上海大金山岛植被功能组成对草本植物、土壤动物和细菌多样性的影响

揭示植物群落对土壤动物和微生物多样性的上行调控效应有助于理解不同营养级生物多样性的维持机制。以往的研究主要集中在植物物种多样性对土壤动物和微生物多样性的影响,而关于植被功能组成自下而上的影响研究较少。以上海大金山岛13个植物群落为对象,在分析落叶木本植物占比与树木和草本物种多样性,以及土壤动物和细菌多样性的关系基础上,利用结构方程模型区分了落叶木本植物占比对土壤动物和细菌多样性的直接与间接影响效应。结果显示：落叶木本植物占比不仅分别对草本物种多样性和土壤动物多样性分别产生直接正效应和负效应（P<0.01;P<0.05）,也会通过草本物种的级联效应间接的降低地下土壤细菌多样性（P<0.10）。然而,木本植物多样性仅与草本物种多样性显著正关联（P<0.10）,与土壤动物和细菌多样性无显著关联（P>0.10）。该研究结果表明,相较于木本植物多样性,落叶植物占比在中亚热带北缘森林生态系统不同营养级生物多样性维持格局中扮演着更为重要的角色。     

农田土壤线虫多样性研究现状及展望

目前土壤生物多样性已成为土壤生态学研究的热点问题之一。土壤生物以不同的方式改变着土壤的物理、化学和生物学特性。在农田生态系统中, 土壤动物是分解作用和养分矿化作用等生态过程的主要调节者。线虫作为土壤中数量最丰富的后生动物, 其生活史和取食类型多样, 在生态系统中发挥着重要作用。本文介绍了农田生态系统中影响线虫多样性的主要因素; 回顾了土壤线虫的物种多样性、营养类群多样性、生活史多样性和功能多样性的研究现状; 并提出了今后农田生态系统线虫多样性研究的重点。建议通过综合土壤线虫的生活史策略和营养类群等信息, 深入了解其生物多样性和土壤生态系统功能, 从而更好地发挥土壤线虫对农田生态系统变化的生物指示作用。     

环境DNA技术在地下生态学中的应用

地下生态过程是生态系统结构、功能和过程研究中最不确定的因素。由于技术和方法的限制,作为"黑箱"的地下生态系统已经成为限制生态学发展的瓶颈,也是未来生态学发展的主要方向。环境DNA技术,是指从土壤等环境样品中直接提取DNA片段,然后通过DNA测序技术来定性或定量化目标生物,以确定目标生物在生态系统中的分布及功能特征。环境DNA技术已成功用于地下生态过程的研究。目前,环境DNA技术在土壤微生物多样性及其功能方面的研究相对成熟,克服了土壤微生物研究中不能培养的问题,可以有效地分析土壤微生物的群落组成、多样性及空间分布,尤其是宏基因组学技术的发展,使得微生物生态功能方面的研究成为可能;而且,环境DNA技术已经在土壤动物生态学的研究中得到了初步应用,可快速分析土壤动物的多样性及其分布特征,更有效地鉴定出未知的或稀少的物种,鉴定土壤动物类群的幅度较宽;部分研究者通过提取分析土壤中DNA片段信息对生态系统植物多样性及植物分类进行了研究,其结果比传统的植物分类及物种多样性测定更精确,改变了以往对植物群落物种多样性模式的理解。同时,环境DNA技术克服传统根系研究方法中需要洗根、分根、只能测定单物种根系的局限,降低根系研究中细根区分的误差,并探索性地用于细根生物量的研究。主要综述了基于环境DNA技术的分子生物学方法在土壤微生物多样性及功能、土壤动物多样性、地下植物多样性及根系生态等地下生态过程研究中的应用进展。环境DNA技术对于以土壤微生物、土壤动物及地下植物根系为主体的地下生态学过程的研究具有革命性意义,并展现出良好的应用前景。可以预期,分子生物学技术与传统的生态学研究相结合将成为未来地下生态学研究的一个发展趋势。     

