Habitat utilization of the Glanville fritillary butterfly in the Tianshan Mountains, China, and its implication for conservation

In 2004 and 2005, we investigated the distribution of the Glanville fritillary butterfly (Melitaea cinxia) and its host plant in the Tianshan Mountains of China, in order to clarify its habitat utilization. Female butterflies were almost captured on dry meadows on slopes, where plenty of host plant (Veronica spicata) is distributed. Although there are host plants on meadows at higher altitude (>2,050 m), no butterfly was found there. Among the meadows with host plants, a patch of dry meadow (newly-found meadow) was considered as a natal site because of the high density and freshness of butterflies. Unlike females, male butterflies were almost captured in valleys, where there are no host plants and fewer nectar plants. It might be related to specific mating system of M. cinxia in the study site, or specific environmental factors. Thus valleys are important habitat for males. Although the status of M. cinxia is yet unknown in China, we give some suggestions for conservation based on this study. First, dry meadows with host plants are the essential component for persistence of M. cinxia, among which the specific sites with more favourable conditions, such as natal site, are most important. Second, as a site with adult resource requirement, valleys should be included as part of the habitat of the butterfly. Finally, meadows at higher altitude are not utilized at present but they are potential habitats which need to be maintained for any shifts in altitudinal range in response to global warming in the future. Hence, the trade-off of present cost and future benefit should be taken into account when formulating a conservation strategy for M. cinxia in the Tianshan Mountains of China.     

Studies on Halimeda

Large areas of the inter-reefal seabed in the Great Barrier Reef are carpeted with vegetation composed almost entirely of the green calcareous alga Halineda. These meadows occur principally in the northern sections between 11°30 and 15°35S at depths of 20 to 40 m, but there are also some in the central and southern sections, where they have been found at depths down to 96 m. The vegetation is dominated by the same sprawling Halimeda species that are common on coral reefs in this region. However, on reefs these species grow on solid substrata, not soft sediments like the Halimeda-rich gravels that underlie the meadows. A total of 12 Halimeda species, together with two Udotea and one Penicillus species, are characteristic components of the shallow meadows. Below 50 m depth, species composition is restricted to only two major components. One, H. copiosa, is also important shallower, but the other is an unusually large and heavily calcified form of H. fragilis, a species that is normally a minor, fragile component of the shallow meadows. The maximum biomass found in these meadows was 4637 gm² of calcareous algae, although the thean for vegetated areas was 525 gm². These meadows are confined to the nutrient-depleted waters of the outer continental shelf just inside the outer barrier reefs, and are usually associated with distinct shoaling of the seabed caused by accumulation of thick deposits of calcareous Halimeda segments. The meadows are probably supported by very localized upwelling of nutrients from the adjacent Coral Sea onto the shelf, where they enrich the otherwise nutrient-depleted waters.Contribution No.367 from the Australian Institute of Marine Science     

Impact of Regional Species Pool on Grasshopper Restoration in Hay Meadows

Agri‐environment schemes are the most widely adopted political measure to maintain and restore farmland biodiversity in Europe. However, abiotic and biotic factors often limit the success of ecological restoration. Among the biotic factors, the size of the local and regional species pool is a major constraint. This is only well documented for plants. We therefore wanted to know if a small regional species pool can also limit restoration efforts of invertebrates. Specifically, we tested if by relocating grasshoppers from further away, we could overcome regional species pool limitations on hay meadows under the Swiss agri‐environment scheme, so‐called Ecological Compensation Area meadows (ECA meadows). All meadows had been under restoration for 6 years and were formerly intensively used hay meadows. Two grasshopper species, Euthystira brachyptera and Mecostethus parapleurus, were selected; E. brachyptera was not found in the regional species pool and M. parapleurus had nearly disappeared. In 2004, 1,400 grasshopper individuals of each species were taken from the nearest large source populations and distributed equally on seven ECA meadows and seven control meadows. In 2005, we evaluated whether the species had successfully established. Only one individual of M. parapleurus was found. We conclude that a small regional species pool is not the only constraint for the reestablishment of grasshoppers on restoration meadows. Also, other factors such as habitat quality appear to constrain the reestablishment of grasshoppers on restoration meadows. Additional restoration efforts specifically targeted at grasshopper restoration are needed, and innovative techniques have to be developed to overcome the relocation constraints.     

