Markus Wagner’s research while affiliated with UK Centre for Ecology & Hydrology and other places

This account presents information on all aspects of the biology of Geranium pratense L. (Meadow Crane's‐Bill). The main topics are presented within the standard framework of the Biological Flora of Britain and Ireland : distribution, habitat, communities, responses to biotic factors, responses to environment, structure and physiology, phenology, floral and seed characters, herbivores and disease, history and conservation. Geranium pratense is a perennial gynodioecious forb of neutral grassland. In Britain and Ireland, it is particularly abundant on roadside verges, railway embankments, the margins of watercourses and woodland rides. It is generally intolerant of grazing and is absent or scarce in livestock‐grazed grassland. Geranium pratense is widespread in England, Wales and Scotland but is scarce in Ireland. It has an extensive native range in Europe and Asia, extending eastwards to Russia, north‐western China and Mongolia. It has been widely introduced to new sites within its native range and has been introduced to Canada, the USA and New Zealand. Geranium pratense usually occurs on free‐draining soils but also infrequently where drainage is impeded. The soils are often nutrient‐rich and weakly acidic to weakly alkaline. The underlying geology is usually non‐acidic sedimentary rocks or superficial deposits. Geranium pratense is protandrous and is pollinated by various insects of the orders Hymenoptera, Diptera and Lepidoptera, particularly bumblebees, solitary bees, hoverflies and butterflies. Eleven species of phytophagous insect have been recorded on G. pratense in Britain and Ireland. Geranium pratense has little or no capacity for vegetative spread. Primary seed dispersal is ballistic and seeds may be flung over distances of up to several metres. The species has a transient seed bank, that is germination typically takes place in the winter and spring after seed production, after the physically dormant seeds have become permeable. Seedling establishment is higher in vegetation‐free gaps than in undisturbed grassland vegetation. There has been no significant change in its distribution between the late 1950s and 2019, although since 2000, it has expanded its range, mainly via introductions, in northern and western Scotland, west Wales and in Ireland. Alien sites have increased markedly since the 1960s due to introductions from wildflower seed sowing and spread from gardens.

Green hay transfer from species‐rich donor sites is now commonly used in Europe to restore species‐rich semi‐natural grassland, both on ex‐arable land and on formerly intensive species‐poor grassland. However, species transfer rates are usually well below 100%, and due to lack of further colonization by additional target species, continued progress towards the target plant community after initial restoration is often very slow. We used data from a restoration experiment aiming to re‐establish species‐rich grazed meadows of the MG5 grassland type according to the British National Vegetation Classification to investigate relationships between species abundance at a donor site, species capture by green hay and its seed content, and success of species establishment on experimental plots in formerly intensively managed species‐poor grassland undergoing restoration. Our results show that species with higher abundance at the donor site got more likely captured as seed in the transferred green hay, and more likely established after hay application at the recipient site. Species with low abundance at the donor site and simultaneously possessing specific germination requirements preventing immediate establishment after hay transfer were particularly unlikely to get established after hay transfer. These findings can provide guidance for additional measures aimed at ensuring establishment of a wider range of target species. Such measures could include the targeted sowing of species in addition to green hay application, and management of restored grassland swards to extend or re‐open an initial window of opportunity for the establishment of green hay species that might not be germinable immediately after hay transfer. This article is protected by copyright. All rights reserved.

