Abundant Species Drive Changes in Functional Quality of Field Margins

Research that connects the effects of urbanization on biodiversity and ecosystem services is lacking. Ants perform multifarious ecological functions that stabilize ecosystems and contribute to a number of ecosystem services. We studied responses of ant communities to urbanization in the Lake Tahoe basin by sampling sites along a gradient of urban land development. We sampled ant communities, measured vegetation characteristics, quantified human activities, and evaluated ant-community responses by grouping ants into service-providing units (SPUs), defined as a group of organisms and their populations that perform specific ecosystem services, to provide an understanding of urbanization impacts on biodiversity and their delivery of ecosystem services. Species richness and abundance peaked at intermediate levels of urban development, as did the richness of 3 types of ant SPUs (aerators, decomposers, and compilers). With increasing land development aerator and decomposer ants significantly declined in abundance, whereas compiler ants significantly increased in abundance. Competing models demonstrated that precipitation was frequently among the strongest influences on ant community structure; however, urban development and human activities also had a strong, negative influence on ants, appearing in most models with DeltaAIC(c) < 2 for species richness and abundance patterns of SPUs and generalists. Response diversity was observed within SPUs, which suggests that the corresponding ecosystem services were maintained until development reached 30-40%. Our data provide evidence that ecosystem functions, such as water infiltration and soil productivity, may be diminished at sites subject to greater levels of urbanization and that conserving ant communities and the ecosystem services they provide could be an important target in land-use planning and conservation efforts.

Landscape structure, habitat fragmentation, and the ecology of insects

Summary 1. Biotic homogenization (BH), a dominant process shaping the response of natural communities to human disturbance, reflects both the expansion of exotic species at large scales and other mechanisms that often operate at smaller scales. 2. Here, we examined the relationship between BH in plant communities and spatio-temporal landscape disturbance (habitat fragmentation and surrounding habitat conversion) at a local scale (1 km²), using data from a standardized monitoring programme in France. We quantified BH using both a spatial partitioning of taxonomic diversity and the average habitat specialization of communities, which informs on functional BH. 3. We observed a positive relationship between local taxonomic diversity and landscape fragmentation or instability. This increase in local taxonomic diversity was, however, paralleled by a decrease in average community specialization in more fragmented landscapes and in more unstable landscapes around forest sites. The decrease in average community specialization suggests that landscape disturbance causes functional BH, but there was limited evidence for concurrent taxonomic BH. 4. Synthesis. Our results show that landscape disturbance is partly responsible for functional BH at small scales via the extirpation of specialist species, with possible consequences for ecosystem functioning. However, this change in community composition is not systematically associated with taxonomic BH. This has direct relevance in designing biodiversity indicators: metrics incorporating species sensitivity to disturbance (such as species specialization to habitat) appear much more reliable than taxonomic diversity for documenting the response of communities to disturbance.

Field margins are an important component of the agri‐environment as they contribute to maintaining ecosystem functions and protecting biodiversity. Field margin structure, landscape attributes, and management practices have been examined as determinants of plant species diversity and composition for mainly cereal field margins; however, relatively little is known about their influence on vegetable field margins. We selected three types of field margins (each n = 4; non‐managed connected to forests, non‐managed isolated, and isolated and managed margins with mowing and organic herbicide) adjacent to organic vegetable crop fields and recorded the species richness and abundance of all vascular plants. The effects of structural connectivity, weed control management, and margin width on the community composition, species richness, and diversity were examined using multivariate statistical techniques. Plant community composition was clearly explained by structural connectivity between field margin and forest, as well as by weed control management. In contrast, species richness of functional guilds was influenced by connectivity and margin width, but not by weed control management. All communities had similar numbers of summer and fall blooming nectar‐ and pollen‐producing plants, an important source of pollination services. In addition, each community of field margin types, despite different species composition, had similar levels of Shannon diversity and evenness. Our results suggest that habitat arrangement is important for determining community composition in field margins. Management practices may be important in determining dominance patterns of individual species. A combination of various margin types and widths may be beneficial for biodiversity conservation and ecosystem services.

