Habitat‐related seed germination traits in alpine habitats

Understanding the key aspects of plant regeneration from seeds is crucial in assessing species assembly to their habitats. However, the regenerative traits of seed dormancy and germination are underrepresented in this context. In the alpine zone, the large species and microhabitat diversity provide an ideal context to assess habitat‐related regenerative strategies. To this end, seeds of 53 species growing in alpine siliceous and calcareous habitats (6230 and 6170 of EU Directive 92/43, respectively) were exposed to different temperature treatments under controlled laboratory conditions. Germination strategies in each habitat were identified by clustering with k‐means. Then, phylogenetic least squares correlations (PGLS) were fitted to assess germination and dormancy differences between species’ main habitat (calcareous and siliceous), microhabitat (grasslands, heaths, rocky, and species with no specific microhabitats), and chorology (arctic–alpine and continental). Calcareous and siliceous grasslands significantly differ in their germination behaviour with a slow, mostly overwinter germination and high germination under all conditions, respectively. Species with high overwinter germination occurs mostly in heaths and have an arctic–alpine distribution. Meanwhile, species with low or high germinability in general inhabit in grasslands or have no specific microhabitat (they belong to generalist), respectively. Alpine species use different germination strategies depending on habitat provenance, species’ main microhabitat, and chorotype. Such differences may reflect adaptations to local environmental conditions and highlight the functional role of germination and dormancy in community ecology.     

Seed bank diversity in mesic grasslands in relation to vegetation type,management and site conditions

Questions: 1. Do different management types (i.e. hay meadow, silage meadow, meadow‐pasture, pasture) have different impact on the size and composition of the seed bank of mesic grassland (Arrhenatheretalia)? 2. How strong is the effect of management on the seed bank in relation to above‐ground vegetation, edaphic factors and land‐use history? 3. Are there differences in C‐S‐R plant strategy types and seed longevity under different management regimes? Location: Lahn‐Dill Highlands in central‐western Germany. Methods: Above‐ground vegetation and the soil seed bank of 63 plots (at 21 sites) in mesic grasslands were studied. Differences between management types in quantitative seed bank traits and functional characteristics were tested by ANOVA. The impact of management, above‐ground vegetation, site conditions and land‐use history on seed bank composition were analysed by partial CCA. Results: Management had no significant impact on species richness and density of the seed bank but significantly influenced their floristic composition and functional characteristics. CCA revealed that even after adjustment for soil chemical parameters and above‐ground vegetation management still had significant impact on seed bank composition. ANOVA revealed that silage meadows contained higher proportions of R‐strategy compared to hay meadows. In contrast, in hay meadows and meadow‐pastures proportions of S‐strategy were higher than in silage meadows. Conclusions: The type of grassland management has little impact on quantitative seed bank traits. Management types with a high degree of disturbance lead to an increase of species following a ruderal strategy in the seed bank. Irrespective of management type only a limited proportion of characteristic grassland species is likely to re‐establish from the seed bank after disappearance from above‐ground vegetation.     

Seed Bank Effects on Recovery after Disturbance in Reconstructed Tallgrass Prairies

Litter‐removing disturbances such as fire in grasslands temporarily increase available resources for plants, opening a window of opportunity for new establishment as communities recover. At this time, new individuals or species could be added to the community as a result of germination from the local seed bank. In reconstructed grasslands this may be problematic, as the seed bank may contain a suite of undesired species reflective of prior and surrounding land uses. In two, 25‐year‐old, low‐diversity reconstructed grasslands, we tested the effect of local seed bank establishment following litter‐removing disturbance using seedling removal plots (1 m²) and plots where natural seedling establishment was allowed. Following disturbance, the vegetation was either left intact or hayed to enhance seedling establishment (a common practice following inter‐seeding efforts). Although the seed bank and seedling community were dominated by resident grasses (Andropogon gerardii and Poa pratensis), recruitment from the seed bank increased species richness and reduced evenness through the addition of forb species (including Cirsium arvense) in one of the study sites. Haying temporarily altered the abundances of the dominant grasses, but did not consistently affect seedling recruitment. Disturbances that facilitate seed bank recruitment may promote establishment of undesired species within reconstructed grassland communities, and we need to take steps to better manage the contributions into and recruitment from the seed bank to reconstruct sustainable grasslands.     