The two most common approaches to target species introduction in European meadow restoration are green‐hay transfer from species‐rich donor sites and the use of diverse seed mixtures reflecting the chosen target community. The potential of both approaches to restore species‐rich grassland has been variously reviewed, but very few studies have experimentally compared them at one and the same site. Moreover, studies involving one or both approaches have rarely taken into account environmental gradients at a site, and measured the impacts of such gradients on restoration outcomes. Such gradients do e.g. exist during grassland restoration on former arable land in river floodplains, where gradients in the occurrence of flooding, and in associated edaphic characteristics such as nutrient availability, might affect restoration outcomes. Using a randomised complete block experimental design, based on five different indicators of restoration progress, we compared the usefulness of green‐hay application and diverse‐seeding to restore species‐rich grazed meadows of the MG5 grassland type according to the British National Vegetation Classification, and also investigated how restoration outcomes differed after four years between areas within experimental plots characterized by high flood risk, and areas characterized by low flood risk. Overall, both restoration approaches yielded similar results over the course of the experiment, whereas high flood risk levels and associated edaphic factors such as high availability of phosphorus negatively affected restoration progress particularly in terms of floristic similarity to restoration targets. These results highlight the need to take into account environmental gradients during meadow restoration.

Calcareous grasslands are highly biodiverse semi-natural habitats. A particular challenge to European calcareous grassland management in recent years has been the increasing dominance of the competitive grass Brachypodium pinnatum. B. pinnatum is difficult to control by traditional means but selective herbicides offer a potential alternative. We trialled five selective herbicides on two levels of B. pinnatum cover (sparse and dense) at a UK calcareous grassland site over three years of repeated treatment. We compared the effect of herbicides with a minimal intervention treatment (cutting) and current management practices (cutting and grazing for sparse cover, broad-spectrum glyphosate application for dense cover) on the cover of B. pinnatum, key indicator species and the composition of the grassland community. Areas with initially sparse B. pinnatum showed no significant reduction under any herbicide, whilst some herbicides (propyzamide, cycloxydim) showed detrimental impacts on non-target species. Cutting and grazing showed some beneficial effects, despite no significant reduction in B. pinnatum. On areas of dense B. pinnatum cover, glyphosate application reduced cover of B. pinnatum but led to colonisation by negative indicators or species typical of agricultural situations and disturbed ground. None of the selective herbicides significantly reduced dense B. pinnatum cover, and some (propyzamide, tepraloxydim, fluazifop-P-butyl) had significant negative impacts on non-target species. Our results suggest herbicide treatments, including glyphosate, are unlikely to offer long-term control of B. pinnatum on calcareous grasslands. A more promising approach is suggested by the effect of cutting and grazing, although further experimentation is required to determine the most effective regimes.

Habitat restoration requires realistic goals. To naturally regenerate European lowland calcareous grassland, whose extent has severely declined, over a century may be required for vegetation to become indistinguishable from that of old calcareous grassland. Progress of natural regeneration can be characterized using member species of the reference vegetation as indicators of favourable site condition. Chronosequence studies have suggested that calcareous-grassland species differ predictably in their ability to colonize ex-arable land, with some usually colonizing early on, and others in later stages. If such patterns are affected by gradually-attenuating establishment limitation, this would have important implications for restoration practice and indication of progress. Particularly, late-colonizing species might be better indicators of favourable site conditions than early colonizers. To explore these aspects, we have reanalysed chronosequence data previously used to investigate causal mechanisms affecting calcareous-grassland restoration progress. We carried out an indicator species analysis to determine which species are indicative of particular stages of natural regeneration. Using correlation analyses, we tested whether species colonization patterns matched those found by previous chronosequence studies that were geographically more limited or relied on more informal approaches to determine species order of colonization. Correlation analyses were also used to test whether order of colonization could be explained by establishment limitation or by dispersal limitation, or by established plant strategies that underlie such limitations. We identified 30 species as indicative of particular stages of natural regeneration, including nine that specifically indicate old calcareous grassland. Correlation results confirmed high congruence with species order of colonization in previous chronosequence studies, and indicated that establishment limitation plays a role in shaping species order of colonization, potentially mediated through differential stress tolerance. We failed to demonstrate a role of dispersal limitation in shaping order of colonization. Based on our results, we derived three categories of indicator species for passively-restored calcareous grassland, mirroring the regeneration stage during which these species usually colonize. This includes a category labelled by us as ‘old-grassland indicators’ that achieve notable abundance only in old grassland. We conclude by discussing how such a categorization can benefit the measurement of restoration progress, the tentative identification of old grassland and its conservation, e.g. through linking agri-environment payments to the occurrence of old-grassland indicators, thus fostering positive change in farmer attitudes towards old grassland.