Hydrology of Dutch Cirsio‐Molinietum meadows: Prospects for restoration

Abstract. Fen meadows (Cirsio dissecti‐Molinietum) are seriously threatened by desiccation, acidification and eutro‐phication. In The Netherlands several projects were launched to restore damaged fen meadows. This review describes how successes and failures of these restoration projects depend on hydrological systems. Six hydrological systems have been distinguished, which all provide the site conditions required by this community. Nowadays, the best developed fen meadows are found in the higher Pleistocene landscape of The Netherlands, where they depend on base‐rich groundwater discharging from local or large groundwater systems. Fen meadows of the lower Holocene landscape usually occur in man‐made surface water systems. Almost all stands have been severely deteriorated. Restoration of fen meadows in the Pleistocene landscape is promising when the hydrology is only slightly disturbed or when hydrological measures are taken in combination with sod cutting. Restoration prospects of fen meadows in the Holocene landscape are low. Until now a complete regeneration of Cirsio‐Molinietum meadows has not been realized. Restoration measures failed to restore high pH values in the top soil. It is hypothesized that viable seeds of many target species lack in the soil seed bank. In addition, the dispersal capacities of these species seem to be limited.     

Notes on the Scottish flora

Background: The degradation of alpine meadows on the Qinghai-Tibetan Plateau (QTP) has an impact on vegetation recruitment from seedlings and ramets.

Aims: Understanding the relative contribution of recruitment by seedling and ramet in alpine meadows is for the ecological restoration of degraded grasslands on the QTP.

Methods: An experiment was conducted to investigate seedling and ramet densities, species composition and their relationships with standing vegetation in plots representative of non-degraded (ND), lightly (LD), moderately (MD) and severely degraded (SD) alpine meadows.

Results: With increasing degradation and the reduction in vegetation cover, the number of seedlings and ramets declined. The proportion of young plants arising from seedlings was low, with the majority of species reproducing clonally. The establishment of seedlings of forbs in SD meadows led to species-rich, forb-dominant vegetation in these areas.

Conclusions: LD and MD meadows appear to be able to be managed by reduced grazing for the restoration of grass- and sedge-dominated pastures. In contrast, restoration of SD meadows will require additional intervention, such as of seeding and weed eradication.     

Floristic composition,site conditions and diversity of poet’s daffodil (Narcissus radiiflorus Salisb.) hay meadows in the Venetian Pre-Alps and outer Dolomites (N-Italy): implications for conservation and restoration

Abstract

Hay meadows are an important component of the alpine landscape, which evolved over millennia of human activities. When traditionally managed, hay meadows support a rich flora and are recognized for high species diversity. However, both intensification and abandonment can lead to a loss of biodiversity in this vegetation. In this paper, the focus was on the hay meadows where Narcissus radiiflorus Salisb. forms white mosaic carpets during the blooming period. This vegetation was studied through 26 phytosociological relevés, taken in the Venetian Pre-Alps and outer Dolomites (Northern Italy). Relevés were numerically classified and analysed in their relationships with site conditions. Moreover, diversity metrics were calculated for detecting the conservation status of hay meadows subjected to different types of disturbance. The results showed that poet’s daffodils’ dominance brings together hay meadows showing a substantial range of floristic and ecologic variation and that part of the stands dominated by Narcissus radiiflorus could be referred to a habitat type regarded as prioritary for nature conservation. Moreover, management-related variations in functional diversity suggested that the best practice recommended for conservation and restoration of this habitat is the continuation of traditional late mowing. This practice will allow preserving both biodiversity and ecosystem functions and services.     

