有机胶结形成土壤团聚体的机理及理论模型

土壤团聚体是土壤结构的基本单位,其组成和稳定性直接影响土壤肥力和农作物的生长,对于有机质含量高的黑土,有机胶结物质是形成土壤团聚体的主要因素。在综合有机胶结剂和土壤团聚体的研究的基础上,阐述了有机胶结物质的特性,土壤生物和植物根系在土壤团聚体形成中的作用,土壤团聚体形成的机理及理论模型。     

盐渍化条件下土壤团聚体及其有机碳研究进展

土壤团聚体是土壤结构的基本单元,对改善土壤结构和增加土壤固碳具有重要作用.盐渍化导致的特殊土壤性质,如高盐分离子(主要为Na+)浓度、低有机质含量和较差的微生物条件等因素,对团聚体的形成和稳定产生障碍作用,因此探讨盐渍化土壤团聚体特征更具有重要性和特殊性.滨海湿地和内陆盐渍化沼泽湿地是盐渍化生态系统的重要组成部分.本文...     

丛枝菌根真菌对中性紫色土土壤团聚体特征的影响

利用分根装置研究了接种丛枝菌根真菌对中性紫色土土壤团聚体数量、大小和稳定性的影响,分析了土壤团聚体数量、分布和分形维数,并运用通径分析对不同影响因子进行了分析。结果表明:接种G. intraradices和G. mosseae的菌根室土壤有机质和总球囊霉素相关土壤蛋白含量有增加的趋势;湿筛条件下菌根室土壤的平均重量直径(MWD)和几何平均直径(GMD)均显著高于根室土壤,而且降低了土壤分形维数,显示了丛枝菌根真菌提升土壤结构特征的作用。通径分析的结果表明,在影响MWD的众多因子中,菌丝密度对MWD有最大的直接作用。两种菌种对土壤结构均有不同程度的改良作用,反映了丛枝菌根真菌功能的多样性。     

不同发育阶段杉木人工林土壤有机质特征及团聚体稳定性

为比较不同发育阶段杉木人工林土壤团聚体稳定性和有机质变化规律,选取杉木幼龄林、中龄林和成熟林为对象,研究不同发育阶段杉木林土壤总碳、总氮、可溶性有机质、微生物生物量、团聚体分布和稳定性。结果表明:随着林分的发育,表层土壤总氮含量呈增加趋势,总碳先减少后增加,3个发育阶段20~100 cm土层的总碳变化不大。可溶性有机质含量和微生物生物量均随土壤加深而显著下降,0~20 cm土层可溶性有机碳含量随着林龄增加而下降,中龄林微生物生物量碳明显低于幼龄林和成熟林,活性有机质与土壤总碳、总氮、土壤容重、p H值和含水量均存在不同程度相关关系,说明杉木人工林土壤活性有机质含量受多个土壤因素的影响。5 mm大团聚体数量和平均重量直径随林分发育呈增加趋势,团聚体破坏率下降。团聚体的稳定性随土层加深而显著下降,中龄林和成熟林深层土壤0.25 mm水稳性团聚体比例、平均重量直径、几何重量直径均大于幼龄林,团聚体破坏率低于幼龄林,表明杉木林分的发育有利于底层土壤结构的稳定。土壤团聚体稳定性与土壤粉粒含量、活性有机碳组分、总碳、总氮呈显著正相关。杉木人工林发育到成熟林阶段,土壤碳和氮得到积累,土壤团聚体稳定性显著提高。     

