本文以宁夏盐池地区典型荒漠草原为研究区域，设置对照、轻度、中度及重度四种放牧强度，系统评估其对植物群落特征、土壤理化性质及土壤微生物群落结构的影响，并探讨三者之间的相互作用机制。研究采用野外调查、理化分析、高通量测序与冗余分析、结构方程模型、Mantel分析方法，旨在揭示放牧干扰下植物群落、土壤环境与微生物组之间互作关系的调控机制，为荒漠草原生态系统的可持续管理与退化草地恢复提供理论支撑。研究结果如下：

（1）轻度放牧促进植物地上和地下生物量积累，分别较对照组增加21.55%和15.80%，而重度放牧显著抑制植物生长，地下生物量减少43.00%。重度放牧下植物碳、氮、磷含量下降最为显著，群落丰富度和复杂度显著降低，Shannon指数与Margalef指数分别下降20.33%和34.32%。

（2）放牧强度增加显著降低土壤全碳和有机碳含量（降幅20.58%~34.40%），重度放牧显著提高铵态氮含量，尤其在20-30 cm土层增幅达70.84%，并导致10-20 cm层土壤全磷含量减少26.07%。土壤pH与容重变化不显著，表现出一定短期稳定性。

（3）土壤细菌群落对放牧响应敏感，重度放牧显著提高细菌Simpson指数，增加变形菌门丰度（提高27.55%），减少芽单胞菌门丰度（下降23%~31%）；真菌群落对放牧干扰相对稳定，Alpha多样性无显著差异，但特有OTUs数量随放牧强度增加而逐渐减少。PCoA分析显示放牧显著重构细菌群落结构（解释度37.2%），对真菌群落影响较小（解释度21.9%）。

（4）冗余分析与结构方程模型结果表明，土壤有机碳为植物群落变异的关键因子（解释量25.8%），而细菌和真菌群落结构分别主要受土壤铵态氮（26.4%）与硝态氮（31.7%）驱动。放牧通过影响地上生物量、土壤pH与总碳等间接调控微生物多样性，模型可解释细菌和真菌多样性变异的68%和45%。Mantel分析进一步证实土壤有机碳、铵态氮含量及pH值是驱动细菌与真菌群落结构变化的关键环境因子。

综上所述，轻度和中度放牧在一定程度上有利于维持植物多样性与土壤养分平衡，重度放牧则导致植被退化、土壤碳氮磷养分流失。土壤有机碳、铵态氮和pH是驱动植物和微生物群落变化的关键因子。本研究系统揭示了放牧强度对荒漠草原生态系统的综合影响，为区域草地退化治理与科学放牧管理提供了理论支撑。

In this paper, four types of grazing intensities, namely, control, light, medium and heavy, were set up in a typical desert grassland in Yanchi area of Ningxia to systematically evaluate their effects on plant community characteristics, soil physicochemical properties and soil microbial community structure, and to explore the interaction mechanisms among them. Field investigation, physicochemical analysis, high-throughput sequencing and redundancy analysis, structural equation modelling, and Mantel analysis were used to reveal the mechanisms of interactions among plant communities, soil environment and microbiome under grazing disturbance, and to provide theoretical support for sustainable management of desert grassland ecosystems and restoration of degraded grasslands. The results of the study are as follows:

Light grazing promoted the accumulation of above- and below-ground biomass of plants, which increased by 21.55% and 15.80%, respectively, compared with the control group, while heavy grazing significantly inhibited plant growth and reduced below-ground biomass by 43.00%. Plant carbon, nitrogen and phosphorus contents decreased most significantly under heavy grazing, and community richness and complexity decreased significantly, with Shannon index and Margalef index decreasing by 20.33% and 34.32%, respectively.

The increase in grazing intensity significantly reduced the soil total carbon and organic carbon content (20.58%~34.40%), and heavy grazing significantly increased the ammonium nitrogen content, especially in the 20-30 cm layer by 70.84%, and caused a 26.07% decrease in the total phosphorus content in the 10-20 cm layer. The overall changes in soil pH and bulk weight were not significant, showing some short-term stability.