Soil seed banks on ex-arable land are dominated by undesirable ruderal species that compete with “desirable” target species during grassland restoration. At the same time, for continued regeneration, the latter often functionally depend on gap colonization from the seed bank, which serves as a buffer against local extinction. Nonetheless, few studies have so far investigated the effects of restoration practices on seed bank dynamics. Using a multisite experiment investigating techniques for restoring lowland mesotrophic grassland, we studied the effects of seedbed preparation (shallow cultivation using harrows or discs vs. deep cultivation using a plow) and of seed mixtures (species-rich grass–forb mixes vs. species-poor grass-only mixes vs. unseeded natural regeneration) on 7 years of post-restoration seed bank dynamics. We assessed how these practices affected density and diversity of sown and unsown species in the seed bank. Seed bank dynamics were much more strongly affected by seed sowing than by cultivation. Grass sowing resulted in stronger seed bank decline of unsown grasses, and additional forb sowing in stronger decline of unsown forbs. Higher seed densities and species richness of sown forbs colonizing from neighboring plots sown with the grass–forb mix were observed under natural regeneration than in the grass-only sown treatment, reflecting grass priority effects on sown forb colonization in the latter. Sowing of diverse target species mixtures was associated with the greatest shift in seed bank composition away from extant ruderal species towards sown target species. Our results illustrate the usefulness of seed bank monitoring for assessing restoration progress.

Interactions between two canopy layers in a designed perennial herbaceous plant community were investigated over a period of four and a half years to see whether it was possible to create an urban landscape vegetation that was both flower rich for an extensive time period and resistant to weed colonization at very low levels of maintenance by sowing seed in situ. The ecologically novel plant community involved a tall over-canopy layer of 18 species of North American prairie and woodland edge forbs, and a shade tolerant under-canopy of eight European and North American, mainly woodland forbs. After 5 years the community was dominated by four over-canopy and two winter green under-canopy species. Interspecific competition generated by the sown biomass restricted weed colonization to very low levels, despite the experiment being surrounded by a weedy brownfield. The winter green canopies of the two dominant under-storey forbs closed down gaps within a winter deciduous, prairie-like vegetation, improving winter appearance and providing a major flowering display in spring. This vegetation is an attractive design model for more sustainable herbaceous planting in urban landscape space.

Modern intensive farming caused pronounced changes to the European arable flora. Many species adapted to less intensive traditional farming declined severely, as did the potential of unsown arable vegetation to support higher trophic levels. To reverse these trends, various agri-environment measures were introduced. One such measure is to manage cereal headlands as conservation headlands, involving strict restrictions on pesticide and fertiliser use. An additional modification to management which could reduce crop competition and thus deliver benefits to arable plants is cereal sowing at reduced rates. However, little is known about its benefits to rare and declining arable plants, or to species of value to higher trophic levels, and whether it can be implemented without concomitant increase in undesirable weeds. We set up identical two-factorial experiments in winter wheat and spring barley, combining a nitrogen fertiliser versus no fertiliser treatment with cereal sowing at economic rates versus sowing at rates reduced by 75 %, with added sowing of a mixture of rare arable species. Both experiments also included an uncropped but cultivated control equivalent to another agri-environment measure. Our results show that reduced cereal sowing in conservation headlands can benefit rare and declining species, as well as arable plant diversity, without necessarily resulting in a concomitant increase in undesirable weeds. While such benefits tended to be larger in uncropped cultivated controls, conservation headlands have the advantage of not requiring land being taken out of production. Moreover, as shown in this study, their benefits to arable plants can be maximised by reduced sowing.

