食真菌线虫对热或铜胁迫下土壤生态功能稳定性的影响

在模拟胁迫条件下(施加 CuSO₄ 的持续胁迫或加热40 ℃的瞬时胁迫),以大麦叶粉短期分解过程代表土壤功能,采用室内培养试验研究了土壤食真菌线虫(Aphelenchus avenae)与微生物的相互作用对土壤生态功能稳定性(抗性和恢复力)的影响.结果表明：无论施加胁迫与否,食真菌线虫的活动都有促进土壤微生物活性的趋势,尤其是在施加铜胁迫后第8 天开始到培养期结束,接种食真菌线虫导致土壤基础呼吸显著增加(P<0.05),但加热胁迫后食真菌线虫对土壤基础呼吸的促进作用仅在第8天有显著差异(P<0.05),反映了食真菌线虫对土壤微生物活性的影响程度与胁迫类型有关.在两种胁迫条件下,接种食真菌线虫对土壤功能的抗性没有影响,但都能促进胁迫条件下土壤功能的恢复.培养后期,两种胁迫条件下接种食真菌线虫处理真菌生物量低于未接种线虫处理,表明胁迫条件下食真菌线虫对真菌的取食可能限制甚至抑制了真菌生长,导致真菌对细菌的竞争压力减少,从而使细菌获得更大的生长优势,间接促进了细菌的生长.     

悉生培养微缩体系食细菌线虫提高土壤激素含量的机制

研究土壤食细菌线虫与细菌的相互作用及其生态功能是土壤生态学的核心内容之一。食细菌线虫取食细菌可以促进土壤中氮素的矿化,提高氮素养分的供给,改善土壤的营养条件,从而促进植物的生长发育。土壤食细菌线虫促进植物根系生长的"养分作用机制"已得到确认,而"激素作用机制"还存在争议。从供试土壤中筛选获得一株高效产IAA细菌和两种不同cp值的食细菌线虫,通过设置简化的悉生培养系统,对这两种土著食细菌线虫与土著产IAA细菌之间的相互作用,及其对土壤中IAA含量变化的影响进行研究。结果表明:两种食细菌线虫的取食均能促进细菌数量和活性的增强,食细菌线虫与产IAA细菌相互作用也能显著增加土壤中IAA的含量;这些促进作用受到接种食细菌线虫的种类以及培养时间的影响:在培养第10天和第20天时,接种cp值为1的中杆属食细菌线虫显著增加了产IAA细菌的数量;在培养第10天和第30天时,相比较接种cp值为2的头叶属食细菌线虫,接种中杆属食细菌线虫显著提高了土壤中IAA的含量。     

土壤食细菌线虫对拟南芥根系生长的影响及机理

通过设置两种孔径(1 mm和5μm)的网袋(25cm×25 cm),采用于土样中添加猪粪的处理,获得有大量食细菌线虫富集(SM1)的,和有少量食细菌线虫富集(SM5)的供试土壤(两者养分状况相近),以研究食细菌线虫对拟南芥根系生长的影响.结果表明,在种植拟南芥15d后,与有少量线虫富集的PSM5处理相比,有大量线虫富集的PSM1处理拟南芥根系显著增长,根的表面积显著增大,根尖数显著增多.PSM1处理在显著增加土壤中NH4+-N的同时,还使土壤中植物激素(GA3和IAA)的含量显著增高.此外,土壤微生物群落对单一碳源的利用能力(Biolog)的差异,表明存在大量食细菌线虫的土壤,微生物群落结构组成发生了变化.此结果说明,土壤食细菌线虫对根系生长影响的效应,除了养分效应外,还存在激素效应,与食细菌原生动物和植物根系生长之间的相互作用的机制相似.     

