Macroarthropod Community Research Articles

Invasive Glossy Buckthorn (Frangula alnus) Has Weak Impact on Native Understory Plant and Saprophagous Macroarthropod Communities

Glossy buckthorn (Frangula alnus Miller) is an invasive alien plant species (IAPS) rapidly expanding in North America but is largely understudied compared to the common buckthorn (Rhamnus cathartica). Our study investigated the effects of a 27-year-old F. alnus invasion on native understory plant and saprophagous macroarthropod communities in a wet deciduous woodland in Southern Québec, Canada. We hypothesized a decreased taxonomic diversity and a change in community composition of both indicator taxa with increasing F. alnus density. The understory plant and saprophagous macroarthropod communities were characterized, respectively, through vegetation surveys and pitfall trapping across a density gradient of 43 plots invaded by F. alnus. Our results demonstrated that F. alnus did not exert a strong influence on species community composition, although the homogenization of understory plant communities was observed. Despite several decades of F. alnus invasion at our study site, the consequences on the selected indicator taxa were overall relatively small, suggesting that the magnitude of effects is variable. We suggest that further investigation at a larger scale should be performed to evaluate the effect of F. alnus on a broad diversity of indicators and understand any context dependency.

Direct and indirect effects of linear non-cultivated habitats on epigaeic macroarthropod assemblages

Non-cultivated habitats are indispensable ecological spaces within agricultural landscapes that support biodiversity and associated ecosystem services on farmland, thereby contributing to sustainable agriculture. The abundance of taxonomic groups within these habitats serves as a reliable indicator of the diversity levels in epigaeic macroarthropod communities, while the functional groups offer insights into the trophic dynamics of macroarthropods. In recent decades, the impact of non-cultivated habitats on biodiversity within agricultural contexts has received increasing attention. However, few studies have focused on the pathways and factors that influence epigaeic macroarthropod assemblages in different non-cultivated habitats. In this study, Changtu County, a typical agricultural county in the Northeastern Black Soil Region of China, was selected as the study area. The functional and taxonomic groups of epigaeic macroarthropod abundance in different non-cultivated habitats were compared. The structural equation model (SEM) was used to evaluate the direct and indirect effects of non-cultivated habitat type, soil nutrients and vegetation structure reflecting major differences in non-cultivated habitat types on epigaeic macroarthropod assemblages. Our results showed that: (1) linear semi-natural non-cultivated habitats around fields can effectively enhance landscape connectivity. Among these habitats, woodlands (WL), grasslands (GL), and ditches (CD) with high herbaceous vegetation density are usually more favorable for biodiversity conservation in agricultural ecosystems. (2) While dirt roads (DR) and paved roads (PR) may affect the mobility and foraging ability of epigaeic macroarthropods, improving herbaceous vegetation structures along road margins (e.g., planting flowering plants, establishing vegetation buffer zones) can effectively enhance field biodiversity. (3) The characteristics of herbaceous vegetation community are the most important factors affecting the functional and taxonomic groups of epigaeic macroarthropods in different non-cultivated habitats, especially the herbaceous vegetation height (PAH) and species abundance (PAB). In addition, for epigaeic macroarthropods taxonomic groups, non-cultivated habitats affect them not only directly through herbaceous vegetation, but also indirectly through soil organic carbon (SOC). Our results emphasize that in the planning of agricultural landscapes, it is feasible to achieve a harmonious synergy between ecosystem stability and agricultural production through strategic allocation and alteration of herbaceous vegetation structure and soil conditions in different types of non-cultivated habitats.

