Benefits and ecological restoration implications of hanging grass fences in Mongolian desert steppe

Tumbleweeds participate in a common seasonal biological process in temperate grasslands,creating hanging grass fences during the grass-withering season that result in distinct ecological phenomena.In this study,we addressed the urgent need to understand and restore the degraded desert steppe in Central Mongolia,particularly considering the observed vegetation edge effects around hanging grass fences.Using field surveys conducted in 2019 and 2021 in the severely degraded desert steppe of Central Mongolia,we assessed vegetation parameters and soil physical and chemical properties influenced by hanging grass fences and identified the key environmental factors affecting vegetation changes.The results indicate that the edge effects of hanging grass fences led to changes in species distributions,resulting in significant differences in species composition between the desert steppe's interior and edge areas.Vegetation parameters and soil physical and chemical properties exhibited nonlinear responses to the edge effects of hanging grass fences,with changes in vegetation coverage,aboveground biomass,and soil sand content peaking at 26.5,16.5,and 6.5 m on the leeward side of hanging grass fences,respectively.In the absence of sand dune formation,the accumulation of soil organic carbon and available potassium were identified as crucial factors driving species composition and increasing vegetation coverage.Changes in species composition and plant density were primarily influenced by soil sand content,electrical conductivity,and sand accumulation thickness.These findings suggest that hanging grass fences have the potential to alter vegetation habitats,promote vegetation growth,and control soil erosion in the degraded desert steppe of Central Mongolia.Therefore,in the degraded desert steppe,the restoration potential of hanging grass fences during the enclosure process should be fully considered.

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.

Studies on Transferrin and Posttremsferr Polymorphism and Their Relationship with Performances in Red Steppe

[Objective] The aim of this study was to investigate the correlation between blood protein polymorphism of red steppe and its performance.[Method]Two blood protein polymorphic loci were detected in transferring(Tf)and posttremsferr(Ptf)from thirteen red steppes and eighteen hybrid of limousin and red steppe by polyacrylamide gel electrophoresis.[Result]Tf and Ptf were controlled by three and two alleles respectively.[Conclusion]The variance analysis of blood protein polymorphic loci and its performance indicates that two protein loci have a positive or negative correlation with some traits of red steppe and the improved limousin cattle population.

Detecting Vegetation Fractional Coverage of Typical Steppe in Northern China Based on Multi-scale Remotely Sensed Data

One of the study objectives of global change is land use/cover change (LUCC) by using multiscale remotely sensed data on global and regional scale. In this paper, field sample, digital camera, Landsat-ETM+ (ETM+, Enhanced Thematic Mapper) image and the National Oceanic and Atmospheric Administration/the advanced very high resolution radiometer (NOAA/AVHRR) image were integrated to detect, simulate and analyze the vegetation fractional coverage of typical steppe in northern China. The results show: (1) Vegetation fractional coverage measured by digital camera is more precise than results measured by other methods. It can be used to validate other measuring results. (2) Vegetation fractional coverage measured by 1 m 2 field sample change fluctuantly for different observers and for different sample areas. In this experiment, the coverage is generally high compared with the result measured by digital camera, and the average absolute error is 9.92%, but two groups measure results, correlation coefficient r(2) = 0.89. (3) Three kinds of methods using remotely sensed data were adopted to simulate the vegetation fractional coverage. Average absolute errors of the vegetation fractional coverage, measured by ETM+ and NOAA, are respectively 7.03% and 7.83% compared with the result measured by digital camera. When NOAA pixel was decomposed by ETM+ pixels after geometrical registry, the average absolute errors measured by this method is 5.68% compared with the digital camera result. Correction coefficients of three results with digital camera result r(2) are respectively 0.78, 0.61 and 0.76. (4) The result of statistic model established by NOAA-NDVI (NDVI, Normalized Difference Vegetation Index) and the vegetation fractional coverage measured by digital camera show lower precision (r(2) = 0.65) than the result of statistic model established by ETM+-NDVI and digital camera coverage then converted to NOAA image (r(2) = 0.80). Pixel decomposability method improves the precision of measuring the vegetation fractional coverage on a large scale. This is a significant practice on scaling by using remotely sensed data. Integrated application of multi-scale remotely sensed data in earth observation will be an important approach to promoting measuring precision of ecological parameters.

