锦鸡儿属灌丛化对草原化荒漠区土壤线虫群落组成和代谢足迹的影响

调查了内蒙古草原化荒漠区3种锦鸡儿[垫状锦鸡儿(Caragana tibetica)、荒漠锦鸡儿(C.roborovskyi)和狭叶锦鸡儿(C.stenophylla)]灌丛内、外土壤线虫群落多样性、组成和代谢足迹,以及相关的土壤理化性质和植物群落特征,旨在探讨锦鸡儿属灌丛对土壤线虫群落的影响,并分析这种影响是否具有灌木种间差异,同时从线虫功能团水平上探究灌丛如何通过非生物因素和生物因素影响线虫群落组成。结果表明：锦鸡儿属灌丛对土壤线虫多度、丰富度和多样性无显著影响,但却显著影响土壤线虫群落组成。原因是灌丛对土壤线虫群落具有物种选择性;灌丛可能主要是通过根系分泌物、凋落物质量等因素,而不是通过土壤理化性质和林下植物影响线虫群落组成。土壤线虫组成的变化引起线虫代谢足迹发生明显变化。灌丛内土壤线虫功能代谢足迹大于灌丛外(除狭叶锦鸡儿外),说明灌丛内土壤线虫群落对碳的利用率更高。3种锦鸡儿属灌木中,狭叶锦鸡儿的结构代谢足迹最大,表明狭叶锦鸡儿对捕食杂食类线虫代谢活性的促进作用更强。土壤线虫组成的变化通过线虫代谢足迹导致土壤食物网结构发生显著性变化。狭叶锦鸡儿灌丛土壤干扰程度低,营养富集状况好...     

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。     

土壤线虫作为生态指示生物的研究进展

土壤线虫广布于各种类型的土壤中, 在维持土壤生态系统的稳定性、促进物质循环和能量流动等方面发挥着重要的作用, 同时也是理想的环境指示生物。简述了土壤线虫的生活史策略和营养类群的多样性、土壤线虫多样性的生态指数、影响土壤线虫群落多样性的环境因素, 以及线虫作为指示生物在农业生态系统、草地生态系统、森林生态系统的功能作用。提出了全球气候变化背景下对青藏高原高寒草地土壤线虫分类、群落结构特征以及土壤线虫的生物指示作用研究的必要性, 并对土壤线虫未来的发展趋势做了展望。     

干扰对东北次生林生态系统土壤线虫群落的影响

土壤线虫作为土壤生态系统中重要的组成部分,在凋落物分解与物质循环中起着重要作用。为明确东北地区不同林型中土壤线虫状况,确定干扰对土壤线虫产生的影响,于2007年5、7、9月调查了次生林、落叶松人工林和裸地3种样地（其干扰强度：次生林<人工林< 裸地）的线虫多样性。结果表明：随着干扰度的增加,土壤线虫丰富度与个体数均减少;通过土壤线虫区系划分,可以确定3种干扰强度下土壤线虫食物网的状况,即裸地环境受到胁迫,食物网受到威胁,其干扰程度最大;人工林与次生林食物网结构相对成熟,二者干扰程度较小。干扰改变了线虫群落的种类组成,随着干扰度增加,线虫多样性减少。上述结果表明,地上部分（森林植被）的干扰已经影响了地下生态系统。     

川西亚高山针叶林土壤动物群落对模拟林下植物丧失的响应

受研究手段的限制,有关森林物种组成对土壤动物群落影响的研究少有报道。采用人工除灌和除草的林地控制实验方法,研究了亚高山人工林灌草层关键物种丧失对土壤动物群落结构的影响。结果表明:(1)灌木层去除后土壤动物密度极显著低于对照(P0.01);线虫纲(Nematoda)优势度持续增加,处理15个月时极显著高于对照(P0.01);土壤动物群落多样性指数极显著低于对照(P0.01);腐食性功能团类群数及个体数百分比有所下降。(2)草本层去除后土壤动物密度显著低于对照(P0.05);线虫纲优势度持续增加,处理15个月时显著高于对照(P0.05);土壤动物群落多样性指数极显著低于对照(P0.01);腐食性功能团类群数略低于对照,个体数百分比无显著差异。综上所述,林下灌草层去除,尤其是灌木层去除,导致土壤动物群落个体数量、多样性指数降低,优势类群格局、腐食性功能团构成发生变化,从而在一定程度上影响到森林生态系统的物质循环功能。     