开放式空气CO2浓度增高对中国稻田生态系统线虫营养类群产生的影响

土壤动物在农田生态系统腐屑食物网中占有重要地位 ,它们参与土壤有机质分解、植物营养矿化及养分循环作用 .国内外许多研究表明 ,土壤动物对全球变化 ,尤其是大气CO2 浓度升高能够产生正向、中性和负向的影响 .土壤线虫是这类土壤动物的典型代表 ,因为它们在大多数土壤中分布是丰富的 ,而且营养类群是多样的 .应用自由空气CO2 浓度增高 (FACE)技术设计 3个处理水稻圈暴露在大气CO2 增高(浓度为 5 70 μmol·mol-1)条件下 ,3个对照水稻圈为环境中的CO2 浓度 (370 μmol·mol-1) .在中国无锡稻田生态系统水稻生长期内 ,本项研究监测了 0～ 5cm和 5～ 10cm土层中线虫营养类群 .研究结果显示 ,线虫总数、食细菌线虫、植物寄生线虫、杂食 捕食类线虫在取样深度和取样日期上存在显著差异 ;在整个取样日期中 ,FACE处理 5～ 10cm深度中线虫总数、食细菌线虫数量比对照中的高 ;在 0～ 5cm深度中 ,FACE处理食细菌线虫数量比对照中的高 ,而杂食 捕食类线虫数量则表现出相反的趋势 .食真菌线虫在FACE处理与对照之间也存在极显著差异 .     

基于土壤线虫群落分析的油页岩废渣地不同植被类型恢复过程中的土壤食物网能流状况

土壤健康与生态系统功能是当前生态学研究的重要课题。土壤线虫是评价生态系统健康状况的指示生物,特别是用于评价土壤污染和恢复的过程。对广东茂名油页岩废渣场人工实施不同生态恢复改造状况下的土壤线虫属的重要值及土壤线虫反映的土壤食物网能量通道进行了分析,以通过污染地土壤食物网内的能量流动状况反映种植不同植物物种相同时间后的土壤养分与健康状况。结果表明在废渣场种植不同植物物种约8年后,乌墨林和大叶相思林下土壤线虫类群数(属)分别为54和45,重要值最高的是食细菌的棱咽属(Prismatolaimus)和拟丽突属(Acrobeloides);而红荷林和荒草地的线虫类群数分别为41和38,重要值最高的是杂食性的真矛线属(Eudorylaimus);废渣地线虫属的数量最少,仅为34个,重要值最高的是食真菌的丝尾垫刃属(Filenchus)和滑刃属(Aphelenchoides)。食物网能流分析表明:细菌能流通道比重最高的是大叶相思林和乌墨林,而真菌能流通道比重最高的是废渣地,红荷林和荒草地居中,各样地植物能流通道比重都比较小,仅为2%—10%之间。总体来讲,在有植被覆盖的生态系统,养分周转更快,特别是乌墨和大叶相思林,而无植被的废渣地,土壤养分周转速率倾向于更慢的真菌能流通道,这表明在养分条件比较差的情况下,真菌通道的食物网可能会起更大的作用。研究还说明了在油页岩废弃地恢复过程中,植物资源的输入不仅仅刺激植物能流通道,同时也会刺激细菌和真菌能流通道,植被是土壤线虫群落发展的主要驱动力。     

不同水分管理方式对稻田土壤生物学特性的影响

在下辽河平原单季稻地区研究了常规浅湿干灌溉 (CK)、浅湿干灌溉薄膜阻渗 (IC)、湿润灌溉薄膜阻渗 (MC)、淹水灌溉薄膜阻渗 (FC) 4种不同水分管理方式下土壤线虫及土壤微生物量的动态变化。结果表明 ,耙耕前 ,CK、FC处理食细菌线虫数量显著高于MC、IC处理 ;薄膜阻渗在黄熟期显著降低了土壤食细菌线虫的数量 ,在耙耕前显著降低了食真菌线虫数量。潮棕壤稻田食真菌线虫与食细菌线虫相比数量较低。在耙耕前不同水分管理方式下土壤微生物量C显著低于对照。不同水分管理方式在水稻分蘖期、抽穗期对食细菌线虫数量、食真菌线虫数量、微生物量C和微生物量N没有影响。土壤食细菌线虫、食真菌线虫数量与土壤微生物量C、N没有达到显著相关。     

