Biodiversity on old permanent versus restored grassland is driven by small‐scale land‐use intensity and habitat connectivity

QuestionsWe investigated the effects of grassland management intensity and temporary conversion to other land uses on abiotic and biotic properties of subtropical grasslands. We used species‐rich permanent grasslands of medium management intensity (PG‐M) as a reference, and asked the following questions: (1) do permanent grasslands with low and high management intensities (PG‐L and PG‐H, respectively) have different plant diversity and species composition than reference grasslands; and (2) do secondary grasslands recovering from conversion to arable fields (SG‐A) or pine plantations (SG‐P) differ from permanent grasslands in their plant species composition and abiotic conditions?LocationHighland grasslands, Campos de Cima da Serra, Rio Grande do Sul (RS), Brazil.MethodsWe analysed variation in plant species composition and diversity among 80 grassland sites, including three types of permanent grassland and two types of secondary grassland. An indicator species analysis was used to identify characteristic species for the different land‐use types. We used a linear discriminant analysis to investigate differences in soil conditions among land‐use types.ResultsBoth PG‐L and PG‐H differed from PG‐M regarding plant species composition. Although PG‐L shared many typical grassland species with PG‐M, their communities were generally less diverse. PG‐H, on the other hand, not only had fewer species but also deviated from PG‐M in species composition. Secondary grasslands on former arable fields and plantations differed from PG‐M in species composition and showed lower diversity. Soil conditions of SG‐P were similar to those of PG‐L and PG‐M, but they were distinct from those of PG‐H and SG‐A.ConclusionsAll land‐use types showed deviations from reference grasslands (PG‐M). The decrease in the number of species in PG‐L may be reversed if traditional management intensity is re‐introduced, whereas strong compositional changes in SG‐P may require the re‐introduction of grassland species. This is also true for PG‐H and SG‐A: both showed marked deviations from reference grasslands in biotic and abiotic components. Overall, restoration of altered land‐use types to near‐natural subtropical grassland seems feasible, but suitable techniques have to be developed.

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

Permanent grasslands cover more than a third of European agricultural land and are important for a number of ecosystem services. Permanent grasslands used for agriculture are broadly separated into agriculturally improved and semi-natural grasslands. High cultural and natural values linked to semi-natural grasslands are well documented. However, in boreal and hemi-boreal agricultural landscapes, less information is available about the areal coverage of improved permanent grasslands and their role for ecosystem service provision and biodiversity. In Sweden, grasslands are administratively separated into semi-natural (i.e., land that cannot be ploughed) or arable (i.e., improved temporary or permanent grassland on land that can be ploughed). We used data from a large-scale environmental monitoring program to show that improved permanent grassland (i.e., permanent grasslands on arable fields) may be a previously unrecognised large area of the agricultural land use in Sweden. We show that improved permanent grasslands together with semi-natural grasslands are both comparable but also complementary providers of a range of ecosystem services (plant species richness, plant resources for pollinators and forage amount for livestock production). However, as expected, semi-natural grasslands with the highest-level AESs (special values) show high species richness values for vascular plants, plants indicating traditional semi-natural management conditions and red-listed species. Improved permanent grasslands on arable fields are likely an underestimated but integral part of the agricultural economy and ecological function in boreal landscapes that together with high nature value semi-natural grasslands provide a broad range of ecosystem services.