若尔盖退化高寒草甸土壤团聚体结合有机碳的变化

选取若尔盖沼泽化草甸及其不同退化程度为研究对象,利用湿筛法进行团聚体分级,并测定各组分有机碳含量,研究了高寒草甸退化对土壤有机碳(SOC,Soil Organic Carbon)、团聚体以及团聚体结合有机碳(OC,Organic Carbon)的影响,旨在从土壤团聚体及其内部组成的角度去解析SOC的变化特征及机制。结果显示：1)退化使大团聚体比例降低且内部组成改变,团聚体稳定性降低。2)退化使各粒级团聚体及大团聚体内部组分结合OC含量均显著降低。3)大团聚体及其内部粗颗粒有机质中OC储量减少是退化中土壤有机碳流失的主要形式,微团聚体、闭蓄态微团聚体和闭蓄态黏粉粒中OC储量随退化增加。4)退化显著降低了高寒草甸SOC含量和储量,表层(0—10 cm)SOC含量变化主要决定于微团聚体和大团聚体OC含量,亚表层(10—20 cm)SOC含量主要受大团聚体OC含量和团聚体平均重量直径(MWD)影响;对于SOC储量,团聚体MWD是表层SOC储量的最重要影响因素,而亚表层SOC储量取决于团聚体组成、土壤理化性质和大团聚体OC含量的综合作用。研究结果表明,改善土壤团聚体组成和稳定性,增加大团聚体有机...     

长期施肥对黑土团聚体分布和碳储量变化的影响

用干筛与湿筛2种方法测定了22年长期田间定位试验地土壤风干及水稳性团聚体含量,研究了施肥对黑土团聚体组成、有机碳含量及有机碳库储量的影响。试验设不施肥（CK）、无机肥（NP、NPK）和无机-有机肥配施（NPK+OM）4个处理。结果表明,黑土团聚体以0.25～1 mm团聚体为主。经过湿筛法土壤各粒级水稳性团聚体含量重新分配,表现为以0.25～1 mm粒级为中心,大团聚体含量减少,微团聚体含量增加。与长期不施肥比较,长期施用化肥及有机-无机肥配施显著增加了>2 mm大团聚体含量和0.05～0.25 mm微团聚体含量,各级团聚体有机碳含量显著增加,总有机碳及各级团聚体储量增加,有机质积累,土壤结构得到改善,固碳潜力增加,有机-无机配施效果更加明显。     

典型喀斯特森林土壤的抗蚀性

喀斯特地区生态脆弱,极易发生土壤侵蚀。受地表要素空间异质性的影响,目前相关研究仍无法完全反映出喀斯特地区不同植被类型土壤抗蚀性的特征。通过野外调查,了解样地植被群落类型及其组成等基本情况,并以"S形布点法"实地采样;通过酒精烘烤法、环刀法等方法,获取土壤含水量、土壤容重、土壤有机质、土壤团聚体、土壤微团聚体及土壤机械组成、土壤抗蚀指数等土壤抗蚀指标值。结果表明,除有机质外的其他抗蚀指标表现出0—10cm土层内与10—20cm土层内的变化规律均和抗蚀指数一致。在土壤深度0—10cm范围内,土壤抗蚀指数表征的土壤抗蚀能力强弱为:阔叶林灌丛针叶林;在10—20cm土层范围为:灌丛针叶林阔叶林。0—10cm土层内各指标表征土壤抗蚀能力的显著程度为:有机质含量、水稳性团聚体、结构破坏率、团聚状况和团聚度较显著,10—20cm土层内为有机质含量、干筛团聚体、团聚度较为显著,水稳性团聚体次之。通过综合两个土层的情况,可认为有机质含量、水稳性团聚体、团聚度能较好地表征喀斯特林地土壤抗蚀性强弱。在喀斯特地区如果以防治土壤侵蚀为目的,应考虑种植阔叶树种,避免针叶树种。     