青藏高原高寒草甸土壤环境对线虫功能多样性的影响

土壤线虫是地下食物网的重要组成部分, 在生态系统能量流动和物质循环中起着至关重要的作用。大量研究报道了肥力等土壤环境对土壤线虫物种多样性及各功能群多度的影响, 而我们对土壤线虫功能多样性如何响应土壤环境变化依然知之甚少。本研究以群落水平个体大小和个体大小多样性表征土壤线虫功能多样性。在青藏高原高寒草甸选择3个研究点, 调查和分析了不同生境(沟底平地、阴坡、阳坡和山顶)土壤线虫物种多样性、各功能群多度和功能多样性及其与土壤理化因子和植物多样性的关系。结果表明: (1)土壤线虫个体多度和物种多样性在阳坡最高, 随土壤pH值和土壤总磷增加而升高; 而基于个体大小的土壤线虫功能多样性主要受土壤养分影响, 随土壤总氮和有机质增加而增加, 随土壤总磷含量增加而减少; (2)食细菌和食真菌线虫多度在沟底最高, 植食与捕食杂食线虫多度在山顶最低; 除捕食杂食线虫外, 各功能群多度也主要随土壤磷增加而升高; 除食真菌线虫外, 各功能群多度随植物物种丰富度的增加而减少。本研究强调了土壤线虫物种和功能多样性受不同土壤环境因子的影响, 丰富了土壤线虫多样性研究的内容, 为理解高寒草甸土壤动物多样性形成、维持和变化提供了更广阔的 视角。     

开放式空气CO2浓度增高对中国稻田生态系统线虫营养类群产生的影响(英)

土壤动物在农田生态系统腐屑食物网中占有重要地位,它们参与土壤有机质分解、植物营养矿化及养分循环作用.国内外许多研究表明,土壤动物对全球变化,尤其是大气CO₂浓度升高能够产生正向、中性和负向的影响.土壤线虫是这类土壤动物的典型代表,因为它们在大多数土壤中分布是丰富的,而且营养类群是多样的.应用自由空气CO₂浓度增高(FACE)技术设计3个处理水稻圈暴露在大气CO₂增高(浓度为570μmol·mol^-1)条件下,3个对照水稻圈为环境中的CO₂浓度(370μmol·mol^-1).在中国无锡稻田生态系统水稻生长期内,本项研究监测了0～5cm和5～10cm土层中线虫营养类群.研究结果显示,线虫总数、食细菌线虫、植物寄生线虫、杂食捕食类线虫在取样深度和取样日期上存在显著差异;在整个取样日期中,FACE处理5～10cm深度中线虫总数、食细菌线虫数量比对照中的高;在0～5cm深度中,FACE处理食细菌线虫数量比对照中的高,而杂食捕食类线虫数量则表现出相反的趋势.食真菌线虫在FACE处理与对照之间也存在极显著差异.     

食根动物与植物的相互关系

食根动物是植物的主要危害者,植物与食根动物之间的相互作用一直备受关注.本文从食根动物与异质性土壤、根系的关系,以及食根动物对植物的影响等方面,探讨了食根动物与根系生物量的变化、再生能力、存活,植物化学物质与其他有机体之间的作用机理和食根动物对植物生理、种群动态、植物结构的影响.建议加强对植物控制食根动物取食时采取的对策、食根动物改变生态系统C、N循环的机制以及植物寄生性线虫存在的生态系统养分的动态变化等方面的研究.     

土壤细菌网络互作调控线虫肠道细菌群落

动物肠道细菌群落在联系宿主与生态系统功能中发挥着至关重要的作用。【目的】本研究旨在评估绿肥翻压和水稻生长不同时期对土壤细菌和线虫肠道细菌群落组成和结构的影响,并探究土壤细菌和线虫肠道细菌群落间的潜在关联关系。【方法】基于盆栽试验,结合16S rRNA基因高通量测序技术,分析黑麦草翻压和对照处理下水稻生长的前期(返青期)和后期(收获期)土壤细菌和线虫肠道细菌群落,结合网络分析研究土壤细菌网络互作对线虫肠道细菌群落的潜在影响。【结果】黑麦草翻压对土壤细菌和线虫肠道细菌群落组成和结构没有显著影响(P>0.05);水稻生长后期样品比前期样品具有更高的α多样性。基于随机森林机器学习法获得的土壤细菌和线虫肠道细菌生物标志物之间存在广泛的显著相关关系,为土壤细菌群落变化调控线虫肠道细菌群落组成提供了有力的证据。共现网络分析表明土壤细菌之间的正相互作用显著促进了土壤细菌和线虫肠道细菌之间的正相互作用(P<0.01),进而影响了线虫肠道细菌之间的网络互作。结构方程模型进一步表明土壤养分含量的降低主要通过降低土壤细菌之间正相互作用,从而间接影响线虫肠道细菌之间的互作。【结论】土壤细菌互作可能在...     