Grassland biomes have developed a multitude of successful strategies and adaptations to various, often adverse environmental conditions through evolution. Grasslands have a wide tolerance to climatic conditions (temperature, precipitation) and can also tolerate temporary drought periods well. An important parameter for assessing drought tolerance of grass stands is the ratio of root biomass to above-ground phytomass, the R:S (root: shoot ratio). A higher value indicates the crop’s adaptation to drought-induced stress. In permanent grasslands in Central Europe, we recorded a significant proportion of root biomass (6.69-10.31 t ha<sup>-1</sup>) with an R:S ratio of 5.16. Other positive strategies include the ability of grasses to reproduce both vegetatively and generatively. Grass species exclusively prefer wind pollination; thus, they are not dependent on insect pollination. For different climatic zones, they have a suitable type of photosynthesis (C<sub>3</sub> or C<sub>4</sub>). Grasslands are very well adapted to frequent grazing of phytomass or defoliation (mowing, fire), subsequently regenerating effectively. They are rich in high species biodiversity, contributing to their high eco-stability in agricultural landscapes. We also recorded grassland responses to the presence of heavy metals in the soil. Based on the bioconcentration factor (BCF < 1), grasslands (in Central Europe) acted as excluders of several heavy metals (Cd, Co, Cr, Pb, Mn, Cu, Fe, and Ni). These heavy metals are primarily accumulated in the soil and roots, with the above-ground part of the crop not being contaminated. Permanent grasslands are also effective in carbon sequestration and, based on several observations, are well adapted to the negative consequences of climate change.

Questions:Which factors influence the persistence of vascular grassland plants in long‐abandoned (at least 50 yr) arable fields and meadows? What might be the implications of current levels of species richness on abandoned arable fields and meadows for future restoration?Location:Forested highlands of Kilsbergen, south central Sweden.Methods:The abundance of all vascular plant species was investigated in three habitat types: former arable fields, hay meadows and outlands (pastures) at 27 farms, abandoned for either approximately 50 yr or 90 yr. Time since abandonment, tree cover, soil depth, degree of soil podsol development, size of the infield area and two measures of connectivity were used as predictors for species richness and species composition.Results:Former outland had denser tree cover, fewer species and fewer grassland species than former arable fields and hay meadows, irrespective of time since abandonment. Former hay meadows and arable fields with a longer time since abandonment were less rich in species, more wooded and had greater podsolization than meadows and fields abandoned at a later stage. Species richness was higher in hay meadows and arable fields at farms with larger infield area and deeper soils compared with farms with smaller infield area and shallower soils. The greatest richness of species and most open habitat were former arable fields at larger farms abandoned 50 yr before the study. Former arable fields had the highest number of grassland species.Conclusion:After 50 yr of abandonment, former arable fields were the most important remnant habitats for grassland species and may be a more promising target for restoration than formerly managed grasslands.

Halting and reversing the ongoing insect decline requires in-depth knowledge on key drivers. Due to their sensitivity to habitat quality, butterflies are valuable indicators for grassland management intensity, including mowing. However, most studies examining mowing regime impacts on butterflies are limited to small spatial extents. Here, we tested the potential of citizen science butterfly monitoring data for assessing landscape-level effects of mowing regimes (number of mowing events and timing of the first event) and edge density (density of boundaries between different land-cover types) on butterfly richness, abundance, and community composition. We used generalised linear mixed-effects models to relate nationwide data from the German Butterfly Monitoring Scheme (DEBMS) to high-resolution satellite imagery on mowing events in permanent grasslands (grasslands excluded from crop rotation). As butterfly transects may not consistently be located within grasslands, we ran our models for different thresholds from 0 to 50%, representing increasing shares of the transect route situated within permanent grasslands (10% intervals). We did not find significant associations between mowing regimes and butterflies when focussing on species richness and abundance of all species inhabiting open land. However, we found strong positive associations of delayed mowing with the abundance of grassland specialists with increasing grassland shares per transect. Further, we found negative associations of delayed mowing with the annual number of generations and of more frequent mowing with the abundance of specialists, depending on the share of grassland per transect. Edge density had a positive association with species richness and abundance of species inhabiting open land, as well as abundance of grassland indicator species and grassland specialists in landscapes with a low grassland share per transect. Our findings underscore the importance of low-intensity managed permanent grasslands at the landscape scale for specialised butterflies. Additionally, we highlight the importance of a high density of boundaries for open-land and specialised butterflies, particularly in landscapes with highly fragmented permanent grasslands. To improve future analyses of grassland management impacts, we recommend expanding DEBMS monitoring sites to cover a larger grassland management intensity gradient and to place more transects within grasslands.

