Plant traits explain the success of vacuum harvesting as a method of seed collection for the restoration of species-rich grasslands

Grassland restoration is a key measure for re-establishing damaged floral communities. As seed banks are often degraded, methods are needed to overcome dispersal limitation of the remnant vegetation. One approach is to vacuum harvest seeds from donor sites. While this is a cost-effective method, individual species’ traits describing reproduction methods and dispersal mechanisms may affect the success with which seeds are collected and subsequently germinate. We collected seeds using low-cost vacuum harvesters in species-rich meadows in Poland. We predicted the relative success with which seedlings emerged from this collected material with respect to their percentage cover in the donor sites on the basis of individual species’ functional traits. Prolific species that rely on seed as opposed to vegetative reproduction, and those that germinate in late summer/autumn, exhibited the highest level of emergence. To a lesser extent, drought-tolerant or shade-intolerant species were well represented in the collected material. There was also weak evidence that wind-dispersed seeds would have a higher likelihood of being collected by this method. Our results suggest that vacuum harvesting is a valuable method to collect seeds for use in grassland restoration; however, it has limitations. In particular, additional methods may be needed to introduce into grassland restoration sites the propagules of species that vegetatively reproduce or seed early. The overrepresentation of species that produce large numbers of seed may potentially introduce priority effects that could also have unintended long-term implications for the structure of the floral community

Network size, structure and mutualism dependence affect the propensity for plant-pollinator extinction cascades

1. Pollinator network structure arising from the extent and strength of interspecific mutualistic interactions can promote species persistence and community robustness. However, environmental change may re-organise network structure limiting capacity to absorb or resist shocks and increasing species extinctions. 2. We investigated if habitat disturbance and the level of mutualism dependence between species affected the robustness of insect–flower visitation networks Following a recently developed Stochastic Co-extinction Model (SCM), we ran simulations to produce the number of extinction episodes (cascade degree), which we correlated with network structure in undisturbed and disturbed habitat. We also explicitly modelled whether a species’ intrinsic dependence on mutualism affected the propensity for extinction cascades in the network. 3. Habitat disturbance generated a gradient in network structure with those from disturbed sites being less connected, but more speciose and so larger. Controlling for network size (z-score standardisation against the null model) revealed that disturbed networks had disproportionately low linkage density, high specialisation, fewer insect visitors per plant species (vulnerability) and lower nestedness (NODF). 4. This network structure gradient driven by disturbance increased and decreased different aspects of robustness to simulated plant extinction. Disturbance decreased the risk that an initial insect extinction would follow a plant species loss. Although, this effect disappeared when network size and connectance were standardised, suggesting the lower connectance of disturbed networks increased robustness to an initial secondary extinction. 5. However, if a secondary extinction occurred then networks from disturbed habitat were more prone to large co-extinction cascades, likely resulting from a greater chance of extinction in these larger, speciose networks. Conversely, when species mutualism dependency was explicit in the SCM simulations the disturbed networks were disproportionately more robust to very large co-extinction cascades, potentially caused by non-random patterns of interaction between species differing in dependence on mutualism. 6. Our results showed disturbance altered the size and the distribution of interspecific interactions in the networks to affect their robustness to co-extinction cascades. Controlling for effects due to network size and the interspecific variation in demographic dependence on mutualism can improve insight into properties conferring the structural robustness of networks to environmental changes

Species richness-environment relationships of European arthropods at two spatial grains : habitats and countries

We study how species richness of arthropods relates to theories concerning net primary productivity, ambient energy, water-energy dynamics and spatial environmental heterogeneity. We use two datasets of arthropod richness with similar spatial extents (Scandinavia to Mediterranean), but contrasting spatial grain (local habitat and country). Samples of ground-dwelling spiders, beetles, bugs and ants were collected from 32 paired habitats at 16 locations across Europe. Species richness of these taxonomic groups was also determined for 25 European countries based on the Fauna Europaea database. We tested effects of net primary productivity (NPP), annual mean temperature (T), annual rainfall (R) and potential evapotranspiration of the coldest month (PETmin) on species richness and turnover. Spatial environmental heterogeneity within countries was considered by including the ranges of NPP, T, R and PETmin. At the local habitat grain, relationships between species richness and environmental variables differed strongly between taxa and trophic groups. However, species turnover across locations was strongly correlated with differences in T. At the country grain, species richness was significantly correlated with environmental variables from all four theories. In particular, species richness within countries increased strongly with spatial heterogeneity in T. The importance of spatial heterogeneity in T for both species turnover across locations and for species richness within countries suggests that the temperature niche is an important determinant of arthropod diversity. We suggest that, unless climatic heterogeneity is constant across sampling units, coarse-grained studies should always account for environmental heterogeneity as a predictor of arthropod species richness, just as studies with variable area of sampling units routinely consider area