Plant traits: Their role in the regeneration of alpine plant communities in sub‐arctic Finland

Abstract. Question: How do the relative frequencies of plant traits (clonality, growth form, seed weight, diaspore morphology) vary during the life cycle and how does this affect regeneration? Location: Alpine meadow and heath communities at Kilpisjärvi, sub‐Arctic Finland. Methods: Control plots and three treatments were used to measure relative species abundances for five life cycle stages: standing vegetation, seed rain, seed bank and seedlings emerging in gaps and in closed vegetation. Results: The relative frequencies of plant traits varied between the life cycle stages. The meadows were dominated by weakly clonal herbs, small or intermediate seeds and unappendaged diaspores, while the heaths were dominated by clonal dwarf shrubs, small seeds and fleshy fruits. In the meadows, species with small seeds dominated during the seed rain and in the seedling stage in gaps, while species with intermediate seeds dominated the seed bank and the seedling stage in closed vegetation. Species with unappendaged diaspores dominated throughout the life cycle. In the heaths, seed bank and seedling stage were practically absent. Conclusions: The observed differences in plant trait spectra between life cycle stages indicate that important environmental factors differ among the stages. Small seeds are advantageous for dispersal, whereas intermediate seeds have a greater probability of germinating and establishing in closed vegetation. Appendages facilitate dispersal, whereas unappendaged diaspores favour seed burial. Although the plant growth form spectrum largely reflects environmental constraints during the regeneration cycle, information on seed weight and diaspore morphology improves our knowledge of the relative importance of morphological adaptations of sexual structures in different stages during the life cycle.     

Edaphic patchiness influences grassland regeneration from the soil seed‐bank in mountain grasslands of central Argentina

The soil seed‐banks in the main natural vegetation patches that make up mountain grasslands on granite substrates in central Argentina were studied. The main natural vegetation types are moist swards, tall‐tussock grasslands and stony grasslands. Ten compound soil samples from each community at two soil depths (0–5 and 5–10 cm) were taken. The density of soil seed‐banks was highest in moist swards, intermediate in stony grasslands and lowest in tall‐tussock grasslands. Low levels of similarity were found between the established vegetation and total soil seed‐bank in tall‐tussock grasslands and stony grasslands, but the similarity was higher in swards. In all three communities the seed‐bank was most frequently transient in nature. Short‐term persistent and long‐term persistent seed‐banks were less frequent. Regeneration from the seed‐banks after disturbance is expected to differ among communities on different edaphic patches. On the basis of the density and longevity of the soil seed‐banks and the similarity to the established vegetation, potential for in situ regeneration should be lower in tall‐tussock grasslands, intermediate in stony grasslands and higher in moist swards.     

Hidden biodiversity in the Arctic – a study of soil seed banks at Disko Island,Qeqertarsuaq, West Greenland

Seed dispersal is a key process in plant community dynamics, and soil seed banks represent seed dispersal in time rather than in space. Despite their potential importance, seed bank dynamics in the Arctic are poorly understood. We investigated soil seed banks and corresponding plant community composition in three contrasting vegetation types in West Greenland, viz. dwarf shrub heaths, herb slopes and fell‐fields. Through germination testing, 31 species were documented in soil seed banks. All of these were herbaceous, while no dwarf‐shrub species, which represents the dominating growth form in the above‐ground vegetation, were emerging from the seed bank. Consequently, across vegetation types, the lowest similarity between seed bank and above‐ground vegetation was found in dwarf shrub heath. Nine plant species were exclusively found in seed bank, all of which were non‐clonal forbs. Seed bank size (total number of seeds) and species richness seemed to increase with the level of natural disturbance. Additionally, we examined the effect of different experimental light and temperature conditions on the quantity and diversity of germinating seeds. The difference in diversity in vegetation and seed bank at the species level will impact population dynamics, regeneration of vegetation after disturbances and its potential to respond to climate change.     