紫色土丘陵坡地恢复中土壤团聚体特征及其与土壤性质的关系

采用空间代替时间序列方法,选择立地基本相似的草本、灌草、灌丛、乔灌和乔木群落,调查了衡阳紫色土丘陵坡地不同恢复阶段土壤团聚体特征及其主要影响因子,并用典范相关分析和主成分分析对二者的相互关系进行定量分析。结果表明:随恢复进行,土壤中大粒级团聚体含量显著增加(P0.05),2 m土层中5 mm粒级团聚体在土壤团粒结构中占主导地位,约占50%~80%,其次是5~2 mm含量,约占10%~15%;随土层加深,草坡、灌草和乔灌群落的团聚体总量显著减小(P0.05),灌丛群落,先降后增再降(P0.05),乔木群落,先增后减(P0.05)。在不同恢复阶段与不同土层中,团聚体平均重量直径呈现不同变化规律,0~40 cm土层,灌丛群落团聚体平均重量直径最大(P0.05),40~80 cm土层,随恢复进行先增后降再增(P0.05),80~130和130~200 cm土层,随恢复进行而显著增加(P0.05)。在草本、灌草和灌丛群落,团聚体平均重量直径随土层加深而显著减小(P0.05);乔灌和乔木群落,随土层加深先增后降(P0.05)。典范相关分析表明,土壤有机质和全氮对5 mm和1~0.5 mm两粒级团聚体的影响较大;Al_2O_3、Fe_2O_3、0.01 mm物理性黏粒对2~1 mm和0.5~0.25 mm两粒级团聚体的影响较大。主成分分析表明,土壤有机质、全氮、Al_2O_3、Fe_2O_3是影响土壤团聚体的主要因子,其次为0.002 mm黏粒和0.01 mm物理性黏粒。研究表明,植被恢复可改变土壤结构,导致土壤团聚体重新分配和土壤大团聚体形成,提高土壤团聚体的稳定性。     

黄土高原长期培肥土壤团聚体中养分和酶的分布

土壤养分和生物酶是衡量土壤肥力的指标,土壤团聚体性质则决定了土壤物理结构的好坏,探讨不同培肥措施下土壤养分和生物酶在团聚体中的分布,对合理培肥和改善土壤性状具有重要的实际意义。对连续25a的长期有机培肥定位试验地进行测定,结果表明：培肥增加了大级别土壤团聚体、特征微团聚体的数量,显著地改善了土壤结构。培肥土壤团聚体平均重量直径、特征微团聚体C／F0.01较无肥对照土壤有显著增加。长期培肥增强了土壤化学、生物性质的“微域”变异性。相同培肥措施下土壤主要养分含量和酶活性均随土壤团聚体直径的增大而减小。除厩肥处理土壤碱性磷酸酶和蔗糖酶外,其它各培肥土壤的养分含量和酶活性均在〈0．01mm级别特征微团聚体中含量高、活性大。相同级别团聚体和特征微团聚体中,养分含量和酶活性在不同培肥土壤间基本表现出施厩肥处理〉施秸秆处理〉施化肥处理〉对照的规律性。将团聚体的含量和养分含量或酶活性在团聚体中的丰度结合考虑,发现〉5mm级别团聚体中养分含量或酶活性对土壤的贡献率最大。结果充分地显示着土壤性质在不同空间尺度下、不同管理措施下变异的复杂性和多样性。     