Natural vegetation occurring on farms in field margins, fallow fields, ditch systems and neighboring forests, provides increased biodiversity, structural diversity, habitat for wildlife and beneficial insects, and can act as a protective buffer against agrochemical drift. Nevertheless, farmers frequently view these areas as non-productive and as potential sources of weeds, insect pests and diseases. Weed species richness and abundance were examined in crop fields in 2002–2003 at the Center for Environmental Farming Systems near Goldsboro, NC to determine if crop field weed infestation was associated with field margin management (managed versus unmanaged). Weed species abundance and richness were measured over two growing seasons on four occasions in crop fields along permanent transects that extended from the field edge toward the center of the field. The presence/absence of data for all plant species in the field margin was also recorded. For both margin types, managed and unmanaged, more weeds were found near the field edge than in the center of the field. Weed species richness was slightly higher in cropland bordering managed margins than in cropland along unmanaged margins. Several significant interactions led to an examination of nine dominant weed species in each field margin type and their distribution in crop fields. When all sampling dates were pooled, only 42 (40%) of 105 species identified in the field margins were observed in the crop field. Managed margins had lower species richness than unmanaged field margins—less than half the mean number of species (15 versus 6 species, respectively). Contingency table analysis did not reveal any association between plant species occurring in the margin and those found in the crop field. Furthermore, margin type and weed presence in the field margin were not effective predictors of weed occurrence in the crop field as determined by logistic regression.

We need to move towards more sustainable farming methods that maximise yields whilst protecting the environment. One approach that would achieve this goal is ecological intensification, which seeks to manage the biodiversity and ecological processes underpinning agricultural production so that damaging farming practices can be replaced or reduced. Forb-rich arable field margins have been shown to benefit flower-visiting insects such as wild bees, and recent evidence suggests that they can also enhance the levels of pollination and pest control in adjacent crop fields. They may also promote a suite of additional ecosystem services of societal and agronomic importance, but this has yet to be established. Furthermore, the ability of forb-rich field margins to deliver multiple benefits (i.e. ecosystem multifunctionality), including pest control and pollination, is likely to be contingent on a range of local and landscape factors. Using a range of pre-existing field margin plots (n = 98) distributed across 16 arable farms in central eastern England, this study first sought to examine whether high quality forb-rich field margins promote ecosystem multifunctionality more effectively than low quality forb-poor field margins. This involved measuring a range ecosystem services within and adjacent to field margin plots, including pest control, pollination, soil carbon storage, flood alleviation, the abundance of invertebrate ecosystem service providers and the amount of invertebrate biodiversity. Secondly, it established whether arable field margins provide adequate foraging resources for flower-visiting insects. And thirdly, it determined the local and landscape factors (including margin quality) that best promote ecosystem service provision and invertebrate biodiversity within agro-ecosystems. The findings indicated that quality was the most important determinant of ecosystem multifunctionality within arable field margins, as high quality margins supported significantly greater levels of pest control, pollination, flood alleviation and invertebrate biodiversity. However, a range of additional local and landscape management prescriptions further enhanced the multifunctionality of arable field margins, such as the level of vehicle traffic margins receive, vegetation height, landscape complexity and the amount of floral resources provided by the adjacent hedgerow. Despite the multiple benefits of high quality field margins, they were also found to enhance invertebrate crop pests. This may reduce the willingness of farmers to adopt forb-rich habitats on their land. Finally, the present study highlights that more consideration should be given to the forb species included within field margin seed mixes, as certain species were found to promote agronomically damaging crop pests, whereas other species not currently included in field margin seed mixes were extremely attractive to several important flower-visiting taxa or flowered during spring; a period in which field margins are floristically poor. This thesis clearly demonstrates that forb-rich field margins provide multiple agronomic, societal and biodiversity benefits, and outlines the important drivers of ecosystem multifunctionality. As such, it provides farmers and landowners with a clear set of management guidelines for promoting biodiversity and ecosystem services within arable field margins.

