Responses of soil microarthropods to warming and increased precipitation in a semiarid temperate steppe

Soil microarthropods are an important component in soil food webs and their responses to climate change could have profound impacts on ecosystem functions. As part of a long-term manipulative experiment, with increased temperature and precipitation in a semiarid temperate steppe in the Mongolian Plateau which started in 2005, this study was conducted to examine effects of climate change on the abundance of soil microarthropods. Experimental warming had slightly negative but insignificant effects on the abundance of mites (−14.6%) and Collembola (−11.7%). Increased precipitation greatly enhanced the abundance of mites and Collembola by 117 and 45.3%, respectively. The response direction and magnitude of mites to warming and increased precipitation varied with suborder, leading to shifts in community structure. The positive relationships of mite abundance with plant cover, plant species richness, and soil microbial biomass nitrogen suggest that the responses of soil microarthropods to climate change are largely regulated by food resource availability. The findings of positive dependence of soil respiration upon mite abundance indicate that the potential contribution of soil fauna to soil CO₂ efflux should be considered when assessing carbon cycling of semiarid grassland ecosystems under climate change scenarios.     

Relating microarthropod community structure and diversity to soil fertility manipulations in temperate grassland

We aimed to identify patterns of diversity in a below-ground community of microarthropods (mites and Collembola) after 15 months of a nutrient (calcium and nitrogen) manipulation experiment, located at the Natural Environment Research Council (NERC) Soil Biodiversity Site in Scotland, UK. We found that microarthropod densities increased with elevated soil fertility, but we detected no concurrent change in the diversity of soil microarthropods (mites and Collembola combined). That microarthropod density increased concurrently with improvements in soil fertility and plant productivity suggests that soil microarthropod communities are predominately regulated by bottom-up forces, driven by increased energy transfer via plant inputs to soil, providing increased food resources for fauna. However, that we found no concurrent change in the diversity of soil microarthropods provides little support for the idea that the diversity of soil fauna is positively related to their population density, primary productivity or improvements in soil conditions resulting from nutrient manipulations. However, we did find that microarthropod communities of more fertile sites contained a greater proportion of predators suggesting that more energy was transferred to higher trophic levels under elevated soil fertility. Our findings suggest that unlike plant communities, soil faunal diversity may not be strongly regulated by competition in productive situations, since competitive exclusion might not occur due to increased predation. Whilst we conclude that soil microarthropod diversity at our study site has not been affected by the nutrient additions to date, in the longer term we predict that changes in community composition and diversity could arise, most likely through top-down regulation of the soil food web.     

Influence of disturbance and nitrogen addition on plant and soil animal diversity in grassland

Two key determinants of biological diversity that have been examined in aboveground and aquatic systems are productivity, or resource supply, and physical disturbance. In this study, we examined how these factors interact under field conditions to determine belowground diversity using microarthropods (mites and Collembola) as our test community. To do this, we established a field manipulation experiment consisting of crossed, continuous gradients of nitrogenous (N) fertilizer addition (up to 240 kg N ha^?1) and disturbance (imitated trampling by cattle) to produce a gradient of soil nutrient availability and disturbance. Due to the relatively short-term nature of our study (i.e. 2 years), we only detected minimal changes in plant diversity due to the experimental manipulations; in the longer term we would expect to detect changes in plant diversity that could potentially impact on soil fauna. However, disturbance reduced, and additions of N increased, aboveground biomass, reflecting the potential effects of these manipulations on resource availability for soil fauna. We found that disturbance strongly reduced the abundance, diversity, and species richness of oribatid mites and Collembola, but had little effect on predatory mites (Mesostigmata). In contrast, N addition, and therefore resource availability, had little effect on microarthropod community structure, but did increase mesostigmatan mite richness and collembolan abundance at high levels of disturbance. Oribatid community structure was mostly influenced by disturbance, whereas collembolan and mesostigmatan diversity were responsive to N addition, suggesting bottom-up control. That maximal species richness of microarthropod groups overall occurred in undisturbed plots, suggests that the microarthropod community was negatively affected by disturbance. We found no change in microarthropod species richness with high N additions, where plant productivity was greatest, indicating that soil biotic communities are unlikely to be strongly regulated by competition. We conclude that the diversity of soil animals is best explained as a combination of their many varied life history tactics, phenology and the heterogeneity of soils that enable so many species to co-exist.     