应用Le Bissonnais 法研究黄土丘陵区植被类型对土壤团聚体稳定性的影响

植被类型直接影响土壤特性,对土壤团聚体的形成和稳定性有重要影响,水稳性团聚体是反映黄土高原土壤抗蚀性的最佳指标。本文选择黄土丘陵区延河流域作为研究区域,应用Le Bissonnais(LB)法和Yoder法测定了森林、森林草原两种植被类型下土壤水稳性团聚体稳定性,对比分析了LB法3种处理的结果,并计算土壤团聚体平均重量直径（MWD）和可蚀性因子K值。结果表明：在LB法3种湿润处理下,预湿后扰动处理（WS）对土壤团聚体结构的破坏程度最大,处理后土壤水稳性团聚体以<0.2 mm为主;快速湿润处理（FW）对团聚体的破坏程度次之;慢速湿润处理(SW)对团聚体的破坏程度最小,处理后土壤水稳性团聚体主要以>2 mm团聚体为主;说明黄土丘陵区延河流域土壤团聚体破坏的主要机制是气爆作用（消散作用）和机械扰动。LB法的3种处理结果中预湿后扰动的测定结果与传统的湿筛法（Yoder法）更接近。LB法包含Yoder法的基本原理,能够全面、准确的测定土壤团聚体结构,适宜作为黄土丘陵区土壤团聚体测定方法。森林植被类型的土壤团聚体平均重量直径（MWD）大于森林草原植被类型,而且SW>FW>WS,但可蚀性因子K值却是森林植被类型小于森林草原植被类型。土壤水稳性团聚体由小颗粒向大颗粒转变,土壤结构趋于稳定。不同植被类型下土壤有机质含量不同,土壤团聚体形成过程及土壤团聚度也有差异,因而造成土壤可蚀性和土壤抗蚀性能不同。     

两种气候条件下不同有机质含量农田黑土真菌群落结构特征

【背景】东北黑土土壤肥沃,有机质含量丰富,是我国重要的粮食生产基地,同时也是受气候变化影响的敏感区。土壤微生物对环境因子变化的响应敏感,并且与土壤肥力密切相关,因此,研究环境因子改变对土壤微生物的影响有助于维持农田黑土生产力。【目的】探究有机质含量与气候条件对农田黑土真菌群落结构、多样性的影响,为全球气候变化条件下黑土区农业可持续发展提供重要基础数据和理论依据。【方法】利用黑土空间移位试验,采用Illumina MiSeq测序技术对农田黑土真菌种类进行预测,并对其进行多样性和群落结构分析。【结果】两种气候条件下不同有机质含量农田黑土真菌种类均较丰富,土壤有机质含量对真菌多样性指数的影响不大,气候条件和施肥对真菌多样性的影响较大。在已知的真菌群落中,5种不同有机质农田黑土的优势菌门均为子囊菌门(Ascomycota)、担子菌门(Basidiomycota)和接合菌门(Zygomycota),占总序列的92.5%。在气候较冷条件下,OTU数量、Chao1指数、Shannon指数和Simpson指数均出现不同程度的降低;施肥也会降低各有机质含量农田黑土中真菌物种数量和多样性,但是降低幅度随有机质含量升高而逐渐减小。气候因子、有机质含量、全氮、施肥和pH是影响不同有机质含量农田黑土中真菌群落结构发生变化的主要因素。【结论】有机质含量、施肥和气候均一定程度上改变了农田黑土中真菌群落多样性和群落结构。气候条件和施肥对农田黑土真菌群落结构影响较大,而有机质含量对其影响较小,但前两者的影响会随土壤有机质含量的增加而呈减弱趋势。这些影响在子囊菌门群落结构中表现明显。     

草原及开垦后土壤有机质性质研究

从土壤有机无机复合状况、腐殖质结合形态和腐殖质组成等方面,研究了供试土壤(草原淡黑钙土、草原风沙土和已开垦的风沙土)有机质的性质．结果表明,不同土壤类型及利用方式对土壤有机质性质的影响有很大的差异．与风沙土相比,淡黑钙土的全土碳、生物量碳、重组碳、可提取腐殖物质(HE)、松结态腐殖质的含量和全土腐殖化度较高．风沙土种向日葵后其全土碳、生物量碳、重组碳和HE含量及各种结合形态腐殖质含量均下降,但腐殖化程度相差不大．     

Soil enzyme activities and organic matter composition in a turfgrass chronosequence