Spatial-temporal Evolvement Characteristics of Climate Productivity for the Plants on Inner Mongolia Desert Steppe

Thornthwaite Memorial model and other statistic methods were used to calculate the climate-productivity of plants with the meteorological data from 1961 to 2007 at 9 stations distributed on Inner Mongolia desert steppe.The spatial and temporal variation characteristics of climate-productivity were analyzed by using the methods of the tendency rate of the climate trend,accumulative anomaly,and spatial difference and so on.The results showed that the climate-productivity kept linear increased trend over Inner Mongolia desert steppe in recent 47 years,but not significant.In spatial distribution,the climate-productivity reduced with the increased latitude.The climate-productivity in southwest part of Inner Mongolia desert steppe was growing while that in the southeast was reducing.The variation rate of the climate-productivity increased from the northwest part to the southeast part of Inner Mongolia desert steppe.In recent 47 years,the climate-productivity in southeast Jurh underwent the greatest decreasing extent,and the region was the sensitive area of the climate-productivity variation.

Influences of Family Ranches Management Mode on Plant Community Characteristic in Hulunber Meadow Steppe

[Objective] The aim was to explore the management mode on optimal re-sources al ocation of family ranch in meadow steppe. [Method] Three double repre-sentative family ranches were selected in meadow steppe of Hulunber Old Barag Banner, and the study was carried out with the baseline survey. Three family ranches were selected as the demonstrative households for the corporation study, while other three family ranches with the similar conditions were looked as the non-demonstrative households for the comparison. Demonstrative households of the fami-ly ranches reduced the stocking rate, optimized the flock structure and took a winter feeding and other means to explore the different management models on plant com-munity characteristic of family ranch. [Result] The seasonal dynamic of community characteristic in family ranches showed the single-peaks curves. The seasonal dy-namics of community coverage, height and biomass in the demonstrative households showed higher compared with the non-demonstrative households, and community density in the experiment households was lower than that of the control experiment households. Community coverage, height and biomass of degraded grassland in family ranch have a great improve after optimization of management. Community coverage, height , density and biomass were increasing in fencing plot, but decreas-ing in free grazing area. Enclosure improved grassland coverage, vegetation height, density and forage yield. Leymus chinensis played an important role in plant com-munity. The important values of Leymus chinensis, Stipa baicalensis, Cleistogenes squarrosa, and Carex duriuscula were high. Leymus chinensis important value in the demonstrative households of optimal management was higher than that in the non-demonstrative households, and Carex duriuscula important value of the non-demon-strative households was significantly higher than that of the demonstrative house-holds. The indexes of Margalef richnes,Shannon-Wiener diversity, Simpson diversity and Pielou uniformity showed that the demonstrative households were higher than the non-demonstrative households. [Conclusion] The research provides theoretical ref-erences for sustainable development of pastures dominated by family ranch.

Food Resource Partitioning in Alpine Weasel,Steppe Polecat and Upland Buzzard:Evidence from Stable Isotope Ratios

Based on mass balance theory and IsoSource program,stable carbon and nitrogen isotopic ratios revealed that small mammals (plateau pika,root vole and plateau zokor) contributed 26.8% and 27.0% and 29.2% to alpine weasel,steppe polecat and upland buzzard of carnivores as food respectively;adult passerine birds contributed 22.3%,47.7% and 69.1%,with hatchlings contributing 50.9%,25.6% and 1.70% to each respectively.δ 13 C values plotted against δ 15 N indicated significant partitioning in two-dimensional space among the three carnivores.It was reasonable to propose a food resource partitioning among alpine weasel,steppe polecat and upland buzzard,which partially revealed their co-existence mechanisms.