The soil bacterial community was sensitive to grazing, and heavy grazing significantly increased the bacterial Simpson's index, promoted the abundance of Ascomycetes (increased by 27.55%), and decreased the abundance of Bacillariophyta (decreased by 23%-31%); the fungal community was relatively stable to the grazing disturbance, and there was no significant difference in the Alpha diversity but the number of endemic OTUs decreased with the increase of the intensity of grazing. PCoA analysis showed that grazing significantly reconfigured the structure of bacterial community (37.2% explained degree), and had less effect on fungal community (21.9% explained degree).

Redundancy analysis and structural equation modeling results indicated that soil organic carbon was a key factor in plant community variation (25.8% explained), while bacterial and fungal community structure was mainly driven by soil ammonium nitrogen (26.4%) and nitrate nitrogen (31.7%), respectively. Grazing indirectly regulated microbial diversity by affecting aboveground biomass and soil pH and total carbon, with the model explaining 68% and 45% of the variation in bacterial and fungal diversity. Mantel analyses further confirmed that soil organic carbon, ammonium nitrogen content and pH were the main environmental factors driving changes in bacterial and fungal community structure.

In conclusion, light and medium grazing is beneficial to maintain plant diversity and soil nutrient balance to a certain extent, which is ecologically sustainable, while heavy grazing leads to degradation of vegetation, loss of soil carbon, nitrogen and phosphorus, and microbial community disruption, which disturb the stability of the ecosystem. This study systematically reveals the comprehensive effects of grazing intensity on desert grassland ecosystems, and provides theoretical support for regional grassland degradation management and scientific grazing management.

[1] Allakonon M G B, Guidigan M G, Belarmain A F. Vulnerability of wild indigenous agroforestry species to climate change in Niger State, Nigeria: A proxy analysis [J]. Environment, Development and Sustainability, 2022, 24(3): 3560-3587.

[2] Sun Y, Sun Y, Yao S, et al. Impact of climate change on plant species richness across drylands in China: From past to present and into the future [J]. Ecological Indicators, 2021, 132: 108288.

[3] Cheng-Jie W, Shi-Ming T, Andreas W, et al. Effect of Stocking Rate on Soil-Atmosphere CH4 Flux during Spring Freeze-Thaw Cycles in a Northern Desert Steppe, China [J]. Plos One, 2012, 7(5): e36794.

[4] 李文怀, 郑淑霞, 白永飞. 放牧强度和地形对内蒙古典型草原物种多度分布的影响 [J]. 植物生态学报, 2014, 38(02): 178-187.

[5] Zheng S, Lan Z, Li W, et al. Differential responses of plant functional trait to grazing between two contrasting dominant C3 and C4 species in a typical steppe of Inner Mongolia, China [J]. Plant and Soil, 2011, 340: 141-155.

[6] Liu N, Kan H, Yang G, et al. Changes in plant, soil, and microbes in a typical steppe from simulated grazing: explaining potential change in soil C [J]. Ecological Monographs, 2015, 85(2): 269-286.

[7] pierce B A. Biotic effects of grazing by tilapia (Oreochromis aureus) on phytoplankton populations in solar silos [J]. Journal of Freshwater Ecology, 1983, 2(3): 293-304.

[8] 侯扶江, 常生华, 于应文, 林慧龙. 放牧家畜的践踏作用研究评述 [J]. 生态学报, 2004, (04): 784-789.

[9] 侯扶江, 杨中艺. 放牧对草地的作用 [J]. 生态学报, 2006, (01): 244-264.

[10] 张成霞, 南志标. 放牧对草地土壤理化特性影响的研究进展 [J]. 草业学报, 2010, 19(04): 204-211.

[11] 苟燕妮, 南志标. 放牧对草地土壤微生物的影响 [J]. 草业学报, 2015, 24(10): 194-205.

[12] 高苏日固嘎, 斯琴朝克图, 乌兰图雅, 等. 克氏针茅草原群落物种多样性与生物量关系对放牧强度的响应 [J]. 生态学报, 2022, 42(23): 9736-9746.

[13] Liu N, Zhang Y, Chang S, et al. Impact of Grazing on Soil Carbon and Microbial Biomass in Typical Steppe and Desert Steppe of Inner Mongolia [J]. PLoS ONE, 2012, 7(5): e36434.