我国土壤线虫生态学研究进展和展望

土壤线虫生态学主要探讨土壤线虫群落和其周围环境(包括生物和非生物)的相互关系, 包括不同生态系统中土壤线虫群落的分布和结构组成、线虫群落与土壤环境及其他土壤生物之间的相互作用等。本文回顾了我国研究者近年来在土壤线虫生态学研究领域的研究现状, 包括不同生态系统土壤线虫群落的分布、组成和多样性及其影响因素, 土壤线虫群落与全球气候环境变化的关系, 土壤线虫群落的生态功能以及土壤线虫群落生态学分析方法的发展及应用。重点评述近年来我国土壤线虫生态学的发展现状, 同时分析和比较了国内外土壤线虫生态学的发展态势, 提出建设全国范围的监测网络的重要性。未来我国土壤线虫生态学的发展方向应继续加强小尺度下土壤微食物网联通性和大尺度下全球气候变化对土壤线虫群落影响的研究以及加强相关新的研究技术方法的应用。     

黄土高原半干旱区不同苜蓿-作物种植方式下土壤线虫群落组成及代谢足迹

线虫群落在土壤生态系统物质循环和能量流动过程中起着重要的作用。本研究以宁夏南部山区3种苜蓿-作物种植方式[苜蓿连作(A-A)、苜蓿-玉米轮作(A-C)、苜蓿-马铃薯轮作(A-P)]为对象,探讨不同种植方式下土壤理化性质、线虫群落组成结构及代谢足迹特征,评价黄土高原半干旱区苜蓿-作物种植方式对土壤食物网结构和功能的影响。结果表明: 1)与苜蓿连作相比,苜蓿-玉米和苜蓿-马铃薯轮作方式下土壤有机碳含量分别增加了4.6%、7.4%,全氮含量分别增加了4.0%、5.2%,土壤微生物生物量碳和氮也有显著提高;2)在苜蓿连作方式下,线虫总多度为211 条·100 g^-1干土,植食线虫为优势营养类群(35.7%),而在苜蓿-玉米和苜蓿-马铃薯轮作方式下,土壤线虫总多度较苜蓿连作有所增加(分别增加49.5%、93.7%),捕-杂食线虫成为优势营养类群(所占比例分别为45.7%、37.6%);3)相较于苜蓿连作,苜蓿-作物轮作方式下,植物寄生线虫指数(PPI)显著降低,表明植物寄生线虫在土壤食物网中的危害减轻;而线虫通路指数(NCR)有所增加,表明苜蓿-作物轮作方式下,土壤有机质分解过程中细菌分解作用进一步增强;4)苜蓿-作物轮作方式下,土壤线虫成熟度指数(MI)及其复合足迹、富集足迹、结构足迹均显著提高,土壤线虫的生产力和代谢活性显著增强,线虫群落的结构和功能更为成熟稳定。研究表明,相比苜蓿连作,苜蓿-作物轮作改善了土壤养分状况,使得土壤食物网的资源输入和能量利用效率均有所增加,受干扰程度显著降低,土壤生态系统更为稳定健康,因而有利于农业的可持续发展。     

