyzed relative ecological value of several major plants in Minqin desert grassland using layered projection of plant canopy. The results showed that ecological functions of natural Nitraria tangutorum and Ephedra sinica woods of a unit area were much better than those of artifi cial Haloxylon ammodendron woods, relative ecological value of N. tangutorum, E. sinica and Artemisia desertorum were much higher than that of artifi cial H. ammodendron woods. Layered projection explains clearly the ecological functions and relative ecological value of desert vegetation of the same coverage. It is inaccurate to indicate wind prevention and sand fi xation of desert vegetation in deserts using ecological function service value and ecological niche calculated on the basis of two-dimensional vegetation coverage, but three-dimensional projection degree should be applied to indicate ecological functions and relative ecological value of vegetation. Application of layered projection of plants in calculating ecological functions and relative ecological value of desert plants(vegetation) is the innovation point of this research.