Deer grazing changes seed traits and functions of grazing-intolerant plants

Grazing by ungulates can affect seed production in plants, and consequently seed recruitment into seed banks, which is a plant strategy to increase their resilience. The impact of grazing on seed quantity has been well studied; however, the impact of grazing on seed quality has received less attention, despite its role in determining the longevity of a seed bank. Here, we examined the impact of ungulate grazing on seed quality in plants, using two grazing-intolerant grassland species (Hemerocallis dumortieri var. esculenta and Geranium yesoense var. nipponicum). We found that grazing reduced seed length and weight, while increasing the germination rate. These changes in seed quality induced by grazing could reduce the persistence of seed banks and would thus seem to be an important mechanism involved in the impact of ungulate grazing on plant population dynamics.     

Plant life history stage and nurse age change the development of ecological networks in an arid ecosystem

Understanding how ecological networks are organised over the course of an organism's lifetime is crucial for predicting the dynamics of interacting populations and communities across temporal scales. However, most studies so far considered only one life history stage at a time, such as adult, when studying networks of interacting species. Therefore, knowledge about how multiple life history stages affect the development and stability of plant–plant association networks is lacking. We measured the understory adult plant community and the soil seed bank across a plant age gradient of the nurse shrub Retama sphaerocarpa in an arid ecosystem in Spain. Using a multilayer network approach, we built adult understory–nurse and seed bank–nurse networks and analysed how network nestedness, species’ role, and species specificity varied between them and with nurse plant age. We found that seed bank and adult understory networks changed depending on nurse plant age in two different ways. With increasing nurse plant age, adult understory networks became significantly more nested than seed bank networks. The nested architecture of seed bank networks was therefore a poor predictor of adult understory network nestedness. The contribution and specificity of species to network nestedness increased with increasing nurse plant age more in the adult understory than in seed bank networks, despite high species turnover. Our data show that life history and ontogeny affect the development of plant–plant association networks. Niche construction and environmental filtering along nurse ontogeny seem pivotal mechanisms structuring adult understory networks while the assembly of seed bank networks seems rather stochastic. We highlight the importance of mature plant communities for maintaining rare species populations and supporting the stability of ecological communities through time.     

Earthworms promote greater richness and abundance in the emergence of plant species across a grassland-forest ecotone

Aims Chalk grasslands are subject to vegetation dynamics that range from species-rich open grasslands to tall and encroached grasslands, and woods and forests. In grasslands, earthworms impact plant communities and ecosystem functioning through the modification of soil physical, chemical and microbiological properties, but also through their selective ingestion and vertical transportation of seeds from the soil seed bank. Laboratory experiments showed that seed–earthworm interactions are species specific, but little is known on the impact of seed–earthworm interactions in the field. The overall aim of this study was to better understand seed–earthworm interactions and their impact on the plant community. First we analyzed the composition of seedlings emerging from casts after earthworm ingestion. Then we compared seedling composition in casts to the plant composition of emerging seedlings from the soil and of the aboveground vegetation along four stages of the secondary succession of chalk grasslands.Methods Four stages of the secondary succession of a chalk grassland—from open sward to woods—were sampled in Upper Normandy, France, in February 2010. Within each successional stage (×3 replicates), we sampled the standing vegetation, soil seed bank at three soil depths (0–2, 2–5 and 5–10cm) and earthworm surface casts along transects. Soil and cast samples were water sieved before samples were spread onto trays and placed into a greenhouse. Emerging seedlings were counted and identified. Effect of successional stage and origin of samples on mean and variability of abundance and species richness of seedlings emerging from casts and soil seed banks were analyzed. Plant compositions were compared between all sample types. We used generalized mixed-effect models and a distance-based redundancy multivariate analysis.Important findings Seedling abundance was always higher in earthworm casts than in the soil seed bank and increased up to 5-fold, 4-fold and 3.5-fold, respectively, in the tall grassland, woods and encroached grassland compared to the soil surface layer. Species richness was also higher in earthworm casts than in the soil seed bank in all successional stages, with a 4-fold increase in the encroached grassland. The plant composition of the standing vegetation was more similar to that of seedlings from casts than to that of seedlings from the soil seed bank. Seedlings diversity emerging from casts in the tall and encroached grasslands tended toward the diversity found in woods. Our results indicate that earthworms may promote the emergence of seedlings. We also suggest that the loss of some plant species in the seed bank and the tall grass vegetation in intermediary successional stages modify the local conditions and prevent the further establishment of early-successional plant species.     