Soil fauna feeding activity in temperate grassland soils increases with legume and grass species richness

Edaphic fauna contributes to important ecosystem functions in grassland soils such as decomposition and nutrient mineralization. Since this functional role is likely to be altered by global change and associated shifts in plant communities, a thorough understanding of large scale drivers on below-ground processes independent of regional differences in soil type or climate is essential. We investigated the relationship between abiotic (soil properties, management practices) and biotic (plant functional group composition, vegetation characteristics, soil fauna abundance) predictors and feeding activity of soil fauna after accounting for sample year and study region. Our study was carried out over a period of two consecutive years in 92 agricultural grasslands in three regions of Germany, spanning a latitudinal gradient of more than 500 km. A structural equation model suggests that feeding activity of soil fauna as measured by the bait-lamina test was positively related to legume and grass species richness in both years. Most probably, a diverse vegetation promotes feeding activity of soil fauna via alterations of both microclimate and resource availability. Feeding activity of soil fauna also increased with earthworm biomass via a pathway over Collembola abundance. The effect of earthworms on the feeding activity in soil may be attributed to their important role as ecosystem engineers. As no additional effects of agricultural management such as fertilization, livestock density or number of cuts on bait consumption were observed, our results suggest that the positive effect of legume and grass species richness on the feeding activity in soil fauna is a general one that will not be overruled by regional differences in management or environmental conditions. We thus suggest that agri-environment schemes aiming at the protection of belowground activity and associated ecosystem functions in temperate grasslands may generally focus on maintaining plant diversity, especially with regard to the potential effects of climate change on future vegetation structure.     

Collembola species composition and diversity effects on ecosystem functioning vary with plant functional group identity

The relationship between decomposer diversity and ecosystem functioning is little understood although soils accommodate a significant proportion of worldwide biodiversity. Collembola are among the most abundant and diverse decomposers and are known to modify plant growth. We examined the effects of Collembola species diversity (one, two and three species belonging to different life history groups) and composition on litter decomposition and the performance of plant communities (above- and belowground productivity) of different functional groups (grasses, forbs and legumes). Collembola densities did not increase with diversity indicating niche overlap. Generally, Collembola species composition was a better predictor for ecosystem functioning than Collembola species number with the impacts of Collembola diversity and composition on ecosystem functioning strongly depending on plant functional group identity. Non-linear effects of Collembola diversity on litter decomposition and plant productivity suggest pronounced and context dependent species interactions and feeding habits. Net surface litter decomposition was decreased by Collembola, whereas root litter decomposition was at maximum in the highest Collembola diversity treatment. Forbs benefitted most from the presence of three Collembola species. Similarly, Collembola diversity influenced root depth distribution in a plant functional group specific way: while grass root biomass decreased with increasing Collembola diversity in the upper and lower soil layer, legume root biomass increased particularly in the lower soil layer. Idiosyncratic and context dependent effects of Collembola diversity and composition even in rather simple assemblages of one to three species suggest that changes in Collembola diversity may have unpredictable consequences for ecosystem functioning. The finding that changes in Collembola performance did not directly translate to alterations in ecosystem functioning indicates that response traits do not necessarily conform to effect traits. Distinct plant functional group specific impacts of Collembola diversity on root depth distribution are likely to modify plant competition in complex plant communities and add a novel mechanism how decomposers may affect plant community assembly.     

铅锌矿区周边农田土壤跳虫群落特征与重金属污染的关联

以云南兰坪铅锌矿区周边的农田为对象,按距矿区距离设四条样带,每个样带按距河流由近至远等距选3个样点进行定量采样,测定和分析土壤跳虫物种多样性和群落结构、土壤重金属含量和理化性质、及跳虫体内的铅含量.共获跳虫26种,平均密度12042 ind·m2.样点与矿区或河流距离增加,土壤中镉、铅和锌含量下降,跳虫体内重金属含量下...     