Diversity and distribution patterns of soil macroarthropod communities in the Nianchu River Basin, Tibet, China

IntroductionThe study of how soil fauna interact with soil ecosystems is an important research field. At present, there has been little research on the diversity and distribution patterns of soil macroarthropods and on the relationship between soil fauna and environmental factors in Tibet.MethodsThe data collection for soil macroarthropods and soil samples was conducted using the plum blossom five-point sampling method. Subsequently, the gathered data were meticulously organized and analyzed through a blend of ecological and statistical approaches.ResultsIn total, 2880 soil macroarthropods were captured from 19 plots in the Nianchu River Basin, and the soil macroarthropod Hill numbers was at its lowest in spring. Sea buckthorn forest habitats had the highest Hill numbers. We found that Carabidae, Lycosidae, and Formicidae were always dominant species during seasonal changes in the Nianchu River Basin. Among the four different habitat types studied, Carabidae always appeared across the four studied habitat types and was one of the most significant taxa. The niche range of soil macroarthropods was wetland habitat > farmland habitat > sea buckthorn forest habitat > grassland habitat, and their community within sea buckthorn forest habitats was stable. The niche breadth of soil macroarthropods was the largest in summer, and the community was stable. Soil temperature and soil water content were the most important factors affecting the alpha diversity of soil macroarthropods, while altitude and soil temperature were the most important factors affecting their beta diversity.DiscussionIn summary, the results provide a comprehensive overview of the seasonal and habitat dynamics of soil macroarthropods in the Nianchu River Basin; it is strongly believed that the research carried out in this paper can contribute valuable information toward further research on the soil fauna diversity and ecological functions in this area and provide a strong scientific basis for the protection and sustainable development of the Nianchu River Basin ecosystem.

Glyphosate reduces the biodiversity of soil macrofauna and benefits exotic over native species in a tropical agroecosystem

Herbicides are the most applied pesticides in the world. Despite numerous laboratory studies demonstrating the toxic effect of herbicides on non-target organisms, the effect of herbicides on soil organisms in the field remains complex to understand and is still controversial. In order to understand how changes in agricultural practices aiming to reduce herbicide use could impact soil biodiversity, we studied the effect of the frequency of herbicide application on soil biodiversity in a tropical agroecosystem.Our study was conducted on banana farms in Martinique, an island with a humid tropical climate belonging to the Caribbean biodiversity hotspot. Thirteen banana plots from five different farms were selected, ranging from plots receiving no herbicides to plots receiving 4–5 applications per year. Soil macro-arthropods were sampled using pitfall traps resulting in the collection of over 6,200 individuals. Of the 100 taxa that were differentiated, 75 could be identified to species level which allowed to assign each taxon to a trophic group and when possible to classify them according to whether they were introduced or native.Macro-arthropod mean species richness was 21% lower in plots with the highest frequency of herbicide application. However, no conclusive effect of herbicides on macro-arthropod abundance was demonstrated. Mean species richness for different trophic groups also decreased with herbicide applications with decreases of 22% for predators, 17% for omnivores, 55% for herbivores, and 55% for decomposers in plots with 4–5 herbicide applications per year compared to plots with no herbicide use. Species composition of macro-arthropod communities varied significantly with herbicide applications. More specifically, we found that native species represented a higher proportion of individuals captured in plots where no herbicides were used; suggesting that agroecological practices implemented at the field level to reduce the frequency of herbicide use potentially play a relevant role in soil biodiversity conservation.

Ants offset bottom-up control of spiders in Amazonian savanna trees

Community trophic structure is shaped by concurrent bottom-up (resources) and top-down effects (predators), but the extent to which they interact remains uncertain. The Exploitation Ecosystems Hypothesis predicts that predators should offset increases in herbivore abundance with plant productivity, which is supported by data. However, the extent to which interactions within trophic levels (e.g. competition, intraguild predation) have similar effects is less clear. Ants and spiders are abundant in vegetation and consume similar arthropod prey (occasionally each other) and plant exudates, with ants generally showing competitive dominance over spiders. We tested whether ants could shape the trophic structure of tree-dwelling macroarthropod communities by offsetting increases in spider abundance with insect prey. We performed three surveys of the macroarthropod community of 97 trees from two sites in the savanna of Northern Amazonia. Together, ants and spiders represented 74% of the sampled individuals per tree. Insect prey abundance increased with tree crown volume and crown flower cover, consistent with bottom-up limitation. Likewise, both ants and spiders increased with insect prey abundance, with ant abundance also varying with tree species, suggesting reliance on both animal and plant resources. However, as predicted, the positive relationship between spider abundance and insect prey abundance disappeared as ant abundance increased. Our results suggest that agonistic interactions within trophic levels can strongly shape community structure and size by modifying bottom-up effects as much as interactions across trophic levels.