Les pelouses à Festuca paniculata du Tessin (Suisse) dans un contexte Alpin

Vittoz P., Selldorf P., Eggenberg S. and Maire S. 2005. Festuca paniculata meadows in Ticino (Switzerland) and their Alpine environment. Bot. Helv. 115: 33–48.Festuca paniculata (L.) Schinz & Thellung locally dominates montane and subalpine meadows of the Alps and other mountains of southern Europe. Vegetation relevés were carried out in Switzerland and northern Italy to study the site conditions under which Festuca paniculata meadows occur in this part of the Alps, their species composition and phytosociological status, and their relationship to Festuca paniculata meadows described previously from the French Alps (Centaureo-Festucetum spadiceae) and Austrian Alps (Hypochaerido uniflorae-Festucetum paniculatae). The Swiss meadows were found to have a similar ecology to those in France and Austria. They occur mostly between 1600 and 2100 m a.s.l on steep slopes with southern aspect, generally on crystalline rocks, but sometimes on calcareous rocks if soils have been decalcified. The species composition of the Swiss meadows is closer to the Austrian than to the French communities, and we attribute them to the association Hypochaerido uniflorae-Festucetum paniculatae with the new subassociation polygaletosum chamaebuxi. Climate is probably the main factor separating vegetation units in the Alps: the Centaureo-Festucetum spadiceae occurs where summers are dry, whereas the Hypochaerido uniflorae-Festucetum paniculatae occurs where rainfall is not a limiting factor in summer.Manuscrit accepté le 10 février 2005     

Ant communities and Solidago plant invasion: Environmental properties and food sources

The invasion of Solidago is one of the main threats to the biodiversity of natural meadows, leading to changes in animal and plant communities, as well as soil features. We compared effects of soil microclimatic conditions (temperature and moisture) and the availability of potential protein sources (dry mass of epigean invertebrates) on ants between meadows invaded by Solidago altissima and S. canadensis and those uninvaded. Our results showed that the ant communities were different between the uninvaded and invaded meadows, with reduction of ant abundance and species richness in the latter. Myrmica spp. were abundant in the uninvaded meadows, whereas Lasius niger was the dominant species in the invaded ones. We found that the lower moisture negatively influenced the abundance of Myrmica species in the Solidago‐invaded meadows. Moreover, the epigean invertebrate dry mass, as an estimation of the availability of protein sources, varied between the two types of meadows, with a higher abundance in the uninvaded ones. The abundance of Myrmica ants with narrower ecological requirements showed a positive correlation with the invertebrate biomass in the invaded meadows. In contrast, the abundance of L. niger with broad ecological requirements was negatively correlated with the invertebrate biomass in the invaded meadows, possibly as a strategy to reduce interspecific competition. Our study showed that the invasion of Solidago plants caused changes in the abundance and species composition of ant communities through modification in microhabitat conditions, that is, decreasing soil moisture, reducing biomass and changing distribution of prey invertebrates.     

Committee for the study of the Scottish Flora

Background: Damage to alpine plant communities is likely to occur when hikers and pack animals trample vegetation. Currently, there is limited research that quantifies and compares impacts from these activities.

Aims: A manipulative experimental protocol was used to assess damage to alpine meadows by pack animals and hikers in the Aconcagua Provincial Park, Andes, Argentina.

Methods: Vegetation height, overall cover, cover of dominant species and species richness were measured immediately after, and 2 weeks after different numbers of passes (0, 25, 100 and 300) by hikers or pack animals in an experiment, using a randomised block design.

Results: Pack animals had two to three times the impact of hiking on the meadows, with greater reductions in plant height, the cover of one of the dominant sedges and declines in overall vegetation cover after 300 passes. Impacts of pack animals were also apparent at lower levels of use than for hikers. These differences occurred despite the meadow community having relatively high resistance to trampling due to the traits of one of the dominant sedges (Carex gayana).

Conclusions: Pack animals caused more damage than hikers to the alpine meadow, but the scale of the difference in short-term impacts depends on the characteristics of the plant community, the amount of use and the vegetation parameters measured. Use of the meadows by hikers and pack animals should be minimised as these meadows are scarce, and have high conservation values.     

