Species groups occupying different trophic levels respond differently to the invasion of semi-natural vegetation by Solidago canadensis

We studied the impact of the invasive plant species Solidago canadensis on the species richness of vascular plants and the abundance, species richness and diversity of butterflies, hoverflies and carabid beetles in herbaceous semi-natural habitats near Ljubljana, Slovenia. The species groups were sampled in sites dominated by S. canadensis and paired nearby sites covered by semi-natural vegetation. Plant species richness and species richness, abundance and diversity of butterfly species were lower in plots dominated by S. canadensis. Hoverfly abundance, diversity and species richness were negatively affected only in July just before the onset of flowering of S. canadensis, but tended to be positively affected in August during the height of flowering of S. canadensis. Only the abundance of carabid beetles was reduced in plots dominated by S. canadensis. The responses of the insect groups seem largely driven by the effects of Solidago on the availability of essential resources like food or larval host plants. Our results suggest that insect species that are closely related to plant species composition are more vulnerable to the effects of invasive plant species than those that are loosely or only indirectly related to plant species composition.     

The influence of plant diversity on people’s perception and aesthetic appreciation of grassland vegetation

The conservation of biodiversity critically depends on the value that humans attach to it. Apart from an ecological and economic value, an aesthetic value has often been assigned to biodiversity. However, it is not known whether lay people appreciate the diversity of species and not just certain individual species or nature as a whole. We studied in a series of experiments and field studies people’s perception and appreciation of species diversity. We presented meadow-like arrays of different species richness and evenness but random species composition to lay people and asked them to estimate plant species richness and rank the arrays by attractiveness. The experiments were complemented by two larger-scale field studies using natural meadows. Both in the experiments and the field studies the mean perception of species richness by people increased with true species richness, but was slightly overestimated at low and increasingly underestimated at high diversity levels. Lay people’s aesthetic appreciation of both the experimental grassland arrays and the natural meadows increased with true species richness. Communities consisting of the same number of species were perceived to be more species-rich and were appreciated more when their evenness was high. Our results demonstrate that plant diversity in itself is attractive to humans. The current reduction of the diversity of grasslands due to intensification of management may thus reduce the attractiveness of regions where grasslands are a dominant feature of the landscape. This could have negative consequences for tourism and may add an economic argument for the conservation of biodiversity in grasslands.     

Assessing habitat quality for butterflies on intensively managed arable farmland

The conservation and management of biodiversity requires accurate, repeatable and cost-effective monitoring techniques. In this study, a simple and rapid methodology was employed to measure the quality of different habitats for butterfly species on 10 arable farms in lowland Britain. This habitat monitoring was seven times more rapid than the traditional species-based butterfly monitoring. Data on butterfly abundance were combined with the information gathered on habitat quality at five of the farms using stepwise regression. These models had a consistently high degree of explanatory power for the summary variables of total butterfly abundance and species richness, and the functional groupings of mobile and immobile species. There was good agreement between observed and predicted estimates of species richness and abundance when the models were validated on a further five independent sites. Models to predict the abundance of 11 common butterfly species were also produced. These varied considerably in their predictive power and validity between species. The results clearly demonstrated the beneficial effects of targeted habitat creation for butterflies which is promoted under the Agri-environment Schemes, especially the recently introduced pollen and nectar seed mixtures (WM2) available under the Countryside Stewardship Scheme. The models confirmed the importance of shelter, floristically diverse field margins and the availability of nectar resources from legume species in explaining the abundance of immobile butterfly species in arable landscapes. These sources of nectar and the presence of larval host plants in the crucifer family were important factors in explaining the abundance of mobile species. The results are discussed in terms of the potential of this approach for: (i) assessing habitat quality for butterflies in intensively managed landscapes; (ii) enhancing the value of butterfly monitoring schemes in explaining changes in butterfly abundance at the site and national scale; and (iii) informing habitat management and restoration guidelines for butterfly conservation on arable farmland.     

Conservation in a city: Do the same principles apply to different taxa?