Across Europe, calcareous grasslands become increasingly fragmented and their quality deteriorates through abandonment and land use intensification, both affecting biodiversity. Here, we investigated local and landscape effects on diversity patterns of several taxonomic groups in a landscape of highly fragmented calcareous grassland remnants. We surveyed 31 grassland fragments near Göttingen, Germany, in spring and summer 2017 for vascular plants, butterflies and birds, with sampling effort adapted to fragment area. Through regression modelling, we tested relationships between species richness and fragment size (from 314 to 51,395 m2), successional stage, habitat connectivity and the per cent cover of arable land in the landscape at several radii. We detected 283 plant species, 53 butterfly species and 70 bird species. Of these, 59 plant species, 19 butterfly species and 9 bird species were grassland specialists. Larger fragments supported twice the species richness of plants than small ones, and hosted more species of butterflies, but not of birds. Larger grassland fragments contained more grassland specialist plants, but not butterfly or bird specialists. Increasing amounts of arable land in the landscape from 20 to 90% was related to the loss of a third of species of plants, and less so, of butterflies, but not of birds. Per cent cover of arable land negatively correlated to richness of grassland specialist plants and butterflies, but positively to grassland specialist birds. We found no effect by successional stages and habitat connectivity. Our multi-taxa approach highlights the need for conservation management at the local scale, complemented by measures at the landscape scale.

Interactions between conservation agricultural practice and landscape composition promote weed seed predation by invertebrates

In suburban regions, vacant lots potentially offer significant opportunities for biodiversity conservation. Recently, in Japan, due to an economic recession, some previously developed lands have become vacant. Little is known, however, about the legacy of earlier earthmoving, which involves topsoil removal and ground leveling before residential construction, on plant community composition in such vacant lots. To understand (dis)assembly processes in vacant lots, we studied 24 grasslands in a suburban region in Japan: 12 grasslands that had experienced earthmoving and 12 that had not. We surveyed plant community composition and species richness, and clarified compositional turnover (replacement of species) and nestedness (nonrandom species loss) by distance‐based β‐diversities, which were summarized by PCoA analysis. We used piecewise structural equation modeling to examine the effects of soil properties, mowing frequency, past and present habitat connectivities on compositional changes. As a result, past earthmoving, mowing frequency, soil properties, and past habitat connectivity were found to be the drivers of compositional turnover. In particular, we found legacy effects of earthmoving: earthmoving promoted turnover from native grassland species to weeds in arable lands or roadside by altering soil properties. Mowing frequency also promoted the same turnover, implying that extensive rather than intensive mowing can modify the negative legacy effects and maintain grassland species. Decrease in present habitat connectivity marginally enhanced nonrandom loss of native grassland species (nestedness). Present habitat connectivity had a positive effect on species richness, highlighting the important roles of contemporary dispersal. Our study demonstrates that community assembly is a result of multiple processes differing in spatial and temporal scales. We suggest that extensive mowing at local scale, as well as giving a high conservation priority to grasslands with high habitat connectivity at regional scale, is the promising actions to maintain endangered native grassland species in suburban landscapes with negative legacy effects of earthmoving.

