The influence of grassland management on ground beetles (Carabidae, Coleoptera) in Swiss montane meadows

Effects of grassland management type and intensity on carabid species richness, number of individuals and species composition were studied in the Swiss Prealps. Carabids were censused in 2001 and 2002 in 21 mown and 20 grazed meadows by means of pitfall traps.Mean species richness was significantly higher in mown plots than in grazed plots and species composition was significantly different between these two management types. Additionally, different species characteristic for mown and grazed plots were found. These results suggest that mown meadows and grazed meadows represent two habitat types for carabid beetles.Within both habitats, management intensity was quantified by fertilizing intensity, the number of cuts, cattle density and/or grazing intensity. The relationship between management intensity and the number of individuals and species was positive. Higher fertilizing intensity was the most important factor for higher species richness and had a significant influence on species composition in both habitats. Other variables positively related to the number of individuals, were the number of cuts in mown meadows and grazing intensity and altitude in grazed meadows. Additionally to fertilizing intensity, cattle density was positively related to the number of species in grazed meadows. These results illustrate that in the extensive management systems found in the Swiss Alps and Prealps, even intensively managed meadows can sustain high carabid diversity and abundance.     

Farming systems and insect predators

Predatory carabids, staphylinids and spiders were monitored from 1981 to 1987 in a Dutch project concerning the development of arable farming systems. During this period epigeic predators in the conventional, integrated and organic systems were sampled using pitfall traps. The effects of crop type and farming system on species diversity, abundance and guild structure was analysed using trap data from wheat, pea, sugar beet, potato, onion and carrot fields. Predator abundance and species composition were found to be clearly affected by the farming system. However, in most cases the type of crop appeared to be of greater importance. Crops with a greater cover early in the season, like winter wheat and peas appeared to be more favourable than late and open crops like onions or carrots. Both system and crop effects were more apparent in carabids than in spiders or staphylinids. Only minor effects of farm management were found on species richness. Again, the crop itself seemed to be the main structuring factor. It is concluded that the presence and quality of predator populations is mainly determined by crop structure and crop-related factors. The role of favourable crops and field size in predator enhancement is discussed in relation to the agroecological infrastructure of the landscape.     

Influence of hedgerow and grassy field borders on ground beetle (Coleoptera: Carabidae) activity in fields of corn

Agricultural landscapes may be manipulated in ways that benefit predatory invertebrates by providing alternate food sources, overwintering sites, and refuge from farming activities. Ecological theory predicts that complex plant communities should support a richer community of natural enemies of pest insects than a simple plant community. A study was conducted in Iowa, USA to investigate the influence of the vegetative diversity of field boarders on the activity, species richness, and community similarities of predatory beetles occurring in corn fields.Ground beetle (Coleoptera: Carabidae) populations were compared among corn fields bounded by either complex hedges or simple grass edges. Directional pitfall traps were used to investigate activity patterns of beetles between border types and their adjacent corn fields. Beetles were trapped during four seasonal periods, based on the growth stage of corn. During corn emergence (May–June) when fields are barren, carabids were more active and species richness was higher in the corn fields bordered by woody hedges. The carabid species Scarites quadriceps, Scarites subterraneus, and Harpalus pensylvanicus, were more dominant in hedge sites as compared to grass sites at this time. Following corn–canopy closure, carabids were now more active in fields bordered by grassy edges, but beetle activity also remained high in the fields adjacent to woody hedges. Further analysis of the carabid communities by Bray–Curtis Similarity Index showed no difference among field edge types at any time of the season. Results indicate that both complex and simple field border habitats support abundant and diverse populations of carabids during most of the growing season. However, during the early growing season hedges appear to be more important than grass edges in supplying carabid beetles to corn fields. Woody hedges may serve as very important overwintering sites and as an early season refuge for predatory beetles in corn.     

Delayed colonisation of arable fields by spring breeding ground beetles (Coleoptera: Carabidae) in landscapes with a high availability of hibernation sites

The colonisation of winter barley fields by spring breeding carabids and its temporal modulation by the amount of potential hibernation sites was studied. Species richness of carabids was lower in landscapes with high length of boundaries and a high amount of non-cropped open habitats during early stages of the beetles’ colonisation of arable fields. Species number of beetles with high dispersal potential responded to this landscape features at coarse spatial scales whereas beetles with low dispersal potential responded to intermediate scales. However, the negative impact of potential hibernation sites on colonisation diminished in later sampling phases. The patterns observed may be explained by both overwintering in arable soils in less complex landscapes and delayed colonisation in more complex landscapes. The seasonal patterns of landscape control suggest a need to account for temporal dynamics in interactions between species or functional groups and landscape properties. A high temporal resolution is needed in studies that focus on ecosystem function and services in agricultural landscapes, as direction of effect (positive/negative) of management on animal communities may change across spatial scales and within short time periods.     