Effects of future agricultural change scenarios on beneficial insects

Insects provide vital ecosystem services to agricultural systems in the form of pollination and natural pest control. However, there are currently widespread declines in the beneficial insects which deliver these services (i.e. pollinators and ‘natural enemies’ such as predators and parasitoids). Two key drivers of these declines have been the expansion of agricultural land and intensification of agricultural production. With an increasing human population requiring additional sources of food, further changes in agricultural land use appear inevitable. Identifying likely trajectories of change and predicting their impacts on beneficial insects provides a scientific basis for making informed decisions on the policies and practices of sustainable agriculture. We created spatially explicit, exploratory scenarios of potential changes in the extent and intensity of agricultural land use across Great Britain (GB). Scenarios covered 52 possible combinations of change in agricultural land cover (i.e. agricultural expansion or grassland restoration) and intensity (i.e. crop type and diversity). We then used these scenarios to predict impacts on beneficial insect species richness and several metrics of functional diversity at a 10km (hectad) resolution. Predictions were based on species distribution models derived from biological records, comprising data on 116 bee species (pollinators) and 81 predatory beetle species (natural enemies). We identified a wide range of possible consequences for beneficial insect species richness and functional diversity as result of future changes in agricultural extent and intensity. Current policies aimed at restoring semi-natural grassland should result in increases in the richness and functional diversity of both pollinators and natural enemies, even if agricultural practices remain intensive on cropped land (i.e. land-sparing). In contrast, any expansion of arable land is likely to be accompanied by widespread declines in richness of beneficial insects, even if cropping practices become less intensive (i.e. land-sharing), although effects of functional diversity are more mixed

Agrochemicals in the wild: identifying links between pesticide use and declines of nontarget organisms

Agricultural pesticides are a key component of the toolbox of most agricultural systems and are likely to continue to play a role in meeting the challenge of feeding a growing global population. However, pesticide use has well documented and often significant consequences for populations of native wildlife. Although rigorous, regulatory processes for the approval of new chemicals for agronomic use do have limitations which may fail to identify real world negative effects of products. Here, we describe a possible approach to complement the existing regulatory process, which is to combine long-term and national-scale data sets on native wildlife with pesticide use data to understand long-term and large-scale impacts of agrochemicals on wildlife populations

Using functional traits to predict pollination services: a review

Pollination is a fundamental ecosystem service. Predictive and mechanistic models linking pollinator community structure to pollination services increasingly incorporate information on unique functional differences among species, so called effects traits. There is little consensus as to which traits are most important in supporting pollination services at either an individual or community level. Here, we synthesise the state of current knowledge regarding the role and efficacy of traits for predicting pollination, as well as the use of different methods for describing the trait structure of pollinator assemblages. We find a wide range of traits are currently used to predict pollination services, including morphological, behavioural and phenological characteristics. However, we show that the evidence demonstrating their importance is often limited or mixed. There is a trade-off in how traits are used between those that are easier to measure, available for many species but have only limited evidence for their role in pollination, vs. those that are harder to measure but with a more robust link with pollination service delivery. We highlight how community weighted means and measures of functional diversity offer important, albeit different insights into pollination service delivery. We discuss how their relative importance is likely to depend on the goals of the study. To maximise fully the utilisation of traits to predict pollination services, future research should be directed towards the widespread and consistent validation of the links among different traits and the pollination service across crop and semi-natural plant communities. Ideally this also needs to address geographical and taxonomic biases in trait collection

The effect of tillage management and its interaction with site conditions and plant functional traits on plant species establishment during meadow restoration