Agricultural intensification is a major threat to farmland biodiversity and associated ecosystem services. Semi-natural habitats are integral to the preservation of farmland biodiversity and ecosystem services, however, the extent in which they contribute to specific services is largely unclear. We studied predation rates of ground-dwelling predatory arthropods, and pollination success within old permanent grasslands, newly established grasslands and arable fields near and far from new grasslands. We evaluated whether grassland restoration can enhance pollination and biological control in crop fields. For this purpose, we established new grassland strips within cereal fields, which directly bordered existing permanent grasslands. We evaluated if the distance to these old and new grasslands affects the delivery of the two ecosystem services within crop fields. We found significantly higher seed numbers and seed weight in sentinel plants placed in old grasslands, new grasslands and nearby arable fields compared to distant arable fields. We also found significantly decreasing seed numbers and seed weight in sentinel plants placed in distant arable fields with increasing distance from old grasslands, while pollination success was not affected by distance in nearby arable fields. Contrary, we did not find any significant effects of new grasslands on biological control. Our study showed that 3 years after establishing grasslands arable fields benefited from the proximity of flower-rich new grasslands through increased pollination success though not regarding biological control. This indicates that, on a short term, establishing new grasslands can support beneficial arthropods in providing ecosystem services such as pollination. Predators, in contrast, might take longer to establish effective populations that denote higher predation rates. Our study provides a baseline for future long-term studies to better evaluate pollination and pest control patterns within arable fields.

Recent studies on the determinants of distribution and abundance of animals at landscape level have emphasized the usefulness of the metapopulation approach, in which patch area and habitat connectivity have often proved to explain satisfactorily existing patch occupancy patterns. A different approach is needed to study the common situation in which suitable habitat is difficult to determine or does not occur in well‐defined habitat patches. We applied a landscape ecological approach to study the determinants of distribution and abundance of the threatened clouded apollo Parnassius mnemosyne butterfly within an area of 6 km 2 of agricultural landscape in south‐western Finland. The relative role of 24 environmental variables potentially affecting the distribution and abundance of the butterfly was studied using a spatial grid system with 2408 grid squares of 0.25 ha, of which 349 were occupied by the clouded apollo. Both the probability of butterfly presence and abundance in a 0.25 ha square increased with the presence of the larval host plant Corydalis solida the cover of semi‐natural grassland, the amount of solar radiation and spalial autocorrelation in butterfly occurrence. Additionally, butterfly abundance increased with overall mean patch size and decreased with maximum slope angle and wind speed. Two advantages of the employment of a spatial grid system included the avoidance of a subjective definition of suitable habitat patches and an evaluation of the relative significance of different components of habitat quality at the same time with habitat availability and connectivity. The large variation in habitat quality was influenced by the abundance of the larval host plant and adult nectar sources but also by climatological. topographical and structural factors. The application of a spatial grid system as used here has potential for a wide use in studies on landscape‐level distribution and abundance patterns in species with complex habitat requirements and habitat availability patterns.

Land‐use intensification has caused dramatic declines in grassland biodiversity, and in Europe this decline has not yet been halted. Therefore, a major challenge in ecological restoration is to effectively restore plant diversity in permanent grasslands, that is, long‐term managed grassland not being used as cropland. As species richness is often limited by seed dispersal, introducing locally absent species is crucial. Seeding diverse seed mixtures is an appropriate tool, but restoration outcomes are highly variable. Considering constraints by land‐use intensity and plant functional traits during restoration could improve the efficacy of restoration efforts. We established a full‐factorial experiment with high‐diversity seeding and topsoil disturbance in 73 grasslands along land‐use intensity and productivity gradients and evaluated the restoration success over 5 years. In addition, after 5 years we assessed the number of established species and tested whether specific traits promoted the establishment of sown species in interaction with productivity. Plant diversity increased considerably when seeding and disturbance were combined while seeding alone only slightly increased species richness. Along land‐use gradients, we found no direct effects of grazing or mowing on the establishment of sown species, but fertilization indirectly limited establishment in the combined treatment via a negative effect of productivity. Functional traits structured the establishment of sown species, especially in the combined treatments, but effects varied with productivity. Species with low seed mass and low specific leaf area had greater establishment success in low‐productivity grasslands, whereas species with high seed mass had greater establishment in high‐productivity grasslands. Synthesis and applications. Our results highlight the potential of using diverse seed mixtures for biodiversity restoration in a wide range of permanent grasslands, especially when combined with topsoil disturbance. However, productivity both limited restoration success and affected establishment via an interaction with plant functional traits. As productivity is a major constraint in grassland restoration, we strongly recommend to first stop fertilization and reduce soil nutrient loads in highly productive grasslands. Restoration by seeding, with or without disturbance, should only be applied when productivity is reduced and the local environment should be considered to compile site‐specific seed mixtures to maximize restoration success. ​