植物多样性对亚热带森林土壤微生物群落的影响

植物群落组成的改变能够直接或间接地影响土壤生态过程并调节参与这些过程的土壤生物,树种特性和多样性是影响土壤微生物多样性和群落结构的关键因素。本项目利用江西新岗山建立的中国亚热带森林生物多样性与生态系统功能(Biodiversity-Ecosystem Functioning Experiment China)BEF-China研究平台,观测了样方水平下不同多样性组成(单物种、2物种、4物种和8物种)对土壤微生物群落结构的影响。结果表明:在森林生态系统演替初期,植物多样性的改变对土壤微生物群落结构具有显著影响,在不同多样性水平处理下,微生物磷脂脂肪酸含量随着植物多样性的增加,表现出先升高后降低的趋势,但各类群微生物磷脂脂肪酸含量并未表现出对植物多样性的明显响应。其中,土壤和凋落物的理化指标能够分别解释微生物群落结构变异的28.4%和12.3%。森林生态系统较高的异质性和地下生态过程响应的滞后性,导致了土壤微生物对植物多样性组成的响应需要较长时间才能显现出来,因此,为了更好地评价地上生物多样性与生态系统功能的关联,应长期监测森林生态系统多样性组成对地下生态过程的影响。     

土壤动物群落空间格局和构建机制研究进展

群落空间格局和构建机制一直是生态学研究的核心内容。在生物多样性严重丧失的背景下, 揭示群落空间格局及其构建机制, 有助于深刻理解生物多样性丧失的原因, 更有助于应对生物多样性保护等重大生态环境问题。然而, 陆地生态系统的研究多集中于地上生物群落, 对地下生态系统, 尤其是土壤动物空间格局和构建机制的研究尚不充分。事实上, 土壤动物多样性是全球生物多样性的关键组成之一, 是地下生态系统结构和功能维持的重要部分。对土壤动物空间格局和构建机制的研究, 能明确不同空间尺度条件下土壤动物多样性的维持机制。土壤动物群落常在多种空间尺度形成复杂的空间分布格局, 因此, 本文首先介绍了不同空间尺度主要土壤动物群落的空间自相关性特征, 阐述了土壤动物群落斑块和孔隙镶嵌分布的复杂空间格局。继而阐明这种空间格局主要受生物间作用、环境过滤和随机扩散的调控, 并说明这三个过程对土壤动物群落的调控能力和作用方式。作者提出, 这三个过程仍是今后土壤动物群落空间格局和构建机制研究的重点内容, 需要进一步加强以土壤动物为研究对象的群落构建理论的验证和发展。我国土壤动物群落空间格局和构建机制起步较晚, 希望本文能够促进我国土壤动物生态学相关领域的研究。     

黄河首曲湿地植物群落生产力、物种多样性及其与生境的关系

近年来,在气候变化与人为干扰等因素的驱动下,高寒湿地退化导致生物多样性的丧失如何影响生态系统功能尚无共识。以黄河首曲高寒湿地为研究对象,基于野外采样数据和植物群落多样性指数,重点分析植物物种多样性、地上生物量空间分布格局及其与土壤因子关系。结果表明：首曲湿地存在一定程度退化,植物群落组成主要集中在菊科和禾本科,莎草科和豆科植物较少;植物群落物种多样性和地上生物量未表现出显著的经纬度和海拔梯度变化;Patrick丰富度指数(R)和Shannon-Weiner多样性指数(H)与地上生物量呈显著正相关,说明保护区植物多样性的保护有利于生产力维持;土壤含水量影响着高寒湿地植被群落结构,与多样性指数呈显著相关性,是高寒湿地植被恢复和重建的关键性因子。该研究结果对于认识黄河首曲高寒湿地植物生物量和物种多样性及土壤因子的空间分异规律具有一定的参考价值,同时为高寒湿地退化生态系统功能的恢复及生物多样性的保护提供科学依据。     