Vegetation landscape structure and dynamics in sandy forest-steppe ecotone

Sandy forest-steppe ecotone in Baiyinaobao Natural Reserve of Inner Mongolia Autonomous Region of China is one of the special landscape types in forest-steppe vegetation zone in China. Vegetation landscape types, landscape patches, and patch size were measured by the field investigation, forest photograph, and airscape. The structure of landscape patches in sandy forest-steppe ecotone, including composition structure, and size structure, was studied and the dynamics and transformation of landscape patches were analyzed. The data obtained in this study could provide theoretical basis for the research on vegetation landscape in forest-steppe ecotones and other vegetation types.

Soil Erosion and Vegetation Succession in Alpine Kobresia Steppe Meadow Caused by Plateau Pika——A Case Study of Nagqu County, Tibet

This paper evaluated the impacts of mounds created by the plateau pika （Ochotona curzoniae） on the vegetation composition, structure, and species diversity of an alpine Kobresia steppe meadow in Nagqu County, Tibet Autonomous Region, China. Based on mound height or the depth of erosion pit, we defined five stages of erosion and compared the floristic features of communities at these stages with those in undisturbed sites. In the study area, the mounds and pits covered up to 7% of the total area. Lancea tibetica, Lamiophlomis rotata, and Potentilla biflarca were the dominant species in erosion pits, and Kobresia pygmaea, the dominant species in undisturbed sites, became a companion species in eroded areas. In the process of erosion, the original vegetation was covered by soil ejected by the pika, then the mounds were gradually eroded by wind and rain, and finally erosion pits formed. The vegetation coverage increased with increasing erosion stages but remained significantly lower than that in undisturbed sites. Improved coverage eventually reduced soil erosion, and pit depth eventually stabilized at around 20cm. Aboveground biomass increased with increasing erosion stage, but the proportion of low-quality forage reached more than 94%. The richness index and Shannon-Wiener index increased significantly with increasing erosion stage, but the richness index in mound and pit areas was significantly lower than that in undisturbed sites.

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.

Degradation induces changes in the soil C:N:P stoichiometry of alpine steppe on the Tibetan Plateau

Due to the Tibetan Plateau’s unique high altitude and low temperature climate conditions,the region’s alpine steppe ecosystem is highly fragile and is suffering from severe degradation under the stress of increasing population,overgrazing,and climate change.The soil stoichiometry,a crucial part of ecological stoichiometry,provides a fundamental approach for understanding ecosystem processes by examining the relative proportions and balance of the three elements.Understanding the impact of degradation on the soil stoichiometry is vital for conservation and management in the alpine steppe on the Tibetan Plateau.This study aims to examine the response of soil stoichiometry to degradation and explore the underlying biotic and abiotic mechanisms in the alpine steppe.We conducted a field survey in a sequent degraded alpine steppe with seven levels inNorthern Tibet.The plant species,aboveground biomass,and physical and chemical soil properties such as the moisture content,temperature,pH,compactness,total carbon(C),total nitrogen(N),and total phosphorus(P)were measured and recorded.The results showed that the contents of soil C/N,C/P,and N/P consistently decreased along intensifying degradation gradients.Using regression analysis and a structural equation model(SEM),we found that the C/N,C/P,and N/P ratios were positively affected by the soil compactness,soil moisture content and species richness of graminoids but negatively affected by soil pH and the proportion of aboveground biomass of forbs.The soil temperature had a negative effect on the C/N ratio but showed positive effect on the C/P and N/P ratios.The current study shows that degradation-induced changes in abiotic and biotic conditions such as soil warming and drying,which accelerated the soil organic carbon mineralization,as well as the increase in the proportion of forbs,whichwere difficult to decompose and input less organic carbon into soil,resulted in the decreases in soil C/N,C/P,and N/P contents to a great extent.Our results provide a sound basis for sustainable conservation and management of the alpine steppe.