模拟氮沉降对温带森林土壤线虫群落组成和代谢足迹的影响

已有研究表明氮沉降可显著影响土壤线虫群落组成和多样性。然而,目前大多数研究集中在无机氮沉降的影响,而对于不同氮素形态对土壤线虫群落影响的研究还不是很清楚。利用运行5年的模拟氮沉降试验平台,开展了4个氮添加处理即对照(无氮添加,CK)、无机氮(硝酸铵,IN),有机氮(尿素和甘氨酸1∶1混合,ON)和混合氮(无机氮和有机氮7∶3混合,MN)添加对温带森林土壤线虫群落组成和多样性的影响研究,采用浅盘法分离线虫,土壤性质如p H、含水量、全碳全氮分别采用电位法、烘干法和元素分析仪法进行测定,应用营养类群组成、区系分析和代谢足迹分析不同形态氮沉降下土壤线虫群落结构特征。共分离线虫50个属,其中在CK样地中共发现29个属,在IN,ON和MN处理中分别发现线虫属37个,34个和29个,盘旋属Rotylenchus和大节片属Macroposthonia在所有处理中均为优势属。结果表明,与CK相比,IN处理、ON处理和MN处理均显著增加了土壤硝态氮含量。与无机氮相比,混合氮处理显著降低了食真菌线虫数量,有机氮处理显著增加了捕食杂食性线虫数量。与对照相比,无机氮处理显著增加了线虫多样性指数(H'),IN处理的均匀度指数(J)显著高于CK和MN处理,混合氮处理对应的优势度指数(λ)显著高于其他3个处理。在CK和ON处理,线虫的结构指数(SI)较高,富集指数(EI)较低,表明这两个处理的土壤受干扰程度较小,食物网处于结构化状态。在IN和MN处理,土壤线虫富集指数和结构指数均较高(50),表明食物网稳定成熟。食真菌线虫代谢足迹和生物量碳在无机氮处理最高。有机氮和混合氮处理显著增加了捕食杂食性线虫代谢足迹和生物量碳。以上结果表明,不同氮素形态不仅对土壤线虫群落组成产生了影响,而且其代谢足迹也发生了显著的变化,这一结果有助于揭示温带森林对氮沉降的响应机制。     

不同植物群丛下铜尾矿复垦地土壤线虫的分布特征

对铜陵市凤凰山铜尾矿复垦地禾本科(矛叶荩草AL、白茅IC)和豆科(野豌豆GS)等3类典型植物群丛及外围对照禾本科(毛马唐)植物群丛下的土壤线虫群落进行调查.共分离得到1277 条土壤线虫,隶属于51属,平均密度590条·100 g^-1干土.采用多样性指数和土壤食物网结构指数等分析铜尾矿复垦地土壤线虫群落的分布特征.结果表明： 铜尾矿复垦地3类植物群丛下土壤线虫群落的类群总数和Shannon〖KG-*4〗多样性指数明显小于毛马唐对照组.对比铜尾矿复垦地和邻近自然栖息地不同植物群丛下的土壤线虫群落生态指数,发现野豌豆群丛下土壤食物网结构较成熟,土壤有机质分解以细菌分解通道为主;生态系统较不稳定,低度干扰;表明该豆科植物群丛下的土壤食物网具有较大的发展潜力,从而提高铜尾矿复垦地的生态稳定性.白茅与矛叶荩草群丛下土壤食物网处于结构化状态,土壤有机质分解以真菌分解通道为主;生态系统较稳定,无干扰;表明禾本科植物群丛下的土壤食物网处于较低层次的发展状态.     

试论土壤线虫多样性在生态系统中的作用

土壤线虫的物种多样性和功能群丰富, 不同功能群的土壤线虫取食习惯也不一样, 而土壤线虫取食习惯的多样性以及它们自身的一些属性决定了它们在土壤中与其他生物之间关系的复杂性。土壤中不同生物之间的相互作用决定了土壤食物网的复杂性, 进而影响着土壤生态系统功能。然而, 有关土壤线虫的多样性与土壤生态系统功能之间的关系的研究还很不足。要全面了解土壤线虫在生态系统中的作用, 研究工作必须: (1) 结合室内模拟和野外控制实验; (2) 结合物种多样性调查和不同功能群的功能分析。     

土壤食物网:结构、能流及稳定性

在国外4个土壤生态学项目的基础上,结合其他学者的研究成果,从连通网、能流网及功能网3个层次分别阐述了土壤食物网的结构、能流与稳定性。在连通网中,主要描述土壤食物网的功能群、营养位及格局;在能流网中,主要描述了面向过程食物网模型及其应用,主要涉及到土壤中的碳流与氮流;在功能网中,以作用强度为中心,描述了土壤食物网的稳定性问题。     