The effects of reduced-impact logging practices on soil animal communities in the Deramakot Forest Reserve in Borneo

The effectiveness of reduced-impact logging practices on the maintenance of biodiversity in Borneo has been recognized for some organisms (e.g., mammals). We investigated the effects of reduced-impact logging and conventional selective logging practices on biodiversity by using soil fauna as indicators of disturbance. The study sites were the production forests of the Deramakot Forest Reserve and the Tangkulap Forest Reserve in Sabah, Malaysian Borneo (5°14–30′ N, 117°11–36′ E). We compared macro- and mesofauna in a pristine forest with no logging, a reduced-impact logged forest in Deramakot Forest Reserve, and a conventionally logged forest in Tangkulap Forest Reserve.The mean density of soil macrofauna (excluding ants) did not differ significantly among the three forest categories (nested ANOVA, p > 0.05). This tendency was also seen in the density and species richness of Oribatida and Collembola, which showed little difference among forest categories. Nonmetrical multidimensional scaling (NMS) ordination diagrams revealed a different community composition in conventionally logged forest sites compared with the other sites. The scores for the NMS first or second axis of soil fauna were correlated with one or more of the values for density, diversity, and species composition of trees. A RELATE test showed the congruence between trees and the Collembola and Oribatida community composition between sites. The results implied that the soil fauna community composition was related to tree communities. In conclusion, the impacts of logging on decomposers in the soil animal communities have been mitigated by the introduction of reduced-impact logging in Deramakot Forest Reserve through the protection of tree vegetation. It is important to consider monitoring the influence of selective logging on soil fauna with regard to the dynamics of the species (or group) composition because total density and species (or group) richness of soil fauna displayed only a marginal response to the different logging practices.     

弹尾目昆虫在土壤重金属污染生态风险评估中的应用

土壤弹尾目昆虫作为无脊椎动物和中型土壤动物的典型代表,其具有丰富的种类和巨大的生物量,在重金属污染环境评估中具有十分重要的地位和独特的优势。本文简要概述弹尾目昆虫在污染土壤生态风险评估中、生态毒理学研究以及其他相关生物标志物研究上的一些方法体系及检测主要指标参数（群落结构,种群特征,生存率,生长率,繁殖率,金属硫蛋白和酶活指标）。最后对弹尾目昆虫在重金属污染土壤生态风险评估应用中目前存在的一些问题和应用前景进行了分析讨论。     

Collembola abundances and assemblage structures in conventionally tilled and conservation tillage arable systems

Reduced biodiversity is associated with increased management intensity and reduced environmental heterogeneity but reduced tillage has been shown to lessen the severity of the effects. In this study we compare the effects, on the abundance and assemblage structure of Collembola, of conventional tillage with a form of reduced tillage management called ECOtillage and we examine the responses of the Collembola to straw incorporation into the soil. Conservation tillage (ECOtillage) resulted in elevated abundances of most collembolan species compared with conventional tillage practices but has little effect on species richness. The addition of straw residue did not enhance the diversity of Collembola and reduced overall abundances.     

人工油松林中跳虫群落恢复状况

Large areas of forest plantations have been developed in China.It is important to evaluate the soil fauna in plantations and the conditions needed for their recovery in view of the large areas of plantations in China.Three Pinus tabulaeformis forests,a 26-year-old plantation (P26) and a 45-year-old plantation (P45),exposed to clear-cutting before plantation,and an 80-260-year-old natural forest (N260),were chosen to study the effects of different forest ages/types on Collembola community in the litter and soil layers during 2008 and 2009.Soil conditions in P26 and P45 were significantly deteriorated when compared to N260.A higher value of soil bulk density and lower values of soil organic matter,soil N,litter depth,soil pH,and soil water content were observed in P26 and P45.Totally,the same genera of Collembola tended to occur in the forests of all ages studied;however,the Collembola community structure was significantly impacted by the differences in forest age.Both in the litter and soil layers,the density and generic richness of the Collembola were the highest in N260 and the lowest in P26.Some collembolan groups were sensitive to soil conditions in particular forest ages.N260 was associated with relatively high abundance of Plutomurus collembolans and P45 with relatively high abundance of Pseudofolsomia collembolans.The canonical correspondence analysis showed that the community structure of Collembola was mainly affected by forest age in both litter and soil layer.The ordination analysis of non-metric multidimensional scaling also found that the Collembola community did not recover to the level of natural forests in 26-year regeneration after clear-cutting.Even in 45-year regeneration after clear-cutting,the Collembola community only showed a slight recovery to the level of natural forests.Our results clearly showed that both Collembola community and soil conditions did not recover in 26-and 45-year regeneration after clear-cutting in P.tabulaeformis plantations;however,they might have the potential to recover in the future because the same genera of Collembola were distributed in the plantations and natural forests.     