Habitat formed by the invasive macroalga Caulerpa filiformis (Suhr) Hering (Caulerpales,Chlorophyta) alters benthic macroinvertebrate assemblages in Peru

The green macroalga Caulerpa filiformis has been spreading on shallow soft sediment habitats along the Peruvian coast, colonizing previously unvegetated sediments to create monospecific meadows. We examined the nature of the impact of C. filiformis meadows on the density, taxonomic richness and assemblage structure of epifaunal and infaunal benthic macroinvertebrates. Specifically, we tested whether the spread of C. filiformis has resulted in different macroinvertebrate assemblages than those formed by the dominant native macroalgae (i.e., Rhodymenia spp.) and unvegetated sediments. Surveys were undertaken in two bays in each of two locations, in central and southern Peru, during winter 2017 and summer 2018. In general, our results show that macroinvertebrate assemblages were similar across all three habitats, although there were some differences, related to location and time, but with no clear patterns observed. Taxonomic richness and density was generally higher in the vegetated habitats than the unvegetated habitat, and where there were differences between the two vegetated habitats there was no consistent pattern of which habitat supported the highest richness or density. Given invading C. filiformis is primarily colonizing unvegetated habitats it would appear that this species is creating a new niche which supports similar assemblages, but higher taxonomic richness and density than unvegetated habitats. While our study suggests that C. filiformis is having a limited ecological impact we recommend that actions be put in place to limit the spread of this invasive species at the same time as increasing monitoring of the ecological impacts of this species as lags in the ecological impacts of invasive species are common.

     

Mechanisms blocking Pinus sylvestris colonization of Mediterranean mountain meadows

Abstract. In southern Mediterranean Pinus sylvestris forests there are grassy meadows that resist invasion of trees despite the proximity to seed sources. In this study, we investigate the mechanisms blocking colonization by Pinus sylvestris of the meadows. Two experiments were conducted in which seeds were sown either at 1 cm depth or on the surface to simulate dispersal, and three treatments of vegetation removal were applied: Disturbed (where the herbaceous layer was eliminated, exposing the mineral soil), Clipped (vegetation cut at ground level) and Control (no disturbance of the herbaceous layer). In addition, the effect of seed predators was controlled by using wire cages in the case of the surface sown experiment. When seeds were sown at 1 cm depth, seedling emergence was not reduced by the herbaceous layer. In contrast, when seeds were surface sown and predators were excluded, the rate of emergence was low in the Control treatment, intermediate in Clipped and high in Disturbed. Seedling emergence was, however, minimal when predators were not excluded, irrespective of the disturbance level. Seedling survival and growth after three years of study were similar among treatments. The results show that the seed predation and the physical barrier created by the herbaceous layer are the two mechanisms blocking the encroachment of Pinus sylvestris onto these Mediterranean mountain meadows, limiting the regeneration and potential expansion of the forest.     

Differential and reversible responses of common fen meadow species to abandonment

Abstract. We studied the effects of abandonment on two common fen plant species. In mown and a chronosequence of abandoned fen meadows spanning 35 yr, we measured fitness traits of the sedge Carex davalliana and the forb Succisa pratensis. Cessation of mowing had little effect on fitness traits and seed production of C. davalliana, but seedling density decreased more than threefold. Population density of S. pratensis decreased with increasing community biomass, but was not affected by the cessation of mowing. However, flowering frequency increased threefold and seed production was 20% higher in fallow meadows. Consequently, seedling density of S. pratensis increased nearly threefold after abandonment. However, these changes were not dependent on the age of the fallow. In a common garden and germination experiment, we found no differences in either species between plants from fallows and mown fen meadows, except for the height of the flowering stalk of S. pratensis. The combined results from the common garden experiment and the field studies indicate that changes in fitness traits observed in fallows were mostly phenotypic and likely to be reversible. If other species react in similar ways, there is a high potential for re‐establishing traditional fen meadow communities from fallows by mowing.     