食真菌线虫与真菌的相互作用及其对土壤氮素矿化的影响

采用悉生培养微缩体系,探讨了食真菌线虫(燕麦真滑刃线虫)与两种真菌(真菌Ⅰ：外皮毛霉和真菌Ⅱ：丛梗孢科的一种)间的相互作用及其对土壤氮素矿化的影响．结果表明,燕麦真滑刃线虫在取食两种真菌时表现为在真菌Ⅱ上的生长优于真菌Ⅰ,两个处理的线虫数达到显著差异．食真菌线虫对真菌的取食活动促进了真菌的增殖：接种真菌Ⅱ加线虫处理中真菌Ⅱ的数量是仅接种真菌Ⅱ处理的2．5～3．5倍,增幅在整个培养期基本稳定;而接种真菌Ⅰ加线虫处理中真菌Ⅰ的数量在培养前期(10d)是仅接种真菌Ⅰ处理的1．1～2．0倍。之后增幅达5．0～5．7倍．线虫和真菌的生长及增殖基本保持同步．食真菌线虫与真菌的相互作用显著提高了土壤铵态氮和矿质态氮含量,促进了土壤氮的矿化,其中线虫与真菌Ⅰ的相互作用对提高矿质态氮含量的贡献显著大于线虫与真菌Ⅱ的相互作用。     

氮磷输入对过度放牧退化草原土壤线虫群落的影响

线虫是陆地生态系统中数量最多的一类无脊椎后生动物,在土壤碎屑食物网中占据多个营养级,并在能量流动和养分循环中发挥重要的生态功能.土壤线虫的群落结构和多样性水平可以反映生态系统功能的变化.多年来,过度放牧等不合理的开发利用导致我国大面积的草原处在不同程度的退化之中,外源性养分输入是维持其养分平衡进而恢复其生态和生产功能的重要措施.本研究以内蒙古锡林郭勒退化草原为对象,就氮磷输入对土壤线虫丰度和群落结构的单独效应和交互效应进行了研究.本研究获得线虫38属,其中垫咽属、滑刃属、索努斯属和盾垫属是该退化草原线虫群落优势属.氮输入降低了土壤线虫总丰度、捕食杂食线虫丰度以及植物寄生线虫丰度,而磷输入提高了土壤线虫总丰度、食真菌线虫丰度、捕食杂食类线虫丰度以及植物寄生线虫丰度,氮输入抑制了磷输入对线虫总丰度、捕食杂食线虫和植物寄生线虫丰度的促进作用.氮磷输入对线虫多样性无影响,可能与不同养分输入下稳定的植物群落多样性有关.氮输入显著提升了退化草原线虫成熟度指数,降低了植物寄生线虫成熟度指数(PPI),并且能缓解磷输入对PPI和瓦斯乐斯卡指数的负面作用,表明氮输入提高退化草地土壤健康程度,促进线虫群落和食物网的稳定性.上述研究结果有助于从土壤生物学角度理解氮磷输入对退化草地恢复的影响机理.     

Linking aboveground and belowground communities: the indirect influence of aphid species identity and diversity on a three trophic level soil food web

There has been a growing recent interest in how foliar herbivory may indirectly affect the belowground sub-system, but little is known about the belowground consequences of the identity, species composition or diversity of foliar herbivores. We performed an experiment, utilising model grassland communities containing three plant species, in which treatments consisted of addition of each of eight aphid species in single and in two- four- and eight-species combinations, as well as an aphid-free treatment. While aphid species treatments did not affect total plant biomass or productivity, aphid species identity had important effects on the relative abundance of the three plant species. This in turn affected the abundances of each of three groups of secondary consumers in the soil food web (bacterial- and fungal-feeding nematodes, and enchytraeids) but not primary consumers (microbes, herbivorous nematodes) or tertiary consumers (predatory nematodes). The fact that some trophic levels responded to treatments while others did not is consistent with trophic dynamic theory. Aphid species treatments also affected the community composition within each of the herbivorous, microbe-feeding and top predatory nematode groups, as well as diversity within the first two of these groups. However, aphid species diversity per se had few effects. There were specific instances in which specific aboveground and belowground response variables in two aphid species combinations differed significantly from those in both of the corresponding single aphid species treatments (apparently as a consequence of resource use complementarity between coexisting aphid species), but no instance in which increasing aphid diversity beyond two species had any effect. Our results provide evidence that the identity of aboveground consumers can have effects that propagate through multiple trophic levels in soil food webs in terms of consumer abundance, and composition and diversity within trophic levels.     