Grassy field margins and arthropod diversity: a case study on ground beetles and spiders in eastern Austria (Coleoptera: Carabidae; Arachnida: Aranei, Opiliones)

In 1983, the species composition and diversity of carabids, spiders and harvestmen was investigated by pitfall traps in a grassy field margin and in an adjacent, biologically farmed wheat field at Obere Lobau, Vienna, Austria.The carabid fauna of both habitats was diverse; it showed a high degree of similarity, the abundant species in both habitats being represented by typical field species. Only Metophonus spp. predominantly lived in the margin. Numerous species of different habitat origin occurred in the margin at low abundances indicating transitional stay rather than permanent populations.In contrast, the spider fauna showed a low degree of similarity, with few agrobiotic species strongly dominating field fauna. In the field margin, a rich spider fauna containing rare elements indicates the general importance of grassy margins for nature conservation. The apparently low faunal exchange of spiders between the two habitat types is discussed. Harvestmen occurred mainly in the field margin; only two thermophilic species invaded the field.Seasonal fluctuations in the trapping numbers of Bembidion lampros, Platynus dorsalis and Brachinus explodens are interpreted as indicating migrations between field margin and field. Poecilus cupreus and certain other field species, however, apparently spend their entire life cycle in the field. The possible function of field margins for restoration of carabid losses due to impacts of intensive cultivation is discussed.It is concluded that both grassy field margins and sustainable farming methods, in particular biological farming, are necessary to maintain a diverse predatory arthropod fauna in agroecosystems.     

Organic versus conventional arable farming systems: Functional grouping helps understand staphylinid response

The response of different feeding groups of staphylinid beetles to organic management, distance to perennial boundary and landscape context was studied in 42 paired organic and conventional winter wheat fields. Management effects were found to strongly depend on feeding group. While the activity-density of predators was higher in the conventional fields, both activity-density and species richness of detritivores were higher in the organic fields. Activity-density and species richness of detritivores were positively correlated to crop yield in the conventional but not in the organic fields. Unexpectedly, species richness as high as in the less productive organic fields was thus found in intensified conventional systems. No significant effects of landscape context could be found on activity-density or species richness of the different feeding groups. More species were caught near the field edge than in the middle, showing the importance of spill-over from field boundaries into arable crops for diversity. In conclusion, separation of species into feeding groups revealed patterns that have not been shown before. Decomposer diversity (but not that of predators and fungivores) was higher in organic fields, but reached similar levels in high-yielding conventional fields. Thus resource quality (purely organic or organic/synthetic fertiliser) and quantity appear to play a major role for this functional group.     

Diversity of cereal aphid parasitoids in simple and complex landscapes

Structurally complex landscapes may enhance local species richness and interactions, which is possibly due to a higher species pool in complex landscapes. This hypothesis was tested using cereal aphid parasitoids (Hymenoptera, Aphidiidae) by comparing 12 winter wheat fields in structurally complex landscapes (>50% semi-natural habitats; n = 6) and structurally simple landscapes dominated by agricultural lands (>80% arable land; n = 6). Surprisingly, landscape structural complexity had no effect on aphid parasitoid species diversity. In complex landscapes 12 and in simple landscapes 11 species were found; 9 species occurred in both landscape types. Hence, arable fields in high-intensity agricultural landscapes with little non-crop area can support a similar diversity of cereal aphid parasitoids as structurally complex landscapes. This finding suggests that cereal aphid parasitoids may find necessary resources even in simple landscapes, making generalisations concerning the relationship between landscape composition and biodiversity in arable fields difficult.     

The role of perennial habitats for Central European farmland spiders

Spiders are important predators of insect pests. Some species invariably dominate spider communities in crop fields over large parts of Europe, and are therefore considered as “agrobionts”. It is however not clear if these species generally prefer arable habitats, or to what degree they utilize other habitats during times when crops are inhospitable. Here, spider abundances in 26 crop fields and 16 perennial habitats in Germany were compared during spring. Overall spider abundance in winter wheat was 75% lower than in perennial habitats, and species richness was reduced by 46%. Out of a total of 91 species, 73 had higher densities in perennial habitats, including the most dominant crop spiders Erigone atra and Tenuiphantes tenuis. Only one species (Oedothorax apicatus) was significantly more abundant in crops than in perennial habitats. Hence, the high dominance of most “agrobiont” species in crops was due to low densities of other species, and not to their own higher abundances. Therefore, perennial habitats adjacent to crop-fields could enhance spider populations and their potential for biological control in arable fields on a landscape level.     