Does habitat type in no‐tillage agroecosystems influence ground‐dwelling macroarthropod community structure? A case study in KwaZulu‐Natal, South Africa

AbstractLoss of biodiversity in agroecosystems has negative implications for crop production and the functioning of the ecosystem. As such, agroecologists advocate minimum tillage practices in order to conserve biological diversity. To establish the influence of agricultural practices on biodiversity, we compared the species richness, abundance and composition of beetles, ants, spiders and small groups of ground dwelling arthropods in a veld and three agroecosystems (maize, sugarcane and multispecies pasture) under minimum tillage. Sampling was by pitfall trapping during the summer rainfall season in December 2019. Although ants were the most abundant (47%), followed by beetles (31%); beetles were the most speciose making up 40% of the morphospecies followed by spiders (31%). The veld had significantly greater relative proportion of species richness of spiders (54%) than the three agroecosystems, while significantly low relative proportion of species richness of ants was in the pasture (6%) compared to the veld (63%). Species richness and abundance of beetles were similar across habitat types. The four habitats supported different assemblages of ants, beetles and spiders. The differences in species composition among the habitats support the notion that agricultural practices with minimum soil disturbance enhance conservation of biological diversity, particularly, specialist species.

Soil macroarthropod community and soil biological quality index in a green manure farming system of the Brazilian semi-arid

Soil macroarthropods are organisms considered as key factors to sustain soil quality and sustainability due to their services to soil ecosystem. The community structure and seasonal variation of soil macroarthropods in 5-year cultivation of green manure plant species in the Brazilian semi-arid, Areia, Paraiba, Brazil were investigated between June and December 2018. Soil samples and macroarthropod specimens were collected using soil cores and Provid-type traps, respectively, during rainy and dry seasons. We characterized both soil chemical properties and macroarthropod community under ten green manure plant species: Brachiaria decumbens Stapf. cv. Basilisk, Canavalia ensiformis (L.) DC, Crotalaria juncea L., Crotalaria ochroleuca G. Don, Crotalaria spectabilis Roth, Lablab purpureus (L.) Sweet, Mucuna pruriens (L.) DC., Neonotonia wightii (Wight & Arn.) J.A. Lackey, Pennisetum glaucum L., and Stilozobium aterrimum Piper & Tracy. The highest values of richness, diversity and dominance in the macroarthropod community during the rainy season were found on the plots where C. spectabilis and M. pruriens were cultivated, whereas during the dry season the highest values were found in the plots where C. ochroleuca, C. spectabilis, and S. aterrimum were cultivated. In the plots where B. decumbens and P. glaucum where cultivated, we found lower values of richness, diversity, and dominance in the macroarthropod community compared to the leguminous plant species during rainy and dry seasons. Our findings suggest that: 1) green manure practice and seasonality changed soil macroarthropod community, trophic structure, and ecological processes in semi-arid conditions; and 2) abundance of predators, ecosystem engineers, decomposers and herbivores was promoted by plant species from Fabaceae family. The results highlight the importance to consider plant species from Fabaceae family as habitat and food resources for soil fauna community.

Correction: Molinas-González, C.R. et al. Effects of Post-Fire Deadwood Management on Soil Macroarthropod Communities. Forests 2019, 10(11), 1046

The authors wish to correct the following corrections in this paper [...]