Population- and ecosystem-level effects of predation on microbial-feeding nematodes

We studied the role of nematode predation in the functioning of detrital food webs assembled in microcosms. The microcosms contained defaunated humus and litter materials, a diverse microbial community with bacteria, fungi and protozoa, and a birch (Betula pendula) seedling infected with mycorrhizal fungi. Different levels of top-down control upon microbivorous nematodes were set up by assembling food webs either without predators, or in combinations with a specialist and a non-specialist predatory mite (Mesostigmata). The nematode community was composed of either (1) three species of bacterivorous, or (2) three species of fungivorous nematodes or (3) both groups together. After two growing periods for the birch (38 weeks), the microcosms were destructively sampled for animal and microbial biomasses, concentration of mineral N in the soil, plant biomass and plant N concentration. The specialist predator reduced biomasses of both bacterial- and fungal-feeding nematodes by more than 50%, whereas the non-specialist predator weakly increased the biomass of fungivorous nematodes. Thus, under high predation pressure, the biomass of microbivores changed as predicted by trophic dynamic models assuming strong top-down control and uniformly behaving trophic levels. Despite this, microbial biomass was unaffected by the predators. However, microbial respiration increased slightly in the presence of predators. Assuming that microbial respiration correlates with microbial productivity, the increase in microbial respiration indicates a cascading productivity regulation. The composition of the microbivore community had only a minor effect on the outcome of the top-down control on microbes. The >50% reduction in nematode biomass and respiration coincided with <16% increase in microbial respiration and did not affect microbial biomass. Presence of the specialist predator slightly reduced soil NH⁺ ₄ concentration in communities with fungivore nematodes but plant growth and N uptake remained unchanged. Thus, the structure of the community only weakly controlled nutrient mineralisation. Received: 18 May 1998 / Accepted: 3 May 1999     

The influence of nematodes on below-ground processes in grassland ecosystems

This review summarises recent information on beneficial roles that soil nematodes play in the cycling of carbon and other plant nutrients in grassland ecosystems. In particular, we focus on the role of the two dominant functional groups of nematodes, namely the microbial- and root-feeders, and how their activities may enhance soil ecosystem-level processes of nutrient cycling and, ultimately, plant productivity in managed and unmanaged grassland ecosystems. We report recent experiments which show that low amounts of root herbivory by nematodes can increase the allocation of photoassimilate carbon to roots, leading to increased root exudation and microbial activity in the rhizosphere. The effects of these interactions on soil nutrient cycling and plant productivity are discussed. Evidence is presented to show that the feeding activities of microbial-feeding nematodes can enhance nutrient mineralization and plant nutrient uptake in grasslands, but that these responses are highly species-specific and appear to be strongly regulated by higher trophic groups of fauna (top-down regulation). We recommend that future studies of the roles of nematodes in grasslands ecosystems should consider these more complex trophic interactions and also the effects of species diversity of nematodes on soil ecosystem-level processes. This revised version was published online in June 2006 with corrections to the Cover Date.     

Regulation of the biomass and activity of soil microorganisms by microfauna

Microcosm experiments showed that the microbial biomass and the respiration activity in soil were regulated by nematodes. Depending on nematode number and plant residue composition, the trophic activity of nematodes can either stimulate or inhibit microbial growth and respiration as compared to soil containing no nematodes. The stimulating effect was observed when nitrogen-free (starch) or low-nitrogen (wheat straw, C : N = 87) organic substrates were applied. Inhibition occurred when a substrate rich in nitrogen (alfalfa meal, C : N = 28) was decomposed and the nematode population exceeded the naturally occurring level. A conceptual model was developed to describe trophic regulation by microfauna (nematodes) of the microbial productivity and respiration ctivity and decomposition of not readily decomposable organic matter in soil. The stimulating and inhibiting influence of microfauna on soil microorganisms was not a linear function of the rate of microbial consumption by nematodes. These effects are largely associated with the induced change in the physiological state of microorganisms rather than with the mobilization of biogenic elements from the decomposed microbial biomass.     

