天然和人工固沙灌木林蜘蛛和甲虫分布与环境因子的关系

干旱区人工植被恢复驱动的土地利用变化强烈影响了地表和土栖的节肢动物群落结构及多样性。然而,我们对地表节肢动物群落关键类群-蜘蛛和甲虫对固沙植被恢复的响应及与环境变化关系的认识还很有限。以天然固沙灌木林和2种人工固沙灌木林为研究对象,运用方差分析和多变量分析等方法定量研究了干旱区天然和人工固沙植被区地表蜘蛛和甲虫分布特征及影响要素。结果表明,天然灌木林与人工梭梭、柽柳林地表蜘蛛和甲虫群落组成明显不同,人工梭梭、柽柳林地表蜘蛛活动密度和甲虫多样性均显著高于天然灌木林,而地表甲虫密度和蜘蛛多样性变化与之相反。两种人工固沙灌木林之间蜘蛛和甲虫群落组成也存在一定差异,人工柽柳林地表蜘蛛活动密度、多样性和甲虫物种丰富度均显著高于人工梭梭林。进一步分析发现,蜘蛛群落中狼蛛科、平腹蛛科、皿蛛亚科和球蛛科与甲虫群落中拟步甲科、步甲科和象甲科等一些甲虫种属对3种生境的选择模式不同决定了蜘蛛和甲虫群落聚集结构。植被、土壤环境因子与蜘蛛和甲虫pRDA和pCCA结果表明,草本生物量、凋落物量、土壤含砂量、电导率和灌木盖度是影响蜘蛛分布的主要环境因子,它们解释了82.1%的蜘蛛群落变异;灌木盖度、草本生物量、土壤pH和砂含量是影响甲虫群落分布的主要环境因子,它们解释了60.6%的甲虫群落变异。总之,人工固沙灌木恢复影响了植被和土壤环境,它们相互作用改变了荒漠-绿洲过渡区蜘蛛和甲虫等地表节肢动物的分布格局。     

拉萨半干旱河谷植被对地表节肢动物多样性的影响

调查不同植被恢复措施下拉萨半干旱河谷地表节肢动物类群多样性以及群落结构,为揭示地表节肢动物多样性对植被恢复措施的响应具有重要意义。采用陷阱法对青藏高原半干旱河谷砂生槐灌丛、人工杨树林和藏沙蒿灌丛样地地表节肢动物群落组成、类群多样性以及功能群结构进行调查,计算各处理地表节肢动物类群相对多度、类群丰富度、多样性指数、Cody指数和S9rensen指数。共采集半干旱河谷地表节肢动物个体数738,隶属5纲15目51科。砂生槐灌丛样地收集节肢动物40科,占所有类群78.4%,杨树人工林和藏沙蒿灌丛样地调查到土壤节肢动物类群为30和23科,分别占总科数的58.8%和45.1%。各植被恢复类型在目的分类单元下,双翅目、膜翅目和弹尾目类群相对多度较高,而在科的分类单元下,驼跳科、蚁科和漏斗网蛛科为拉萨半干旱河谷优势地表节肢动物类群。砂生槐灌丛节肢动物类群丰富度和多样性指数最高,人工杨树林最低。砂生槐灌丛和藏沙蒿灌丛地表节肢动物营养功能群均以捕食性为主。不同植被群落间群落相似性也有差异,砂生槐与藏沙蒿灌丛间相似性较高,而人工杨树林与藏沙蒿之间较低。不同植物群落组成和结构影响土壤理化特性、地表凋落物数量、质量和微生境条件,进而影响地表节肢动物群落组成、数量和营养功能群。砂生槐灌丛样地具有较高节肢动物类群丰富度和捕食性动物类群,有利于拉萨半干旱河谷地区地表节肢动物多样性维护。     