C:N:P stoichiometry of perennial herbs’ organs in the alpine steppe of the northern Tibetan Plateau

The patterns of C:N:P stoichiometry across ecosystems are important in understanding biogeochemical processes. The stoichiometry of nutrients at the leaf and root level have been reported previously, but relationships of other plant organs, such as stems and the reproductive organs, remain unclear. We collected 228 samples of leaves, roots, stems and reproductive organs from 11 common plant species at 25 sites on the Tibetan Plateau to explore the relationships of C:N:P stoichiometry both within and across plant organs. The average C concentrations in the roots, leaves, stems and reproductive organs were 427.32, 410.51, 421.11 and 416.72 mg g-1, respectively. The shoot tissues(leaves, stems and reproductive organs) had significantly higher N and P concentrations than the roots. The N and P concentrations had a significant positive correlation within the same organ. The nutrient concentrations(N and P) and nutrient ratios(C:N, C:P and N:P) were significantly correlated across all pairwise organ combinations. Our data suggest that alpine perennial herbs share similar evolutionary histories and have constrained patterns of covariation for C concentrations, with differential patterns for N and P stoichiometry across organs. Our data also indicate that covarying sets of nutrient traits are consistent across environments and biogeographical regions and demonstrate convergent evolution in plant nutritional characteristics in extreme alpine environments.

Comparison of CO_(2) Effluxes and Their Driving Factors Between Two Temperate Steppes in Inner Mongolia, China

Soil respiration is a key component of the global terrestrial ecosystem carbon cycle. The static opaque chamber method was used to measure the CO2 effiuxes from soil of a semiarid Aneurolepidium chinense steppe and a Stipa krylovii steppe in the Xilin River Basin of Inner Mongolia, China from March 2002 to December 2004. The results indicated that the soil respiration rates of the semiarid Aneurolepidium chinense steppe and the Stipa krylovii steppe were both relatively high from mid-May to mid-September of each year and remained low during the rest of the year. The minimum value of soil respiration occurred in December or January and negative effiuxes of CO2 appeared for several days during the non-growing season of individual years at the two sampling sites. A high annual variation was found in the two steppes with the coefficients of variance （CV） being over 94%, even high to 131%. The annual sums of soil CO2 effiux of the Aneurolepidium chinense steppe varied between 356.4 gC m^-2 yr^-1 and 408.8 gC m^-2 yr^-1, while those of the Stipa krylovii steppe in the three years were in the range of 110.6 gC m^-2 yr^-1 to 148.6 g Cm^-2 yr^-1. The mean respiration rates of the Aneurolepidium chinense steppe were significantly higher than those of the Stipa krylovii steppe in different statistical periods with the exception of the non-growing season. About 59.9% and 80.6% of the soil respiration variations in both steppes for the whole sampling period were caused by the changes of temperature and soil water content. In the Aneurolepidium chinense steppe, the soil respiration rate has significant or extremely significant positive correlation （r = 0.58 - 0.85, p 〈 0.05 or p 〈 0.01） with air temperature and ground temperature of the topsoil except in 2002; the unique contributions of temperature change to the soil respiration variation of the three years were 53.3%, 81.0% and 58.6%, respectively. But, for the Stipa krylovii steppe in the same time interval, the soil water content （especially that of the 10-20 cm layer） has a greater effect on the change of soil respiration, and the unique contributions of the change of the 10-20 cm soil water content to the variations of soil respiration in 2002 and 2003 were 60.0% and 54.3%, respectively. In 2004, in spite of the higher contribution of temperature than soil water content, the contribution of ground temperature at a depth of 10 cm was only 46.2%, much weaker than that of any single year in the Aneurolepidium chinense steppe.