祁连山东段高寒植被群落特征及其与地形气候因子关系研究

地形气候因子与物种分布的关系影响着高寒植被群落的演替,同时对山地水源涵养林功能和结构的维持具有重要的意义。以祁连山东段水源涵养林为研究对象,基于野外植物群落物种组成及地形气候因子调查数据,运用数量分类与排序等方法,探究了高寒植物群落特征及其与地形气候因子的关系。结果表明:65个调查样方中出现181个植物种,隶属40科,124属。科的物种组成及占总物种数比例分别为菊科30个种,占16.57%;蔷薇科17个,占9.44%;禾本科13个种,占7.22%;豆科11个种,占6.11%。毛茛科10个种,占5.56%。单属种82个,占总属数的66.13%。群落层片由乔木层、灌木层和草本层组成,乔木8种,灌木25种,草本148种。乔木层优势种有青海云杉、祁连圆柏、红桦。灌木层优势种有金露梅、山生柳、匙叶小檗、高山绣线菊。草本层优势种有甘肃薹草、珠芽蓼、早熟禾、唐松草、甘青蒿。TWINSPAN将高寒植被群落划分为7个群丛类型:群丛I红桦-红花蔷薇-甘肃薹草B.albosinensis-Rosa moyesii-C.kansuensis,群丛II青海云杉-匙叶小檗-甘肃薹草P.crassifolia-B.vernae-C.kansuensis,群丛III祁连圆柏-高山绣线菊-珠芽蓼Sabina chinensis-Spiraea alpine-P.viviparum,群丛IV高山绣线菊+鬼箭锦鸡儿-珠芽蓼S.alpine+Caragana jubata-P.viviparum,群丛V沙棘+甘青蒿+鼠掌老鹳草Hippophae rhamnoides+A.tangutica+Geranium sibiricum,群丛VI沙棘+苦荬菜+苦荞麦H.rhamnoides+Ixeris polycephala+Fagopyrum tataricum,群丛VII沙棘-冰草+西北沼委陵菜H.rhamnoides-Agropyron cristatum+Comarum salesovianum。7个群丛在DCA排序图上聚集分布,反映了较好的环境梯度。CCA排序结果表明,海拔是祁连山高寒植被群落植物种分布的最重要环境因子,其次是降水、温度、坡向、坡度。     

Integral assessment of the regrow capacity of alpine plants

A method for the comparative assessment of the regrow capacity (the ability of plants to the after-mowing recovery of above-ground biomass) of herbs in natural plant communities has been proposed. The method is based on the combined use of biomass parameters and the data on the number of shoots for the cases of the single and double removal of the biomass. The regrow capacity of 42 alpine species from four different plant communities has been assessed. The average weighted regrow capacity score decreases in the following series: Geranium-Hedysarum meadows > alpine lichen heaths ≥ alpine snow-bed communities ≥ Festuca varia meadows.     