Management of natural <Emphasis Type="Italic">Ulva</Emphasis> spp. blooms in San Quintin Bay,Baja California: Is it justified?

According to Zertuche-González et al. (2009), Ulva spp. blooms, favored by oyster cultivation, are likely displacing subtidal meadows of Zostera marina in San Quintin Bay, Baja California. The authors propose a partial removal of the seaweed to reduce the risk of eutrophication and eelgrass displacement in the bay. We warn about the removal of Ulva spp. biomass by raising six arguments that emphasize the necessity of a historical and ecosystem-based management for San Quintin Bay. First, processes other than competitive exclusion by Ulva spp. blooms more likely explain changes of Z. marina subtidal meadows in the past decade. Second, there is no consistent evidence that oyster cultivation is promoting blooms of Ulva spp. and the loss of eelgrass. Third, the removal of Ulva spp. biomass is based on experiences of heavily anthropogenically eutrophic systems, while San Quintin Bay is not. Fourth, the proposed course of actions to restore eelgrass meadows ignores general historical baselines of estuarine and coastal systems by confusing what it means to be “pristine.” Fifth, despite the important experimental evidence indicating strong top–down control in temperate seagrass meadows, Zertuche-González et al. (2009) underestimated the capacity of consumers in structuring dynamics of vegetated soft-bottom communities in San Quintin Bay. Sixth, Ulva expansa may exert positive effects on seagrass ecosystem properties and functions. Instead, we propose protection against the propagation of unsustainable practices in the bay, and the reintroduction of large consumers that are now absent in this ecosystem. An ecosystem-based analysis of the role of Ulva spp. on eelgrass dynamics is needed.     

草地退化对三江源国家公园高寒草甸表层土壤有机碳、全氮、全磷的空间驱动

草地退化显著削弱了三江源高寒草甸的土壤肥力及生态承载功能,但空间尺度上的驱动强度和环境调控尚不清晰。在2020年7—8月,基于三江源国家公园高寒草甸典型分布区原生植被和退化植被的60个配对采样,研究表层(0—30 cm)土壤有机碳(SOC)、全氮(TN)和全磷(TP)含量对草地退化的空间响应特征。三江源国家公园高寒草甸原生植被SOC和TN含量分别为(2.45±2.05)%(平均值±标准差,下同)和(0.25±0.20)%,配对样本t-检验的结果表明草地退化导致SOC和TN分别极显著(P<0.001)下降了44.0%和35.6%。TP对草地退化无显著响应(P=0.22)。原生植被的土壤C∶N∶P平均为59.6∶6.2∶1.0,草地退化导致化学计量值平均下降28.3%。一般线性模型的结果表明草地退化对SOC和TN及土壤生态化学计量特征的空间降低强度主要取决于纬度和海拔(P<0.01),与经度和土壤深度关系较弱(P>0.30),即低纬度高海拔的高寒草甸响应相对强烈。草地退化导致三江源国家公园高寒草甸土壤碳氮损失严重,降低了土壤生态化学计量。研究结果可为三江源退化高寒草甸土壤...     

Detection of environmental impacts by bottom trawling onPosidonia oceanica (L.) Delile meadows: sensitivity of fish and macroinvertebrate communities

Along the Mediterranean coast,Posidonia oceanica (L.) Delile meadows have a great ecological and economical importance. However, there is a general regression of these meadows due to human activities such as illegal bottom trawling, may be affecting to overall ecosystem health. We examined changes in the community structure of mobile fauna associated withP. oceanica meadows at different spatial scales and taxonomic levels. The aim of this paper was to identify the most efficient taxonomic level to use in environmental impact studies of bottom trawling. At the macroscale level (10 to 100 m), there were significant differences between sites in the densities of some fish species and also the total fish assemblage structure, at both family and species taxonomical levels. At the microscale (0.1 to 1 m), some species of amphipods and isopods showed significant differences in their population densities. In the overall analysis of community structure, the coarse taxonomical levels, such as phyla and class, did not show significant differences, however amphipods and isopods showed significant differences at family and species levels. From these results, both study scales are required to detect changes onPosidonia meadows' fauna. Monitoring of some fish species such asDiplodus annularis (Linnaeus, 1758) and the overall fish assemblage as well as the structure of the amphipod and isopod communities appears to be the most efficient tool in the assessment of environmental impacts by bottom trawling onP. oceanica meadows.     