Factors shaping overall species richness and representation of endangered species of vascular flora and butterflies were determined in 48 nature reserves in Prague, Czech Republic. Total species richness of both groups, and the presence of endangered butterflies, reflect the present status of habitats, while that of endangered plants reflects habitat composition at the time of reserve establishment. Reserve area has a much stronger effect on the species richness of sessile plants than mobile butterflies which, especially endangered species, respond more positively to heterogeneity than to area. Both species richness and endangered species peak in reserves half covered with forest, likely because they harbor species of both woodland and non-woodland habitats, and edge specialists. Solely relying on area and disregarding habitat quality, or a failure to conserve small but high quality sites, may be counterproductive for conserving endangered plant and butterfly species. To conserve diversity of plants and butterflies current management practices, often aimed at maintaining large blocks of pre-selected plant communities, should change to include maintenance of fallows, edges and transient zones.     

Indirect evidence for an extinction debt of grassland butterflies half century after habitat loss

Habitat loss often leads to a substantial decline in species richness. However, the extinction of species is typically not instant, but rather involves a time lag. Species richness in recently disturbed habitats is therefore expected to reflect past rather than current habitat availability, with the set of species eventually going extinct representing extinction debt. We explored current species richness of butterflies (Lepidoptera: Rhopalocera) and burnet moths (Lepidoptera: Zygaenidae) with respect to past and current habitat characteristics. The study was conducted in calcareous grasslands, a habitat that has suffered a rapid decline in Europe during the last century. We showed that species richness of habitat specialists correlated positively with both past (75 years ago) and current habitat area, and was best explained by a model incorporating both of these variables. The independent effect of past habitat area presumably indicates the presence of extinction debt in the study region. Species requiring large habitat areas were more likely to show signs of extinction debt. Species richness of other grassland butterflies (those not confined to the focal habitat type) was not associated with past or current habitat area, the pattern indicating their lower sensitivity to changes in focal habitats. The response to habitat loss in specialist butterflies appears faster than in specialist plants, studied in the same landscape earlier. We conclude that linking patterns of species diversity with the temporal dynamics of habitats substantially improves the understanding of the variation in species diversity, and thus helps to identify species of conservation concern.     

Landscape elements as potential barriers and corridors for bees, wasps and parasitoids

Habitat loss and fragmentation in agricultural landscapes lead to severe declines of abundance and richness of many insect species in the remaining isolated semi-natural habitats. We analysed possible barrier effects of large hedges and corridor effects of narrow grass strips that were hypothesized to affect foraging and dispersal of hymenopterans. We selected calcareous grasslands in the vicinity of Göttingen (Germany), which harbour high Hymenoptera diversity and are starting points for foraging and dispersal in the landscape. We installed pan traps to sample bees (i) on the grasslands; (ii) on grassland edges behind adjacent hedges (potential barriers) and without hedges; (iii) on grass strips in 100 m distance to the grassland, which were connected or unconnected to the grassland; and (iv) unconnected (isolated) grass strips in 300 m and 750 m distance to test for corridor and isolation effects on abundance and species richness of foraging wild bees. Additionally we provided trap nests for bees, wasps and their parasitoids on the grasslands and the strips. Species abundance and richness declined with increasing isolation from grasslands for foraging solitary bees, trap-nesting bees, wasps and parasitoids, but not for foraging bumblebees. Hedges did not confine movement of foraging bees. We found no mitigating effects of (100 m) corridor strips on any of the observed groups. We conclude that conservation of semi-natural habitats as sources of bee and wasp diversity is important and that grass strips act as sinks rather than corridors when high quality patches are nearby.     