[14] 安慧, 李国旗. 放牧对荒漠草原植物生物量及土壤养分的影响 [J]. 植物营养与肥料学报, 2013, 19(03): 705-712.

[15] 张蒙蒙, 徐国策, 张铁钢, 等. 放牧强度对荒漠草原土壤微生物群落特征的影响 [J]. 水土保持学报, 2024, 38(03): 306-313.

[16] Mafa-Attoye T G, Thevathasan N V, Dunfield K E. Indications of shifting microbial communities associated with growing biomass crops on marginal lands in Southern Ontario [J]. Agroforestry Systems, 2020, 94(3): 735-746.

[17] 陈伟立, 李娟, 朱红惠, 等. 根际微生物调控植物根系构型研究进展 [J]. 生态学报, 2016, 36(17): 5285-5297.

[18] 潘庆民, 薛建国, 陶金, 等. 中国北方草原退化现状与恢复技术 [J]. 科学通报, 2018, 63(17): 1642-1650.

[19] 左万庆, 王玉辉, 王风玉, 等. 围栏封育措施对退化羊草草原植物群落特征影响研究 [J]. 草业学报, 2009, 18(03): 12-19.

[20] 谷昌军, 张镱锂, 刘林山, 等. 放牧压力表述的分异及其适用场景 [J]. 应用生态学报, 2023, 34(02): 433-441.

[21] 魏伯平, 赵生国, 焦婷. 放牧对温性荒漠草原植物群落及草地土壤肥力的影响 [J]. 草地学报, 2012, 20(05): 855-862.

[22] 宋伟江, 苏纪帅, 张梦迪, 等. 中国北方草地植物补偿性生长与合理放牧强度:基于放牧实验的整合分析 [J]. 科学通报, 2023, 68(11): 1330-1342.

[23] 高承芳, 张晓佩, 李兆龙. 放牧对土壤理化性状及植被多样性的影响 [J]. 中国农学通报, 2020, 36(08): 98-104.

[24] 刘娜, 白可喻, 杨云卉, 等. 放牧对内蒙古荒漠草原草地植被及土壤养分的影响 [J]. 草业科学, 2018, 35(06): 1323-1331.

[25] 放牧强度对新疆昭苏草甸草原群落特征的影响[J]. 中国草地学报, 2013, 35: 75-79.

[26] 段敏杰, 高清竹, 万运帆, 等. 放牧对藏北紫花针茅高寒草原植物群落特征的影响 [J]. 生态学报, 2010, 30(14): 3892-3900.

[27] 范月君. 围栏与放牧对三江源区高山嵩草草甸植物形态、群落特征及碳平衡的影响 [D]. 甘肃农业大学, 2013.

[28] Cingolani A M, Posse G, Collantes M B. Plant functional traits, herbivore selectivity and response to sheep grazing in Patagonian steppe grasslands [J]. Journal of Applied Ecology, 2005, 42(1): 50-59.

[29] Altesor A, Oesterheld M, Leoni E, et al. Effect of grazing on community structure and productivity of a Uruguayan grassland [J]. Plant Ecology, 2005, 179: 83-91.

[30] Luo G, Han Q, Zhou D, et al. Moderate grazing can promote aboveground primary production of grassland under water stress [J]. Ecological Complexity, 2012, 11: 126-136.

[31] Kauffman J B, Thorpe A S, Brookshire E J. Livestock exclusion and belowground ecosystem responses in riparian meadows of eastern Oregon [J]. Ecological Applications, 2004, 14(6): 1671-1679.

[32] Zhao H-L, Zhao X-Y, Zhou R-L, et al. Desertification processes due to heavy grazing in sandy rangeland, Inner Mongolia [J]. Journal of arid environments, 2005, 62(2): 309-319.

[33] Derner J D, Boutton T W, Briske D D. Grazing and ecosystem carbon storage in the North American Great Plains [J]. Plant and Soil, 2006, 280: 77-90.

[34] Pucheta E, Bonamici I, Cabido M, et al. Below‐ground biomass and productivity of a grazed site and a neighbouring ungrazed exclosure in a grassland in central Argentina [J]. Austral Ecology, 2004, 29(2): 201-208.