The effects of mowing and fertilization on carbohydrate reserves and regrowth of grasses: do they promote plant coexistence in species-rich meadows?

After the cessation of regular management and after fertilization a single clonal species tends to dominate in many types of grasslands, whereas in regularly managed meadows these potential dominants usually attain a low cover. It has been hypothesized that plants reaching a high dominance in abandoned and fertilized meadows are selectively suppressed by mowing so that a balanced competition is maintained and competitive exclusion is postponed. We compared regeneration capacity and carbohydrate reserves accumulated by three species of clonal grasses, which markedly increase their dominance in irregularly mown, un-mown or fertilized meadows. Above-ground biomass and the amount of storage carbohydrates of the two largest species, (Molinia arundinacea, Calamagrostis epigejos) were reduced in a mown meadow. This effect was weaker in Bromus erectus, which produces smaller shoots. Shoots of Molinia were most impacted by mowing but their regeneration was efficient due to the large carbohydrate reserves in the shoot bases. Fertilization did not affect Bromus and Calamagrostis. In contrast, fertilized plants of Molinia produced larger storage organs and accumulated more carbohydrates. We conclude that plant size and growth form are important features promoting the ability of potential dominants to tolerate mowing and regenerate after it. Our results confirm that taller plants are selectively suppressed by this type of disturbance, thereby potentially promoting plant coexistence.     

Airborne Laser Scanning as a Tool for Lowland Floodplain Vegetation Monitoring

Monitoring of three-dimensional floodplain vegetation structure is essential for ecological studies, as well as for hydrodynamic modelling of rivers. Height and density of submerged vegetation and density of emergent vegetation are the key characteristics from which roughness parameters in hydraulic models are derived. Airborne laser scanning is a technique with broad applications in vegetation structure mapping, which therefore may be a promising tool in monitoring floodplain vegetation for river management applications. This paper first provides an introduction to the laser scanning technique, and reviews previous studies on the extraction of vegetation height and density of forests, low vegetation and meadows or unvegetated areas. Reliable predictions using laser scan data have been reported for forest height (R²=0.64–0.98), parameters related to forest density, such as stem number, stem diameter, biomass, timber volume or basal area (R²=0.42–0.93), and herbaceous vegetation height (summer condition; R²=0.75–0.89). No empirical relations have been reported on density of herbaceous vegetation. Laser data of meadows and unvegetated areas show too much noise to predict vegetation structure correctly. In a case study for the lower Rhine river, the potential of laser scan mapping of vegetation structure was further explored for winter conditions. Three laser-derived metrics that are often reported in the literature have been applied to characterize local vertical distributions of laser reflections. The laser data clearly show the large structural differences both between and within vegetation units that currently are the basis of floodplain vegetation and roughness mapping. The results indicate that airborne laser scanning is a promising technique for extraction of 3D-structure of floodplain vegetation in winter, except for meadows and unvegetated areas.     

Land-use,environment, and their impact on butterfly populations in a mountainous pastoral landscape: species richness and family-level abundance