Aims Our objective is to determine: 1) how species richness and abundance vary with grazing intensity and topography (i.e., flat vs. slope) in typical steppe of Inner Mongolia grassland, and 2) how common and rare species respond to grazing intensity and what role they play in species diversity maintenance. Methods The study was carried out at the Sino-German grazing experiment site, which was established in June 2004, and located in the typical steppe region of Inner Mongolia grassland dominated by Leymus chinensis and Stipa grandis. The experimental treatments included seven levels of stocking rates (i.e., 0, 1.5, 3.0, 4.5, 6.0, 7.5, 9.0 sheep·hm) and two topographical systems (i.e., flat and slope). Three hundred quadrats (1 m × 1 m each) were investigated on each plot in August 2009, and the total number of species and the number of individuals for each species were measured within each quadrat. The log-normal model, log-series model, and power fraction model were used to fit the observational data. Important findings Our results showed that the species richness and abundance increased at low stocking rates (1.5, 3.0 sheep·hm), but decreased at high stocking rates (7.5, 9.0 sheep·hm) on the flat, which partially supported the grazing optimization hypothesis. The power fraction model well fitted for entire species abundance at most of stocking rates, while the log-normal model only fitted well for entire species abundance just at the high stocking rates. The species richness and abundance decreased greatly with stocking rates on slopes. Abundance 李文怀等: 放牧强度和地形对内蒙古典型草原物种多度分布的影响 179 doi: 10.3724/SP.J.1258.2014.00016 distribution of entire species at each of the stocking rates followed the log-normal function and power fraction function. The groups of common species and the entire species had similar responses in abundance to grazing at each of the stocking rates on both the flat and the slope, which were well fitted by both the power fraction model and log-normal model; whereas the groups of rare species and the entire species had similar richness responses to grazing at each of the stocking rates under both topographical features, which were well fitted by the power fraction model. It is suggested that the effect of grazing on species abundance in plant community depends on common species; whilst grazing effect on species richness depends on rare species. Our findings indicate that the niche partitioning mechanism plays an important role in species abundance maintenance in grassland ecosystems. To restore and maintain a high level of biodiversity and primary productivity in the Inner Mongolia grassland, it is necessary to reduce the excessively high stocking rate at present to a moderate level in future.

Case-specific monitoring of butterflies to determine potential effects of transgenic Bt-maize in Switzerland

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

Temporal and spatial changes in the copepod community during the 1974–1998 spring seasons in the Kuroshio region; a time period of profound changes in pelagic fish populations

Field margin vegetation is among the last vestiges of semi-natural habitat for birds in many agricultural landscapes of tropical regions. However, field margins differ in size, structure, and flora, and their value to birds depends on all these factors and on species-specific habitat preferences. Therefore, we analyzed data on resident and neotropical migratory birds found in 40 field margins of the agricultural landscape of El Bajio, Guanajuato, Mexico. The structural and botanical characteristics of the field margin, and those of the adjacent landscape, were related to bird species richness and abundance. We recorded 61 species of birds of which 36 were migratory. Locally, the size of the field margin (width, height, volume), its vegetative vertical complexity, and the abundance of trees and tree species had a positive effect on bird species richness and abundance. Native trees, especially mesquites, were especially important for many birds observed foraging, nesting, and perching. The most important landscape-scale variables were the density of hedgerows around field margins and the distance to natural vegetation remnants (scrub forest). Bird species richness and abundance were positively affected by the length of the hedgerows within 100 and 200-m-radius circles centered on each field margin. Field margins closer to natural vegetation also had more bird species and individuals. On the basis of our results, we suggest some general management recommendations for improving the habitat for birds in tropical agricultural landscapes.