Grazing as a management tool in dune grasslands: Evidence of soil and scale dependence of the effect of large herbivores on plant diversity

In nature management, the introduction of large herbivores into human-influenced grasslands is thought to be effective to maintain or enhance plant diversity. In order to test the validity of this assumption, we studied the effect of grazing by large herbivores on plant species richness and community heterogeneity across a soil acidity gradient at different spatial scales in dry coastal dune grasslands in western Belgium and north-western France. The effect of grazing on plant richness varied with scale and soil acidity. Grazing had a predominantly positive effect on plant species richness in all habitats at the small scale (0.25 × 0.25 m). However, at site scale (8 × 8 m) it had only positive effects in grasslands with higher soil pH (6-7.4). Similarly, grazing resulted in a homogenization of grassland vegetation at lower pH, while heterogeneity increased with grazing on soil with higher pH. In general, grazing increased the number of rare species, independent of soil pH. The results confirm that the impact of grazing on plant diversity depends on the scale considered and that the effects further depend on soil acidity which was correlated to biomass production at the given soil pH range in this study. Although grazing seems an appropriate management tool to maintain and even enhance plant biodiversity under many circumstances, it may negatively affect plant species richness, where soil resources limit plant biomass production.     

Landscape occupancy and local population size depends on host plant distribution in the butterfly Cupido minimus

We tested whether the landscape occupancy and local population size of the monophagous butterfly Cupido minimus can be predicted by patch size and isolation of its host plant or by other habitat characteristics. C. minimus and its larval food plant Anthyllis vulneraria are classified as rare and endangered in northern Germany. Adults of C. minimus are ranked as the most sedentary butterfly species in northern Europe.Around the city of Göttingen (Germany), we checked all known locations of A. vulneraria (n=70) in June 2002 for butterfly eggs (in blooming flowerheads) and adult butterflies (within 20-min transects).We found eggs of C. minimus or a high number of adults (>7) in all habitats with A. vulneraria (which are calcareous grasslands) even when isolated up to 2-4 km. In multiple regression analyses, local population size of adult butterflies was positively related to the cover of its larval food plant A. vulneraria explaining 65% of variance. Cover of A. vulneraria increased with increasing habitat area and increasing cover of plant species in flower and decreased with increasing cover of shrub layer. Habitat isolation and further factors describing habitat quality were not related to C. minimus population size or cover of its larval food plant.The results suggest that dispersal ability of C. minimus is greater than expected and that management should focus to increase A. vulneraria patches. For conservation, low impact grazing once a year and removing of excessive shrubs in winter seems to be the most appropriate strategies.     

Conservation value of forest fragments to Palaeotropical bats

Forested landscapes in Southeast Asia are becoming increasingly fragmented, making this region a conservation and research priority. Despite its importance, few empirical studies of effects of fragmentation on biodiversity have been undertaken in the region, limiting our ability to inform land-use regimes at a time of increased pressure on forests. We estimated the biodiversity value of forest fragments in peninsular Malaysia by studying fragmentation impacts on insectivorous bat species that vary in dependence of forest. We sampled bats at seven continuous forest sites and 27 forest fragments, and tested the influence of fragment isolation and area on the abundance, species richness, diversity, composition and nestedness of assemblages, and the abundance of the ten most common species. Overall, isolation was a poor predictor of these variables. Conversely, forest area was positively related with abundance and species richness of cavity/foliage-roosting bats, but not for that of cave-roosting or edge/open space foraging species. The smallest of fragments (<150 ha) were more variable in species composition than larger fragments or continuous forest, and larger fragments retained substantial bat diversity, comparable to continuous forest. Some fragments exhibited higher bat abundance and species richness than continuous forest, though declines might occur in the future because of time lags in the manifestation of fragmentation effects. Our findings suggest that fragments >300 ha contribute substantially to landscape-level bat diversity, and that small fragments also have some value. However, large tracts are needed to support rare, forest specialist species and should be the conservation priority in landscape-level planning. Species that roost in tree cavities or foliage may be more vulnerable to habitat fragmentation than those that roost in caves.     

Butterflies and diurnal moths along road verges: Does road type affect diversity and abundance?

