A question of origin: Where and how to collect seed for ecological restoration

Native plant species are routinely planted or sown in ecological restoration projects, but successful establishment and survival depend on where and how seeds are collected. Research suggests that it is important to use locally adapted seeds. Local populations often show a home-site advantage and non-local genotypes may be maladapted to local environmental conditions. Furthermore, intraspecific hybridisation of local and non-local genotypes may have a negative impact on the genetic structure of local populations via mechanisms such as outbreeding depression. Many species show a strong small-scale genetic differentiation between different habitats so that matching habitats of the restoration and donor site can be more important than minimizing geographical separation. It is a challenge to identify appropriate seed sources because strong small-scale population differentiation makes it difficult to delineate geographically defined seed zones to which seed exchange should be limited. Moreover, it is important to consider the genetic diversity of introduced material because it may be crucial to avoid genetic bottlenecks, inbreeding depression and poor establishment of plant populations. Repeated propagation in stock, which is often required to obtain a sufficient amount of seeds, can further reduce genetic diversity and may select for particular genotypes. Negative impacts of improper seed choice for nursery planting stock may become detectable only after many years, especially in long-lived and slow growing plants. Although scientific information on many species remains limited, the increasing demand for translocation of seed means that mandatory regulations are necessary. Guidelines should prescribe a specification of seed provenance, a record of genetic diversity of wild collections and rules for subsequent processing such as direct transfer and propagation of stock or seed orchards. We use a literature review to evaluate current legislation and to develop recommendations for herbaceous and woody species.     

Species introduction in restoration projects – Evaluation of different techniques for the establishment of semi-natural grasslands in Central and Northwestern Europe

During recent decades, many studies have shown that the successful restoration of species-rich grasslands is often seed-limited because of depleted seed banks and limited seed dispersal in modern fragmented landscapes. In Europe, commercial seed mixtures, which are widely used for restoration measures, mostly consist of species and varieties of non-local provenance. The regional biodiversity of a given landscape, however, can be preserved only when seeds or plants of local provenance are used in restoration projects. Furthermore, the transfer of suitable target species of local provenance can strongly enhance restoration success.We review and evaluate the success of currently used near-natural methods for the introduction of target plant species (e.g. seeding of site-specific seed mixtures, transfer of fresh seed-containing hay, vacuum harvesting, transfer of turves or seed-containing soil) on restoration sites, ranging from dry and mesic meadows to floodplain grasslands and fens. Own data combined with literature findings show species establishment rates during the initial phase as well as the persistence of target species during long-term vegetation development on restoration sites.In conclusion, our review indicates that seed limitation can be overcome successfully by most of the reviewed measures for species introduction. The establishment of species-rich grasslands is most successful when seeds, seed-containing plant material or soil are spread on bare soil of ex-arable fields after tilling or topsoil removal, or on raw soils, e.g. in mined areas. In species-poor grasslands without soil disturbance and on older ex-arable fields with dense weed vegetation, final transfer rates were the lowest. For future restoration projects, suitable measures have to be chosen carefully from case to case as they differ considerably in costs and logistic effort. Long-term prospects for restored grassland are especially good when management can be incorporated in agricultural systems.     

Using prioritisation tools to strategically restore vegetation communities in fragmented agricultural landscapes

Restoring native habitats in heavily cleared and fragmented areas such as agricultural landscapes is important to maintain and increase remaining native floral and faunal communities. Identifying priority vegetation types for restoration – as well as the parcels of land where this restoration could take place at a landscape scale – may assist in strategically protecting these biodiversity assets. To prioritise the restoration of terrestrial habitats around an ecologically and culturally significant Ramsar‐listed wetland in South Australia, we used the spatial prioritisation tool Marxan. Originally designed for prioritising the protection of reserve areas, Marxan can also be used to identify parcels of land for restoration purposes. We tested how Marxan prioritised the restoration of four distinct vegetation types around the Coorong and Lower Lakes region of South Australia using the inverse of habitat remnancy as a cost and soil type and distance to ecologically significant bird species as a conservation feature. By prioritising restoration activities around certain landscape features, such as remnant areas, our results indicate that we would be able to strategically restore parcels of native habitat that would maximise biodiversity outcomes. This study highlights the need for robust input data, such as priority vegetation types and bird species associated with these habitats, to ensure informative modelling outputs. It also suggests that other measures, such as the cost of different land types, should be included in future restoration planning. Finally, we illustrate how prioritisation tools such as Marxan can be used by natural resource managers to restore areas within fragmented agricultural landscapes.     