皖北石灰岩山地植被对地表节肢动物组成及多样性的影响

调查皖北石灰岩山地退化生态系统不同植被恢复类型地表节肢动物群落组成、类群多样性以及功能群组成,揭示退化生态系统植被恢复进程中土壤地表节肢动物群多样性变化规律及其影响因素,为石灰岩山地植被恢复成效评价提供科学依据。采用陷阱法对皖北石灰岩山地侧柏+构树混交林、酸枣+牡荆灌丛和荩草+牡荆草灌丛样地地表节肢动物群落组成、多样性以及功能群进行调查。共采节肢动物个体数11601,隶属8纲14目44科。酸枣+牡荆灌丛样地采集到节肢动物37科,占所有类群的84.1%,荩草+牡荆草灌丛和侧柏+构树混交林采集到土壤节肢动物类群为35和26科,分别占总科数的79.6%和59.1%。在目的分类单元下,直翅目、等足目和鞘翅目类群相对多度较高,而科的分类单元下,潮虫科、金龟甲科、蚁科和蟋蟀科为皖北石灰岩山地优势地表节肢动物类群。酸枣+牡荆灌丛节肢动物类群丰富度和荩草+牡荆草灌丛多样性指数最高,侧柏+构树混交林两者均最低。3个样地地表节肢动物营养功能群均以植食性为主。不同植被恢复类型间群落相似性也有变化,酸枣+牡荆灌丛和荩草+牡荆草灌丛间相似性较高,而侧柏+构树混交林与其他2种类型之间相似度均较低。研究结果表明石灰岩山地生境不同植被群落组成、数量和结构及其驱动形成的土壤理化特性、表层的凋落物数量、质量和微生境条件的变异,引起地表节肢动物群落组成、结构和多样性和营养功能群的不同。     

东北黑土区耕作措施对地表节肢动物多样性的影响

【目的】调查不同耕作措施下东北黑土地表节肢动物群落类群多样性以及营养功能群结构, 有利于揭示地表节肢动物多样性对土地管理措施的响应。【方法】本研究于2012年7－9月在黑龙江海伦中国科学院海伦农田生态系统国家野外科学观测研究站采用陷阱法对东北典型黑土区免耕、 少耕、 平翻、 旋耕和组合5种耕作措施长期定位试验区的地表节肢动物群落组成、 类群多样性以及功能群结构进行调查, 计算各处理地表节肢动物类群相对多度、 类群丰富度、 Shannon Wiener多样性指数、 Pielou均匀度指数、 Simpson优势度指数、 Cody指数和Srensen指数。【结果】本次调查共收集黑土农田地表节肢动物个体数为2 942, 隶属7目18科。免耕样地收集节肢动物15科, 占所有类群83.34%; 少耕和组合样地均为11科, 占61.12%。所有耕作措施下鞘翅目和蜘蛛目类群相对多度最高, 步甲科为黑土农田优势地表节肢动物类群。免耕样地节肢动物类群丰富度和多样性指数最高, 少耕样地最低。除旋耕样地外, 其他耕作样地地表节肢动物功能群均以捕食性为主。群落相似性指数分析表明, 不同耕作措施间群落相似性不同, 免耕与组合之间相似性较高, 而平翻与组合之间较低。【结论】步甲科是黑土农田地表节肢动物群落中的优势类群。不同耕作措施影响近地表土壤以及植被微生境, 进而影响地表节肢动物群落组成、 数量和营养功能群。免耕样地具有较高节肢动物类群丰富度和捕食性动物类群, 有利于维持黑土农田地表节肢动物多样性。     