Sowing of regionally specific seed mixtures on former arable land is increasingly used to restore species‐rich grasslands but it often faces important obstacles in environmental conditions and colonisation from preserved surrounding grasslands. Long‐term landscape scale studies, which explore the processes governing plant establishment from seed mixtures and later colonisation from the surrounding landscape are scarce. We studied the species and functional trait composition of 32 grasslands restored 1–11 years before the first sampling by sowing regional seed mixtures in the White Carpathian Mts (SE Czech Republic). We compared them with 23 well‐preserved permanent grasslands in their surroundings. In each grassland, we estimated plant species cover in three plots of 25 m2, in restored grasslands in 2009, 2014 and 2019, in permanent grasslands in 2009. The species composition of the restored grasslands converged towards the permanent grasslands due to expansion of dry grassland species and retreat of mesic grassland and weed species. The majority (60%–71%) of the vegetation cover of restored grasslands was formed by sown species, while the species number was mainly determined by colonising unsown species (61%–63%). The species number of restored grasslands remained lower than that in permanent grasslands. Functional trait composition (community weighted mean) of the sown seed mixtures, permanent grasslands and restored grasslands overlapped in all three samplings. With increasing grassland age, species with resource‐retaining traits of low specific leaf area and high leaf dry matter content, lower stature, higher seed mass and lower capacity for clonal reproduction expanded. Functional trait diversity of the plots was mostly lower than expected by null model randomisations of community, which indicates strong environmental filtering. Comparison of newly colonising species and extinct species indicated that mainly species with traits similar to the rest of the community are able to colonise the grasslands successfully. Synthesis and applications: Sowing of regionally specific seed mixtures was successful and demonstrated to be a fast way of grassland restoration, particularly in terms of functional trait composition. The resulting species diversity depended on the colonisation processes, which are controlled by the functional composition of the local communities.

Woody plant encroachment restructures bird communities in semiarid grasslands

Questions Which trends and patterns of community change occurred in Nardus grasslands over recent decades in parts of the Continental biogeographic region of Germany? Are patterns and trends consistent across two study regions? Do impacts of environmental changes on Nardus grasslands in Central Europe correspond to those identified in the European Atlantic biogeographic region? Location East Hesse Highlands, Germany. Methods In 2012–2015, we re‐surveyed quasi‐permanent plots that had been initially surveyed between 1971 and 1987, and re‐measured soil parameters. We tested for differences in species frequency and cover, mean Ellenberg indicator values, species richness, and soil variables. Nitrogen and sulphur deposition data were analysed to evaluate possible effects of atmospheric pollutants. We used regression and redundancy analyses to identify environmental drivers responsible for changes in species composition. Results Across regions, we found significant increases in soil pH, Ellenberg R and N indicator values, plant nutrient indicators, forbs, species of agricultural grasslands and of fallows. By contrast, the C:N ratio , Nardus grassland specialists, low‐nutrient indicators, and graminoids declined. Changes in species composition were related to changes in pH and management. There was a strong decrease in sulphur and a moderate increase in nitrogen deposition, whose local‐scale pattern did not correlate with changes in soil parameters. However, there was an effect of local NH y changes on species composition. Conclusions The findings indicate significant overall eutrophication, a trend towards less acidic conditions and insufficient management, which are widely consistent across our study regions and correspond to recent reports of vegetation changes and recovery from acidification in the Atlantic biogeographic region. We assume the reduced sulphur deposition during recent decades to be a major driver of these changes, combined with increased nitrogen deposition and reduced management intensity. This suggests a large‐scale validity of processes that influenced changes in Nardus grasslands of Western and Central Europe.