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。     

植物-土壤反馈理论及其在自然和农田生态系统中的应用研究进展

植物-土壤反馈理论最早源于农业生产,近年来已成为生态学上研究植被动态变化、群落组成和功能,以及生态系统响应人为干扰、气候变化等众多热点问题的重要理论和方法支撑。总结了植物-土壤反馈定义和类型,分析了反馈机制,在此基础上综述了该理论在自然生态系统中的应用,包括物种入侵、群落演替、植物共存及多样性形成、植物多样性-生产力关系、多营养级交互作用以及响应气候变化等关键生态学命题。探讨了植物-土壤反馈理论在农田生态系统中的应用,介绍了该理论在提高多样化种植体系生产力、土壤污染修复、种植体系设计等方面的进展和潜在应用价值。提出了植物-土壤反馈理论在未来发展中进一步研究的方向,对应用该理论提高生态系统服务功能,促进可持续发展等方面进行了展望。     

植物-土壤反馈与草地群落演替:菌根真菌和土壤病原菌的调控作用

由植物引起的根际土壤生物或非生物环境的改变能够反馈影响群落中不同植物的生长,直接改变共存植物的相对竞争关系,推动群落结构的动态变化。作为土壤生物群落的重要组成部分,土壤微生物在植物-土壤反馈关系中起到重要的调控作用,对解释植物群落的演替进程和方向有着重要的意义。在草地植物群落演替的早期阶段和外来物种入侵的过程中,宿主植物对丛枝菌根真菌（AMF）的依赖性较低,受本地病原菌的影响较小,一般不存在负反馈。在演替后期,植物对AMF更具依赖性,而积累的病原菌则产生较强的负反馈效应,从而促进群落物种共存和植物多样性,提高草地生产力和稳定性。研究微生物-植物反馈机制不仅有助于完善草地退化与恢复理论,还对退化草地恢复治理的实践有着指导意义。未来关于根际微生物-植物反馈在草地群落演替中的作用应该加强以下几方面的研究：（1）在实验方法上,开展专性微生物-植物反馈研究;（2）在测定指标上,进一步量化不同微生物在反馈关系中的功能差异;（3）在研究对象上,加强土壤微生物在植物群落水平的反馈研究;（4）在应用上,明晰植物-土壤反馈在退化草地恢复过程中的作用,指导草地管理实践。     

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。     

群落生态学中的植物-土壤反馈研究

植物-土壤反馈是指植物改变了其生长环境中土壤的生物和非生物属性,改变后的土壤进而影响植物适合度的过程。植物-土壤反馈的一个根本前提是:植物在根际周围产生由专化病原菌和共生菌构成的特异性微生物群落,专化微生物对宿主植物种群有很大的影响,对非宿主植物没有或者有微弱影响。自从20世纪90年代被明确提出后,植物-土壤反馈被广泛用于揭示不同尺度的生态学过程,诸如演替、竞争、生物入侵、全球变化对生态系统的影响等。近年来,植物-土壤反馈与群落生态学主要研究领域之间的整合取得了实质性进展。该文主要关注的是土壤微生物介导的植物-土壤反馈及其对植物物种共存、群落结构和生态系统功能的影响。土壤微生物不仅可以产生稳定化力量促进物种共存,也可以改变均一化力量或者种间适合度差异,从而影响植物种间共存。在群落生态学中通常假设稀有种受土壤负反馈的影响更弱,从而预测植物局域丰富度与土壤反馈强度具有负相关关系。然而实验证据却揭示了不同的模式,加强对植物与土壤病原菌之间的进化动态的关注是调和这些不一致模式的关键。土壤微生物也是驱动植物群落演替的关键因子。土壤微生物通过稀释效应影响植物多样性-群落生产力关系。专化土壤病原菌或...     

不同放牧强度下羊草草原群落斑块植被-土壤特征

植物群落斑块化是天然放牧草地最基本的特征之一,影响着草地生态系统结构和功能。本研究以不同放牧强度下典型羊草草原植物群落斑块为研究对象,对植物群落多样性特征、初级生产力、土壤理化性质、植物养分含量及其相关关系进行研究。结果表明:随着放牧强度的增加,斑块群落内植物种类组成发生改变并趋于简单化,放牧敏感物种消失,物种多样性降低;高放牧强度显著降低了植物群落的地上净初级生产力;初级生产力与土壤氮含量具有显著的正相关关系;随着放牧强度增加,土壤碳、氮、磷含量呈现增加趋势;由于放牧强度及斑块结构的影响,土壤碳、氮、磷含量存在空间分布差异;同时,斑块群落中植被碳、氮、磷含量与土壤碳、氮、磷含量之间没有显著的相关性。研究表明,放牧能够改变草地群落结构和功能,引起植被-土壤养分之间的非同步性发展。     