Impact of nitrogen addition on plant community in a semi-arid temperate steppe in China

Increased nitrogen （N） deposition will often lead to a decline in species richness in grassland ecosystems but the shifts in functional groups and plant traits are still poorly understood in China. A field experiment was conducted at Duolun, Inner Mongolia, China, to investigate the effects of N addition on a temperate steppe ecosystem. Six N levels （0, 3, 6, 12, 24, and 48 g N/（m2-a）） were added as three applications per year from 2005 to 2010. Enhanced N deposition, even as little as 3 g N/（m2.a） above ambient N deposition （1.2 g N/（m2.a））, led to a decline in species richness of the whole community. Increasing N addition can significantly stimulate aboveground biomass of perennial bunchgrasses （PB） but decrease perennial forbs （PF）, and induce a slight change in the biomass of shrubs and semi-shrubs （SS）. The biomass of annuals （AS） and perennial rhizome grasses （PR） accounts for only a small part of the total biomass. Species richness of PF decreased significantly with increasing N addition rate but there was a little change in the other functional groups. PB, as the dominant functional group, has a relatively higher height than others. Differences in the response of each functional group to N addition have site-specific and species-specific characteristics. We initially infer that N enrichment stimulated the growth of PB, which further suppressed the growth of other functional groups.

Interactions of water and nitrogen addition on soil microbial community composition and functional diversity depending on the inter-annual precipitation in a Chinese steppe

Water and nitrogen are primary limiting factors in semiarid grassland ecosystems. Our knowledge is still poor regarding the interactive effects of water and N addition on soil microbial communities, although this information is crucial to reveal the mechanisms of the terrestrial ecosystem response to global changes. We addressed this problem by conducting a field experiment with a 15% surplus of the average rainfall under three levels of N addition（50, 100, and 200 kg N ha–1 yr–1） in two consecutive years in Inner Mongolia, China. Microbial community composition and functional diversity were analyzed based on phospholipid fatty acids（PLFA） and BIOLOG techniques, respectively. The results showed that water addition did not affect the soil microbial community composition, but much more yearly precipitation generally decreased the PLFA concentration, which implied a fast response of soil microbes to changes of water condition. Soil fungi was depressed only by N addition at the high level（200 kg N ha–1 yr–1） and without hydrologic leaching, while Gram-negative bacteria was suppressed probably by plant competition at high level N addition but with hydrologic leaching. The study found unilateral positive/negative interactions between water and N addition in affecting soil microbial community, however, climate condition（precipitation） could be a significant factor in disturbing the interactions. This study highlighted that：（1） The sustained effect of pulsed water addition was minimal on the soil microbial community composition but significant on the microbial community functional diversity and（2） the complex interaction between water and N addition on soil microbial community related to the inter-annual variation of the climate and plant response.

Effects of Irrigation on Nitrous Oxide,Methane and Carbon Dioxide Fluxes in an Inner Mongolian Steppe

Increased precipitation during the vegetation periods was observed in and further predicted for Inner Mongolia. The changes in the associated soil moisture may affect the biosphere-atmosphere exchange of greenhouse gases. Therefore, we set up an irrigation experiment with one watered （W） and one unwatered plot （UW） at a winter-grazed Leymus chinensis-steppe site in the Xilin River catchment, Inner Mongolia. UW only received the natural precipitation of 2005 （129 mm）, whereas W was additionally watered after the precipitation data of 1998 （in total 427 mm）. In the 3-hour resolution, we determined nitrous oxide （N20）, methane （CH4） and carbon dioxide （CO2） fluxes at both plots between May and September 2005, using a fully automated, chamber-based measuring system. N20 fluxes in the steppe were very low, with mean emissions （±s.e.） of 0.9-4-0.5 and 0.7-4-0.5 μg N m^-2 h^-1 at W and UW, respectively. The steppe soil always served as a CH4 sink, with mean fluxes of -24.1-4-3.9 and -31.1-4- 5.3 μg C m^-2 h^-1 at W and UW. Nighttime mean CO2 emissions were 82.6±8.7 and 26.3±1.7 mg C m^-2 h^-1 at W and UW, respectively, coinciding with an almost doubled aboveground plant biomass at W. Our results indicate that the ecosystem CO2 respiration responded sensitively to increased water input during the vegetation period, whereas the effects on CH4 and N2O fluxes were weak, most likely due to the high evapotranspiration and the lack of substrate for N2O producing processes. Based on our results, we hypothesize that with the gradual increase of summertime precipitation in Inner Mongolia, ecosystem CO2 respiration will be enhanced and CH4 uptake by the steppe soils will be lightly inhibited.