青藏高原高寒草地地下生物多样性: 进展、问题与展望

栖息于土壤中的微生物和微型动物种类繁多、数量巨大, 在对地上生物多样性的调控和在生态系统功能与服务的维系中, 具有举足轻重的作用。虽然对土壤微生物以及土壤动物已经开展了广泛的调查, 但是整体上对于地下生物多样性的分布格局、驱动机制及其对全球变化的响应与适应过程, 仍缺乏深刻的认识。青藏高原是全球变化的敏感区域, 其中高寒草地是高原最主要的植被类型, 占高原面积的60%左右, 在高寒生态系统生物多样性维持中具有重要意义。近年来, 已有大量研究关注于高寒草地地下生物多样性, 但是缺乏系统的总结与论述。基于此, 本文从细菌、真菌、古菌、线虫、节肢动物五大土壤生物类群出发, 阐述了青藏高原高寒草地的地下物种丰富度、分布格局及其影响因素, 重点探讨了它们对气候变化和人类活动的响应, 并就未来高寒草地地下生物多样性亟需关注的关键问题进行了展望, 包括: (1)地下各个生物类群的分布格局、各类群之间的联系及驱动机制; (2)地上与地下生物多样性耦联的机制; (3)地下生物多样性对生态系统功能和健康的影响; (4)地下生物多样性的调控实验研究。     

滇西北县域生物多样性本底调查与评估

中国是世界上生物多样性最丰富的国家之一, 同时也是生物多样性受威胁最严重的国家之一。为了有效保护生物多样性, 2010年国务院批准实施了《中国生物多样性保护战略与行动计划(2010-2030年)》, 划定了32个陆地生物多样性保护优先区, 并设定了开展优先区生物多样性本底调查的战略目标、优先领域与优先行动。为此, 2010-2011年, 环境保护部联合中国科学院和高校的科研人员, 在滇西北开展了18个县的以县域为单元的生物多样性本底示范调查与研究。调查内容包括生态系统(植被类型)和物种两个层次。生态系统主要调查县域内植被类型的多样性, 完成了以群系为单位的植被类型编目; 物种层次主要调查县域内高等植物、脊椎动物、大型真菌的物种多样性组成、数量和用途等, 分析了特有物种和珍稀濒危物种数量等, 完成了县域物种编目。本文基于调查结果, 比较研究了不同县域间的生物多样性组成, 发现植被类型(108个群系)和物种(高等植物4,481种、脊椎动物625种、大型真菌222种)最丰富的县均为玉龙县。同时, 与历史记录对比研究发现, 滇西北的生物多样性分布数据十分欠缺, 严重影响了生物多样性保护的客观有效决策。生物多样性本底调查是生物多样性保护的一项基础工作, 本研究为中国未来开展大规模的生物多样性本底调查与评估提供了案例。     

植物寄生对生态系统结构和功能的影响

寄生植物是生态系统中的特殊类群之一。植物寄生可以驱动生态系统中生物与非生物因子的变化,在生态系统结构与功能中起关键作用。寄生植物可以通过对寄主营养的集聚、改变凋落物的质量与数量、改变根的周转与分泌物格局、改变土壤水势,从而影响土壤理化特性。寄生植物会改变寄主的行为,改变寄主与非寄主植物之间的相互作用,从而影响植物群落的结构、多样性和动态,进而影响植被演替和植被生产力等。寄生植物与寄主均可被消费者取食,可直接或间接地影响生态系统的食草动物,包括草食昆虫等。寄生植物与寄主的其它寄生物存在竞争关系,可以直接或间接地影响寄主的其它寄生植物或病原真菌。寄生植物可以明显地改变土壤地球化学循环,将固有的不可动的成分转变为可利用的营养成分,改变土壤生物群落的结构与功能,从而显著影响地下生物群落。这些表明,植物寄生对生态系统的结构和功能有重要影响。针对特殊的被入侵的植物群落,该地寄生植物可以通过影响入侵植物寄主的生长、繁殖、生物量分配格局,改变土壤的理化特性,促进非寄主的非优势本地植物的生长,从而改变被入侵植物群落结构与多样性,达到生物防治及生态恢复的目的。     