Differentiation between native and exotic plant species from a dry grassland: fundamental responses to resource availability,and growth rates

Abstract Species from a mixed native/exotic dry grassland community in New Zealand were experimentally assessed for three ecophysiological parameters: nutrient response, water response and maximum relative growth rate (RGR_max). These are parameters that relate to factors proposed as important in structuring plant communities in dry environments. Native and exotic species did not differ consistently in water response. Exotic species tended to have a greater response to nutrients, but there was considerable overlap between native and exotic guilds. However, exotic species did have a higher intrinsic growth rate, and this effect was not attributable to differences in life histories. The results suggest that the exotic species are more competitive and more generalist than the native species. These traits are compatible with the concept of the ‘ideal invader’, and suggest the C‐R strategy of Grime’s theory. The native species showed characteristics consistent with stress tolerance (sensu Grime). The paucity of evidence for ecophysiological differentiation between the native and exotic guilds, except in intrinsic growth rate, indicates that the exotic species were able to invade not because they had superior adaptation to the physical environment, but because they possessed, by pre‐adaptation, the same ways of coping with that environment as the existing species. However, their ability to invade can be related to their growth rates.     

Seed-to-seed potential allelopathic effects between <Emphasis Type="Italic">Ligularia virgaurea</Emphasis> and native grass species of Tibetan alpine grasslands

Allelopathy is an important process in plant communities, but the role of seed allelopathy in natural ecosystems remains poorly understood. In the present study, we examined the potential allelopathic effects of Ligularia virgaurea (a dominant species in degraded Tibetan grasslands) seeds on the germination of four native grass species (Festuca sinensis, Agrostis gigantean, Bromus inermis, and Elymus nutans). The results showed that L. virgaurea seeds can have potential allelopathic effects on seed germination, mean time to germination and root growth rates of native grass species. We further demonstrate that these effects are driven by a water-soluble seed leachate. Species with smaller seeds were generally more sensitive than larger seeded species. The results suggest that seed-to-seed allelopathic potential may be an important mechanism driving the dominance of L. virgaurea in degraded alpine grasslands on the Tibetan Plateau. Further studies are required to demonstrate effects of seed-to-seed potential allelopathy in a field setting.     

Persistent soil seed banks in old-growth Hyrcanian Box tree (Buxus hyrcana) stands in northern Iran

Little is known about the soil seed bank and the influence of plant communities on the interaction between the seed bank and aboveground vegetation in the Hyrcanian temperate deciduous forest. We surveyed species composition and diversity of the persistent soil seed bank and the aboveground vegetation in six community types in old-growth Hyrcanian Box tree (Buxus hyrcana) stands in northern Iran. Fifty-two species with an average of 3,808 seeds/spores m⁻² germinated; forbs accounted for 64% of the seed bank flora. Thirty-four species in the aboveground vegetation were not presented in the seed bank, 32 species in the seed bank were not found in the vegetation, and 20 species were in both. The dominant tree species were Diospyros lotus and Alnus subcordata with an average of 17 and 4.6 seeds m⁻², respectively. Our results suggest that (1) vernal geophytes and shade-tolerant perennials are not incorporated in the seed bank, (2) early successional species are well represented in the seed bank, (3) plant community type has significant impacts on seed bank densities, and seed bank richness and diversity were significantly related to presence/absence of Box tree in the aboveground vegetation. The persistent seed bank contained species that potentially have a negative impact on the regeneration of forests, thus forest managers should retain old-growth Hyrcanian Box tree stands to conserve disturbance-sensitive indicator forest species.     