ABSTRACT of the Articles Printed in Journal of the Science of Soil and Manure,Japan

Changes in soil moisture determine the reproductive, respiratory, and metabolic activities of soil microorganisms and hence the rate of microbial nitrogen (N) mineralization. Soil moisture also affects the feeding activity and movement of soil invertebrates. Bacterial and fungal grazing by soil invertebrates such as Collembola and nematodes is known to increase N mineralization by increasing the reproductive, respiratory, and metabolic activities of microorganisms. Therefore, to assess the effect of soil moisture on N mineralization, faunal responses need to be considered. We used microcosms to investigate the effect of soil moisture on N mineralization mediated by a species of Collembola, Folsomia candida Willem. We used four moisture levels corresponding to matric potentials of ?42.5, ?11.8, ?0.8, and ?0.5 kPa and investigated the effects of these on Collembola with respect to feeding activity, growth, and contribution to N mineralization. The microbial biomass and ratio of bacterial to fungal biomass tended to increase with increasing soil moisture. Collembola feeding activity and growth increased with increasing soil moisture conditions. Collembola significantly enhanced N mineralization in soil at water potentials of ?11.8 and ?0.5?kPa. The greatest relative increase in N mineralization attributed to Collembola occurred in the ?11.8?kPa treatment. The change in contribution of the Collembola to N mineralization with soil moisture was most likely induced by changes in Collembola feeding activity and microbial community structure. The growth in body length of the Collembola was significantly greater at higher moisture conditions than at the lowest moisture condition, indicating that increases in both metabolic activity and biomass of the Collembola population contributed to the enhanced N mineralization.     

The Collembola community of pure and mixed stands of beech (Fagus sylvatica) and spruce (Picea abies) of different age

The idea of establishing mixed forests that are better adapted to site conditions than spruce monocultures has attracted increasing attention of forest owners and governmental institutions over the last decades. Currently, beech is being replanted and an increasing proportion of German forests are mixed stands. Focusing on the reaction of the soil fauna to forest conversion, this study investigates the response of the Collembola community to replacement of beech by spruce or by mixed stands of beech and spruce. Stands of different age were investigated in a factorial design with the factors stand type (beech, spruce and mixed stands) and stand age (30 and 120 years). Collembola communities did not differ strongly between stand types and stand age and were dominated by Folsomia quadrioculata and Mesaphorura species (e.g. Mesaphorura macrochaeta). Moreover, neither total abundance of Collembola nor densities of the fungal feeding euedaphic Onychiurinae and Tullbergiinae significantly responded to stand type and stand age. The density of the epedaphic and partly herbivorous groups Symphypleona/Neelipleona and Entomobryidae in the 120-year-old stands significantly exceeded that in the 30-year-old stands; presumably, this was due to the well developed herb layer in the 120-year-old stands with more open canopies. Canonical correspondence analysis (CCA) of the Collembola community of the L/F horizon also indicated that most of the epigeic species were associated with the 120-year-old stands. Moreover, the diversity of Collembola significantly increased with forest age which likely reflects increased amount and diversity of food resources in the 120-year-old stands. The density of the hygrophilous species Fo. quadrioculata was significantly higher in the spruce than in the beech stands; probably this was due to the higher water content in litter of the spruce stands. Moreover, the results of the CCAs indicated that soil pH is an important structuring force for the Collembola communities. Overall, the results suggest that stand type and forest age impact Collembola communities, presumably via changes in the amount and quality of food resources, such as living plant and herb litter materials. The pronounced changes which occurred with forest age likely were related to the development of more dense and diverse herb layer in mature forests which provides additional food resources in particular for epedaphic species. On the other hand, dominant species/functional groups of Collembola, such as hemiedaphic species, appear to depend predominantly on abiotic factors, most importantly soil pH and soil water content.     