Effects of Post-Fire Deadwood Management on Soil Macroarthropod Communities

Dead wood comprises a vast amount of biological legacies that set the scene for ecological regeneration after wildfires, yet its removal is the most frequent management strategy worldwide. Soil-dwelling organisms are conspicuous, and they provide essential ecosystem functions, but their possible affection by different post-fire management strategies has so far been neglected. We analyzed the abundance, richness, and composition of belowground macroarthropod communities under two contrasting dead-wood management regimes after a large wildfire in the Sierra Nevada Natural and National Park (Southeast Spain). Two plots at different elevation were established, each containing three replicates of two experimental treatments: partial cut, where trees were cut and their branches lopped off and left over the ground, and salvage logging, where all the trees were cut, logs were piled, branches were mechanically masticated, and slash was spread on the ground. Ten years after the application of the treatments, soil cores were extracted from two types of microhabitat created by these treatments: bare-soil (in both treatments) and under-logs (in the partial cut treatment only). Soil macroarthropod assemblages were dominated by Hemiptera and Hymenoptera (mostly ants) and were more abundant and richer in the lowest plot. The differences between dead-wood treatments were most evident at the scale of management interventions: abundance and richness were lowest after salvage logging, even under similar microhabitats (bare-soil). However, there were no significant differences between microhabitat types on abundance and richness within the partial cut treatment. Higher abundance and richness in the partial cut treatment likely resulted from higher resource availability and higher plant diversity after natural regeneration. Our results suggest that belowground macroarthropod communities are sensitive to the manipulation of dead-wood legacies and that management through salvage logging could reduce soil macroarthropod recuperation compared to other treatments with less intense management even a decade after application.

Vegetation Heterogeneity Effects on Soil Macro-Arthropods in an Alpine Tundra of the Changbai Mountains, China.

The harsh environmental conditions in alpine tundra exert a significant influence on soil macro-arthropod communities, yet few studies have been performed regarding the effects of vegetation heterogeneity on these communities. In order to better understand this question, a total of 96 soil macro-arthropod samples were collected from four habitats in the Changbai Mountains in China, namely, the Vaccinium uliginosum habitat, Sanguisorba sitchensis habitat, Rhododendron aureum habitat, and Deyeuxia angustifolia habitat. The results revealed that the taxonomic composition of the soil macro-arthropods varied among the habitats, and that dissimilarities existed in these communities. The abundance, richness and diversity in the D. angustifolia habitat were all at their maximum during the sampling period. The vegetation heterogeneity affected the different taxa of the soil macro-arthropods at various levels. In addition, the vegetation heterogeneity had direct effects not only on soil macro-arthropod communities, but also indirectly impacted the abundance, richness and diversity by altering the soil fertility and soil texture. Overall, our results provide experimental evidence that vegetation heterogeneity can promote the abundance, richness and diversity of soil macro-arthropods, yet the responses of soil macro-arthropods to vegetation heterogeneity differed among their taxa.

Cover crop farming system affects macroarthropods community diversity in Regosol of Caatinga, Brazil

The influence of a 3-years cultivation of legumes on macroarthropod community composition was investigated. Soil samples were taken from a field experiment which was conducted for three years to characterize the agronomic characteristics of eight cover crops: Crotalaria juncea L., Crotalaria spectabilis Roth, Crotalaria ochroleuca G. Don., Canavalia ensiformis (L.) DC., Mucuna pruriens (L.) DC., Dolichos lablab L., Neonotonia wightii (Wight & Arn.) J.A. Lackey, and Brachiaria decumbens Stapf. cv. Basilisk. The highest values of diversity in the macroarthropod community were found on the plot where M. pruriens was cultivated. Brachiaria decumbens cultivation showed lower values of species richness, Shannon’s diversity index and Simpson’s dominance index compared to the other studied plant species. Our findings suggest that the cultivation of legume cover crops can change positively the macroarthropod community composition. The results highlight the importance of considering the effects of legumes on the diversity of this biological component and their effect on plant growth and soil organic carbon contents. Thus, legumes may exploit positive feedback in semiarid conditions on a Regosol.

Variability of beetle assemblages in Mediterranean cork oak woodlands: does the higher taxa approach reliably characterize a specific response to grazing?