Influence of habitat type and surrounding landscape on spider diversity in Swedish agroecosystems

Lycosid and linyphiid spiders were collected over a full cropping season around Uppsala, Sweden, in eight organic spring sown cereal fields in three different habitat types: field margin, field, and the edge between the two. The sites were located in landscapes with different proportions of non-crops, forest, perennial crops, annual crops, and number and sizes of arable fields. The field margin, compared with the field habitat, was found to be important for the activity density of lycosids, and for the species richness and composition of linyphiids. Landscape parameters were central for the activity density of linyphiids and for the species richness and composition of Lycosidae. A diverse landscape with easy access to perennial crops and forest in addition to field margins will augment both the number of species and individuals of the two spider families.     

Development of biodiversity in field margins recently taken out of production and adjacent ditch banks in arable areas

Taking field margins out of intensive cultivation is a common form of agri-environmental scheme and on-farm nature management. Typically, no nutrients or pesticides are applied in these margins, which may be sown either with a crop or with grasses and native flowering plants. In some cases the margins are mown, while in others they are left alone. Newly established grass margins are less species-rich than field boundaries or road verges with a long history, justifying the expectation that field margins, if properly managed and given time and appropriate seed sources, could develop into relatively species-rich vegetation. We studied the biodiversity of both margins taken out of production and adjacent ditch banks in the years following initial establishment of the margins. To this end we combined the data of three different projects in order to increase the sensitivity of the statistical analyses. The results showed that the plant species richness of the field margins increased in the years following establishment over a period of four years. In addition, shifts in species composition indicated a decrease in soil nitrate concentrations. The species richness of both butterflies and dragonflies may increase. The most striking result was the marked increase in the plant species richness of the adjacent ditch banks in the five years following creation of the margins. Here, too, changes in species composition indicated a decrease in soil nitrate. In the years following establishment of the field margins there was no increase in the cover of agriculturally harmful weeds in these margins. However, the number of harmful nematodes increased. Our results show the short term effect of establishing field margins. Long term effects are still in need for further research.     

Strategy for conservation of wild bees in an agricultural landscape

Investigations carried out by the author for 15 years on the Wielkopolsko-Kujawska Lowland (Western Poland) showed that wild bees (Apoidea) are today under strong human pressure. About 260 bee species were found in the area of 20 000 km². A similar number of species was recorded in this area by investigators half a century ago, which indicates that the survival of the fauna seems to be the result of some compensating factors reducing the effects of intensive agricultural management. The main factor among these is the mosaic structure of the landscape, consisting of meadows and residues of natural and semi-natural plant communities as a fauna refuge system and crop fields as an additional nutritive system. It was found that in a normally functioning agricultural landscape, the share of farmland should not exceed three-quarters of the total surface. The remaining part of the landscape should be made up of refuge habitats for Apoidea. Within such a system, qualitative and quantitative changes of the bee fauna can occur on a microregional scale and are usually of temporary character. On a regional scale they are not perceivable and probably not so important. Hence, instead of changes in fauna, one should rather speak about quantitative oscillations inside a given region. The second factor decreasing the negative effects of management is the introduction of extensive areas of some nutritive plants, e.g. rape.     

Effects of irrigation and landscape heterogeneity on butterfly diversity in Mediterranean farmlands