Highly managed turfgrass systems accumulate considerable soil organic C, which supports a diverse and robust soil microbial community. Degradation of this soil organic C is mediated by a suite of soil enzymes. The relationship between these enzyme activities and the quality of soil organic C is central to understanding the dynamics of soil organic matter. We examined the activities of several soil enzymes involved in microbial C acquisition, including β-glucosidase, N-acetyl-β-glucosaminidase, cellulase, chitinase, and phenol oxidase, and characterized the chemical composition of soil organic matter using Fourier transform infrared spectroscopy (FTIR) in a turfgrass chronosequence (1–95 years old) and adjacent native pines. Non-metric multidimensional scaling analysis showed that the chemical composition of soil organic matter varied with turf age and land use (turf versus pines). Using the polysaccharide peak (1,060 cm⁻¹) as a reference, both aliphatic (2,930 cm⁻¹) and carboxylic (1,650 and 1,380 cm⁻¹) compounds increased with turf age, indicating that soil organic matter became more recalcitrant. Soil enzyme activities per unit soil mass increased with turf age and were correlated to soil C content. Most soil enzyme activities in native pines were similar to those in young turf, but the cellulase activity was similar to or greater than the activity in old turfgrass systems. On a soil C basis, however, the activities of N-acetyl-β-glucosaminidase and cellulase decreased with turf age; this reduction was correlated to the relative changes in the chemical composition of soil organic matter. We observed that the chemical composition of soil organic matter was significantly correlated with the enzyme activity profile when expressed per unit microbial biomass C, but not per unit soil organic C. Our results suggest that chemical composition of soil organic matter changes with turf age and this change partially determines the relative abundance of C-degrading soil enzymes, likely through the influence on microbial community composition.     

氮沉降对森林土壤有机质和凋落物分解的影响及其微生物学机制

氮沉降持续增加背景下土壤C∶N∶P化学计量比和pH环境等的改变及其可能的土壤微生物学机制已经成为陆地生态系统与全球变化研究的新生长点和科学研究前沿.以生态化学计量学和土壤微生物生态学为理论基础,综述了氮沉降对森林土壤有机质和凋落物分解的影响及其微生物学机制的基本理论、最新进展、研究热点与难点,旨在促进全球变化背景下陆地生态系统地下生态学的研究.氮沉降持续增加会导致森林生态系统磷循环加速,导致磷限制.氮沉降不但改变森林土壤有机质和凋落物的C∶N∶P化学计量比和降低土壤pH值,而且改变土壤微生物生物量碳氮磷、细菌、真菌和放线菌的组成以及影响碳氮磷分解的关键酶活性.氮沉降对森林土壤有机质和凋落物分解的影响表现为促进、抑制和无影响,其影响的差异可能来源于微生物效应的不同.叶片在凋落前有显著的氮磷养分回收,但是根无明显的养分回收,造成土壤有机质和凋落物的C∶N∶P化学计量比存在明显差异.基于DNA/RNA等分子生物学方法为土壤微生物生态学研究提供了强有力的手段,将促进氮沉降对森林土壤有机质和凋落物化学计量比改变的微生物学机制研究.     

Temporal and spatial variability in soil food web structure

Heterogeneity is a prominent feature of most ecosystems. As a result of environmental heterogeneity the distribution of many soil organisms shows a temporal as well as horizontal and vertical spatial patterning. In spite of this, food webs are usually portrayed as static networks with highly aggregated trophic groups over broader scales of time and space. The variability in food web structure and its consequences have seldom been examined. Using data from a Scots pine forest soil in the Netherlands, we explored (1) the temporal and spatial variability of a detrital food web and its components, (2) the effect of taxonomic resolution on the perception of variability over time and across space, and (3) the importance of organic matter quality as an explanatory factor for variability in food web composition. Compositional variability, expressed using the Bray‐Curtis similarity index, was measured over 2.5 years using a stratified litterbag design with three organic horizons per litterbag set. Variability in community composition and organic matter degradation increased over time in the litter horizon only. Seasonal variation in community composition was larger than variation between samples from the same season in different years. Horizontal spatial variability in community composition and organic matter degradation was relatively low, with no increase in variability with increasing distance between samples. Vertically, communities and organic matter degradation was more different between the non‐adjacent litter and humus horizons than between adjacent layers. These findings imply that soil food webs, at least in temperate forest plantations, are more variable than is currently appreciated in experiments and model studies, and that organic matter turnover might be an important factor explaining variability in community composition. Species composition was more variable than functional group composition, which implies that aggregated food webs will seem less sensitive to local temporal and spatial changes than they in fact are.     