放牧强度对短花针茅荒漠草原甲虫群落分布格局的影响

放牧对脆弱的荒漠草原生态系统有着重要影响,且随放牧强度及持续时间不同而变化。鞘翅目昆虫是环境监测与生物多样性变化的指示生物。利用巴氏罐诱法对短花针茅荒漠草原不同放牧强度草地的甲虫群落组成和多样性进行调查,探究放牧对荒漠草原甲虫群落的影响。结果表明:(1)步甲科、金龟科为短花针茅荒漠草原甲虫群落优势类群,埋葬甲科、芫菁科、拟步甲科和花金龟科为常见类群。(2)放牧强度增加不利于维持更多的捕食性甲虫;对照和轻度放牧样地可维持更多的腐食性甲虫。(3)甲虫数量随放牧强度增加而递减;群落多样性以重度放牧草地最大,轻度放牧草地最小;群落优势度为对照、中度、重度显著高于轻度放牧草地。各甲虫类群在不同放牧强度草地出现时间、高峰期均不同。(4)对照、轻度、重度放牧样地的甲虫优势类群群落结构不同于其他生境,但均与中度放牧样地存在相似性。轻度、中度、重度放牧样地的甲虫稀有类群群落结构不同于其他生境,但均与对照样地存在相似性。(5)甲虫群落个体数与植物群落物种丰富度、盖度、植物平均高度、生物量呈显著正相关。Shannon-Wiener多样性指数、Margalef丰富度指数均与植物群落物种丰富度、生物量显著负相关。研究结果为荒漠草原甲虫多样性保护提供参考依据。     

胜山阔叶红松林蚂蚁巢穴对其他地表节肢动物多样性的影响

为了阐明蚂蚁巢穴对其他地表节肢动物群落组成和多样性的影响,于2019年在胜山自然保护区的原始阔叶红松林内开展实验,并采用陷阱法收集地表节肢动物。共捕获地表节肢动物92266只,分别为蜈蚣目、盲蛛目、马陆目、蜘蛛目,大头蚁属和步甲科、隐翅虫科、葬甲科这8个类群;蚂蚁巢穴存在及到蚂蚁巢穴的不同距离对其他地表节肢动物个体数量存在显著影响,其影响因类群而异。蚂蚁巢穴对蜈蚣和蜘蛛有促进作用,对盲蛛、马陆和步甲科类群有抑制作用,对葬甲科与隐翅虫科无显著影响;对照样地和距蚂蚁巢穴较远群落的Shannon指数、Pielou指数和Simpson指数更高;蚂蚁巢穴样地群落Beta多样性更高,且Beta多样性主要由空间物种转换组成,表明存在较高的空间物种替换,即蚂蚁巢穴导致群落类群组成较大的差异。本研究表明,蚂蚁巢穴存在和距离远近都是影响其他地表节肢动物群落多样性的因素。     

环境因子对甘南高寒草甸地表大型节肢动物多样性的影响

地表节肢动物是生态系统的重要生物指示物,研究甘南高寒草甸地表节肢动物群落多样性与环境因子的关系,有助于揭示其分布格局对高寒草甸生态环境变化的响应。2018年5至9月,采用陷阱法调查甘南高寒草甸4种典型类型生境,即沼泽湿地、沼泽化草甸、草甸和成熟草甸地表大型节肢动物群落组成与多样性。研究时段共采集地表大型节肢动物2 545头,属于3纲9目29科30属,以狼蛛属(Lycosa)、弓背蚁属(Camponotus)和蚁属(Formica)为优势类群。营养功能群以捕食类和植食类为主。研究结果显示,成熟草甸生境大型节肢动物类群数明显高于沼泽化草甸和草甸生境的类群数(P <0.05);沼泽湿地生境Pielou均匀度指数(Js)明显大于草甸和成熟草甸生境的Pielou均匀度指数(P <0.05);Shannon-Wiener多样性指数(H′)差异不显著(P> 0.05);4种生境之间地表大型节肢动物群落相似性指数较低。研究时段基于物种“出现-不出现”C-score、V-ratio、SES与Pianka生态重叠指数的实测值与预测值的差异均没有规律性,显示研究区域地表大型节肢动物群落随机...     