Irrigation effects on biodiversity are poorly known, particularly in Mediterranean agro-ecosystems. In this study we analyzed irrigation effects on butterfly species richness, abundance and diversity as well as on species composition in a farmed landscape under Mediterranean climate. The study area consisted of four contiguous agricultural sub-areas with a decreasing degree of intensification: irrigated, mixed (dry and irrigated), dry and environmentally protected (i.e. Special Protection Area, SPA) dry farmland. Forty one km-transects (ten per sub-area) were searched for butterflies in 2008 and 2009. Contrary to expectations, species richness (alfa, beta and gamma diversity) was highest in both years in the most intensified sub-area (i.e. irrigated) followed by SPA, dry and mixed sub-areas. Landscape characteristics accounted for most of the between-subareas differences in species richness. Species richness was negatively related to mean field size at the landscape level and positively related to the number of trees and large shrubs along transects. Therefore, the higher number of butterfly species recorded in the irrigated farmland could be due to a more complex landscape. In contrast, butterfly abundance was highest in cereal steppes (i.e. dry and SPA sub-areas), with abundance being negatively affected by mean field size. Inter-annual change in butterfly abundance was much sharper in rainfed (i.e. dry and SPA) than in irrigated (i.e. irrigated and mixed) sub-areas. Irrigated farmland may provide more favorable conditions for butterflies by buffering the (year-to-year and summer) drought periods characterising Mediterranean climate. Species composition differed among sub-areas, with differences being partly explained by field size and number of trees and shrubs along transects. Our study suggest an important role of landscape characteristics in boosting butterfly biodiversity in intensively managed irrigated croplands and emphasizes the importance of encouraging studies on farmland butterfly diversity in different (bioclimatic) regions allowing the design of region-specific agri-environmental schemes.     

新疆鸟类和哺乳动物物种丰富度空间异质性及其多尺度效应

基于新疆维吾尔自治区鸟类和哺乳动10km×10km物种空间分布数据及1km×1km土地利用数据,引入NDVI、海拔和地理纬度等辅助数据,分别对物种和土地利用数据进行尺度变换,计算分析了1~10km尺度下的景观指数,并进一步在生态系统层面进行尺度效应研究,以探究表征物种多样性空间异质性的合理尺度.结果表明：新疆总体的景观类型较为丰富,北疆的景观丰富度和破碎度都相对高于南疆,并且各类型斑块分布不均匀,景观中存在具有优势度的斑块.鸟类在聚落、水体和湿地生态系统中的尺度效应明显,而哺乳动物的尺度效应在农田、森林生态系统比较显著.7~10km尺度下,聚落景观面积越小,分割度越高,水体景观越破碎,越离散,形状越复杂,鸟类丰富度越高.农田和森林生态系统的景观特征对哺乳动物丰富度具有较高的参考价值.7~10km下,农田斑块越离散、形状越复杂,哺乳动物物种丰富度越低;4km尺度下,森林景观斑块形状越复杂、连接度越高,哺乳动物物种越丰富.     

Design and use of a time-sorting pitfall trap for predatory arthropods

An electronically-controlled time-sorting pitfall trap was designed which improves upon earlier models in having a 24-h rotation time, and in being capable of running continuously for at least one week without attention. Four prototypes were built, using readily available, inexpensive components, and used from June to October, 1995, to collect carabid beetles and linyphiid spiders in clover-undersown and weeded cabbages. The traps operated without malfunction during the hottest weather ever recorded in Aberdeen, when soil surface temperatures exceeded 40°C, and also during periods of torrential rain. Three spider and two carabid species dominated the catch, their nocturnal and diurnal patterns of activity being in general agreement with other published data. Some predators were apparently able to adapt to the contrasting vegetation in the two treatments, two species of Erigone spiders being nocturnal in weeded cabbages but tending to be diurnal in undersown crops.     

Conserving the species-rich meadows of Europe

Owing to changes in agricultural practices throughout Europe, with greater emphasis on intensification, traditionally managed hay meadows have become scarce. Their loss has also meant the loss of species diversity. One of the few areas of Europe where traditional management is still practised is in Northern Spain.The hay meadows of Northern Spain can be defined as semi-natural, species-rich communities that are maintained by one or more factors which are under the direct control of man. The traditional management to which they are subjected has led to a high species diversity. For centuries the meadows have been important to man in supporting cattle during the winter. There is now little need for further increase of production. However, the importance of the need for conservation of species diversity and protection of ecologically sensitive areas is now recognised. Although the biological richness of the hay meadows is well known, few studies have been made of the effects of different traditional management regimes on the diversity and floristic composition of these grasslands.A survey was carried out to examine the effects of traditional management on the floristic composition, diversity and production of these meadows. The area studied is situated in the Valdeón valley, northwestern Spain (Cantabrian Mountains) and consists of a deep valley in which arboreal vegetation is represented by beech (Fagus sylvatica) forests. The survival of semi-natural habitats and traditional forms of management and also the low use of chemical fertilisers compared with Northern Europe are the most important reasons for the richness of these habitats. In this study, cutting for hay once per year, non-irrigation non-manuring and grazing in autumn was correlated with high species diversity. The future conservation of these habitats will depend on the formulation of support to continue with traditional management practices.     