海岸守护神

红树林、珊瑚礁、盐沼和上升流是地球上生物多样性最丰富、生产力最高的四大海洋生态系统。许许多多的海洋生物依赖于红树林生长,它们跟红树植物一道有机地构成了地球上一类独特的生态系统,其中一种生物消失就可能引起与之相关的几个物种的衰亡。联合国环境规划署指出的殃及人类的全球十大环境祸患中,与红树林生态系统有关的包括：土壤遭到破坏、气候变化、生物多样性减少、     

云南松天然次生林物种丰富度与生态系统多功能性的关系

全球气候变化、森林采伐和生境破碎化导致全球生物多样性迅速下降,并对生态系统功能产生了严重的影响。近年来,生物多样性与生态系统功能的关系成为生态学研究的热点,但以往的研究多关注生物多样性与单一生态系统功能的关系,对生态系统尤其是森林生态系统多功能性的研究亟待加强。本文基于云南松(Pinus yunnanensis)天然次生林94个样地的调查数据,选取木本植物生物量、土壤有机碳含量、植物氮、植物磷、土壤全氮、土壤水解性氮、土壤全磷和土壤有效磷等8个生态系统功能变量,采用平均值法、单阈值法和多阈值法综合评价了云南松天然次生林物种丰富度与生态系统多功能性的关系及影响因子。结果表明:(1)云南松天然次生林物种丰富度与生态系统多功能性的关系强于它与单一生态系统功能间的关系;(2)在3–88%阈值范围内,物种丰富度对于多功能性具有显著正影响,在中等阈值水平(54%)上,物种丰富度效应最大,此时可能的最大物种丰富度作用实现百分比为53.53%;(3)云南松天然次生林中物种丰富度对多功能性的影响最大,表现为极显著正相关;年均气温、年均降水量和土壤p H对多功能性无显著直接影响,但均可通过对物种丰富度的影响而产生间接影响。物种丰富度对生态系统多功能性具有重要意义,但是物种数目的增加并不能保证所有功能均达到最佳状态,在中等功能水平时,物种数目的增加对多功能性的影响最大。     

高寒草甸植物群落中物种多样性与生产力关系研究

通过对高寒草甸植物群落中物种多样性(Shannon多样性指数)与生产力(地上生物量)的关系的研究表明多样性与生产力的总体关系呈对数线性增加关系,随着观测时间和环境条件(生境)的改变,多样性与生产力的关系会发生一些变化,这是因为当观测时间和环境条件不同时,物种丰富度和物种构成以及其它的生物或非生物条件发生了相应的变化,而它们对多样性和生产力各自造成的影响是非同步性的(这种非同步实际上就是物种在时间和空间生态位上的分化);而可能由于高寒草甸生态系统的生长季较短,环境条件的改变比观测时间改变对多样性与生产力关系造成的影响更显著.观测时间和环境条件的不同可能是造成许多实验研究中得不到一个一致的多样性与生产力关系的主要原因.此外,通过对各种多样性指标进行综合分析可以对多样性与生产力的关系有一个更加全面的了解,并从中得到一些关于产生这种关系的机制的一些启示.     

消费者多样性对食物网结构和生态系统功能的影响

前所未有的生物多样性丧失使人们越来越关注生物多样性的生态系统功能.现有的绝大多数研究都是局限在单一营养级别上,主要是植物上,但是今天越来越多的证明表明消费者的多样性对生态系统结构和功能具有深刻影响.综述了消费者多样性对相邻或非相邻营养级的种群密度、物种多样性和生产力等方面影响的最新进展,同时也提出了若干研究展望.总体上.消费者多样性,无论是草食动物还是肉食动物,都倾向于增加该消费者所在营养级的养分和能量利用效率,以及生产力.这可能源于取样效应,或者物种之间的互补作用,类似于植物物种多样性影响初级生产力的机制.草食动物可能降低或者提高植物物种多样性,或者没有显著影响,其具体效应取决于生态系统生产力水平和草食动物的大小.捕食者哌能通过直接抑制草食动物而间接提高植物的多样性和生产力,但这种效应的大小差异很大,甚至效应的方向,都可能随团体内捕食者所占的比例而改变.未来的研究,应该考虑应用较大尺度的实验来检测食物网复杂营养关系对生态系统特性的影响,继续探讨消费者对生态系统功能的影响机制.认为异速生长法则和生态化学计量学在食物网组分关系研究中的应用将有利于增强人们对消费者.生态系统功能关系的理解.另外,全球变暖和转基因植物对食物网中消费者结构和生态系统的功能的影响也将是未来的一个重要研究方向.     