太原市农业土壤全氮和有机质的空间分布特征及其影响因素

利用GPS定位,2005年在山西省太原市主要农业用地采集土样1821个,分析了全氮和有机质的含量.应用传统统计学和地质统计学方法对数据进行了分析.结果表明,按照1980年全国第二次土壤普查养分分级标准,土壤全氮和有机质的平均含量均属中等水平.通过半方差函数分析,土壤全氮和有机质在一定范围内存在空间相关性;它们的空间相关距离分别为122.4 km和75.6 km;全氮的空间变异主要受结构性因素的影响,而土壤有机质的空间变异是由结构性因素和随机性因素共同作用引起的.太原市土壤全氮含量的空间分布呈现由西南向东北逐渐降低的趋势,而有机质的分布规律较为复杂,它们的空间分布主要受土壤类型、海拔高度、土地利用方式和人类生产活动等因素的影响.土壤全氮与有机质的空间分布存在很大的差异,这与娄烦县、古交市当地土壤受煤粉尘污染严重以及所处地形地貌密切相关.研究揭示了在自然和社会条件十分复杂的情况下太原市土壤全氮和有机质的空间变异规律及其影响因素,为实现土壤肥力评价和养分资源精准管理提供了科学依据.     

土壤碳库构成研究进展

土壤碳库是陆地生态系统中最大的碳库。土壤碳库的构成影响其累积和分解,并直接影响全球陆地生态系统碳平衡,同时也影响土壤质量变化。弄清土壤碳库的组分及构成,是进一步研究土壤碳库变化机制的关键。综述了土壤碳库的组分和构成,对有机碳库进行不稳定性有机碳库和稳定有机碳库归类,描述各类碳库的性质,并对各类碳库的分析测定方法进行了评述。提出在土壤碳构成中增加黑碳和煤炭(碳)以完善土壤有机碳构成框架。在未来研究中,应加强土壤无机碳及湿地土壤和新开发新复垦的重构土壤碳库构成及变化,各类碳库化学构成,交叉重叠的定量关系,碳库之间的转化及在土壤中的迁移,黑碳对土壤碳库稳定性及土壤质量的影响,煤开采扰动区煤炭(碳)对土壤质量的影响及环境效应等科学问题的研究。     

Depth-dependent effects of ericoid mycorrhizal shrubs on soil carbon and nitrogen pools are accentuated under arbuscular mycorrhizal trees

Plant mycorrhizal associations influence the accumulation and persistence of soil organic matter and could therefore shape ecosystem biogeochemical responses to global changes that are altering forest composition. For instance, arbuscular mycorrhizal (AM) tree dominance is increasing in temperate forests, and ericoid mycorrhizal (ErM) shrubs can respond positively to canopy disturbances. Yet how shifts in the co-occurrence of trees and shrubs with different mycorrhizal associations will affect soil organic matter pools remains largely unknown. We examine the effects of ErM shrubs on soil carbon and nitrogen stocks and indicators of microbial activity at different depths across gradients of AM versus ectomycorrhizal (EcM) tree dominance in three temperate forest sites. We find that ErM shrubs strongly modulate tree mycorrhizal dominance effects. In surface soils, ErM shrubs increase particulate organic matter accumulation and weaken the positive relationship between soil organic matter stocks and indicators of microbial activity. These effects are strongest under AM trees that lack fungal symbionts that can degrade organic matter. In subsurface soil organic matter pools, by contrast, tree mycorrhizal dominance effects are stronger than those of ErM shrubs. Ectomycorrhizal tree dominance has a negative influence on particulate and mineral-associated soil organic matter pools, and these effects are stronger for nitrogen than for carbon stocks. Our findings suggest that increasing co-occurrence of ErM shrubs and AM trees will enhance particulate organic matter accumulation in surface soils by suppressing microbial activity while having little influence on mineral-associated organic matter in subsurface soils. Our study highlights the importance of considering interactions between co-occurring plant mycorrhizal types, as well as their depth-dependent effects, for projecting changes in soil carbon and nitrogen stocks in response to compositional shifts in temperate forests driven by disturbances and global change.     