Biocrust lichen and moss species most suitable for restoration projects

Reintroducing lichens and mosses to areas slated for restoration or rehabilitation may prove integral to project success by filling the biocrust component (niche) of arid ecosystems. In doing so, it is important to select appropriate species and genetic source material. Some bryophyte and lichen species are early pioneers and are potentially well‐suited for restoration projects. Species traits such as high reproductive rates, rapid establishment rates, and large asexual reproductive propagules can be beneficial for restoration. For instance, the large number of spores produced by some mosses are beneficial for reproductive success in arid environments. In addition to identifying the benefit of reproductive strategies, it is important to take habitat needs into consideration; lichen and moss species that are wide‐ranging both geographically and ecologically are recommended over geographically and edaphically restricted species that occur only in specific habitats, such as calcareous soils. Biocrusts used in specific restoration areas should have similar genetic source material (local provenance), and harsh environmental conditions should be ameliorated.     

Limited Effects of Large‐Scale Riparian Restoration on Seed Banks in Agriculture

I examined the effect of riparian forest restoration on plant abundance and diversity, including weed species, on agricultural lands along the Sacramento River in California (United States). Riparian forest restoration on the Sacramento River is occurring on a large‐scale, with a goal of restoring approximately 80,000 ha over 160 km of the river. In multiuse habitats, such as the Sacramento River, effects of adjoining habitat types and movement of species across these habitats can have important management implications in terms of landscape‐scale patterns of species distributions. Increased numbers of pest animals and weeds on agricultural lands associated with restored habitats could have negative economic impacts, and in turn affect support for restoration of natural areas. In order to determine the distribution and abundance of weeds associated with large‐scale restoration, I collected seed bank soil samples on orchards between 0 and 5.6 km from adjacent restored riparian, remnant riparian, and agricultural habitats. I determined the abundance, species richness, and dispersal mode of plant species in the seed bank and analyzed these variables in terms of adjacent habitat type and age of restored habitat. I found that agricultural weed species had higher densities at the edge of restored riparian habitat and that native plants had higher densities adjacent to remnant riparian habitat. Weed seed abundance increased significantly on walnut farms adjacent to restored habitat with time since restored. I supply strong empirical evidence that large areas of natural and restored habitats do not lead to a greater penetration of weed species into agricultural areas, but rather that weed penetration is both temporally and spatially limited.     

“How Local Is Local?”—A Review of Practical and Conceptual Issues in the Genetics of Restoration

In plant conservation, restoration (the augmentation or reestablishment of an extinct population or community) is a valuable tool to mitigate the loss of habitat. However, restoration efforts can result in the introduction of novel genes and genotypes into populations when plant materials used are not of local origin. This movement is potentially important because many plant species are subdivided into populations that are adapted to local environmental conditions. Here we focus on genetic concerns arising from ongoing restoration efforts, where often little is known about “How local is local?” (i.e., the geographic or environmental scale over which plant species are adapted). We review the major issues regarding gene flow and local adaptation in the restoration of natural plant populations. Finally, we offer some practical, commonsense guidelines for the consideration of genetic structure when restoring natural plant populations.     

Comparison of genetic variation between the seed bank and above ground vegetation of a wetland species

The seed bank is thought to be important for the conservation and restoration of the genetic diversity of the above ground plant population. It has been proposed that it may be no use to compare the genetic diversity between seed bank and above ground plants if there was no habitat fragmentation. Whether this prediction holds for aquatic plants is still unknown. Here, ISSR analysis of a common wetland species Heleocharis valleculosa (Cyperaceae) was conducted to evaluate if the seed bank has higher, equal or lower genetic variation than the above ground vegetation. Our results showed high genetic diversity in the seed bank, so the seedbank can act as a storehouse of genetic variation for the above ground vegetation, especially in unfavorable conditions. Thus, unlike terrestrial habitats where genetic diversity is often low, wetlands that are connected with water flow can accumulate many genotypes in the seed bank and the question of how genetic diversity varies above and below ground is still open.     