百草清除草剂对农田生态系统土壤动物群落结构的影响

用百草清除草剂对农田生态系统土壤动物进行染毒模拟实验,共获得土壤动物967个,隶属3门,6纲,10目。其中弹尾目、甲螨亚目为优势类群,其余为常见类群和稀有类群。实验结果表明,百草清除草剂处理组的动物种类和数量与对照组相比较明显减少,动物种类的减少主要取决于常见种类和稀有种类,动物数量的变化则主要是优势类群的数量消长。并且随着百草清溶液处理浓度的增加,土壤动物的种类和数量显著减少,但上、下层动物随染毒历时递减规律有所不同。     

退耕还茶地土壤动物群落结构及其动态变化

[目的]研究退耕还茶地土壤动物群落结构和季节变化特征,旨在为深入了解退耕还茶后土壤质量变化趋势及研究区生态系统的健康评价提供科学依据。[方法]以川西低山丘陵区名山区退林还茶地为对象,采用手捡法和干、湿漏斗法,并以相邻退耕还林地为对照进行研究。[结果]退耕还茶地土壤动物群落以蜱螨目(A)、线虫纲和弹尾目(C)为优势类群,其类群数、密度、Shannon-Wiener指数、密度—类群指数和群落复杂性指数均低于退耕还林地,而群落A/C值较大,且差异多达显著(p0.05)或极显著水平(p0.01)。退耕还茶地土壤动物类群数、个体数、密度—类群指数均以秋季最高,呈单峰曲线变化,且季节间波动大于退耕还林地。受2008年春季的冰冻天气影响,退耕还茶地土壤动物个体数、类群数和密度类群指数明显降低,并在2009年有一定回升,而退耕还林地动物群落结构受气候影响较小。[结论]退耕还茶地土壤动物群落对季节变化和低温天气等外界干扰反应较退耕还林地强烈,且对生态环境给予的负面刺激的反馈能力相对较差。与退耕还林相比,退耕还茶地生态系统可能存在更大的潜在风险。     

Limits to the bioindication potential of Collembola in environmental impact analysis: a case study of forest soil-liming and fertilization

We tested the suitability of the collembolan community as a bioindicator for assessing the effects of forest soil-liming and fertilization on the belowground decomposer community. Our investigation was based on a 5-year survey that took place in a German oak-hornbeam and spruce forest in which amelioration measures took place in 1988, 1994 and 1995, with chemical parameters and Collembola being sampled between 1993 and 1997. To address these questions, we applied new methods which have not yet, to our knowledge, been used in biomonitoring studies on forest soils. We used a time-lag analysis for the detection of directional change and a regression-tree induction to show the relationship between Collembola and soil factors. Soil parameters changed considerably after the onset of liming and fertilization. However, no change was detected in community composition over time, nor was there a relationship between Collembola and soil parameters that would make possible the development of a model with at least a moderate predictive success. Taking into account the effort invested in this study (5-year sampling period, identification of 35,000 Collembola, 99 species, 1,170 chemical analyses), we question the suitability of collembolan communities as a bioindicator for forest disturbance.     

模拟增温和降水调控对土壤微生物碳氮、群落基质利用模式及群落组成的短期影响

Soil microorganisms are major drivers of soil carbon(C) cycling;however,the response of these microorganisms to climate change remains unclear.In the present study,we investigated how 18 months of multifactor climate treatments(warmed air temperature by 3℃ and decreased or increased precipitation manipulation by 30%) affected soil microbial biomass C and nitrogen(N),community substrate utilization patterns,and community composition.Decreased and increased precipitation significantly reduced microbial biomass C by 13.5% and 24.9% and microbial biomass N by 22.9% and 17.6% in unwarmed plots,respectively(P0.01).Warming enhanced community substrate utilization by 89.8%,20.4%,and 141.4% in the natural,decreased,and increased precipitation plots,respectively.Particularly,warming significantly enhanced the utilization of amine and carboxylic acid substrates among all precipitation manipulation plots.Compared with the natural air temperature with natural precipitation treatment,other treatments affected fungal community richness by -0.9% to 33.6% and reduced the relative abundance of the dominant bacterial and fungal groups by 0.5% to 6.8% and 4.3% to 10.7%,respectively.The warming and/or precipitation manipulation treatments significantly altered Zygomycota abundance(P0.05).Our results indicate that climate change drivers and their interactions may cause changes in soil microbial biomass C and N,community substrate utilization patterns,and community composition,particularly for the fungal community,and shifts in the microorganism community may further shape the ecosystems function.     