Contributions of freshwater mussels (Unionidae) to nutrient cycling in an urban river: filtration,recycling, storage,and removal

Physical separation of soil into different soil organic matter (SOM) fractions is widely used to identify organic carbon pools that are differently stabilized and have distinct chemical composition. However, the mechanisms underlying these differences in stability and chemical composition are only partly understood. To provide new insights into the stabilization of different chemical compound classes in physically-separated SOM fractions, we assessed shifts in the biomolecular composition of bulk soils and individual particle size fractions that were incubated in the laboratory for 345 days. After the incubation, also the incubated bulk soil was fractionated. The chemical composition of organic matter in bulk soils and fractions was characterized by ¹³C-CPMAS nuclear magnetic resonance spectroscopy and sequential chemical extraction followed by GC/MS measurements. Plant-derived lipids and lignin were abundant in particulate organic matter (POM) fractions of sand-, silt-, and clay-size and the mineral-bound, clay-sized organic matter. These results indicate that recent conceptualizations of SOM stabilization probably understate the contribution of plant-derived organic matter to stable SOM pools. Although our data indicate that inherent recalcitrance could be important in soils with limited aggregation, organo-mineral interactions and aggregation were responsible for long-term SOM stabilization. In particular, we observed consistently higher concentrations of plant-derived lipids in POM fractions that were incubated individually, where aggregates were disrupted, as compared to those incubated as bulk soil, where aggregates stayed intact. This finding emphasizes the importance of aggregation for the stabilization of less ‘recalcitrant’ biomolecules in the POM fractions. Because also the abundance of lipids and lignin in clay-sized, mineral-associated SOM was substantially influenced by aggregation, the bioavailability of mineral-associated SOM likely increases after the destruction of intact soil structures.     

Ecosystem changes associated with grazing in subhumid South American grasslands

Question: What are the changes in vegetation structure, soil attributes and mesofauna associated with grazing in mesic grasslands? Location: Southern Campos of the Río de la Plata grasslands, in south‐central Uruguay. Methods: We surveyed seven continuously grazed and ungrazed paired plots. Plant and litter cover were recorded on three 5‐m interception lines placed parallel to the fence in each plot. We extracted soil fauna from a 10 cm deep composite sample and analysed the oribatids. Soil attributes included bulk density, water content, organic carbon (in particulate and mineral associated organic matter) and nitrogen content and root biomass at different depths. Changes in floristic, Plant Functional Types and mesofauna composition were analysed by Non‐metric Multidimensional Scaling. Results: Species number was lower in ungrazed than in grazed plots. Of 105 species in grazed plots only three were exotics. Shrub and litter cover were significantly higher inside the exclosures, while the cover of Cyperaceae‐Juncaceae was lower. Grazing treatments differed significantly in plant and oribatid species composition. Grazing exclusion significantly reduced soil bulk density and increased soil water content. Carbon content in particulate organic matter was lower in the upper soil of ungrazed sites, but deeper in the profile, grazing exclosures had 8% more carbon in the mineral associated organic matter. Conclusions Our results generally agree with previous studies but deviate from the results of previous analyses in (1) the increase of shrub cover in ungrazed sites; (2) the redistribution of the soil organic carbon in the profile and (3) the low invasibility of the prairies regardless of grazing regime.