Roadsides form potential habitats for several grassland species adapted to regular mowing management. We studied the communities of butterflies and day-active moths in 51 sites along the verges of the three road types, i.e., highways, urban roads and rural roads. Despite different traffic densities and widths of the road and verge, the groups were rather similar with regard to soil properties, vegetation structure and mowing intensity. The species richness and total abundance of butterflies (53 species, 5964 individuals) and diurnal moths (46 species, 4626 individuals) were also rather similar in each road type, although a preference for wider verges was observed. Butterfly diversity increased (but not significantly) from the verges of narrow rural roads to wider highways. The highest numbers of meadow species were recorded along highways and the total abundance, especially of diurnal moths, decreased in accordance with the road size. High nectar abundance was the most important factor increasing the numbers of meadow butterflies along road verges, while meadow moths were mostly favoured by shelter provided by tall vegetation. Verges surrounded by cultivated fields were generally related to low numbers of both Lepidoptera groups, whereas adjacent forests increased the total number of all species and favoured several butterflies inhabiting forest edges. The adjacent environment inflicted compositional differences on the Lepidoptera fauna of the three road types. The results indicate that road verges should be considered an important reserve for species dependent on semi-natural grasslands in Finland. A growing interest in accommodating current roadside management for conserving biodiversity is likely to benefit Lepidoptera communities in the verge habitats.     

东北平原典型玉米种植区农业景观植物多样性研究——以昌图县为例

非耕作生境是农业景观中的重要组成部分,为生物提供食物和栖息地,对生物多样性保护具有重要意义。本文以辽宁省昌图县为例,选取了20个非耕作生境比例为0~50%的网格(1 km?1 km)为样区,采用典型样地法对调查区域内农业景观中的林地、田间路、草地、沟渠、果园5类主要非耕作生境中的植物群落进行调查,探讨不同非耕作生境类型和比例中植物多样性及其与景观异质性之间的关系。研究结果表明,随着非耕作生境比例增加,植物物种多样性和均匀度先增加后减小,在20%~30%时达到峰值;非耕作生境比例在0~40%范围内时,植物物种丰富度同样呈现先增加后减小,且在20%~30%时达到峰值;非耕作生境比例高于40%时,植物物种丰富度再次出现峰值且高于20%~30%。随着非耕作生境比例的增加,农业景观香浓多样性、香浓均匀度指数和景观斑块形状复杂程度逐渐增加,蔓延度恰好相反。不同生境中重要值最高的均为禾本科植物,但植物种不同;优势种优势度为果园沟渠草地田间路林地。果园、草地和沟渠的物种多样性和均匀度指数显著高于林地和田间路,丰富度指数为草地林地沟渠果园田间路,且草地、果园和田间路的不同调查区域间植物群落指数存在较大的变异性。草地、果园、沟渠、田间路和林地中景观异质性与物种多样性相关性顺次降低。研究结论表明,东北平原典型玉米种植区农业景观中,最适宜非耕作生境比例为20%~30%;非耕作生境中林地、沟渠对物种多样性维持、湿生植物多样性保护具有积极作用;不同生境干扰类型和方式不同,景观异质性与植物物种多样性相关性程度也不同。在今后农业景观生物多样性保护中应综合考虑非耕作生境的类型和比例,干扰的类型和方式等多种因素对生物多样性、生态服务及农业产量的影响。     

Wild pollinator communities are negatively affected by invasion of alien goldenrods in grassland landscapes

The increasing spread of invasive alien plants has changed biodiversity throughout the world. To date research in this area has focused on how invasive plant species affect pollinator behaviour, but there is a lack of data on the impact that alien plant species have on wild pollinator populations. Since their introduction in the 19th century, and rapid spread after the 1950s, alien goldenrods (Solidago canadensis, Solidago gigantea) have been among the most successful invasive plant species in Europe. We studied the effects of goldenrods on wild pollinator communities in SE Poland. The abundance, species richness and diversity of wild bees, hoverflies and butterflies were compared between wet meadows invaded by goldenrod (10 transects) and non-invaded controls (10 transects). Furthermore, we compared the plant diversity and average cover between the two groups of sites. Invasion of goldenrods had a very strong negative effect on wild pollinator diversity as well as abundance. Plant diversity and average cover were also negatively affected by goldenrod invasion. Wild pollinators were grouped according to their nesting and food specialization, but none were resistant to the invasion, indicating that introduced goldenrod may affect the entire wild pollinator community. Our study emphasises the urgent need to develop specific protection plans for wild pollinators in habitats threatened by foreign plants and we call for the introduction of programs to stop the invasion of goldenrod not only in Poland, but also on a continental scale.     