Ecological Theory and Community Restoration Ecology

Community ecological theory may play an important role in the development of a science of restoration ecology. Not only will the practice of restoration benefit from an increased focus on theory, but basic research in community ecology will also benefit. We pose several major thematic questions that are relevant to restoration from the perspective of community ecological theory and, for each, identify specific areas that are in critical need of further research to advance the science of restoration ecology. We ask, what are appropriate restoration endpoints from a community ecology perspective? The problem of measuring restoration at the community level, particularly given the high amount of variability inherent in most natural communities, is not easy, and may require a focus on restoration of community function (e.g., trophic structure) rather than a focus on the restoration of particular species. We ask, what are the benefits and limitations of using species composition or biodiversity measures as endpoints in restoration ecology? Since reestablishing all native species may rarely be possible, research is needed on the relationship between species richness and community stability of restored sites and on functional redundancy among species in regional colonist “pools.” Efforts targeted at restoring system function must take into account the role of individual species, particularly if some species play a disproportionate role in processing material or are strong interactors. We ask, is restoration of habitat a sufficient approach to reestablish species and function? Many untested assumptions concerning the relationship between physical habitat structure and restoration ecology are being made in practical restoration efforts. We need rigorous testing of these assumptions, particularly to determine how generally they apply to different taxa and habitats. We ask, to what extent can empirical and theoretical work on community succession and dispersal contribute to restoration ecology? We distinguish systems in which succession theory may be broadly applicable from those in which it is probably not. If community development is highly predictable, it may be feasible to manipulate natural succession processes to accelerate restoration. We close by stressing that the science of restoration ecology is so intertwined with basic ecological theory that practical restoration efforts should rely heavily on what is known from theoretical and empirical research on how communities develop and are structured over time.     

Fitness in Naturally Occurring and Restored Populations of a Grassland Plant Lychnis flos‐cuculi in a Swiss Agricultural Landscape

Wildflower seed mixtures are widely used for restoration of grasslands. However, the genetic and fitness consequences of using seed mixes have not been fully evaluated. Here, we studied the role of genetic diversity, origin (commercial regional seed mixtures, natural populations), and environmental conditions for the fitness of a grassland species Lychnis flos‐cuculi. First, we examined the relationship between genetic diversity, environmental parameters, and fitness in sown and natural populations of this species in a Swiss agricultural landscape. Second, we established an experiment in the study area and in an experimental garden to study the implications of local adaptation for plant fitness. Third, to examine the response of plants to different soil properties, we conducted an experiment in climate chambers, where we grew plants from sown and natural populations of L. flos‐cuculi as well as from seed suppliers on soils with different nutrient and moisture content. We detected no significant effect of genetic diversity on the fitness of sown and natural populations. There was no clear indication that plants from natural populations were better adapted to local environment than plants from sown populations or seed suppliers. However, plants of natural origin invested more into generative reproduction than plants from sown populations or seed suppliers. Furthermore, in the climate chamber, plants originating from natural populations tended to flower earlier. Our results indicate that using nonlocal seeds for habitat recreation may influence restoration success even if the seeds originate from the same seed zone as the restored site.     

Scale-dependent diversity effects of seed dispersal by a wild herbivore in fragmented grasslands

Dispersal limitation between habitat fragments is a known driver of landscape-scale biodiversity loss. In Europe, agricultural intensification during the twentieth century resulted in losses of both grassland habitat and traditional grassland seed dispersal vectors such as livestock. During the same period, populations of large wild herbivores have increased in the landscape. Usually studied in woodland ecosystems, these animals are found to disperse seeds from grasslands and other open habitats. We studied endozoochorous seed dispersal by roe deer (Capreolus capreolus) in fragmented grasslands and grassland remnants, comparing dispersed subcommunities of plant species to those in the established vegetation and the seed bank. A total of 652 seedlings of 67 species emerged from 219 samples of roe deer dung. This included many grassland species, and several local grassland specialists. Dispersal had potentially different effects on diversity at different spatial scales. Almost all sites received seeds of species not observed in the vegetation or seed bank at that site, suggesting that local diversity might not be dispersal limited. This pattern was less evident at the landscape scale, where fewer new species were introduced. Nonetheless, long-distance dispersal by large wild herbivores might still provide connectivity between fragmented habitats within a landscape in the areas in which they are active. Finally, as only a subset of the available species were found to disperse in space as well as time, the danger of future biodiversity loss might still exist in many isolated grassland habitats.     