Management intensity affects traits of soil microarthropod community in montane spruce forest

This study examined the influence of forest management intensity (3 unmanaged, 3 mild managed, 5 intensively managed stands) on soil microarthropods in montane spruce forest. We particularly focused on Oribatida and Collembola which play important roles in organic matter decomposition and nutrient cycling. Our results showed a significant shift from fungivory and carnivory to detritivory in the Oribatida community accompanying management intensification. Similarly, parthenogenetic oribatid mite species contributed more to the community in intensively managed forests and the presence of Collembola species with developed furca increased with management intensification. Although there was no remarkable influence of management intensity on total densities or diversity indices, important and significant shifts in species composition and functional groups showed that soil functions and processes were affected by forest management. Trait assessment indicates a shift in roles Oribatida play in decomposition; fragmentation and comminuting of undecomposed litter seems to gain importance in the intensively managed forest, whereas fungivorous species affect primary decomposers through feeding on fungi in the unmanaged forest.     

土壤动物与土壤健康

土壤动物与土壤健康息息相关,土壤动物多样性和功能能够灵敏反映人类活动和气候变化引起的土壤扰动。同时,土壤动物还通过与生物和非生物组分间的相互作用对地上生态系统产生反馈作用。当前土壤动物在土壤健康评价体系中的应用相对较少,主要集中在土壤线虫、节肢动物和蚯蚓等类群,仍缺乏基于土壤动物的系统性评价指标。因此,本文围绕土壤动物在指示土壤健康方面的潜力,系统总结了现有基于土壤动物的土壤健康评价指标,强调未来应建立和完善土壤动物基因组信息数据库,挖掘土壤动物的功能性状,加强土壤食物网结构和生态功能的研究,建立集成土壤动物物种多样性、功能性状和土壤食物网的指标体系,从而促进土壤健康和生态系统的可持续发展。     

浙江天台山七子花林土壤动物群落结构特征与动态变化

2000年4月至2001年4月逐月对浙江天台山七子花林土壤动物群落特征进行调查研究,初步分析凋落物、季节、海拔等因素对土壤动物群落结构的影响。结果表明:(1)蜱螨目(57.06%)和弹尾目(21.21%)为七子花林的优势类群,膜翅目(4.72%)、双翅目(3.65%)、综合纲(2.74%)、寡毛纲(2.68%)和鞘翅目(2.57%)为常见类群。(2)七子花林各样地土壤动物的个体数量在5月份和11月份都表现为峰值,在7月份至8月份的干热期个体数量明显下降。(3)处于中海拔地区(780m)呈共优群落的七子花林样地土壤动物的密度最大、类群数最多、多样性指数最高。(4)各样地土壤动物在土层中的垂直分布表现出明显表聚性特点,然而,在7月份至8月份的干热期,出现底层土壤动物个体数量多于表层的逆分布现象。     

Soil arthropods beneficially rather than detrimentally impact plant performance in experimental grassland systems of different diversity

Impacts of belowground insecticide application on plant performance and changes in plant community structure almost uniformly have been ascribed to reduced belowground herbivory, although recent studies reported distinct side effects on detritivore soil animals, particularly on Collembola. Consequently, it remains controversial if the resulting soil feedbacks on plants are due to alterations in arthropod herbivory or to changes in the activity of detritivores. We investigated the impacts of the application of a commonly used belowground insecticide (chlorpyrifos) on soil animals and soil feedbacks on model plant species representing two main plant functional groups of grassland communities, the grass Lolium perenne and the forb Centaurea jacea.Insecticide application decreased soil insect herbivore densities considerably. However, also Collembola densities and diversity decreased markedly due to insecticide application and this was most pronounced in Entomobryidae, Isotomidae, Hypogastruridae, and Sminthuridae. While densities of other detritivore taxa were not affected or even increased (Oribatida) in insecticide subplots, that of predators mostly decreased.Both model plant species built considerably more biomass in control subplots than in insecticide subplots irrespective of characteristics of the resident plant community. This suggests that soil feedbacks on plants were not due to belowground herbivory and highlights the significance of alternative mechanisms responsible for insecticide-mediated soil feedbacks on plants. The deterioration of model plant species’ performances in insecticide subplots most likely was due to decreased densities of Collembola resulting in the deceleration of nutrient cycling and plant nutrition. The results suggest that it is oversimplistic to only ascribe insecticide-mediated soil feedbacks on plants to belowground herbivores. The results further indicate that in the present study the impact of arthropod detritivores on plant productivity was more important than that of belowground herbivores. This emphasizes that plant-soil arthropod interactions in grassland might be based on both facilitative and antagonistic interrelationships.