黄河下游农业景观中不同生境类型地表节肢动物优势类群

生物多样性是连接景观异质性与生态系统服务的桥梁。在区域尺度上,以指示类群代替地表节肢动物类群,可以有效的开展生物多样性的保护工作。但是,在黄河下游农业景观中,关于地表节肢动物指示类群的研究报道较少。以黄河下游农业景观中4种生境类型(农田、林地、树篱和沟渠)为研究样地,且在农田生境中划分不同尺度(尺度1,3.6 hm2、尺度2,14 hm2和尺度3,28 hm2),通过调查不同生境中地表节肢动物分布及其多样性,结合地表节肢动物优势类群的辨识,分析了优势类群和地表节肢动物多样性的相关性,确定了研究区内地表节肢动物多样性的指示类群。结果发现:研究区内地表节肢动物优势类群为膜翅目、鞘翅目和蜘蛛目。树篱和林地生境的地表节肢动物多样性指示类群是膜翅目,农田生境中地表节肢动物多样性指示类群是鞘翅目,沟渠生境中地表节肢动物多样性指示类群是蜘蛛目。农田生境中优势类群间无相关性(P0.05);林地、沟渠和树篱生境中鞘翅目与蜘蛛目之间存在显著正相关(P0.01);林地和沟渠生境中,鞘翅目与膜翅目之间存在正相关(P0.05)。在农田生境中优势类群之间的相关性存在尺度依赖性,随着空间尺度的增大,相关性有一定的增强。在尺度2和尺度3上膜翅目和鞘翅目均存在正相关(P0.05),并且随着尺度增加而呈上升趋势。研究表明,黄河下游农业景观中不同生境类型地表节肢动物多样性的指示类群差别较大,其中树篱和林地生境具有较高的相似性,而农田生境地表节肢动物优势类群相关性存在尺度依赖性。在黄河下游农业景观中,以优势类群多样性代替地表节肢动物类群的多样性,可以在条件不足、时间紧迫的情况下更加有效的开展生物多样性的保护工作。     

乌拉特荒漠草原红砂(Reaumuria soongorica)灌丛林地地面节肢动物群落季节分布特征

以乌拉特荒漠草原红砂(Reaumuria soongorica)灌丛林地作为研究样地,分别于2018年春季、夏季和秋季,利用国际通用的陷阱诱捕法,调查了地面节肢动物群落季节动态分布特征及其与环境因子间的关系。结果显示:(1)3个季节内共捕获地面节肢动物560只,隶属于10目23科。其中,春季优势类群为拟步甲科,夏季为拟步甲科和蚁科,秋季为拟步甲科,其个体数分别占总个体数的51.54%、59.11%和64.88%;常见类群春季和夏季均有8类,秋季有10类,其个体数分别占总个体数的43.08%,37.33%和32.68%;稀有类群春季有7类,夏季有6类,秋季有3类,其个体数分别占总个体数的5.38%、3.56%和2.44%。(2)3个季节内生物量占比超过10%的地面节肢动物类群仅有拟步甲科,春季、夏季和秋季其分别占群落总生物量的88.59%、72.56%和80.90%;1%—10%的地面节肢动物类群生物量,春季、夏季和秋季其分别占群落总生物量的9.76%、25.51%和17.78%;小于1%的地面节肢动物类群生物量,春季、夏季和秋季其分别占群落总生物量的1.62%、1.94%和1.32%。(3)随季节变化,地面节肢动物的密度、类群数、Shannon-Wiener指数和Simpson指数均存在显著差异性(P0.05),表现为夏季显著高于春季或秋季。(4)RDA和Spearman相关分析结果表明,降雨量、气温、土壤含水量、土壤pH和电导率及土壤粒径组成是地面节肢动物季节分布的重要影响因素。研究表明,随着季节更替乌拉特荒漠草原红砂灌丛林地地面节肢动物群落组成季节分布差异性较大,夏季地面节肢动物多样性较高,而且不同类型环境因子对于地面节肢动物的个体数分布影响不同。     

辽东山区次生林与人工林大型地表节肢动物多样性

采用陷阱法在地表节肢动物活动高峰期(7—8月)对辽东山区蒙古栎(Quercus mongolica)林、胡桃楸(Juglans mandshurica)林和阔叶混交林3种次生林以及红松(Pinus koraiensis)人工林和落叶松(Larix spp.)人工林地表节肢动物群落进行了调查。共捕获地表节肢动物5135头,隶属于7纲18目66个类群,优势类群为蚁科(20.4%)、葬甲科(19.5%)、蜣螂科(17.2%)和步甲科(14.5%);地表节肢动物的功能群丰度依次为:腐食性杂食性捕食性植食性;系统聚类分析表明,地表节肢动物群落和地表甲虫群落均显示红松人工林、落叶松人工林和胡桃楸林群落结构聚为一类,蒙古栎林和阔叶混交林群落聚为一类;冗余度分析表明,凋落物厚度、植被盖度与树高因子可以解释地表节肢动物及地表甲虫群落差异的85.9%和81.9%。研究结果表明,研究区森林植被及凋落物状况、人为干扰是影响研究区大型地表节肢动物群落多样性的重要因素。     