AimRecent works on biodiversity–ecosystem functioning (BEF) relationships highlight abundance fluctuations of common species as more important for delivering ecosystem services than changes in species richness and composition in real‐world ecosystems. However, evidence on BEF relationships in natural ecosystems is still limited, especially for large vertebrates. Here, we aimed to disentangle the relative roles of species richness, composition and abundance of vertebrate scavenger communities in the ecological process of carcass elimination, a pivotal ecosystem service, in natural ecosystems. We evaluated the variability in the scavenging function across ecosystems, and examined the factors explaining it.LocationNine natural ecosystems, seven in Europe and two in Africa.Major taxa studiedVertebrates.Time period2006–2013.MethodsWe obtained BEF relationships from vertebrate scavengers consuming ungulate carcasses monitored through motion‐triggered remote cameras. We used the Price equation to tease out the relative roles of species richness, composition and abundance in the scavenging efficiency of vertebrates.ResultsWe recorded 46 vertebrate scavenging species, 30 in Spain and 16 in South Africa. Two main patterns drove BEF relationships. Species richness and composition drove carcass consumption in ecosystems where functionally dominant scavengers were rare, whilst context dependent effects (including species abundance) did so where functionally dominant species were common. Contrastingly to previous studies, abundance fluctuations in vertebrate scavengers were not exclusively related to common species but to the specialization of obligate scavengers (i.e., Gyps vultures) to rapidly gather at carcasses and to the top‐down control exerted by large predators.Main conclusionsRare and threatened species such as vultures and top predators become functionally key species in scavenging processes, highlighting that the delivery of ecosystem services still stands as a general argument for biodiversity conservation in vertebrate communities. Human persecution of vultures and top predators worldwide is expected to alter ecosystem functioning and services such as nutrient recycling or disease control.

Remaining semi-natural habitats are important refuges for farmland biodiversity, and field margins are one such habitat. Field margins consist of strips of herbaceous vegetation that are located between field boundary features such as hedgerows and the main grassland or arable field. However, little is known about their extent or ecological quality on intensively managed farmlands in Ireland. This lack of knowledge can only be addressed through the application of a standardised assessment methodology, which we developed and implemented in this study. A survey of field margins was conducted on 92 intensively managed farms, across three enterprise types (arable, beef and dairy farms) in Ireland. We describe the botanical composition and assess the ecological quality of field margins based on threshold levels of the percentage cover of positive, neutral and negative botanical indicator species that are predominantly informed by existing European Union (EU)-accepted methods for vegetation classification. Positive indicator species occurred in 77% of margins and had a mean cover of 10%. There was a high incidence of negative indicator species, occurring in 93% of margins with a mean cover of 55%. Using our quality appraisal system, 16% of field margins were of high or very high quality, and the majority (55%) were of low or very low quality. Compared to either arable or dairy farms, beef farms had a greater percentage of higher-quality margins, higher species richness and greater percentage of positive indicator species. Retaining areas of high-quality farmland habitat and enhancing those areas that have become ecologically degraded will be key to achieving the Common Agricultural Policy (CAP) objective of protecting landscapes and biodiversity. However, the implementation of appropriate management decisions requires effective evaluation of the current ecological condition of these habitats. Field margins are ubiquitous habitats in Irish farmlands and comprise a significant proportion of overall farmland habitat area. However, our results show that the majority in more intensively managed systems are in a botanically impoverished condition. Our standardised field margin quality assessment technique may offer an appropriate method of tracking change in habitat quality in response to conservation actions to improve habitat quality.

Nutrient enrichment is a significant cause of ecosystem change in coastal habitats worldwide. This study focuses on the change in a benthic macroinvertebrate community and environmental quality as assessed through different biotic indices following the construction of a sewage outfall pipe in the west of Scotland, from first implementation to seven years after operation of the pipe. Benthic macroinvertebrates are an important part of marine ecosystems because they mediate ecosystem processes and functions, are a key part of food webs and they provide many ecosystem services. Results indicated a clear change in benthic communities over time with an increase in species richness and changes to benthic community composition (specifically feeding type, bioturbation mode and ecological group) towards those indicative of organic enrichment. No clear spatial zonation was observed because organic carbon content increased over the entire area. According to a suite of benthic indices calculated, some negative changes were detectable following the start of sewage disposal, but largely negative community changes, and a change from ‘good’ to ‘moderate’ quality, only occurred seven years after implementation. The increase in species richness in response to increasing disturbance reduced the utility of a multi-metric index, the Infaunal Quality Index, which, instead of amplifying the signal of negative impact, dampened it. We suggest that any change in communities, regardless of direction, should be heeded, and species richness is a particularly sensitive and early warning indicator for this, but a suite of approaches is required to understand benthic community changes.

On the use of automated cameras to estimate species richness for large‐ and medium‐sized rainforest mammals