Extensive grasslands are considered to be of high biodiversity value, but are under threat from intensification and abandonment. We studied butterfly species richness and abundance in 47 hay and grazing meadows in the Picos de Europa, northern Spain in 2004. Nine transects were walked around the perimeter of the meadows from the 1 June to 28 July with butterflies recorded to species or species-group. Land-use, abiotic, and sward variables were also recorded. Change in meadow extent was estimated by comparing a digital map of open meadows with a cadastral map with 1950s provenance. We found: A decrease in open area, mostly attributable to reduction in grazing meadows. 75 or more butterfly species with species richness principally, and positively, influenced by altitude and presence of scrub in the body of the meadow. Hay meadow management was a positive influence on richness of satyrids. When all butterflies were considered together, the only significant factor influencing abundance was Plantago lanceolata (−ve). For sub-groups of the butterfly community there was no consistent pattern, although P. lanceolata was identified as a (−ve) factor in relation to hesperiid, nymphalid, satyrid, and Viola-feeding fritillary groups. Several regression models included components that could be linked to abiotic influences (water, aspect, altitude) but many were indicative of abandonment or relaxation of management intensity (scrub, Pteridium aquilinum, Asphodelus albus), sward components, fragmentation (distance to nearest meadow, number of meadows within 100 m), and land use (hay management, summer grazing). The results are discussed in relation to changing socio-economics, including the potential impact of tourism, and the need for financial instruments to support extensive farming.     

Restoration Potential of Sedge Meadows in Hand‐Cultivated Soybean Fields in Northeastern China

Sedge meadows can be difficult to restore from farmed fields if key structural dominants are missing from propagule banks. In hand‐cultivated soybean fields in northeastern China, we asked if tussock‐forming Carex and other wetland species were present as seed or asexual propagules. In the Sanjiang Plain, China, we compared the seed banks, vegetative propagules (below‐ground) and standing vegetation of natural and restored sedge meadows, and hand‐cultivated soybean fields in drained and flooded conditions. We found that important wetland species survived cultivation as seeds for some time (e.g. Calamogrostis angustifolia and Potamogeton crispus) and as field weeds (e.g. C. angustifolia and Phragmites australis). Key structural species were missing in these fields, for example, Carex meyeriana. We also observed that sedge meadows restored without planting or seeding lacked tussock‐forming sedges. The structure of the seed bank was related to experimental water regime, and field environments of tussock height, thatch depth, and presence of burning as based on Nonmetric Multidimensional Scaling analysis. To re‐establish the structure imposed by tussock sedges, specific technologies might be developed to encourage the development of tussocks in restored sedge meadows.     

Effects of light competition and litter on the performance of Viola palustris and on species composition and diversity of an abandoned fen meadow

Theeffects of light competition and litter on seedling recruitment and theperformance of established individuals were examined in Violapalustris. This polycarpic perennial plant was a common component ofspecies-rich fen meadows in northwestern Germany until the middle of thiscentury, but today is considered to be regionally endangered. From summer 1996until summer 1998 a bi-factorial field experiment combining three standing croptreatments (mowing, thinning, control) with two litter layer treatments (litterremoval, no litter removal) was carried out in an abandoned fen meadow toinvestigate the effects of these factors both on V.palustris and on aboveground species composition and diversity.MANOVAs (multivariate analysis of variance) revealed significant treatmenteffects for the performance of V. palustris related toexperimental manipulation. Mowing increased vital attributes including thenumber of rosette leaves, the percentage of individuals with chasmogamous andcleistogamous flowers and the number of rhizomes. In contrast, the length of theleafstalk, mean leaf area and the length of rhizomes were negatively associatedwith mowing. Litter removal significantly increased the number of V.palustris seedlings. The removal of the litter layer already resultedin an increase in aboveground species richness in the first year of theexperiment. After three years of experimental manipulation, both abovegroundspecies richness and diversity were positively associated with mowing.Redundancy Analysis showed that typical wet meadow species (Cardaminepratensis, Lychnis flos-cuculi, Lotuspedunculatus) and species of mesotrophic fens (Violapalustris, Agrostis canina, Potentillapalustris) were positively influenced by mowing. It can be concludedthat V. palustris recruitment and growth is promoted by aregular disturbance regime on fen meadows. The conservation of many typicalspecies of wet meadows and fens in northwestern Germany depends on moderategrazing or cutting. These management types prevent successional changes whichlead to an increase in standing crop and the development of a litter layer, bothof which can cause local extinction.