Negative plant-soil feedbacks may limit persistence of an invasive tree due to rapid accumulation of soil pathogens

Soil organisms influence plant species coexistence and invasion potential. Plant-soil feedbacks occur when plants change soil community composition such that interactions with that soil community in turn may positively or negatively affect the performance of conspecifics. Theories predict and studies show that invasions may be promoted by stronger negative soil feedbacks for native compared with exotic species. We present a counter-example of a successful invader with strong negative soil feedbacks apparently caused by host-specific, pathogenic soil fungi. Using a feedback experiment in pots, we investigated whether the relative strength of plant-soil feedbacks experienced by a non-native woody invader, Sapium sebiferum, differed from several native tree species by examining their performance in soils collected near conspecifics ('home soils') or heterospecifics ('away soils') in the introduced range. Sapium seedlings, but no native seedlings, had lower survival and biomass in its home soils compared with soils of other species (negative feedback'). To investigate biotic agents potentially responsible for the observed negative feedbacks, we conducted two additional experiments designed to eliminate different soil taxa ('rescue experiments'). We found that soil sterilization (pot experiment ) or soil fungicide applications (pot and field experiments) restored Sapium performance in home soil thereby eliminating the negative feedbacks we observed in the original experiment. Such negative feedbacks apparently mediated by soil fungi could have important effects on persistence of this invader by limiting Sapium seedling success in Sapium dominated forests (home soils) though their weak effects in heterospecific (away) soils suggest a weak role in limiting initial establishment.     

Soil arthropod composition differs between old-fields dominated by exotic plant species and remnant native grasslands

Secondary succession after agriculture abandonment (old-fields) is mostly dominated by exotic grass species. Non-native plant invasions may alter soil fauna, potentially inducing plant-soil feedbacks. Despite their importance in nutrient cycling and plant-soil interactions, meso and macrofauna received less attention than bacteria or fungi. Here we compared the composition of the soil arthropod community in native remnants and plant exotic-dominated old-fields grasslands in the Inland Pampa, Argentina. We sampled independent remnants and old-field grassland plots within a 100 km² agricultural landscape to test the hypothesis that the abundance of soil arthropod organisms is related to the quality of the plant biomass, whereas the diversity of the soil biota is related to plant species richness, resulting in a different soil biota composition because of differing plant communities. When compared to non-invaded remnant grasslands, soil activity and soil food-web characteristics of the old-fields sites included: 1. Higher total arthropod abundance, particularly of Isopoda, Pseudoescorpionida and Blattaria; 2. Lower abundance of Hymenoptera and Enthomobryomorpha (Collembola); 3. Lower diversity, and evenness, but similar richness of soil organisms orders; 4. Higher soil respiration rates and soil temperature; and 5. Higher total soil N and K⁺content, but lower soil P content. These results illustrate that soil arthropod composition can vary widely within grasslands patches depending on plant species composition. Also, the more diverse plant community of remnant grasslands supports a more diverse soil biota, although soil activity is slower. Our results support the strong linkage between plant community and soil arthropod composition and suggest that changes in soil biota composition might promote plant-soil feedback interactions inducing the persistence of these alternative grassland states in new agricultural human-modified landscapes.     

Grazing-induced effects on soil properties modify plant competitive interactions in semi-natural mountain grasslands

Plant-soil feedbacks are widely recognized as playing a significant role in structuring plant communities through their effects on plant-plant interactions. However, the question of whether plant-soil feedbacks can be indirectly driven by other ecological agents, such as large herbivores, which are known to strongly modify plant community structure and soil properties, remains poorly explored. We tested in a glasshouse experiment how changes in soil properties resulting from long-term sheep grazing affect competitive interactions (intra- and inter-specific) of two graminoid species: Nardus stricta, which is typically abundant under high sheep grazing pressure in British mountain grasslands; and Eriophorum vaginatum, whose abundance is typically diminished under grazing. Both species were grown in monocultures and mixtures at different densities in soils taken from adjacent grazed and ungrazed mountain grassland in the Yorkshire Dales, northern England. Nardus stricta performed better (shoot and root biomass) when grown in grazing-conditioned soil, independent of whether or not it grew under inter-specific competition. Eriophorum vaginatum also grew better when planted in soil from the grazed site, but this occurred only when it did not experience inter-specific competition with N. stricta. This indicates that plant-soil feedback for E. vaginatum is dependent on the presence of an inter-specific competitor. A yield density model showed that indirect effects of grazing increased the intensity of intra-specific competition in both species in comparison with ungrazed-conditioned soil. However, indirect effects of grazing on the intensity of inter-specific competition were species-specific favouring N. stricta. We explain these asymmetric grazing-induced effects on competition on the basis of traits of the superior competitor and grazing effects on soil nutrients. Finally, we discuss the relevance of our findings for plant community dynamics in grazed, semi-natural grasslands.     