Density and nutritional condition of carabid beetles in wildflower areas of different age

Density and nutritional condition of the five carabid beetle species Agonum mülleri, Anchomenus dorsalis, Anisodactylus binotatus, Pterostichus vernalis and Poecilus cupreus was studied. Carabids were caught in sixteen 1–4-year-old wildflower areas, identified and counted, their nutritional condition was calculated and calculations were related to habitat parameters (i.e. wildflower area age, vegetation cover, soil water content, habitat size, surrounding landscape composition) and sex.Whereas the number of Anisodactylus binotatus caught responded positively to succession in wildflower areas, A. mülleri numbers tended to decrease and the other three species were unaffected. In a stepwise multiple regression species affiliation, sex and age of wildflower area explained together 98.5% of the variance in the pooled nutritional condition of Anchomenus dorsalis, Anisodactylus binotatus, A. mülleri and P. vernalis. Age of wildflower area alone explained 61.7% of the variance and age increased the nutritional condition of carabids. Correspondingly, nutritional condition of Poecilus cupreus was positively correlated with the age of wildflower area. Overall, the nutritional condition of the carabid assemblage studied increased from the first to the second year and then remained stable. To keep the proportion of 1-year-old wildflower areas low, wildflower areas should therefore be maintained for several years to improve the life conditions of carabid beetles and to enhance their beneficial effects in agroecosystems.     

人工林与其紧邻农田中野生植物与土壤线虫群落特征对比

我国北方农耕区休耕地种植杨树现象较为普遍,但是人工林对农业生态系统中生物多样性的保护作用却鲜有关注.在山东省宁津县选取3块样地,均为休耕地种植杨树林且紧邻小麦玉米轮作田,对比人工林下、田埂及农田内的草本植物群落特征、土壤线虫群落特征及土壤化学性质,以探究人工林对农业生态系统中生物多样性的作用.结果表明:①植物样方总物种数和样方平均物种数均呈现农田 < 距田埂30 m人工林下 < 距田埂10 m人工林下 < 田埂 < 距田埂20 m人工林下 < 距田埂5 m人工林下的变化规律,其中,距田埂5 m人工林下植物样方总物种数为21种,农田内11种.人工林下草本植物群落多样性指数、丰富度指数均显著高于农田内杂草植物群落相应指数（P < 0.05）.②农田、田埂及距田埂5 m的人工林下的土壤线虫组成存在差异,农田和人工林下土壤线虫优势属为头叶属（Cephalobus）,而田埂中为真头叶属（Eucephalobus）.土壤线虫群落多样性指数、成熟指数、植物寄生线虫成熟指数及线虫通路比在人工林下、田埂和农田之间差异均不显著（P≥0.05）,土壤线虫均为耐环境压力类群.③人工林下与农田土壤中总氮（TN）、总碳（TC）含量差异不显著（P≥0.05）,而田埂和人工林下土壤碳氮比（C/N）显著高于农田内（P < 0.01）,表明林下和田埂土壤中有机物分解矿化速度低于农田内.土壤TN含量、TC含量、C/N和pH均与植物群落具有显著关联,而对土壤线虫群落均无显著影响.研究显示,在我国北方休耕地种植杨树林,对于农业生态系统中草本植物多样性保护具有积极作用,但是难以在几年内有效地改善土壤质量.      

Gradient analysis and numerical classification of apple orchard weed vegetation

Importance values based on cover and frequency were determined for 36 weed species in understory samples from 47 apple orchards located in Henderson County, North Carolina. Orchard sub-groups identified by cluster analysis of the weed composition data included two major groupings dominated by grasses and woody perennials, respectively. Ordination by detrended correspondence analysis (DECORANA) was used to extract axes of compositional variation in orchard weed vegetation. Orchard sub-groups identified by cluster analysis could be recognized in the DECORANA ordinations. All grasses, most perennial forbs and all summer-annual forbs decreased in importance along a first ordination axis based upon data from 43 orchards. Two perennial forbs and all woody perennials increased in importance along the same axis, while species-richness of weeds declined. Results of multiple regression indicated that the annual frequency of paraquat application from 1976 to 1979 was the single factor accounting for the greatest compositional variation in the first two axes of the 43-orchard ordination. Tree canopy width and in-row spacing, total extractable soil cations, and percentage soil organic matter also accounted for significant amounts of variation in weed composition. Similar results were obtained from models developed for an ordination of the 35 grass-dominated orchards, suggesting the importance of management, structural and soil factors in determining weed composition in apple orchards.