中国井冈山生态系统多样性

从不同尺度对井冈山生态系统进行了研究分析,并论述生态系统与生物物种多样性的关系,为井冈山生态环境保护与管理提供依据。研究发现,井冈山拥有IUCN/SSC一级生境类型9个,几乎涵盖了除海洋以外的所有生境类型,反映出井冈山生境类型非常丰富。井冈山一级生境中的面积最大的森林是井冈山自然生态系统类型及植被类型的重要基础;灌丛、草地及水域等次要的生境类型,提高了生态系统类型的复杂性和复合性。井冈山的一级生境类型是其生态系统分类的宏观基础,生境类型的丰富程度与生态系统类型的多样性密切相关。根据起源、地貌、生境和属性,以及结构和功能对井冈山生态系统类型进行逐级划分。调查发现,井冈山生态系统类型共有53类,其中自然生态系统21类(包括类型多样的森林生态系统、草地生态系统、静水生态系统等),人工生态系统14类(包括类型多样的人工湿地生态系统、人工林生态系统、农业自然复合生态系统等),复合生态系统18类(包括类型多样的人工复合生态系统、半自然复合生态系统等)。将生态系统只分到四级水平,四级以下还有丰富的生态系统类型。井冈山植物群落可分14个植被型,90个群系,180个群丛。与周围遗产地相比,井冈山的群系数量最多,与面积更大的三清山和武夷山相比,井冈山植被群系数量接近它们的3倍,表现出极其丰富的植被多样性。井冈山物种极其丰富,维管束植物和两栖动物最多,其昆虫数量仅次于武夷山,鸟类数量仅次于丹霞山。井冈山植物物种数最高。虽然井冈山总体空间(分布面积)有限,但这种分化出的丰富的生态位空间使井冈山在有限面积的植被上容纳更多的生物物种成为可能。     

The activity of a subterranean small mammal alters Afroalpine vegetation patterns and is positively affected by livestock grazing

Subterranean rodents can act as ecosystem engineers by shaping the landscape due to soil perturbation and herbivory. At the same time, their burrow density is affected by environmental conditions, vegetation and anthropogenic factors. Disentangling this complex interplay between subterranean rodents and their environment remains challenging. In our study, we analysed the interplay of abiotic conditions, vegetation patterns and human land-use and the burrow density of the giant root-rat (GRR; Tachyoryctes macrocephalus), a subterranean rodent endemic to the Afroalpine ecosystem of the Bale Mountains in south-east Ethiopia. Specifically, we examined the effects of GRR on plant species richness and vegetation cover and vice-versa, and how these reciprocal effects might be modulated by temperature, habitat wetness and grazing. Our results showed that increasing GRR burrow density led to decreased vegetation cover, and that effects of GRR on vegetation cover were slightly stronger than vice-versa. Considering the reciprocal causation models, we found that increasing plant species richness led to increased GRR burrow density, while GRR burrow density decreased as vegetation cover increased. Increases in habitat wetness and livestock grazing intensity also directly led to increased GRR burrow density. Our results stress the importance of subterranean ecosystem engineers on vegetation and highlight the vulnerability of these complex interactions to human activity.     