Even the Smallest Non-Crop Habitat Islands Could Be Beneficial: Distribution of Carabid Beetles and Spiders in Agricultural Landscape

Carabid beetles and ground-dwelling spiders inhabiting agroecosystems are beneficial organisms with a potential to control pest species. Intensification of agricultural management and reduction of areas covered by non-crop vegetation during recent decades in some areas has led to many potentially serious environmental problems including a decline in the diversity and abundance of beneficial arthropods in agricultural landscapes. This study investigated carabid beetle and spider assemblages in non-crop habitat islands of various sizes (50 to 18,000 square metres) within one large field, as well as the arable land within the field, using pitfall traps in two consecutive sampling periods (spring to early summer and peak summer). The non-crop habitat islands situated inside arable land hosted many unique ground-dwelling arthropod species that were not present within the surrounding arable land. Even the smallest non-crop habitat islands with areas of tens of square metres were inhabited by assemblages substantially different from these inhabiting arable land and thus enhanced the biodiversity of agricultural landscapes. The non-crop habitat area substantially affected the activity density, recorded species richness and recorded species composition of carabid and ground-dwelling spider assemblages; however, the effects were weakened when species specialised to non-crop habitats species were analysed separately. Interestingly, recorded species richness of spiders increased with non-crop habitat area, whereas recorded species richness of carabid beetles exhibited an opposite trend. There was substantial temporal variation in the spatial distribution of ground-dwelling arthropods, and contrasting patterns were observed for particular taxa (carabid beetles and spiders). In general, local environmental conditions (i.e., non-crop habitat island tree cover, shrub cover, grass cover and litter depth) were better determinants of arthropod assemblages than non-crop habitat island size, indicating that the creation of quite small but diversified (e.g., differing in vegetation cover) non-crop habitat islands could be the most efficient tool for the maintenance and enhancement of diversity of ground-dwelling carabids and spiders in agricultural landscapes.     

Structure of ground-dwelling arthropod assemblages in vegetation units of Área Natural Protegida Península Valdés,Patagonia, Argentina

Knowing the spatial variation of insect and arachnid assemblages and their relationship with habitat variables is critical to understand the structure and dynamics of these communities in arid environments. The aim of this paper was to analyze the variation in ground-dwelling arthropod assemblages across three representative vegetation units of the Área Natural Protegida Península Valdés (Patagonia, Argentina). We asked whether environmental differences among representative vegetation units were associated to distinct arthropod assemblages. We selected three plant communities: grass, dwarf-shrub, and shrub steppes, and established three sampling sites within each of them. We measured variables of vegetation structure and soil characteristics and collected the arthropods using 10 pitfall traps per site. We analyzed the structure of arthropod assemblages at both family and ant species taxonomic levels. Each plant community displayed a distinctive assemblage, with differences in diversity, taxa abundance, trophic structure and functional groups of ants. Vegetation variables explained a higher proportion of the variation in the structure of the ground-dwelling arthropod assemblages than the soil variables. This work highlights the importance of the different vegetation units for the conservation of ground-dwelling arthropod biodiversity in Península Valdés.     