Studying macroarthropod community responses to different land uses is particularly interesting in agroforestry for the conservation of Mediterranean landscapes, which need to be managed in terms of ecological and functional sustainability. Because of the sensitivity of many taxa to human impacts, we assessed the response of beetle assemblages at low taxonomic resolution (i.e. family level) to grazing in Mediterranean cork oak woodlands in northern Sardinia (Italy). Scarab assemblages were also analysed at the species level because of their ecological role in grazed areas. Cork oak woodland descriptors were also recorded in order to relate beetle assemblages to the forest structure. Over the entire sampling period, 4550 beetles belonging to 47 families were captured using pitfall traps. Multivariate analyses performed on ground-dwelling beetle data showed a distinct separation in terms of assemblages between grazed and ungrazed sites. The average diameter of cork oak trees and the degree of shrub cover were significantly linked to the beetle family assemblages. Constrained multivariate analyses indicated the significance of grazing, by both large and small domestic herbivores, and altitude, as variables determining the pattern of scarab beetle assemblages. Mantel test showed a significant correlation between the beetle and scarab dissimilarity matrices indicating a similar pattern for the two levels of identification. Our results show the predictive power of beetles at the family taxonomic level, as well as scarab beetles at the species level. These turned out to be valuable indicators in biomonitoring programmes in Mediterranean cork oak woodlands in order to increase the resilience of cork oak agroforestry systems under future global change scenarios.

Characteristics of ground-dwelling soil macro-arthropod communities in a biodiversity monitoring plot of black soil cropland, northeastern China

Agro-ecosystem is an important component of terrestrial ecosystems and it is one of the key areas of global ecological and environmental studies. A 16 hm2 permanent plot in black soil cropland was built to study the community structure of soil biodiversity in typical black soil region in Northeast China. Pitfall trap was used to investigate the ground-dwelling soil macro-arthropods from August to October 2015 in accordance with the three crop growth stages: whirling stage, silking stage, and milk stage. A total of 5284 ground-dwelling soil macro-arthropods belonging to 47 species were captured sorted into 3 classes, 12 orders, 32 families. 3 dominant groups and 11 common groups were found. Phytophages and Omnivores were dominant groups. The individuals and species numbers of ground-dwelling soil macro-arthropods had significant changes with the vegetative growth period. The maximum values of the Shannon index, Margalef index, Pielou index of soil macro-arthropods all appeared in September, but the maximum dominant index appeared in August. From the variation coefficient (CV) and spatial interpolation of different species, it could be seen that there was heterogeneity in the horizontal direction of the ground-dwelling soil macro-arthropod communities. Regarding the relationships between the ground-dwelling soil macro-arthropod communities and soil environmental factors including soil pH, soil organic matter, total nitrogen and soil water content, the bivariate correlation analysis showed there was no significant correlation between them. Results of canonical correspondence analysis (CCA) further indicated that the dominant and common groups were adaptable to environmental factors and widely distributed in the study area. The results showed that the species richness of ground-dwelling soil macro-arthropods was very high in cropland, and the dynamic of soil arthropod's composition and spatial distribution pattern in diffe-rent crop growth stages were significantly changed. It was indicated that biodiversity plot monitoring of black soil cropland had become important means to solve the formation and maintenance mechanism of soil fauna community through large-scale and long-term investigation.

Impacts of Myriophyllum aquaticum invasion in a Mediterranean wetland on plant and macro-arthropod communities

The invasion by alien macrophytes in aquatic ecosystems may produce a strong alteration of the native aquatic vegetation leading to heavy impacts for both plant and faunal native diversity. Myriophyllum aquaticum is an aquatic plant native of Southern America, invasive in several part of the world. We studied the effects of M. aquaticum invasion on plant and macro-arthropod communities in the canals around a protected wetland in the Mediterranean basin. We sampled plant and macro-arthropod communities in 10 transects in invaded and non-invaded tracts of the canals. We assessed the differences in plant and macro-arthropod species richness, diversity, taxonomic diversity and species composition between invaded and non-invaded habitats by means of univariate and multivariate analyses. Our study shows a significant loss of plant diversity between non-invaded to invaded sites, leading to communities numerically and taxonomically impoverished and highly divergent in the species composition. We also detected significant differences in arthropod species composition between invaded and non-invaded transects. Some taxa such as mosquitoes and malacostraca were more frequent in the M. aquaticum-dominated stands. Furthermore, the study shows a positive relation between invaded habitats and juvenile individuals of the invasive alien crayfish Procambarus clarkii.