贡嘎山冰川退缩区植物-土壤反馈与植物间相互作用

植物-土壤反馈是揭示陆地生物群落动态变化的关键环节,为理解植物间相互作用及植被群落变化过程奠定基础。本研究以贡嘎山冰川退缩区原生演替早(5~10年)、中(30~40年)和晚期(80~100年)3个阶段典型土壤以及各阶段优势植物为对象,采用盆栽控制试验,比较优势植物在不同土壤条件下的生物量,并量化植物间相互作用以及植物-土壤反馈的方向与强度,为探究贡嘎山冰川退缩区植被群落演替规律提供依据。结果表明:(1)植物-土壤反馈作用显著影响植物在本土中的生物量,早期沙棘(Hippophae rhamnoides)在本土中生长最差,沙棘的植物-土壤反馈系数为负值;演替中期冬瓜杨(Populus purdomii)的反馈系数趋于零;晚期峨眉冷杉(Abies fabri)在本土中生长最好,峨眉冷杉的反馈系数为正值。(2)混种时,早期沙棘与演替中、晚期植物间相互作用指数为负值;中期冬瓜杨、川滇柳(Salix rehderiana)与演替早、晚期植物的相互作用指数接近于零,晚期植物峨眉冷杉、麦吊云杉(Picea brachytyla)与演替早、中期植物相互作用指数为正值。从植物-土壤反馈的方向来看,贡嘎山植被演替从早期负反馈,中期中性反馈,过渡到晚期正反馈。此外,演替早期沙棘促进演替中晚期植物生长,演替中期冬瓜杨、川滇柳对演替早晚期植物无显著影响,晚期峨眉冷杉、麦吊云杉更利于与演替早中期植物相互竞争。结果显示,植物-土壤反馈与植物间相互作用共同驱动了贡嘎山冰川退缩区植被快速演替,直至顶极群落。     

Plant-soil Interactions in Temperate Grasslands

We present a conceptual model in which plant-soil interactions in grasslands are characterized by the extent to which water is limiting. Plant-soil interactions in dry grasslands, those dominated by water limitation (belowground-dominance), are fundamentally different from plant-soil interactions in subhumid grasslands, where resource limitations vary in time and space among water, nitrogen, and light (indeterminate dominance). In the belowground-dominance grasslands, the strong limitation of soil water leads to complete (though uneven) occupation of the soil by roots, but insufficient resources to support continuous aboveground plant cover. Discontinuous aboveground plant cover leads to strong biological and physical forces that result in the accumulation of soil materials beneath individual plants in resource islands. The degree of accumulation in these resource islands is strongly influenced by plant functional type (lifespan, growth form, root:shoot ratio, photosynthetic pathway), with the largest resource islands accumulating under perennial bunchgrasses. Resource islands develop over decadal time scales, but may be reduced to the level of bare ground following death of an individual plant in as little as 3 years. These resource islands may have a great deal of significance as an index of recovery from disturbance, an indicator of ecosystem stability or harbinger of desertification, or may be significant because of possible feedbacks to plant establishment. In the grasslands in which the dominant resource limiting plant community dynamics is indeterminate, plant cover is relatively continuous, and thus the major force in plant-soil interactions is related to the feedbacks among plant biomass production, litter quality and nutrient availability. With increasing precipitation, the over-riding importance of water as a limiting factor diminishes, and four other factors become important in determining plant community and ecosystem dynamics: soil nitrogen, herbivory, fire, and light. Thus, several different strategies for competing for resources are present in this portion of the gradient. These strategies are represented by different plant traits, for example root:shoot allocation, height and photosynthetic pathway type (C3 vs. C4) and nitrogen fixation, each of which has a different influence on litter quality and thus nutrient availability. Recent work has indicated that there are strong feedbacks between plant community structure, diversity, and soil attributes including nitrogen availability and carbon storage. Across both types of grasslands, there is strong evidence that human forces that alter plant community structure, such as invasions by nonnative annual plants or changes in grazing or fire regime, alters the pattern, quantity, and quality of soil organic matter in grassland ecosystems. The reverse influence of soils on plant communities is also strong; in turn, alterations of soil nutrient supply in grasslands can have major influences on plant species composition, plant diversity, and primary productivity.     