放牧对草地的作用

从牧草生长、种群、群落、土壤和生态系统5个方面分析了放牧的作用、机理与途径。放牧改变牧草的物质与能量分配格局,多途径地诱导牧草的补偿性生长,取决于放牧制度等因素。放牧还改变种间竞争格局、调控种群更新,以及群落结构和功能。介绍了草地健康管理的阈限双因子法,讨论了稳定态一过渡态假说和草地灌丛化。家畜对土壤有直接和间接两种作用途径,作用效果与放牧强度、季节、地形有密切关系,重点分析了放牧对土壤C贮量的作用机制。阐述了提高放牧系统生产力的系统耦合机制,以及放牧对生态系统物质循环的影响。根据放牧生态学的发展趋势和我国放牧管理现状,提出7项值得深入研究的问题。     

Sharing the Space: Distribution,Habitat Segregation and Delimitation of a New Sympatric Area of Subterranean Rodents

Subterranean rodents of the genus Ctenomys usually present an allopatric or parapatric distribution. Currently, two cases of sympatry have been recognized for the genus in the coastal dunes of southern Argentina and southern Brazil. In this context, they are ideal models to test hypotheses about the factors that delimit the patterns of space use and to understand interspecific interactions in small mammals. We investigated the vegetation structure, plant biomass and soil hardness selected by two species of subterranean rodents (Ctenomys flamarioni and C. minutus) when distributed in sympatry and allopatry from nine different areas along the line of coastal dunes in southern Brazil. In addition, our work presents a new record of a third area of sympatry for the genus Ctenomys. Ctenomys flamarioni and C. minutus show habitat segregation in the area where they occur in sympatry. These species show segregation in their selection of microhabitats, differing in relation to soil hardness, plant biomass, and plant cover. Ctenomys flamarioni showed a distinction in habitat selection when occurring in allopatry and sympatry, whereas C. minutus selected the same habitat characteristics under both conditions. A possible explanation to the observed pattern is that these species have acquired different adaptations over time which allows them the ability to exploit different resources and thus avoid competitive interactions all together.     

Comparative respiratory strategies of subterranean and fossorial octodontid rodents to cope with hypoxic and hypercapnic atmospheres

Subterranean rodents construct large and complex burrows and spend most of their lives underground, while fossorial species construct simpler burrows and are more active above ground. An important constraint faced by subterranean mammals is the chronic hypoxia and hypercapnia of the burrow atmosphere. The traits, regarded as “adaptations of rodents to hypoxia and hypercapnia”, have been evaluated in only a few subterranean species. In addition, well-studied subterranean taxa are very divergent to their sister groups, making it difficult to assess the adaptive path leading to subterranean life. The closely related sister genera Octodon and Spalacopus of Neotropical rodents offer a unique opportunity to trace the evolution of physiological mechanisms. We studied the ventilatory responses of selected octodontid rodents to selective pressures imposed by the subterranean niche under the working hypothesis that life underground, in hypoxic and hypercapnic conditions, promotes convergent physiological changes. To perform this study we used the following species: Spalacopus cyanus (the subterranean coruros) and Octodon degus (the fossorial degus) from central Chile. Ventilatory tidal volume and respiratory frequency were measured in non-anaesthetized spontaneously breathing animals. Acute hypoxic challenges (O₂ 1–15%) and hypercapnia (CO₂ 10%) were induced to study respiratory strategies using non-invasive whole body pletismography techniques. Our results show that coruros have a larger ventilatory response to acute hypoxia as than degus. On the other hand, hypercapnic respiratory responses in coruros seem to be attenuated when compared to those in degus. Our results suggest that coruros and degus have different respiratory strategies to survive in the hypoxic and hypercapnic atmospheres present in their burrows.     

ARE RATES OF DIVERSIFICATION IN SUBTERRANEAN SOUTH AMERICAN TUCO-TUCOS (GENUS CTENOMYS,RODENTIA: OCTODONTIDAE) UNUSUALLY HIGH?

Subterranean rodents have been used frequently as examples of explosive speciation in mammals. We tested for differential rates of diversification by using information from molecular phylogenies to focus primarily on tuco-tucos (Rodentia: Octodontidae), the most speciose lineage of subterranean rodents. Tuco-tucos were not significantly more diverse than their sister taxon (octodontines); however, a lineages-through-time analysis suggests an increase in diversification at the base of the tuco-tuco clade.     