Effects of competition with Bromus tectorum on early establishment of Poa secunda accessions: can seed source impact restoration success?

When landscapes are heavily impacted by biological invasion, local populations of native plant species may no longer be adapted to altered environmental conditions. In these cases, it is useful to investigate alternative sources of germplasm, such as cultivated varieties, for planting at restoration sites. This study compared cultivated and wild (local) varieties of the native perennial bunchgrass, Poa secunda J. Presl, grown with and without the exotic, invasive Bromus tectorum L. in a greenhouse setting. While P. secunda cultivars emerged and grew more rapidly than wild seed sources, this advantage declined in the presence of B. tectorum and cultivated germplasm did not outperform wild accessions in the presence of an invasive species. Given the novel genetic background of cultivars and their potential to alter patterns of dominance in native plant communities, we recommend the use of local or regional wild seed sources when possible to conserve regional patterns of genetic diversity and adaptation. Use of multiple seed sources may increase the potential for capturing vigorous genotypes in the restoration seed mix. In cases where sites are heavily impacted by exotic, invasive species, other control measures will be necessary to improve establishment of native species in grassland restoration programs.     

Soil texture as an influence on the distribution of the desert seed-harvester ants Pogonomyrmex rugosus and Messor pergandei

Summary Pogonomyrmex rugosus and Messor pergandei are ecologically similar species of desert seed-harvester ants that coexist in numerous areas throughout the Sonoran and Mohave Deserts. However, these two species also commonly segregate along physical gradients, with each species predominating in areas that differ in soil texture and/or topographic relief. Along gradients that included bajada and alluvial flat habitats, P. rugosus occurred alone in coarse-textured soils near mountains, while M. pergandei occurred alone in finer-textured soils further away. Conversely, along a vegetation gradient that included creosote bush and saltbush habitats, P. rugosus occurred alone in finer-textured soils than those occupied by either M. pergandei alone or both species in coexistence. However, in both situations clay content was significantly higher in areas occupied by P. rugosus alone, and at the latter site clay content was correlated with relative abundance of each species. Moreover, local distribution pattern of these two species may be related to the effects of clay on water retention, with retention being highest in areas occupied by P. rugosus alone. Differences in reproductive ecology may also affect these patterns as P. rugosus reproductive flights follow summer monsoon rains, while those of M. pergandei occur during the milder winter and spring.     

林业活动和森林片断化对甲虫多样性的影响及保护对策

森林片断化是造成生物多样性丧失的主要原因之一,而林业活动是导致森林片断化的重要因素,同时也在森林恢复中起重要作用。本文从小尺度、局域尺度以及生物地理尺度（大尺度）3个生态尺度分析林业活动和森林片断化对甲虫多样性的影响。在小尺度下,林业活动能够通过改变森林生境或微生境的类型和特性而影响甲虫物种分布。在局域尺度下,林业活动（尤其是森林砍伐）往往能提高许多甲虫类群（如步甲）的物种丰富度（α多样性）,这主要与来自周围环境物种扩散以及保留了若干耐受新环境能力较强的森林物种有关;然而,对森林生境依赖性很强的特有种受到了森林片断化的负面影响,面临局域种群灭绝的危险。在生物地理尺度下,林业活动（伐木或森林恢复）使森林生境单一化、异质性降低,从而导致对森林生境变化敏感的物种种群数量降低甚至灭绝。基于以上结果,可以归纳出3个基本原则用于指导林业管理,既能保证林业经济收益,又能维持森林生物多样性。首先,保留大面积的原始森林作为特有种的栖息环境基地,为这些物种在将来森林恢复后重新定居提供资源;其次,由于保护区内原始森林面积有限,且所代表的生境类型有限,所以发展依据自然干扰模式的新伐木方法十分必要;最后,依据自然规律（如火灾）进行森林恢复和天然演替,避免森林的单一化,丰富森林生境类型。     

Food webs: a ladder for picking strawberries or a practical tool for practical problems?

While food webs have provided a rich vein of research material over the last 50 years, they have largely been the subject matter of the pure ecologist working in natural habitats. While there are some notable exceptions to this trend, there are, as I explain in this paper, many applied questions that could be answered using a food web approach. The paper is divided into two halves. The first half provides a brief review of six areas where food webs have begun to be used as an applied tool: restoration ecology, alien species, biological control, conservation ecology, habitat management and global warming. The second half outlines five areas in which a food web approach could prove very rewarding: urban ecology, agroecology, habitat fragmentation, cross-habitat food webs and ecosystem services.     