[35] McNaughton S, Banyikwa F F, McNaughton M. Root biomass and productivity in a grazing ecosystem: the Serengeti [J]. Ecology, 1998, 79(2): 587-592.

[36] Tilman D, Wedin D, Knops J. Productivity and sustainability influenced by biodiversity in grassland ecosystems [J]. Nature, 1996, 379(6567): 718-720.

[37] Alrababah M, Alhamad M, Suwaileh A, et al. Biodiversity of semi‐arid Mediterranean grasslands: Impact of grazing and afforestation [J]. Applied Vegetation Science, 2007, 10(2): 257-264.

[38] Dong S, Shang Z, Gao J, et al. Enhancing sustainability of grassland ecosystems through ecological restoration and grazing management in an era of climate change on Qinghai-Tibetan Plateau [J]. Agriculture, Ecosystems & Environment, 2020, 287: 106684.

[39] 李永宏. 放牧影响下羊草草原和大针茅草原植物多样性的变化 [J]. Journal of Integrative Plant Biology, 1993, (11): 877-884.

[40] Joubert L, Pryke J S, Samways M J. Moderate grazing sustains plant diversity in Afromontane grassland [J]. Applied vegetation science, 2017, 20(3): 340-351.

[41] Krzic M, Broersma K, Thompson D J, et al. Soil properties and species diversity of grazed crested wheatgrass and native rangelands [J]. 2000.

[42] 李镇清. 中国东北样带 (NECT)植物群落复杂性与多样性研究 [J]. 植物学报, 2000, (09): 971-978.

[43] 安慧, 徐坤. 放牧干扰对荒漠草原土壤性状的影响 [J]. 草业学报, 2013, 22(04): 35-42.

[44] 桑亚转, 尤杨, 李多才, 等. 放牧对祁连山高寒典型草原土壤质量的影响 [J]. 生态学报, 2023, 43(15): 6364-6377.

[45] Proffitt A, Jarvis R, Bendotti S. The impact of sheep trampling and stocking rate on the physical properties of a red duplex soil with two initially different structures [J]. Australian Journal of Agricultural Research, 1995, 46(4): 733-747.

[46] 王晓朦, 乌云娜, 宋彦涛, 等. 放牧对克氏针茅(Stipa krylovii)草原土壤物理、化学及微生物性状的影响 [J]. 中国沙漠, 2015, 35(05): 1193-1199.

[47] 伊犁绢蒿荒漠不同退化阶段草地特征与载畜力研究[J]. 草地学报, 2013, 21: 50-55.

[48] Snyman H d, Du Preez C. Rangeland degradation in a semi-arid South Africa—II: influence on soil quality [J]. Journal of arid environments, 2005, 60(3): 483-507.

[49] 高英志, 韩兴国, 汪诗平. 放牧对草原土壤的影响 [J]. 生态学报, 2004, (04): 790-797.

[50] 付华, 王彦荣, 吴彩霞, 塔拉腾. 放牧对阿拉善荒漠草地土壤性状的影响 [J]. 中国沙漠, 2002, (04): 32-36.

[51] 戎郁萍, 韩建国, 王培, 毛培胜. 放牧强度对草地土壤理化性质的影响 [J]. 中国草地, 2001, (04): 42-48.

[52] 谈嫣蓉, 杜国祯, 陈懂懂, 等. 放牧对青藏高原东缘高寒草甸土壤酶活性及土壤养分的影响 [J]. 兰州大学学报(自然科学版), 2012, 48(01): 86-91.

[53] Han G, Hao X, Zhao M, et al. Effect of grazing intensity on carbon and nitrogen in soil and vegetation in a meadow steppe in Inner Mongolia [J]. Agriculture, Ecosystems & Environment, 2008, 125(1-4): 21-32.

[54] Ji L, Qin Y, Jimoh S O, et al. Impacts of livestock grazing on vegetation characteristics and soil chemical properties of alpine meadows in the eastern Qinghai-Tibetan Plateau [J]. Ecoscience, 2020, 27(2): 107-118.

[55] 苏振声, 孙永芳, 付娟娟, 等. 不同放牧强度下西藏高山嵩草草甸土壤养分的变化 [J]. 草业科学, 2015, 32(03): 322-328.