Plant density can increase invertebrate postdispersal seed predation in an experimental grassland community

Janzen–Connell effects are negative effects on the survival of a plant's progeny at high conspecific densities or close to its conspecifics. Although the role of Janzen–Connell effects on the maintenance of plant diversity was frequently studied, only few studies targeted Janzen–Connell effects via postdispersal seed predation in temperate grassland systems. We examined effects of conspecific density (abundance of conspecific adult plants) on postdispersal seed predation by invertebrates of three grassland species (Centaurea jacea, Geranium pratense, and Knautia arvensis) in experimental plant communities. Additionally, we examined the impact of plant species richness and different seed predator communities on total and relative seed predation (= seed predation of one plant species relative to others). We offered seeds in an exclusion experiment, where treatments allowed access for (1) arthropods and slugs, (2) arthropods only, (3) small arthropods only, and (4) slugs only. Treatments were placed in plots covering a gradient of abundance of conspecific adults at different levels of plant species richness (1, 2, 3, 4, 8 species). Two of the plant species (C. jacea and K. arvensis) experienced higher rates of seed predation and relative predation with increasing abundance of conspecific adults. For C. jacea, this effect was mitigated with increasing plant species richness. Differences in seed predator communities shifted seed predation between the plant species and changed the magnitude of seed predation of one plant species relative to the others. We exemplify density‐dependent increase in seed predation via invertebrates in grassland communities shaping both the total magnitude of species‐specific seed predation and seed predation of one species relative to others. Further differences in seed predator groups shift the magnitude of seed predation between different plant species. This highlights the importance of invertebrate seed predation to structure grasslands via density‐dependent effects and differing preferences of consumer groups.     

Experimental comparison of competition and facilitation in alpine communities varying in productivity

Question. Competitive and facilitative interactions among plant species in different abiotic environments potentially link productivity, vegetation structure, species composition and functional diversity. We investigated these interactions among four alpine communities along an environmental productivity gradient in a generally harsh climate. We hypothesised that the importance of competition would be higher in more productive sites. Location. Mt. M. Khatipara (43°27′N, 41°41′E, altitude 2750 m), NW Caucasus, Russia. Communities ranged from low‐productivity alpine lichen heath (ALH) and snowbed communities (SBC), to intermediate productivity Festuca grassland (FVG), and high‐productivity Geranium‐Hedysarum meadow (GHM). Methods. We quantified the relative influence of competition and facilitation on community structure by expressing biomass of target species within each natural community proportionally to biomass of the species in a “null community” with experimental release from interspecific competition by removing all other species (for 6 years). An overall index of change in community composition due to interspecific interactions was calculated as the sum of absolute or proportional differences of the component species. Results. Species responses to neighbour removal ranged from positive to neutral. There was no evidence of facilitation among the selected dominant species. As expected, competition was generally most important in the most productive alpine community (GHM). The intermediate position for low‐productivity communities of stressful environments (ALH, SBC) and the last position of intermediately productive FVG were unexpected. Conclusions. Our results appear to support the Fretwell‐Oksanen hypothesis in that competition in communities of intermediate productivity was less intense than in low‐ or high‐productive communities. However, the zero net effect of competition and facilitation in FVG might be the result of abiotic stress due to strong sun exposure and high soil temperatures after neighbour removal. Thus, non‐linear relationships between soil fertility, productivity and different abiotic stresses may also determine the balance between competition and facilitation.     

On community structure in high alpine grasslands

Previously published data on production biology, energy use efficiency, nutrient availability and vulnerability were reinterpreted for the explanation of community processing and structure in high altitude grasslands of the Alps. The final goal of the approach was to present a characterization of these plant communities in generalized terms.The keystone-concept was applied, and the alpine grasslands then defined as plant communities with one or a few keystone species. Associated species show a varying degree of interdependence from these keystones. They form guilds exploiting resources not needed by the latter. As many of these species belong to these groups, and alpine grasslands are commonly species rich, a high functional redundancy is typical for these communities.     

