分类： 地球科学 >> 地理学 提交时间： 2022-10-14 合作期刊: 《干旱区科学》
摘要：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 isotopes δD and δ18O 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.
分类： 地球科学 >> 地理学 提交时间： 2023-02-07 合作期刊: 《干旱区科学》
摘要： 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) 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 18O 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 05 cm soil layer could be found in the surface soil layer covered by BSCs (8000 cm/m3) than without BSCs (3200 cm/m3), 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.
分类： 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间： 2018-04-24 合作期刊: 《干旱区科学》
摘要： 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 EcoSim 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.
分类： 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间： 2018-04-24 合作期刊: 《干旱区科学》
摘要： 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.
分类： 生物学 >> 生态学 提交时间： 2024-03-13 合作期刊: 《干旱区科学》
摘要： 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.
分类： 农、林、牧、渔 >> 土壤学 提交时间： 2024-03-13 合作期刊: 《干旱区科学》
摘要： 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.
分类： 地球科学 >> 地理学 提交时间： 2021-02-10 合作期刊: 《干旱区科学》
摘要： Frequent periods of drought conditions are known to limit plant performance, primary production, and ecosystem stability in arid and semi-arid desert steppe environments. Plants often avoid competition by shifting their water use seasonally, which affects the water-use patterns of dominant species as well as the composition and structure of plant communities. However, the water-use strategies of dominant herbaceous species, which grow under natural field conditions in the desert steppe region of Ningxia Hui Autonomous Region, China, are poorly known. Here, we explored the possible sources of water uptake and water-use efficiency (WUE) of three dominant herbaceous plant species (Stipa breviflora, Agropyron mongolicum, and Glycyrrhiza uralensis) in a native desert steppe in the semi-arid area of Ningxia through an analysis of multiple parameters, including (1) the stable isotopic oxygen and hydrogen (δ18O and δ2H) compositions of precipitation, soil water, and stem water, (2) the carbon isotope (13C) composition of leaves, and (3) the soil water contents, based on field sampling across varying water conditions from June to September, 2017. Frequent small precipitation events replenished shallow soil water, whereas large events only percolated down to the deep soil layers. Changes in soil water availability affected the water-use patterns of plants. Generally, during light precipitation periods, the deep root system of G. uralensis accessed deeper (>80 cm) soil water, whereas S. breviflora and A. mongolicum, which only have shallow roots, primarily absorbed water from the shallow and middle soil layers. As precipitation increased, all three plant species primarily obtained water from the shallow soil layers. Variation in soil water uptake between the dry and wet seasons enabled plants to make better use of existing satoil water. In addition, the δ13C values of G. uralensis and S. breviflora were higher than those of A. mongolicum. The δ13C values of the three plant species were significantly negatively correlated with soil water content. Therefore, G. uralensis and S. breviflora maintained a higher WUE through their conservative and water-saving strategies across the entire growing season. In contrast, A. mongolicum, with a relatively low WUE in the wet season but a high WUE in the dry season, exhibited a more flexible water-use strategy. The different water-use strategies of these dominant plant species demonstrated the mechanisms by which plant communities can respond to drought.
分类： 生物学 >> 生态学 提交时间： 2023-10-17 合作期刊: 《干旱区科学》
摘要： 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/(m2a)) 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% (P0.05). 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
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