Progressively excluding mammals of different body size affects community and trait structure of ground beetles

Mammalian grazing induces changes in vegetation properties in grasslands, which can affect a wide variety of other animals including many arthropods. However, the impacts may depend on the type and body size of these mammals. Furthermore, how mammals influence functional trait syndromes of arthropod communities is not well known. We progressively excluded large (e.g. red deer, chamois), medium (e.g. alpine marmot, mountain hare), and small (e.g. mice) mammals using size‐selective fences in two vegetation types (short‐ and tall‐grass vegetation) of subalpine grasslands. We then assessed how these exclusions affected the community composition and functional traits of ground beetles (Coleoptera, Carabidae), and which vegetation characteristic mediated the observed effects. Total carabid biomass, the activity densities of carabids with specific traits (i.e. small eyes, short wings), the richness of small‐eyed species and the richness of herbivorous species were significantly higher when certain mammals were excluded compared to when all mammals had access, regardless of vegetation type. Excluding large and medium mammals increased the activity density of herbivorous carabid species, but only in short‐grass vegetation. Similarly, excluding large mammals (ungulates) altered carabid species composition in the short‐, but not in the tall‐grass vegetation. All these responses were related to aboveground plant biomass, but not to plant Shannon diversity or vegetation structural heterogeneity. Our results indicate that changes in aboveground plant biomass are key drivers of mammalian grazers’ influence on carabids, suggesting that bottom–up forces are important in subalpine grassland systems. The exclusion of ungulates provoked the strongest carabid response. Our results, however, also highlight the ecological significance of smaller herbivorous mammals. Our study furthermore shows that mammalian grazing not only altered carabid community composition, but also caused community‐wide functional trait shifts, which could potentially have a wider impact on species interactions and ecosystem functioning.     

螺类牧食对伊乐藻与苦草种间关系的影响

动物牧食可以调节植物种间的相对竞争能力,从而改变物种在群落中的竞争地位.外来植物伊乐藻生长迅速、具有较强的光竞争能力,土著种苦草根系发达、具有较强的地下资源竞争能力.选择这两种各具竞争特色的沉水植物为模式生物,通过室外受控实验研究了螺类牧食对两种沉水植物种间关系的影响.结果表明:不管有无螺类牧食,伊乐藻的相对生长率为苦草的2～5倍,伊乐藻具有明显的竞争优势.苦草低密度种植时,螺类牧食与种间竞争对其生长没有显著影响;高密度种植时,螺类牧食活动促进了苦草的生长,种间竞争则使苦草的生长率明显降低.无论伊乐藻种植密度如何,螺类牧食均使其生长率明显降低,混栽高密度的苦草也能抑制伊乐藻生长.探讨了螺类牧食对沉水植物的种间竞争关系的作用机理.     

Vole mound effects and disturbance rate in a mediterranean plant community under different grazing and irrigation regimes

A factorial field experiment was used to assess the influence of soil-disturber mammals in the structure of a 9-year-old Mediterranean annual plant community subjected to different sheep grazing and irrigation regimes. We estimated the disturbance rate (mound building activity) by Mediterranean voles, their effects on vegetation and the mechanisms of these effects during a period of vole outbreak. The effects on vegetation were analysed at the levels of species, functional groups and plant community. Disturbance rate was high and voles can disturb the entire soil surface once every four or five years. The availability of certain trophic resources (perennial plants) appeared to drive vole expansion in the experimental plots and it was independent of the irrigation and grazing treatments. Mound building activities largely affected vegetation but conserved plot differences. Total vegetation cover, absolute cover of all functional groups, mean vegetation height and species richness were less on mounds than on undisturbed ground. These effects did not change the relative abundance of annuals, perennials, grasses and forbs. Only the relative abundance of small-seeded species decreased on mounds. As the proportion of these seeds was similar in both types of patches, we suggest that small-seeded species had more difficulties for germinating or emerging when they are buried during mound formation. Irrigation and sheep grazing promoted large changes in the vegetation parameters but these effects were, in general, similar on mounds and undisturbed ground. Our results show that the availability of germinable seeds may be the major limitation for mound revegetation, probably due to the scarcity of seeds existing at the depths from which soils are excavated. Our results also suggested a resource limitation on mounds. The results provide additional evidence that soil disturbances by small herbivore mammals exert relevant ecological effects on abandoned Mediterranean croplands. We discuss the ecological implications of vole mound-building activities for plant succession, plant species conservation and forage resource availability for livestock. This revised version was published online in June 2006 with corrections to the Cover Date.     