The impact of forest ski-pistes on diversity of ground-dwelling arthropods and small mammals in the Alps

Forest clearing for winter sport activities is the major force driving loss and fragmentation of the alpine forests. The establishment of ski-pistes involves impacts on every ecosystem component. To assess the extent of this threat we studied ground-dwelling arthropods (namely ground beetles and spiders) and small mammals (shrews and voles) at two ski resorts in north-western Italian Alps by pitfall trapping. Diversity parameters (mean abundance, species richness and Shannon index) of spiders and macropterous carabids increased from forest interior to open habitats (i.e., ski-piste or pasture), whereas parameters of brachypterous carabids significantly decreased from forest interior to open habitats. Diversity parameters of macropterous ground beetles were higher on pastures than on ski-pistes. Small mammals were virtually absent from ski-pistes. Observed frequencies in the three adjacent habitats were significantly different from expected ones for the bank vole Myodes glareolus and the pygmy shrew Sorex minutus. Generalized linear models showed that abundance, species richness and diversity of spiders and macropterous carabids of ski-pistes were best modelled by combination of factors, including grass cover and width of the ski-piste. Indicator Species Analysis showed that species that significantly preferred ski-pistes were less than those preferring pastures, and species which were exclusive of ski-pistes were very few. To retain arthropod ground-dwelling fauna of open habitats environmentally friendly ways of constructing pistes should be developed. After tree clearing, only the roughest ground surfaces should be levelled, in order to preserve as much natural vegetation as possible. Where necessary, ski-pistes should be restored through the recovery of local vegetation.     

Shrubs and species identity effects on the distribution and diversity of ground-dwelling arthropods in a Gobi desert

Disentangling the relationship between shrub vegetation and ground-dwelling arthropods at multiple levels of taxonomic resolution is essential to developing a suitable management strategy for the conservation of shrub-associated arthropod biodiversity in shrubland ecosystems. Using Gobi desert (dominated by shrub species Nitraria sphaerocarpa and Reaumuria soongorica) occurring widely in inland arid areas of northwest China as a model system, we sampled ground-dwelling arthropods by pitfall trapping method under canopies of both shrubs and in intershrub bare areas during spring, summer and autumn. Our aim was to determine whether the presence and species identity of shrubs influence the distribution of ground-dwelling arthropods and whether the influence of shrub presence and species identity differs among trophic and taxonomic groups. At the community level, total arthropod abundance and species richness were significantly greater under shrubs than in intershrub bare habitats, whereas more arthropods were captured under N. sphaerocarpa than under R. soongorica. At the trophic group level, the abundance of predator and decomposer arthropods was significantly greater under shrubs than in intershrub bare habitats, whereas herbivore and decomposer arthropods were more abundant under N. sphaerocarpa than under R. soongorica. At the family level, the abundance of Carabidae, Gnaphosidae, Karschiidae, Tenebrionidae and Thomisidae was consistently much greater under shrubs than in intershrub bare habitats, whereas that of Formicidae, Philodromidae and Tettigoniidae did not differ between the shrub microhabitats and the intershrub bare habitats. However, the abundance of Curculionidae under R. soongorica and the abundance of Geotrupidae under N. sphaerocarpa were significantly lower than that in intershrub bare habitats. N. sphaerocarpa was commonly preferred by arthropods in the families of Curculionidae and Tenebrionidae, whereas R. soongorica was commonly preferred by arthropods in the family Geotrupidae, but shrub species identity did not affect the abundance of the remaining families. Our results suggest that shrubs and species identity play important roles in structuring ground-dwelling arthropod communities, but the response of arthropods differed among trophic or taxonomic groups. This study may have important implications for the conservation of invertebrate biodiversity in Gobi desert ecosystems.     

Changes in arthropod diversity along a land use driven gradient of shrub cover in savanna rangelands: identification of suitable indicators