桂北喀斯特石漠化地区不同植物群落土壤种子库特征及其与土壤养分关系

土壤种子库作为地上植被遗传信息库，对植被自然演替更新以及生态修复建设具有重要作用。为探明桂北喀斯特石漠化地区植被自然恢复潜力和恢复策略，该文选取恭城瑶族自治县喀斯特石漠化地区3种典型植物群落为研究对象，分析不同群落的土壤种子库结构、多样性及其对土壤养分特征的响应，以期为该地区石漠化治理和植被恢复提供理论依据。结果表明：(1)共计监测到幼苗3 648株，隶属于33科51属55种，其中1年生和2年生草本幼苗共20种，多年生草本幼苗21种，藤本幼苗5种、灌木幼苗3种、乔木幼苗6种；不同植物群落土壤种子库平均密度为三华李经济林(22 493 grain·m^-2)>青冈次生林(1 033 grain·m^-2)>金竹灌丛(793 grain·m^-2)。(2)土壤种子库植物生活型方面，三华李经济林主要分布1年生恶性杂草，青冈次生林和金竹灌丛则以多年生草本为主，木本植物占比较少；不同植被类型中土壤种子库物种多样性和相似性总体较低，同时与地上群落物种组成的相似性也较低。(3)研究区域的土壤元素存在高氮低磷的现象，其中磷元素为金...     

Potential of endozoochorous seed dispersal by sheep in calcareous grasslands: correlations with seed traits

Questions: What is the potential of sheep to serve as seed dispersers via ingestion and defecation in calcareous grasslands? Is the presence of viable seeds from dung correlated with specific seed traits? Location: Calcareous grasslands, South Limburg, the Netherlands/Belgium. Methods: Dung samples (n=24) from sheep were collected between September 2006 and November 2007 from five sites with Mesobromion plant communities, and communities of Nardo‐Galion saxatilis. Germinability and identity of seeds in the dung samples were ascertained from germination of seedlings under glasshouse conditions. Seed traits of species with viable seeds in dung were compared with those present in the local species pool. Results: Seventy‐two plant species from 23 plant families had viable seeds in sheep dung. The plant families encountered most frequently were Gramineae and Compositae. The most abundant and frequently recorded plant species in dung samples was Urtica dioica, accounting for >80% of the total number of seeds. Mean seed density in sheep dung was 0.8 seeds g^?1 dry matter. Seeds with low seed mass and a high seed longevity index were over‐represented in dung. Viable seeds >2.5 mg were infrequent in the dung samples. Conclusions: We conclude that sheep are potentially important dispersers of plant species in Dutch calcareous grasslands. Although smaller seeds were relatively abundant in sheep dung, it cannot be excluded that this was mainly caused by differences in seed abundance.     

Naturally recruited herbaceous vegetation in abandoned Belgian limestone quarries: towards habitats of conservation interest analogues?

We examined if naturally recruited herbaceous vegetation in abandoned Belgian limestone quarries tend towards plant communities analogous to semi-natural habitats of conservation interest. We studied taxon-based assemblages (using two-dimensional non-metric multidimensional scaling ordination) and functional patterns (relative to Grime’s competitor, stress tolerator and ruderal plant strategies (CSR) classification) of plant communities (n = 360 plots) among three different time periods after quarry abandonment (< 3 y, 3–20 y, >?20 y). We compared those successional assemblages with those of habitat of conservation interest plant communities (n = 53 plots): lowland hay meadows and rupicolous, xerophilous and mesophilous calcareous grasslands. Our results indicate that naturally recruited herbaceous vegetation compositionally resembled mesophilous grassland, even though initial substrate conditions were more similar to rupicolous or xerophilous grasslands. The specific successional pathway we found in CSR state-space differs from Grime's predictions because there was a functional shift in plant assemblages from dominance by ruderals to dominance by stress-tolerant species. The differences in successional trajectories we found on different types of rock substrate suggest that conservation management should adopt a site-specific approach, recognizing that the highest probabilities of success on hard limestone will be restoration to calcareous grassland analogues.