[56] 闫瑞瑞, 卫智军, 辛晓平, 等. 放牧制度对荒漠草原生态系统土壤养分状况的影响 [J]. 生态学报, 2010, 30(01): 43-51.

[57] 萨仁高娃, 曹芙, 敖特根, 等. 短期放牧强度对典型草原土壤有机碳及pH值的影响 [J]. 畜牧与饲料科学, 2014, 35(03): 5-7.

[58] 孙宗玖, 朱进忠, 张鲜花, 等. 短期放牧强度对昭苏草甸草原土壤全量氮磷钾的影响 [J]. 草地学报, 2013, 21(05): 895-901.

[59] 孙翼飞, 沈菊培, 张翠景, 等. 不同放牧强度下土壤氨氧化和反硝化微生物的变化特征 [J]. 生态学报, 2018, 38(08): 2874-2883.

[60] Xun W, Yan R, Ren Y, et al. Grazing-induced microbiome alterations drive soil organic carbon turnover and productivity in meadow steppe [J]. Microbiome, 2018, 6(1).

[61] 高雪峰, 韩国栋. 放牧对羊草草原土壤氮素循环的影响 [J]. 土壤, 2011, 43(02): 161-166.

[62] Wang Z, Jiang S, Struik P C, et al. Plant and soil responses to grazing intensity drive changes in the soil microbiome in a desert steppe [J]. Plant & Soil, 2023, 491(1/2).

[63] Mencel J, Mocek-Płóciniak A, Kryszak A. Soil microbial community and enzymatic activity of grasslands under different use practices: a review [J]. Agronomy, 2022, 12(5): 1136.

[64] Ortiz A, Sansinenea E. The role of beneficial microorganisms in soil quality and plant health [J]. Sustainability, 2022, 14(9): 5358.

[65] 郭良栋. 内生真菌研究进展 [J]. 菌物系统, 2001, 20(001): 148-152.

[66] López-Mondéjar R, Brabcová V, Štursová M, et al. Decomposer food web in a deciduous forest shows high share of generalist microorganisms and importance of microbial biomass recycling [J]. The ISME journal, 2018, 12(7): 1768-1778.

[67] 何振立. 土壤微生物量及其在养分循环和环境质量评价中的意义 [J]. 土壤, 1997, 29(2): 61-69.

[68] 王立, 贾文奇, 马放, 等. 菌根技术在环境修复领域中的应用及展望 [J]. 生态环境学报, 2010, 19(02): 487-493.

[69] Zhang T, Sun Y, Feng S G. Arbuscular Mycorrhizal Fungi Can Accelerate the Restoration of Degraded Spring Grassland in Central Asia [J]. Rangeland Ecology & Management, 2012, 65(4): 426-432.

[70] 蒋婧, 宋明华. 植物与土壤微生物在调控生态系统养分循环中的作用 [J]. 植物生态学报, 2010, 34(8): 979-988.

[71] 陈雅涵, 谢宗强, 薛丽萍. 碳氮元素分析仪测试土壤与植物样品的流程优化 [J]. 现代化工, 2016, 36(04): 185-187+189.

[72] 王雪晴, 阮文渊, 易可可. 植物体内磷素状况测定方法的研究进展 [J]. 植物生理学报, 2016, 52(09): 1327-1332.

[73] 向晓黎, 马小宁, 魏向利, 等. 土壤全磷测定方法要点分析[J]. 农业灾害研究, 2015, 5: 30-31.

[74] 朱靖蓉, 马磊, 康露, 等. 降低样品采集制备过程中土壤硝态氮和铵态氮测定误差的方法[J]. 新疆农业科学, 2020, 57: 553-561.

[75] 李静. 碳酸氢钠浸提测定土壤有效磷研究 [J]. 资源节约与环保, 2019, (10): 105.

[76] 鲍士旦. 土壤农化分析 [D], 2000.

[77] Connell J H. Diversity in tropical rain forests and coral reefs: high diversity of trees and corals is maintained only in a nonequilibrium state [J]. Science, 1978, 199(4335): 1302-1310.

[78] 候伟峰, 乌恩, 敖特根, 等. 放牧强度对克氏针茅典型草原地上生物量的影响 [J]. 中国草地学报, 2016, 38(06): 71-77.