As a K-strategist and comparatively sedentary species, the lesser horseshoe bat Rhinolophus hipposideros is considered sensitive to changes in habitat quality. Knowledge of the species' dietary requirements and use of foraging habitats is thus considered an essential prerequisite to manage its habitats adequately. Based on four large annual samples of faecal pellets from three different nursery colonies, including two consecutive years of sampling from one colony, we studied the diet of Central German populations of R. hipposideros. Consistent with findings of similar studies carried out in other parts of the distribution range of R. hipposideros, in our study, Diptera, Lepidoptera, and Neuroptera represented the most important groups of prey for the studied colonies. However, Hemiptera made a comparatively larger contribution in our study than in others, and so did Hymenoptera in one of the colonies. We found seasonal compositional variation in all four annual samples, as well as compositional variation between samples from different colonies, but not between the two annual samples obtained in consecutive years from the same colony. Differences between colonies appeared at least to some extent to reflect differences in availability of foraging habitats. Our results are thus in agreement with the assumption of R. hipposideros being a largely opportunistic, generalist forager. Our findings are also consistent with a. known preference by R. hipposideros of woodland as main foraging habitat, as previously established by other studies carried out in the northern part of the distribution range. However, the relative importance of Hemiptera, and in particular of Psyllidae, at certain times during the foraging season, suggests that the Central German colonies of R. hipposideros might have utilized commercial orchards and private fruit gardens for foraging during seasonal peaks in abundance of pest species of fruit trees. The implied ability of R. hipposideros to respond to seasonal abundance peaks of particular groups of prey in a range of habitats suggests that structural diversity might be key in maintaining viable populations of this species. The potential importance of orchards and fruit gardens in regions where such habitats are prevalent is likely to have relevant management implications.

QuestionsWhat types of pre-sowing disturbance are most suitable to establish specialist forbs of calcareous grassland at previously agriculturally improved restored sites? What impact does management regime have on post-establishment abundance-dynamics?LocationPegsdon Hills, Bedfordshire, UK.Methods We set up a 4-yr experiment using a split-plot design to combine pre-sowing disturbance treatments at sub-plot level (undisturbed control, glyphosate spraying, harrowing, and creation of ridge-and-furrow features) with three post-establishment management regimes applied at main plot level in years 2–4, involving either summer cutting or summer cattle grazing, and presence or absence of spring sheep grazing, along with autumn cattle grazing in all regimes. After disturbance application, we sowed a seed mixture containing ten specialist species of calcareous grassland. Using quadrat-based methods, we monitored first-year establishment and subsequent dynamics, including reproductive status of species at quadrat level. Initial establishment and subsequent dynamics were analysed separately using LMM.ResultsInitial establishment of sown species was promoted both by harrowing and by ridge-and-furrow creation. While some species were about equally promoted by both, several other species benefited more strongly or exclusively from ridge-and-furrow creation. Effects of disturbance largely persisted in subsequent years, but for some species, different dynamics were observed for harrowed and ridge-and-furrow treatments. Thymus pulegioides and Hippocrepis comosa gradually achieved higher abundances in the ridge-and-furrow treatment, in which notable levels of bare ground persisted for much longer than in the harrowed treatment. In contrast, Filipendula vulgaris and Pimpinella saxifraga achieved higher abundance in the harrowed treatment. Sown species tended to reach reproductive stage faster in the ridge-and-furrow treatment than in the harrowed treatment. By the end of the study, management regimes had resulted in few effects on species dynamics.Conclusions Establishment of specialist species of calcareous grassland crucially depended on bare ground creation prior to sowing. Ridge-and-furrow creation resulted in more persistent reduction of competition than the standard practice of harrowing, provided more suitable conditions for low-statured specialist species, and generally enabled faster transition of introduced specialist species to reproductive stage. Our results thus illustrate potential benefits of using more severe disturbance when introducing specialist species of calcareous grassland at restored sites.