Long-term effects of alternative and conventional fertilization on macroarthropod community composition: a field study with wheat (Triticum aestivum L) cultivated on a ferralsol

The influence of long-term fertilization on macroarthropod community composition from a field study with wheat (Triticum aestivum) was investigated. Soil samples were taken from a long-term field experiment which was conducted for 5 years to explore the effect of three treatments: control (non-fertilization), conventional (mineral fertilizers—NPK), and alternative (organic fertilizers—farmyard manure). The highest values of macroarthropod community composition were found in the alternative fertilization system after the 30 years of its utilization. After 30 years, the conventional fertilization system showed lower values for these studied variables compared to alternative fertilization system. Our findings suggest that inputs of organic matter source can change positively the macroarthropod community composition, and these results highlight the importance of considering the long-term effect of mineral and organic fertilizers on the diversity of this biological component and their effect on wheat growth and soil fertility. Thus, the long-term utilization of an alternative fertilization system with continuous input of organic matter may exploit positive situations of jointly beneficial biotic and abiotic conditions.

Community responses of arthropods to a range of traditional and manipulated grazing in shortgrass steppe.

Responses of plants to grazing are better understood, and more predictable, than those of consumers in North American grasslands. In 2003, we began a large-scale, replicated experiment that examined the effects of grazing on three important arthropod groups-beetles, spiders, and grasshoppers-in shortgrass steppe of north-central Colorado. We investigated whether modifications of the intensity and seasonality of livestock grazing alter the structure and diversity of macroarthropod communities compared with traditional grazing practices. Treatments represented a gradient of grazing intensity by cattle and native herbivores: long-term grazing exclosures; moderate summer grazing (the traditional regime); intensive spring grazing; intensive summer grazing; and moderately summer-grazed pastures also inhabited by black-tailed prairie dogs (Cynomys ludovicianus Ord). Beetles and spiders were the most common groups captured, comprising 60% and 21%, respectively, of 4,378 total pitfall captures. Grasshopper counts were generally low, with 3,799 individuals observed and densities <4 m(-2). Two years after treatments were applied, vegetation structure differed among grazing treatments, responding not only to long-term grazing conditions, but also to the short-term, more-intensive grazing manipulations. In response, arthropods were, in general, relatively insensitive to these grazing-induced structural changes. However, species-level analyses of one group (Tenebrionidae) revealed both positive and negative effects of grazing treatments on beetle richness and activity-density. Importantly, these responses to grazing were more pronounced in a year when spring-summer rainfall was low, suggesting that both grazing and precipitation-which together may create the greatest heterogeneity in vegetation structure-are drivers of consumer responses in this system.

Effects of desertification on temporal and spatial distribution of soil macro-arthropods in Horqin sandy grassland, Inner Mongolia

The richness and density of soil macro-arthropods in 0–30cm soil were investigated by a method of space-for-time substitution from spring to autumn of 2008–2009 in Horqin Sand Land, Inner Mongolia, to understand the effects of grassland desertification on the temporal and spatial distribution of the soil macro-arthropod community. The results showed that: 1) grassland desertification had a serious damage to the soil macro-arthropod community, more serious in the summer than in the spring and autumn, and resulting in obvious change on seasonal distribution pattern of the soil macro-arthropod community; 2) the effects of desertification on trophic groups differed among seasons, with greater effects on predators in spring, phytozoa in summer, and omnivores in autumn; 3) from large to small, the order of richness and density was 0–10cm soil>10–20cm soil>20–30cm soil and 10–20cm>0–10cm soil>20–30cm in non-desertified grassland, respectively, and both changed gradually to 0–10cm soil≥20–30cm soil>10–20cm soil with desertification development; 4) with desertification development, the richness and density of phytozoa, predators, and omnivores all decreased significantly in different soil layers, with the magnitude of the decrease being lower for predators in 0–10cm soil and omnivores in 10–20cm and 20–30cm soil and greatest for phytozoa in all three soil layers; 5) with desertification development, the dominant family in the community changed gradually and the dominance of the dominant family intensified significantly; and 6) changes in the soil macro-arthropod community were attributed to the degradation of vegetation and deterioration of the soil environment in the desertification process, including notable decreases in vegetation cover, litter, soil clay and silt, soil organic carbon, and soil N and P.