Plant conservation ecology for management and restoration of riparian habitats of lowland Japan

Conservation ecology is a new paradigm of ecology that aims at scientific contributions to maintaining earth's biodiversity and is committed to ecosystem management indispensable to intergenerational long-term sustainability. Population ecology plays a central role in conservation ecology. Persistence of the metapopulation rather than that of each local population should be pursued in species conservation management. Biological interactions essential to reproduction and soil seed bank components of the population should be investigated and applied to planning for the conservation of a plant population. Gravelly floodplains and moist tall grasslands are among typical riparian habitats containing many threatened plants in Japan. These riparian habitats are now subjected not only to heavy fragmentation but also to intensive invasion of highly competitive alien (nonnative) plants. Extreme habitat isolation may result in reproductive failure or fertility selection in a plant population without pollinators, as exemplified by a nature reserve population of Primula sieboldii. Biological invasions, which are facilitated by extensive changes in the river environment including decreased seasonal flooding, abandonment of traditional vegetation management, eutrophication, and extensive clearing of the land for recreational use, threaten endemic riparian species. To preserve safe sites and growing conditions for threatened plants such as Aster kantoensis, active management to suppress the dominance of alien invader plants is necessary. Population management and habitat restoration should be based on sound information on the population ecology of both threatened and alien invader plants, designed as an ecological experiment to clarify effective ways for management. Received: September 18, 1998 / Revised: October 22, 2001 / Accepted: October 23, 2001     

湿地公园鸟类栖息地营建研究——以北京琉璃河湿地公园为例

北京地区处于全球候鸟东亚-澳大利西亚的迁徙路线上,是候鸟重要的迁徙路线,近些年,随着人为活动的影响,该区生境破碎化问题愈发突出,直接威胁着本地鸟种和过境迁徙鸟类的生存。为达到保护鸟类多样性的目的,需开展相应的栖息地恢复工作。不同生态类群的鸟类对栖息地有着不同的要求,相同鸟种在不同空间、季节和生活期对栖息地的选择也有着不同的特点。因而,鸟类栖息地恢复应针对目标鸟种根据其繁殖特点、巢位空间分布、食性特点、活动空间特点等进行规划营造。以北京房山琉璃河湿地公园为例,针对项目所在区域的鸟类分布特征,确定目标恢复鸟种,结合项目区现场条件,围绕目标鸟种对于栖息地水系、植被等方面的需求,从岸线重塑、水深设计、植物配置、生态鸟岛等方面规划设计鸟类栖息地修复措施。     

Riparian buffer zones as elements of ecological networks: Case study on Parnassius mnemosyne distribution in Estonia

Territorial ecological networks (in US and some other countries known as greenways) are coherent assemblages of areas representing the natural and semi-natural landscape elements that need to be conserved, managed or, where appropriate, enriched or restored in order to ensure the favourable conservation status of the ecosystems, habitats, species and landscapes across their traditional range. An ecologically compensating areas network is a hierarchical system with the following levels: (1) core areas, (2) buffer zones of core areas, (3) corridors and stepping stones, and (4) nature development and/or restoration areas that support resources, habitats and species. Rivers form natural ecological networks and riparian buffer zones of rivers are typical elements of ecological networks. We studied the distribution of Clouded Apollo (Parnassius mnemosyne) and its habitat requirements in Estonia. Seventy-eight percent of all Clouded Apollo observations were recorded in riparian meadows along the banks of rivers with riparian strips consisting of bushes and trees. Detailed study showed that the butterfly is in most cases associated with meadows with a riparian strip of alder. This is the habitat of the food plant (fumeworth—Corydalis solida) of the larvae, the feeding and mating place of adults, and the migration and hiding site for the Clouded Apollo. The population area and number of individuals have been increasing during the last years, and a new growing South-Estonian sub-population of Clouded Apollo has also been discovered in Estonia.     