[79] Schmidt L, Hummel G M, Thiele B, et al. Leaf wounding or simulated herbivory in young N. attenuata plants reduces carbon delivery to roots and root tips [J]. Planta, 2015, 241: 917-928.

[80] 道日娜, 宋彦涛, 乌云娜, 等. 克氏针茅草原植物叶片性状对放牧强度的响应 [J]. 应用生态学报, 2016, 27(07): 2231-2238.

[81] Hevia V, Carmona C P, Azcárate F M, et al. Effects of land use on taxonomic and functional diversity: a cross-taxon analysis in a Mediterranean landscape [J]. Oecologia, 2016, 181: 959-970.

[82] 张扬建, 朱军涛, 沈若楠, 等. 放牧对草地生态系统影响的研究进展 [J]. 植物生态学报, 2020, 44(05): 553-564.

[83] Lal R. Carbon sequestration in dryland ecosystems [J]. Environmental management, 2004, 33: 528-544.

[84] 巨晓棠, 李生秀. 培养条件对土壤氮素矿化的影响 [J]. 西北农业学报, 1997, (02): 67-70.

[85] 刘敏, 赵财, 范虹, 等. 长期间作及免耕对土壤物理性状及作物产量的影响 [J]. 中国农学通报, 2023, 39(02): 28-35.

[86] Bardgett R D. The Biology of Soil: A Community and Ecosystem Approach [J]. Soil Use & Management, 2010.

[87] 张振, 李元恒, 丁勇, 等. 典型草原群落及功能群物种多样性对放牧因素分解的响应 [J]. 中国草地学报, 2020, 42(05): 48-54.

[88] 陈霄龙, 郭腾飞, 张倩, 等. 基于稳定性同位素核酸探针技术的同化利用玉米秸秆碳微生物群落演替研究 [J]. 植物营养与肥料学报, 2024, 30(03): 430-440.

[89] Frey S D, Elliott E T, Paustian K, et al. Fungal translocation as a mechanism for soil nitrogen inputs to surface residue decomposition in a no-tillage agroecosystem [J]. Soil Biology and Biochemistry, 2000, 32(5): 689-698.

[90] 李涛, 李芹, 陈林杨, 等. 不同林龄橡胶林土壤肥力变化差异研究 [J]. 云南农业大学学报(自然科学), 2017, 32(02): 303-309.

[91] 王常慧, 邢雪荣, 韩兴国. 草地生态系统中土壤氮素矿化影响因素的研究进展 [J]. 应用生态学报, 2004, (11): 2184-2188.

[92] Yang G, Wagg C, Veresoglou S D, et al. How Soil Biota Drive Ecosystem Stability [J]. Trends in Plant ence, 2018, 23.

[93] 杨永, 卫伟, 王琳, 等. 中国旱区样带尺度植物多样性和生产力与环境因子的关系 [J]. 生态学报, 2023, 43(04): 1563-1571.

[94] 毛忆莲, 葛晓改, 周军刚, 等. 生物质炭配施氮肥对雷竹林土壤微生物碳氮利用效率的影响 [J]. 生态学报, 2024, 44(24): 11220-11228.

[95] Li W, Jiang L, Zhang Y, et al. Structure and driving factors of the soil microbial community associated with Alhagi sparsifolia in an arid desert [J]. PLoS ONE, 2021, 16(7): e0254065.

[96] 孟兆云, 李敏, 杨勋爵, 等. 寒温带地区典型森林类型中外生菌根真菌多样性和群落组成及其影响因素 [J]. 生态学报, 2023, 43(01): 38-47.

[97] Zhao T, Lu N, Guo J, et al. Long-term sheep grazing reduces fungal necromass carbon contribution to soil organic carbon in the desert steppe [J]. Frontiers in Microbiology, 2024.

[98] Xu M P, Wang J Y, Zhu Y F, et al. Plant Biomass and Soil Nutrients Mainly Explain the Variation of Soil Microbial Communities During Secondary Succession on the Loess Plateau [J]. Microbial Ecology, 2022, 83(1): 114-126.

[99] Zhang Y, Chen Y, An B, et al. The succession patterns and drivers of soil bacterial and fungal communities with stand development in Chinese fir plantations [J]. Plant & Soil, 2024, 500(1/2).