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.

Effects of Rest Grazing on Organic Carbon Storage in Stipa grandis Steppe in Inner Mongolia, China

This study was aimed to evaluate the potential effects of rest grazing on organic carbon storage in Stipa grandis steppe of Inner Mongolia, China. Using potassium dichromate heating method, we analyzed the organic carbon storage of plant and soil in Stipa grand＆ steppe after rest grazing for 3, 6, and 9 yr. The results indicated that as the rest grazing ages prolonged, the biomass of aboveground parts, litter and belowground plant parts （roots） of the plant communities all increased, meanwhile the C content of the biomass increased with the rest grazing ages prolonging. For RG0, RG3a, RG6a, and RG9a, C storage in aboveground vegetation were 60.7, 76.9, 82.8 and 122.2 g C m2, respectively; C storage of litter were 5.1, 5.8, 20.4 and 25.5 g C m^-2, respectively; C storage of belowground roots （0-100 cm） were 475.2, 663.0, 1 115.0 and 1 867.3 g C m^-2, respectively; C storage in 0-100 cm soil were 13.97, 15.76, 18.60 and 32.41 kg C m^-2, respectively. As the rest grazing ages prolonged, the organic C storage in plant communities and soil increased. The C storage ofbelowground roots and soil organic C was mainly concentrated in 0-40 cm soil body. The increased soil organic C for RG3a accounted for 89.8% of the increased carbon in vegetation-soil system, 87.2% for RG6a, and 92.6% for RG9a. From the perspective of C sequestration cost, total cost for RG3a, RG6,, and RG9a were 2 903.4, 5 806.8 and 8 710.2 CNY haq, respectively. The cost reduced with the extension of rest grazing ages, 0.15 CNY kg^-1 C for RG3a, 0.11 CNY kg-~ C for RG6a and 0.04 CNY kg℃ for RG9a. From the growth characteristics of grassland plants, the spring was one of the two avoided grazing periods, timely rest grazing could effectively restore and update grassland vegetation, and was beneficial to the sustainable use of grassland. Organic C storage for RG9a was the highest, while the cost of C sequestration was the lowest. Therefore, spring rest grazing should be encouraged because it was proved to be a very efficient grassland use pattern.

Emission characteristics of carbon dioxide in the semiarid Stipa grandis steppe in Inner Mongolia, China

Using the static opaque chamber method, the soil respiration rates （SR） were measured through the continuous experiments in situ in semiarid Stipa grandis steppe in Xilin River Basin of Inner Mongolia, China from June 2001 to June 2003, in parallel, the difference between the SR and the ecosystem respiration rates （TER） were compared. The results indicated that the seasonal variations of the SR and TER were obvious with higher emissions in growing season and a relatively low efflux level in non-growing season, furthermore, the negative effluxes were found in the observation site in winter; the annual CO2 efflux of total ecosystem ranged from 160.5 gC/（m^2·a） to 162.8 gC/（m^2·a） and that of soil ranged from 118.7 gC/（m^2·a） to 152.3 gC/（m^2·a）. The annual SR accounted for about 74.0% to 93.5% of the annual TER, but the results of Analysis of Variance （ANOVA） indicated that the difference between the annual average TER and SR did not reach the significance level of 0.05. The TER was under similar environmental controls as SR, in growing seasons of drought years, the variations of soil moisture at 0-10 cm and 10-20 cm depth could account for 79,1% 95.6% of the changes of the SR and TER, but in non-growing season, more than 75% of the variations of the SR and TER could be explained by the changes of the ground temperature of soil surface layers.