Humus characteristics and seasonal changes of soil arthropod communities in a natural sessile oak (Quercus petraea L.) stand and adjacent Austrian pine (Pinus nigra Arnold) plantation

In order to assess the effects of conversion of natural stands into plantations, soil invertebrate micro- and macroarthropod communities were evaluated for their abundance and richness in a sessile oak (SO; Quercus petraea L.) stand and adjacent Austrian pine (AP; Pinus nigra Arnold) plantation. Sites were sampled four times a year in 3-month intervals from May 2009 to February 2010. Humus characteristics such as total mass; carbon, lignin, and cellulose contents; and C/N ratio were significantly different between SO and AP. Statistically significant differences were detected on soil pH, carbon and nitrogen contents, and electrical conductivity between the two sites. The number of microarthropods was higher in AP than in the SO site. The annual mean abundance values of microarthropods in a square meter were 67,763 in AP and 50,542 in SO, and the annual mean abundance values of macroarthropods were 921 m(-2) in AP and 427 m(-2) in SO. Among the soil microarthropods, Acari and Collembola were the dominant groups. Shannon's diversity index was more affected by evenness than species number despite the species diversity (H') of soil arthropods being generally higher in the SO stand. The abundance of microarthropods showed clear seasonal trends depending upon the humidity of the soil.

The “bug island” effect of shrubs and its formation mechanism in Horqin Sand Land, Inner Mongolia

Abstract In the moving sand dune of Horqin Sand Land (Inner Mongolia), the diversity of the soil macro-arthropod communities beneath the canopies of two shrub species (Caragana microphylla and Salix gordejevii) and in open areas was investigated in order to determine the effect of shrubs on these soil communities. The results showed that the shrubs facilitated the aggregation of soil macro-arthropods, resulting in significantly higher diversity and individual density of macro-arthropods in the soil beneath the shrub canopy compared to the open areas. This is known as the “bug island” effect. Although the dominant families in these three soil macro-arthropod communities were the same beneath the shrub canopy compared to open areas, many new macro-arthropod families also occurred in the shrub canopy communities, resulting in significant changes in the composition and structure of these soil communities. The “bug island” effect of the shrubs resulted from the “fertile island” effect generated by these shrubs, i.e., reduced wind velocity, retained dust and sand, increased soil litter biomass and soil moisture, improved soil texture and soil fertility. Between the two shrub species investigated C. microphylla had a greater “bug island” effect than S. gordejevii, as C. microphylla had a higher “fertile island” effect than S. gordejevii.

Effects of Land Cover Changes on Soil Arthropod Community in Horqin Sand Land, China

The composition and diversity of soil macroarthropod communities in six types of land cover were studied during 2008 and 2009 in Horqin Sand Land, Inner Mongolia, to understand effects of land cover changes on soil macro-arthropod. The results showed that species richness, diversity and population density of the soil arthropods were the highest in the natural grasslands, followed by the fixed sand-lands and the plantations. Although the richness, diversity and population density were lower in the dry and irrigated farmlands, they were significantly higher than those in the moving sand dunes. Anthicidae were numerically dominant in natural grasslands, fixed sand dunes, plantations and irrigated farmlands, while Tenebrionidae were most common in the dry farmlands. There were no significantly dominant species in the moving sand dunes. The proportion of herbivore and omnivores was higher in fixed sand dunes compared with moving sand dunes, and likewise, the proportions of predators and omnivores were higher in irrigated farmlands compared with dry farmlands. In addition, the proportion of predators and omnivores were lower in plantations compared with fixed sand dunes or natural grasslands. The abundance and diversity of soil arthropods was most closely correlated with soil temperature, soil organic matter and total P content. 