Nematode Indicators of Organic Enrichment

The organisms of the soil food web, dependent on resources from plants or on amendment from other sources, respond characteristically to enrichment of their environment by organic matter. Primary consumers of the incoming substrate, including bacteria, fungi, plant-feeding nematodes, annelids, and some microarthropods, are entry-level indicators of enrichment. However, the quantification of abundance and biomass of this diverse group, as an indicator of resource status, requires a plethora of extraction and assessment techniques. Soluble organic compounds are absorbed by bacteria and fungi, while fungi also degrade more recalcitrant sources. These organisms are potential indicators of the nature of incoming substrate, but current methods of biomass determination do not reliably indicate their community composition. Guilds of nematodes that feed on bacteria (e.g., Rhabditidae, Panagrolaimidae) and fungi (e.g., Aphelenchidae, Aphelenchoididae) are responsive to changes in abundance of their food. Through direct herbivory, plant-feeding nematodes (e.g., many species of Tylenchina) also contribute to food web resources. Thus, analysis of the nematode community of a single sample provides indication of carbon flow through an important herbivore channel and through channels mediated by bacteria and fungi. Some nematode guilds are more responsive than others to resource enrichment. Generally, those bacterivores with short lifecycles and high reproductive potential (e.g., Rhabditidae) most closely mirror the bloom of bacteria or respond most rapidly to active plant growth. The feeding habits of some groups remain unclear. For example, nematodes of the Tylenchidae may constitute 30% or more of the individuals in a soil sample; further study is necessary to determine which resource channels they portray and the appropriate level of taxonomic resolution for this group. A graphic representation of the relative biomass of bacterivorous, fungivorous, and herbivorous nematodes provides a useful tool for assessing the importance of the bacterial, fungal, and plant resource channels in an extant food web.     

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.     

Reduced tillage,but not organic matter input,increased nematode diversity and food web stability in European long‐term field experiments

Soil nematode communities and food web indices can inform about the complexity, nutrient flows and decomposition pathways of soil food webs, reflecting soil quality. Relative abundance of nematode feeding and life‐history groups are used for calculating food web indices, i.e., maturity index (MI), enrichment index (EI), structure index (SI) and channel index (CI). Molecular methods to study nematode communities potentially offer advantages compared to traditional methods in terms of resolution, throughput, cost and time. In spite of such advantages, molecular data have not often been adopted so far to assess the effects of soil management on nematode communities and to calculate these food web indices. Here, we used high‐throughput amplicon sequencing to investigate the effects of tillage (conventional vs. reduced) and organic matter addition (low vs. high) on nematode communities and food web indices in 10 European long‐term field experiments and we assessed the relationship between nematode communities and soil parameters. We found that nematode communities were more strongly affected by tillage than by organic matter addition. Compared to conventional tillage, reduced tillage increased nematode diversity (23% higher Shannon diversity index), nematode community stability (12% higher MI), structure (24% higher SI), and the fungal decomposition channel (59% higher CI), and also the number of herbivorous nematodes (70% higher). Total and labile organic carbon, available K and microbial parameters explained nematode community structure. Our findings show that nematode communities are sensitive indicators of soil quality and that molecular profiling of nematode communities has the potential to reveal the effects of soil management on soil quality.     

农田土壤食物网管理的原理与方法

土壤食物网在维持生态系统生产力和健康等方面起着重要作用,但现代农业中,化肥农药等外部投入已经改变或部分替代了土壤食物网的功能,由此也造成一系列的环境问题。为了协调作物高产与环境保护的利益,需要对土壤食物网进行管理,使土壤食物网符合作物生长的需要,即建立健康土壤食物网。管理土壤食物网有两种方式:(1)直接方式,即通过调节食物网各个功能群的组成来管理土壤食物网;(2)间接方式,即根据农田土壤食物网以自下而上调控方式为主、强调低营养阶层的资源限制的原理,通过调节碎屑的数量和质量来管理食物网。在这两种调控方式中,都需要对被管理的食物网进行监测,监测的方式也分两种,一种是直接测定食物网各功能群的数量和生物量,另外一种方式即以线虫为工具来反应土壤食物网的结构。     

SSU Ribosomal DNA-Based Monitoring of Nematode Assemblages Reveals Distinct Seasonal Fluctuations within Evolutionary Heterogeneous Feeding Guilds