Cattle grazing, raptor abundance and small mammal communities in Mediterranean grasslands

Abundance and diversity of small mammals are usually affected strongly by grazing either due to decreased food availability or quality, decreased suitability of soil for building burrow systems due to trampling and/or due to increased predation risk in the structurally simpler grazed areas. We estimated the effects of grazing-induced changes in vegetation and soil and of increased predation on small mammals in a Mediterranean grassland landscape. We measured vegetation structure, soil compaction and small mammal abundance and species composition in 22 plots of 8 Sherman live traps each, arranged according to an unbalanced two-way ANOVA design with two grazing levels (grazed areas and cattle exclosures) and two predator abundance levels (increased densities of Eurasian kestrels Falco tinnunculus by means of nest boxes and control). Plots were sampled during 2 consecutive years in early summer and early fall. Exclosure from cattle increased significantly vegetation height and volume and decreased soil compaction. Grazing-induced changes in vegetation height and volume and in soil compaction produced strong effects on small mammal abundance and species richness. Increased kestrel densities did not have significant additive or interactive effects, with the effects of grazing-induced vegetation and soil gradients on abundance or richness of small mammals. Our results suggest that the effects of grazing on small mammal communities in Mediterranean montane grasslands were mainly due to reduced food availability and by negative effects of trampling on the suitability of soils for building burrow systems. Decreased food quality and increased predation in grazed areas seemed to play a minor role, if any. Reductions in stock densities would then favor generalist predator populations in Mediterranean grasslands through the expected positive effects of such reductions on the availability of food and burrows for small mammals.     

Large herbivores in sagebrush steppe ecosystems: livestock and wild ungulates influence structure and function

Improving understanding of the connections between vegetation, herbivory, and ecosystem function offers a fundamental challenge in contemporary terrestrial ecology. Using exclosures constructed during the late 1950s, we examined effects of grazing by wild and domestic herbivores on plant community structure, aboveground herbaceous primary production, and nutrient cycling at six sites in semi-arid, sagebrush rangelands during 2001-2002 in Colorado, USA. Enclosures provided three treatments: no grazing, grazing by wild ungulates only, and grazing by wild and domestic ungulates. Excluding all grazing caused an increase in shrub cover (F = 4.97, P = 0.033) and decrease in bare ground (F = 4.74, P = 0.037), but also a decrease in plant species richness (F = 6.19, P = 0.018) and plant diversity (F = 7.93, P = 0.008). Effects of wild ungulate grazing on plant cover and diversity were intermediate to the effects of combined domestic and wild grazing. Aboveground net primary production was higher in both grazed treatments than in the ungrazed one (F(wild + domestic) = 2.98, P = 0.0936 and F(wild only) = 3.55, P = 0.0684). We were unable to detect significant effects of grazing on other ecosystem states and processes including C:N ratios of standing crops, N mineralization potential, or nitrification potential. Best approximating models revealed positive correlation between N availability and herbaceous cover and a negative correlation between herbaceous primary production and the ratio of shrub-herb cover and plant diversity. We conclude that ungulate herbivory, including both wild and domestic ungulates, had significant effects on plant community structure and ecosystem function during this 42-year span. Responses to the wild ungulate treatment were consistently intermediate to responses to the no grazing and wild + domestic grazing treatments. However, we were unable to detect statistical difference between effects of wild ungulates alone and wild ungulates in combination with livestock.