Scale-dependent homogenization: Changes in breeding bird diversity in the Netherlands over a 25-year period

Changes in breeding bird diversity in the Netherlands between 1973-1977 and 1998-2000 were evaluated by testing three hypotheses related to the loss of biodiversity: (1) species diversity is declining, (2) biotic homogenization is increasing and (3) rare species are declining more severely than abundant species. Using data collected for two successive national breeding bird atlases, changes in diversity were assessed at different spatial scales (local, regional and national) and among species characteristic for different landscapes (farmland, woodland, heathland, wetland, coastal habitats and urban habitats). National species richness, diversity and equitability had increased between the two atlas periods, with more species increasing than decreasing in range and abundance. Most species in the large groups of woodland and wetland birds showed positive trends, whereas most in the smaller groups of heathland, reed-breeding and meadow birds showed negative trends. However, findings varied between regions and localities. Increases in species richness occurred mainly in regions in the low-lying, western part of the country which were previously relatively poor in species. By contrast, species richness decreased in some previously species-rich regions in the eastern part of the country. This has resulted in a homogenization of breeding bird communities between regions. We advocate the conservation and restoration of regional identity as a priority for landscape planning in the Netherlands. We did not find a clear relation between species abundance and trends, although both rare and very abundant species tended to decrease on average.     

Remnant grassland habitats as source communities for plant diversification in agricultural landscapes

Lately there has been a shift in Sweden from grazing species-rich semi-natural grasslands towards grazing ex-arable fields in the modern agricultural landscape. These fields normally contain a fraction of the plant species richness compared to semi-natural grasslands. However, small remnant habitats have been suggested as important for plant species diversity and conservation as they may function as refugia for grassland specialists in fragmented and highly modified agricultural landscapes. In this study, we examined whether plant communities on small remnant habitats, i.e. midfield islets, can function as sources for grassland species to disperse out into surrounding grazed ex-fields (former arable fields). We examined species richness and grassland specialists (species favoured by grazing) and their ability to colonize fields after 5 and 11 years of grazing. The fields that had been grazed for a shorter time were fairly species-poor with few grassland specialists. A longer period of grazing had a positive effect on total and small-scale species diversity in both islets and fields. Species composition became more similar with time, and the number of grassland specialists in both habitats increased. We found that grassland specialists dispersed step-wise into the fields, and the number of grassland specialists decreased with distance from the source. Our study suggests that remnant habitats, such as midfield islets, do function as a source community for grassland specialists and enhance diversification of grassland species when grazing is introduced. For long-term conservation of plant species, incorporating small refugia into larger grazing complexes may thus enhance species richness.     

Magnitude of Species Diversity Effect on Aboveground Plant Biomass Increases Through Successional Time of Abandoned Farmlands on the Eastern Tibetan Plateau of China

Recent empirical and theoretical studies have shown that magnitude and direction of biodiversity effects on ecosystem functioning can shifts over time. Here, we used species richness and plant abundance (total individual plant stem density) as proxies for species diversity and aboveground biomass for productivity. We used an analytical approach combining both chronosequence and 6 year of vegetation monitoring in a subalpine ecosystem as a model system to assess temporal species richness–abundance–aboveground biomass relationships at different successional stages and spatial scales. We observed that both species richness and plant aboveground biomass increased rapidly early in succession after land abandonment, then after 10 years of abandonment reached a steady state. We found that the relationship between species richness and plant abundance with aboveground biomass was strengthening over successional time. In all successional stages, species richness had stronger positive effects as compared with plant abundance on plant aboveground biomass. Species richness was linearly correlated with aboveground biomass, whereas plant abundance showed a humped‐back relationship with aboveground biomass across all successional stages. Our results showed an increase in the effect of plant diversity over time, and a combination of both plant species richness and abundance is correlated with plant productivity throughout successional time, knowledge that maybe important to managing ecological restoration and conservation. Copyright © 2016 John Wiley & Sons, Ltd.     