Soils are among the most complex, diverse and competitive habitats on Earth and soil biota are responsible for ecosystem services such as nutrient cycling, carbon sequestration and remediation of freshwater. The extreme biodiversity prohibits the making of a full inventory of soil life. Hence, an appropriate indicator group should be selected to determine the biological condition of soil systems. Due to their ubiquity and the diverse responses to abiotic and biotic changes, nematodes are suitable indicators for environmental monitoring. However, the time-consuming microscopic analysis of nematode communities has limited the scale at which this indicator group is used. In an attempt to circumvent this problem, a quantitative PCR-based tool for the detection of a consistent part of the soil nematofauna was developed based on a phylum-wide molecular framework consisting of 2,400 full-length SSU rDNA sequences. Taxon-specific primers were designed and tested for specificity. Furthermore, relationships were determined between the quantitative PCR output and numbers of target nematodes. As a first field test for this DNA sequence signature-based approach, seasonal fluctuations of nematode assemblages under open canopy (one field) and closed canopy (one forest) were monitored. Fifteen taxa from four feeding guilds (covering ∼ 65% of the free-living nematode biodiversity at higher taxonomical level) were detected at two trophic levels. These four feeding guilds are composed of taxa that developed independently by parallel evolution and we detected ecologically interpretable patterns for free-living nematodes belonging to the lower trophic level of soil food webs. Our results show temporal fluctuations, which can be even opposite within taxa belonging to the same guild. This research on nematode assemblages revealed ecological information about the soil food web that had been partly overlooked.     

增施氮肥能够缓解麦田土壤线虫群落对O3浓度升高的响应

在辽宁沈阳农田生态系统国家野外科学观测研究站,利用运行2a的开顶式气室,研究了臭氧(O3)浓度升高和不同氮肥施用水平对土壤线虫群落的影响。结果表明:(1)O3浓度升高降低了成熟期小麦根生物量。O3浓度升高和不同氮肥施用水平的交互作用改变了小麦成熟期土壤微生物生物量碳、氮和水溶性有机碳的含量。低氮条件下,O3浓度升高降低了土壤微生物生物量碳、氮和水溶性有机碳的含量;而高氮条件下则表现出相反的趋势。(2)O3浓度升高和不同氮肥施用水平对土壤线虫总数没有产生显著影响,而在灌浆期,食细菌线虫和食真菌线虫中c-p值为4(Ba4 and Fu4)的功能团对O3浓度升高和不同氮肥施用水平的响应敏感;与对照相比,不同氮处理中,O3浓度升高均降低了灌浆期Ba4功能团线虫的数量。灌浆期,O3浓度升高条件下,与对照相比Fu4功能团线虫数量在高氮条件下表现出增加的趋势,而在低氮条件表现出降低的趋势。(3)O3浓度升高和不同氮肥施用水平的交互作用显著影响了小麦灌浆期线虫的成熟度指数(MI)和结构指数(SI)。与对照相比,线虫成熟度指数和结构指数在低氮条件下随O3浓度升高而降低;而在高氮条件下随O3浓度升高而升高。上述结果表明,氮肥的施用能够缓解O3浓度升高对土壤食物网的扰动。     

Global patterns of guild composition and functional diversity of spiders

The objectives of this work are: (1) to define spider guilds for all extant families worldwide; (2) test if guilds defined at family level are good surrogates of species guilds; (3) compare the taxonomic and guild composition of spider assemblages from different parts of the world; (4) compare the taxonomic and functional diversity of spider assemblages and; (5) relate functional diversity with habitat structure. Data on foraging strategy, prey range, vertical stratification and circadian activity was collected for 108 families. Spider guilds were defined by hierarchical clustering. We searched for inconsistencies between family guild placement and the known guild of each species. Richness and abundance per guild before and after correcting guild placement were compared, as were the proportions of each guild and family between all possible pairs of sites. Functional diversity per site was calculated based on hierarchical clustering. Eight guilds were discriminated: (1) sensing, (2) sheet, (3) space, and (4) orb web weavers; (5) specialists; (6) ambush, (7) ground, and (8) other hunters. Sixteen percent of the species richness corresponding to 11% of all captured individuals was incorrectly attributed to a guild by family surrogacy; however, the correlation of uncorrected vs. corrected guilds was invariably high. The correlation of guild richness or abundances was generally higher than the correlation of family richness or abundances. Functional diversity was not always higher in the tropics than in temperate regions. Families may potentially serve as ecological surrogates for species. Different families may present similar roles in the ecosystems, with replacement of some taxa by other within the same guild. Spiders in tropical regions seem to have higher redundancy of functional roles and/or finer resource partitioning than in temperate regions. Although species and family diversity were higher in the tropics, functional diversity seems to be also influenced by altitude and habitat structure.