Species-specific effects of live roots and shoot litter on soil decomposer abundances do not forecast plant litter-nitrogen uptake

Plant species produce litter of varying quality and differ in the quality and quantity of compounds they release from live roots, which both can induce different decomposer growth in the soil. To test whether differences in decomposer growth can forecast the amount of N species acquire from plant litter, as suggested by theory, we grew individuals of three grassland plants—Holcus lanatus, Plantago lanceolata and Lotus corniculatus—in soils into which ¹⁵N-labelled litter of either Holcus, Plantago or Lotus was added. We measured the effects of live roots and litter of each species on soil microbes and their protozoan and nematode feeders, and to link decomposer growth and plant nutrient uptake, we measured the amount of N taken up by plants from the added litter. We hypothesised that those species that induce the highest growth of microbes, and especially that of microbial feeders, will also take up the highest amount of N from the litter. We found, however, that although numbers of bacterial-feeding Protozoa and nematodes were on average lower after addition of Holcus than Plantago or Lotus litter, N uptake was higher from Holcus litter. Further, although the effects on Protozoa and bacterial- and fungal-feeding nematodes did not differ between the live plants, litter-N uptake differed, with Holcus being the most efficient compared to Plantago and Lotus. Hence, although microbes and their feeders unquestionably control N mineralization in the soil, and their growth differs among plant species, these differences cannot predict differences in litter-N uptake among plant species. A likely reason is that for nutrient uptake, other species-specific plant traits, such as litter chemistry, root proliferation ability and competitiveness for soil N, override in significance the species-specific ability of plants to induce decomposer growth.     

Effects of native and exotic range‐expanding plant species on taxonomic and functional composition of nematodes in the soil food web

Due to climate warming, many plant species shift ranges towards higher latitudes. Plants can disperse faster than most soil biota, however, little is known about how range‐expanding plants in the new range will establish interactions with the resident soil food web. In this paper we examine how the soil nematode community from the new range responds to range‐expanding plant species compared to related natives. We focused on nematodes, because they are important components in various trophic levels of the soil food web, some feeding on plant roots, others on microbes or on invertebrates. We expected that range expanding plant species have fewer root‐feeding nematodes, as predicted by enemy release hypothesis. We therefore expected that range expanders affect the taxonomic and functional composition of the nematode community, but that these effects would diminish with increasing trophic position of nematodes in the soil food web. We exposed six range expanders (including three intercontinental exotics) and nine related native plant species to soil from the invaded range and show that range expanders on average had fewer root‐feeding nematodes per unit root biomass than related natives. The range expanders showed resistance against rather than tolerance for root‐feeding nematodes from the new range. On the other hand, the overall taxonomic and functional nematode community composition was influenced by plant species rather than by plant origin. The plant identity effects declined with trophic position of nematodes in the soil food web, as plant feeders were influenced more than other feeding guilds. We conclude that range‐expanding plant species can have fewer root‐feeding nematodes per unit root biomass than related natives, but that the taxonomic and functional nematode community composition is determined more by plant identity than by plant origin. Plant species identity effects decreased with trophic position of nematodes in the soil food web.     

不同食细菌线虫取食密度下线虫对细菌数量、活性及土壤氮素矿化的影响

采用悉生培养微缩体系,探讨了不同食细菌线虫取食密度下线虫(Caenorhabditis elegans) 对细菌(Bacillus subtilis)数量和活性及土壤氮素矿化的影响.结果表明,线虫对细菌的取食,促进了细菌的增殖,并在不同线虫取食密度下对细菌的增殖促进作用总体表现为:接种20条·g^-1＞10条·g^-1＞40条线虫·g^-1处理.线虫在促进细菌增殖的同时,明显提高了土壤呼吸强度和土壤蔗糖酶、脲酶和磷酸酶的活性,但不同取食密度处理间差异不明显.线虫与细菌之间的相互作用显著提高了土壤铵态氮和矿质态氮含量,促进了土壤氮的矿化.不同取食密度处理间,线虫对土壤氮素矿化的促进作用与对细菌的增殖促进作用趋势一致.