Plant species extinction debt in a temperate biodiversity hotspot: Community, species and functional traits approaches

Destruction and fragmentation of (semi-) natural habitats are considered the main causes of biodiversity loss worldwide. Plant species may exhibit a slow response to fragmentation, resulting in the development of an extinction debt in fragmented plant communities. The detection of extinction debt is of primary importance in habitat conservation strategies. We applied two different approaches proposed in the literature to identify extinction debt in South-East Belgium calcareous grasslands. The first method compared species richness between stable and fragmented habitat patches. The second explored correlations between current species richness and current and past landscape configurations using multiple regression analyses. We subsequently examined results generated by both methods. In addition, we proposed techniques to identify species that are more likely to support extinction debt and associated functional traits. We estimated a respective extinction debt of approximately 28% and 35% of the total and specialist species richness. Similar results were obtained from both methods. We identified 15 threatened specialist species under the current landscape configuration. It is likely the landscape configuration no longer supports the species habitat requirements. We demonstrated that non-clonal species are most threatened, as well as taxa that cannot persist in degraded habitats and form only sparsely distributed populations. We discussed our results in light of other studies in similar habitats, and the overall implications for habitat conservation.     

Impact of farm size and topography on plant and insect diversity of managed grasslands in the Alps

Since the second half of the 20th century, the intensification of land-use practices and the associated decline in semi-natural habitats have been the major drivers of farmland biodiversity loss. In many marginal agricultural systems, a structural transformation of farms, from small and traditional to large and intensive, has also been observed. We unravelled the impact of farm size and slope on plant, orthopteran and butterfly diversity in 132 hay meadows in a region of the Italian Alps. We defined three farm size classes representing different levels of intensification and used mixed models to test the influence of farm size along with topographic slope. The diversity of plants, orthopterans and butterflies declined with management intensity at the field scale, which mainly depended on farm size and grassland topography. We found a positive effect of slope and a negative influence of farm size on species richness of the three taxonomic groups. Large farms were strongly associated with higher production of organic fertilizers and higher soil fertility than small traditional farms, irrespective of meadow slope. At the regional scale, we found that large farms managed flatter meadows (slope = 9.0) than small traditional farms (slope = 13.5), contributing to the abandonment of steep species-rich grassland areas. Regional stakeholders should consider targeted conservation schemes to prevent the ongoing substitution of small farms with large intensive farms. A complementary solution could be to target future conservation measures to support farms with low production of organic fertilizers and to reward the maintenance of the current management of steep meadows.     

Butterflies highlight the conservation value of hay meadows highly threatened by land-use changes in a protected Mediterranean area

Butterfly assemblages were used to characterize and evaluate the conservation value of the main habitat types in the Aiguamolls de l’Empordà Natural Park (north-eastern Spain), an important protected wetland area on the Mediterranean coast. Butterfly data were obtained from a number of transects walked as part of the Catalan Butterfly Monitoring Scheme, which uses a standardized methodology for monitoring butterflies. A Mantel test indicated a strong association between habitat types and the composition of butterfly assemblages and a principal component analysis ordinated individual butterfly species along a gradient from woodland to open areas, thereby indicating various degrees of shade tolerance. In addition, cluster analysis distinguished two main groups of habitats based on the similarities of their butterfly fauna: woodland and bramble clumps and a group of three different kinds of grasslands (traditionally hay meadows, pastures, and alfalfa fields). Hay meadows flooded in winter (the so-called closes) appeared always as the highest ranked habitat in terms of conservation evaluation: they have more butterflies and a slight tendency to harbor more and generally rarer species. This conclusion coincides with that of previous investigations that have indicated that the most diverse and rare plant communities in the whole Natural Park are present in the closes, and highlights the importance of traditionally managed hay meadows for wildlife. However, these hay meadows - one of the rarest habitats in the Mediterranean region - are in alarming decline and have become the most threatened habitat in this protected area: no longer profitable, we believe that the future of the closes will depend ultimately on the existence of agri-environmental schemes.