Shrub encroachment linked to heavy grazing has dramatically changed savanna landscapes, and is a major form of rangeland degradation. Our understanding of how shrub encroachment affects arthropod communities is poor, however. Here, we investigate the effects of shrub encroachment on abundance and diversity of ground-dwelling (wingless) arthropods at varying levels of shrub cover in the southern Kalahari. We also ascertain if invertebrate assemblage composition changes with habitat structure and identify which aspects of habitat structure (e.g., grass cover, herbaceous plant cover, shrub density) correlate most strongly with these changes. Ant, scorpion and dung beetle abundance increased with shrub cover, whereas grasshoppers and solifuges declined. Spider and beetle abundance exhibited hump-shaped relationships with shrub cover. RTU richness within orders either mirrored abundances, or exhibited no trend. Shrub density was the habitat component most correlated with similarities between invertebrate assemblages. Ground-dwelling arthropods showed clear shifts in species assemblage composition at a similarity level of 65% according to shrub density. Changes in indicator species showed that within the Tenebrionidae (darkling beetles), certain species respond positively to shrub thickening, replacing other species within the Family. Small-bodied, wingless Scarabaeidae (dung beetles) tended to increase with increased shrub density and three species emerged as significant indicators of more thickened habitats, although this might be a response to greater dung availability, rather than habitat structure itself. We conclude that because ground-dwelling invertebrates showed such clear responses in species assemblage composition, they present excellent candidates for use as indicator species in further studies into bush encroachment.     

Declines in a ground-dwelling arthropod community during an invasion by Sahara mustard (Brassica tournefortii) in aeolian sand habitats

Sahara Mustard (Brassica tournefortii; hereafter mustard), an exotic plant species, has invaded habitats throughout the arid southwestern United States. Mustard has reached high densities across aeolian sand habitats of southwestern deserts, including five distinct sand habitats in the eastern Coachella Valley, California. We examined trends in ground-dwelling arthropod community structure concurrent with mustard invasion in 90 plots within those habitats from 2003 to 2011 (n = 773 plot·years). We expected arthropod communities to respond negatively to mustard invasion because previous work documented significant negative impacts of mustard on diversity and biomass of native plants, the primary resource base for many of the arthropods. Arthropod abundance and species richness declined during the study period while mustard cover increased, and arthropod metrics were negatively related to mustard cover across all plots. When controlling for non-target environmental correlates (e.g. perennial frequency and precipitation) and for potential factors that we suspected of mediating mustard effects (e.g. native cover and sand compaction), negative relationships with mustard remained statistically supported. Nevertheless, arthropod richness’s relationship decreased slightly in strength and significance suggesting that mechanistic pathways may be both direct (via habitat structure) and indirect (via native cover suppression and sand compaction). However, mechanistic pathways for mustard effects, particularly on arthropod abundance, remain unclear. Most arthropod taxa, including most detritivores, decreased through time and were negatively related to mustard cover. In contrast, many predators were positively related to mustard. In total, our study provides substantial evidence for a negative effect of Sahara mustard on the structure of a ground-dwelling arthropod community.     

Impact of the invasive moss Campylopus introflexus on carabid beetles (Coleoptera: Carabidae) and spiders (Araneae) in acidic coastal dunes at the southern Baltic Sea

Campylopus introflexus is an invasive moss in Europe and North America that is adapted to acidic and nutrient-poor sandy soils with sparse vegetation. In habitats like acidic coastal dunes (grey dunes) it can reach high densities, build dense carpets and modify habitat conditions. While the impact of the moss invasion on the vegetation is well analyzed, there is a lack of knowledge regarding possible effects on arthropods. In the present study we analyzed the impact of Campylopus introflexus on the ground-dwelling arthropods carabid beetles and spiders, as both taxa are known to be useful indicator taxa even on a small-scale level. In 2009 we compared species composition in a) invaded, moss-rich (C. introflexus) and b) native, lichen-rich (Cladonia spp.) acidic coastal dunes by using pitfall traps. A total of 1,846 carabid beetles (39 species) and 2,682 spiders (66 species) were caught. Species richness of both taxa and activity densities of spiders were lower in invaded sites. Species assemblages of carabids and spiders differed clearly between the two habitat types and single species were displaced by the moss encroachment. Phytophagous carabid beetles, web-building spiders and wolf spiders were more abundant in native, lichen-rich sites. Shifts in species composition can be explained by differences in the vegetation structure, microclimate conditions and most likely a reduced food supply in invaded sites. By forming dense carpets and covering large areas, the moss invasion strongly alters typical arthropod assemblages of endangered and protected (EU-directive) acidic coastal dunes.