The restoration of grasslands is a key management practice that supports biodiversity across Europe. On species poor grasslands and ex-arable fields, the establishment of plant species is often limited by the availability of habitat niches, in particular space to germinate. We investigated the impacts of full inversion tillage and its interaction with site conditions and functional traits on the abundance of 51 plant species sown into a 2 ha ex-arable site in Poland. Soils of the donor site were characterized by high levels of heterogeneity in terms of water content and plant availability of N, P and K. One year after sowing the cover of species typical of semi-natural grasslands was significantly higher on the tilled plots than on the non-tilled plots. However, in the case of widespread generalist species the tillage of soil resulted in no significant effect on their establishing percentage cover. The establishment of plants on the tilled area was more successful where soils were relatively rich in mineral N. It was also more successful for species with low Ellenberg’s N values. Species indicative of moist soil established poorly where the soil was tilled. This study has clear implications for the applied restoration of grasslands, demonstrating a vital role of soil tillage to promote the establishment of species typical of semi-natural grasslands. This is particularly important where seed mixtures may contain both desirable and undesirable competitive species that would disproportionately benefit from the absence of tillage management

Predicting invasive species impacts: a community module functional response approach reveals context dependencies

1. Predatory functional responses play integral roles in predator–prey dynamics, and their assessment promises greater understanding and prediction of the predatory impacts of invasive species. . 2. Other interspecific interactions, however, such as parasitism and higher-order predation, have the potential to modify predator–prey interactions and thus the predictive capability of the comparative functional response approach. . 3. We used a four-species community module (higher-order predator; focal native or invasive predators; parasites of focal predators; native prey) to compare the predatory functional responses of native Gammarus duebeni celticus and invasive Gammarus pulex amphipods towards three invertebrate prey species (Asellus aquaticus, Simulium spp., Baetis rhodani), thus, quantifying the context dependencies of parasitism and a higher-order fish predator on these functional responses. . 4. Our functional response experiments demonstrated that the invasive amphipod had a higher predatory impact (lower handling time) on two of three prey species, which reflects patterns of impact observed in the field. The community module also revealed that parasitism had context-dependent influences, for one prey species, with the potential to further reduce the predatory impact of the invasive amphipod or increase the predatory impact of the native amphipod in the presence of a higher-order fish predator. . 5. Partial consumption of prey was similar for both predators and occurred increasingly in the order A. aquaticus, Simulium spp. and B. rhodani. This was associated with increasing prey densities, but showed no context dependencies with parasitism or higher-order fish predator. . 6. This study supports the applicability of comparative functional responses as a tool to predict and assess invasive species impacts incorporating multiple context dependencies.

Wildlife-friendly farming increases crop yield: evidence for ecological intensification

Ecological intensification has been promoted as a means to achieve environmentally sustainable increases in crop yields by enhancing ecosystem functions that regulate and support production. There is, however, little direct evidence of yield benefits from ecological intensification on commercial farms growing globally important foodstuffs (grains, oilseeds and pulses). We replicated two treatments removing 3 or 8% of land at the field edge from production to create wildlife habitat in 50–60 ha patches over a 900 ha commercial arable farm in central England, and compared these to a business as usual control (no land removed). In the control fields, crop yields were reduced by as much as 38% at the field edge. Habitat creation in these lower yielding areas led to increased yield in the cropped areas of the fields, and this positive effect became more pronounced over 6 years. As a consequence, yields at the field scale were maintained—and, indeed, enhanced for some crops—despite the loss of cropland for habitat creation. These results suggested that over a 5-year crop rotation, there would be no adverse impact on overall yield in terms of monetary value or nutritional energy. This study provides a clear demonstration that wildlife-friendly management which supports ecosystem services is compatible with, and can even increase, crop yields

Impacts of neonicotinoid use on long-term population changes in wild bees in England

Wild bee declines have been ascribed in part to neonicotinoid insecticides. While short-term laboratory studies on commercially-bred species (principally honeybees and bumblebees) have identified sub-lethal effects, there is no strong evidence linking these insecticides to losses of the majority of wild bee species. We relate 18 years of UK national wild bee distribution data for 62 species to amounts of neonicotinoid use in oilseed rape. Using a multi-species dynamic Bayesian occupancy analysis, we find evidence of increased population extinction rates in response to neonicotinoid seed treatment use on oilseed rape. Species foraging on oilseed rape benefit from the cover of this crop, but were on average three times more negatively affected by exposure to neonicotinoids than non-crop foragers. Our results suggest that sub-lethal effects of neonicotinoids could scale-up to cause losses of bee biodiversity. Restrictions on neonicotinoid use may reduce population declines