Implementation of Basic Studies in the Ecological Restoration of Surface-Mined Land

This paper focuses on attempts to encourage a new state of the art in the ecological restoration of surface‐mined land in Germany. On most of these sites, the application of traditional recultivation methods often destroys valuable ecological potential by leveling of the surface, ameliorating of nutrient‐poor substrates, and seeding or planting of species not suited to the present habitat conditions. Many studies have shown that even highly disturbed ecosystems, such as large mining areas, can regenerate spontaneously over long‐term periods. Colonization processes were influenced by the availability of diaspore sources as well as the suitability of sites for establishment. The predictability of succession could be improved by the identification of switch points in successional pathways depending on age and conditions of the sites. Based on the developmental potential, orientation by nature and biodiversity are selected as main targets for priority areas for nature conservation in mining sites. On priority areas restoration measures must be restricted to the use of near‐natural methods (e.g., application of fresh, diaspore‐rich plant clipping material, dumping of overburden with seed bank and vegetative propagules, seeding of site‐specific, local seed mixtures) that are very successful in preventing erosion and accelerating vegetation development. Despite the success of these methods, the transfer of knowledge between scientists, practitioners, and administrative organizations has proved to be insufficient. Therefore, one of the main tasks in ecological restoration must be the inclusion of all stakeholders involved in decision‐making processes and the establishment of a network of excellence to enhance the exchange of knowledge.     

植物群落中物种小尺度空间结构研究

植物群落中, 物种小尺度空间结构影响着种群或群落的动态及有关的生态学过程。植物主要是和它同种或异种的邻近个体相互作用,植物个体周围的局部环境和大空间尺度下群落的平均水平是完全不同的。群落中的许多过程都影响小尺度空间结构的形成和动态,同样,局部空间结构反过来影响着植物的生长、更新和凋亡等重要过程。鉴于目前对小尺度空间结构进行的大量研究以及其重要性,有必要对其研究进展进行适当的总结,以期明确将来进一步的研究方向。该文以此为出发点,首先介绍了植物群落中物种小尺度空间结构产生的6个原因:1)生境的空间异质性;2)植物繁殖体的传播;3)植物之间的相互作用;4)生物环境(动物和微生物)的作用;5)外界干扰的作用;6)多因子综合作用。然后阐述了小尺度空间结构意义及对生物多样性、植物种群遗传学和恢复生态学研究的影响。最后对目前物种小尺度空间结构研究存在的几点问题及将来的研究方向作以下归纳:1)大尺度植被动态的研究应该整合小尺度空间结构的信息;2)不论从生物学还是生态学上来讲, 植被小尺度空间结构的研究应该把植物作为中心,确定适当的尺度和采取合理的空间统计方法;3)充分重视小尺度空间结构在退化生态系统恢复中的应用意义;4)注重从小尺度的局部格局研究入手对群落总体特征进行整合;5)植物群落动态研究中,物种小尺度空间结构与平均场假说相结合的必要性。     

Impact of flooding on potential and realised grassland species richness

In order to reduce flood risk, river management policies advise floodplain restoration and the recreation of water retention areas. These measures may also offer opportunities for the restoration of species-rich floodplain habitats through rewetting and the restoration of flood dynamics. The potential to enhance biodiversity in such flood restoration areas is, however, still subject to debate. In this paper we investigate whether flooding along a small altered lowland river can contribute to the potential and realised species richness of semi-natural meadows. We compare the seed bank and vegetation composition of flooded and non-flooded semi-natural meadows and test the hypothesis that flooding contributes to an input of diaspores into the meadow seed banks, thereby promoting seed density and potential species richness. Furthermore we hypothesise that, where habitat conditions are suitable, flooding leads to a higher realised species richness. Results showed that seed densities in flooded meadows were significantly higher than in non-flooded meadows. The seed banks of flooded meadows also contained a higher proportion of exclusively hydrochorous species. However, the seed bank species richness, as well as the species richness realised in the vegetation did not differ significantly between flooded and non-flooded meadows. Finally, the seed bank and standing vegetation of flooded sites showed larger differences in species composition and Ellenberg nitrogen distribution than non-flooded sites. From these results we conclude that, although flooding does contribute to the density and composition of the seed bank, most imported seeds belong to only a few species. Therefore, it is unlikely that flooding substantially enhances the potential species richness. Furthermore, even if new species are imported as seeds into the seed bank, it seems unlikely that they would be able to establish in the standing vegetation. However, it is unclear which factors impede the establishment of imported species in the vegetation. The implications of our findings for flood meadow restoration are discussed.