Nitrogen enrichment modifies plant community structure via changes to plant–soil feedback

We tested the hypothesis that N enrichment modifies plant-soil feedback relationships, resulting in changes to plant community composition. This was done in a two-phase glasshouse experiment. In the first phase, we grew eight annual plant species in monoculture at two levels of N addition. Plants were harvested at senescence and the effect of each species on a range of soil properties was measured. In the second phase, the eight plant species were grown in multi-species mixtures in the eight soils conditioned by the species in the first phase, at both levels of N addition. At senescence, species performance was measured as aboveground biomass. We found that in the first phase, plant species identity strongly influenced several soil properties, including microbial and protist biomass, soil moisture content and the availability of several soil nutrients. Species effects on the soil were mostly independent of N addition and several were strongly correlated with plant biomass. In the second phase, both the performance of individual species and overall community structure were influenced by the interacting effects of the species identity of the previous soil occupant and the rate of N addition. This indicates that N enrichment modified plant-soil feedback. The performance of two species correlated with differences in soil N availability that were generated by the species formerly occupying the soil. However, negative feedback (poorer performance on the soil of conspecifics relative to that of heterospecifics) was only observed for one species. In conclusion, we provide evidence that N enrichment modifies plant-soil feedback relationships and that these modifications may affect plant community composition. Field testing and further investigations into which mechanisms dominate feedback are required before we fully understand how and when feedback processes determine plant community responses to N enrichment.     

Above- and belowground effects of plant-soil feedback from exotic Solidago canadensis on native Tanacetum vulgare

Plant-soil feedback responses for native and invasive plant species are well documented, but little is known about how feedback effects from the soil biota community affect plant interactions with herbivores. Here we examine whether changes of the soil biota community by the successful invader Solidago canadensis influence growth and herbivore susceptibility of two coexisting native plant species (Tanacetum vulgare, Melilotus albus). Root zone soil from two different habitat types (‘urban’ and ‘suburban’) was collected and used as inocula in a plant-soil feedback study. Each plant species was grown either in its own soil biota community or with the community with a history from the competitive invasive or native plant species. To identify potential drivers of responses to the different soil biota communities, we analyzed root colonization by arbuscular mycorrhizal fungi and dark-septate endophytes (DSE), and the community composition of soil inhabiting nematodes at the end of our experiment. Results show that S. canadensis and M. albus were not affected by soil history. In contrast, T. vulgare showed increased plant growth in ‘foreign’ soil derived from S. canadensis root zone compared with its ‘home’ soil suggesting a growth promotion by the soil biota community of S. canadensis. From the examined drivers, the abundance of DSE explained the growth response of T. vulgare to the S. canadensis soil biota community best. However, shoot herbivory by banded snails (Cepaea nemoralis, C. hortensis) was not affected by soil history, but by the habitat type where the soil inocula originated. Our study shows that a native plant species may profit from the presence of an invasive competitor mediated by changes in the soil biota community.     

Native and non‐native grasses generate common types of plant–soil feedbacks by altering soil nutrients and microbial communities

Soil conditioning occurs when plants alter features of their soil environment. When these alterations affect subsequent plant growth, it is a plant soil feedback. Plant–soil feedbacks are an important and understudied aspect of aboveground–belowground linkages in plant ecology that influence plant coexistence, invasion and restoration. Here, we examine plant–soil feedback dynamics of seven co‐occurring native and non‐native grass species to address the questions of how plants modify their soil environment, do those modifications inhibit or favor their own species relative to other species, and do non‐natives exhibit different plant–soil feedback dynamics than natives. We used a two‐phase design, wherein a first generation of plants was grown to induce species‐specific changes in the soil and a second generation of plants was used as a bioassay to determine the effects of those changes. We also used path‐analysis to examine the potential chain of effects of the first generation on soil nutrients and soil microbial composition and on bioassay plant performance. Our findings show species‐specific (rather than consistent within groups of natives and non‐natives) soil conditioning effects on both soil nutrients and the soil microbial community by plants. Additionally, native species produced plant–soil feedback types that benefit other species more than themselves and non‐native invasive species tended to produce plant–soil feedback types that benefit themselves more than other species. These results, coupled with previous field observations, support hypotheses that plant–soil feedbacks may be a mechanism by which some non‐native species increase their invasive potential and plant–soil feedbacks may influence the vulnerability of a site to invasion.