Diet selection of lesser white-fronted geese Anser erythropus at a spring staging area

We studied diet selection of the globally threatened lesser white-fronted goose Anser eythropus at a spring staging area on the island of Hailuoto (64°00'N, 24°45'E), off the western coast of Finland. We determined the diet using droppings, which were collected in late May, when the geese had left the area and migrated northwards. The sample potentially comprised of ejecta from 31 different individuals. Plant idengification was based on visual determination of epidermal fragments. A total of 100 droppings were sampled using a point quadrat method. We calculated the percentage of each idengified taxon in each dropping and related this to the availability of the corresponding taxon in the meadow. We measured preference for each taxon using Chesson's electivity index (ɛ_i) and tested them by bootstrap resampling. The diet contained 9 taxa of the ca 40 available. Almost all dietary items were Monocotyledons (99.9%), mostly grasses (88.7%) including Festuca rubra (43%), Phragmites australis (30%) and Calamagrostis stricta (13%). Only Phragmites (ɛ=0.73, p=0.000), Festuca (ɛ=0.52, p=0.004) and possibly Triglochin palustris (ɛ=0.70, p=0.125) were preferred, all other species were avoided. All preferred species were quite common and other goose species exploit them too. The lesser white-fronted geese preferred large natural meadows that were five times broader than an "average" Bothnian Bay meadow. All forms of mowing and grazing management benefit the restoration of lesser white-fronted goose habitats at the landscape level. Festuca and especially Triglochin benefit from such management. Reeds, Phragmites , whose spread has been the main cause of coastal meadow deterioration, can be controlled by management, but can also be maintained among other vegetation if mowing is less frequent or grazing not too intensive.     

Dynamics of common reed (Phragmites australisTrin.) in Swiss fens with different management

Dynamics of common reed (Phragmites australisTrin.) in Central Europe have so far mostly beeninvestigated in connection with studies on reed`die-back' along lake shores. However, there hasrecently been increasing concern about reed expansionat terrestrial sites, such as fens and wet grasslands.In this paper we report on the results of fourseparate studies which monitored reed dynamics inSwiss fens with various mowing regimes over a periodof 4 to 15 years. The first study compared unmownplots with plots mown in winter in a triennialrotation; the second one included unmown plots, plotsmown in summer, and plots mown in winter; the thirdone compared plots mown in June and September withplots only mown in September; the fourth studyinvestigated only plots mown in September. Shootnumber and shoot size were recorded in permanentquadrats. In all studies the performance of P.australisfluctuated without trend or tended todecrease during the period investigated. Thedecreasing tendency concerned shoot size rather thanshoot number, and within a given study it was strongerfor plots with initially taller shoots. The variousmowing regimes did hardly influence these changes.Mowing in winter every three years reduced shoot sizein the year after mowing, but not on the long term.Mowing every year in late summer reduced the shootsize compared with unmown plots on the short term, butthis effect almost disappeared on the long term, aftermowing had become biennial. Mowing in June (inaddition to in September) caused no noticeableeffects. We conclude that other factors (e.g. weatherconditions, competition, or population processes) aremore important than management in determining theabundance of P. australisin the fen communitiesinvestigated here, although long-term effects ofmowing in summer still need more investigation. As apractical consequence it is suggested that at siteswhich are not strongly dominated by P.australis, as most of those investigated here,reducing the performance of this species should notconstitute a major target of nature conservationmanagement, nor can its dynamics be used as anindicator for management success before underlyingcauses are better understood.     

Changes in a salt-marsh vegetation as a result of grazing and mowing — A five-year study of permanent plots

Summary Part of a salt-marsh (32 ha), ungrazed from 1958 until 1971, was grazed again from 1972 onwards with young cattle (1.3–1.7 per ha, May–October). In five vegetation types management experiments, including doing nothing (control). June mowing, August mowing, June and August mowing, all in combination or not in combination with grazing have been started with the objective to compare annually their effects on the vegetational structure and composition by means of permanent plots (2×2 m).Thirteen years (1958–1971) after the grazing had ceased the vegetation types of Festuca rubra/Armeria maritima, Artemisia maritima, Juncus maritimus and Elytrigia pungens hardly changed anymore. The vegetation type of Festuca rubra/Limonium vulgare, changed considerably. The experiments showed rather specific effects during the period 1971–1975 for each type of vegetation. Changes in the Festuca rubra/Armeria maritima vegetation were small and gradually under all treatments. Changes in The Artemisia maritima, Festuca rubra/Limonium vulgare and Juncus maritimus vegetation types were rather great under the different grazing treatments, the changes being abrupt and especially taking place in the third and fourth year of the experiments. The Elytrigia pungens vegetation showed large changes under all treatments, except the control plot, whereas these changes were abrupt, particularly occurring in the first and second year of the experiments. The study is continued.Nomenclature of taxa follows Heukels & van Ooststroom (1970), that of syntaxa Westhoff & den Held (1969).Contribution to the Symposium of the Working Group for Succession research on permanent plots of the International Society for Vegetation Science, held at Yerseke, the Netherlands, October 1975.Thanks are due to Prof. Dr. D. Bakker for his interest in the present study and his critical reading of the text, and to Drs D.C.P. Thalen for critical reading and correction of the English text. Thanks are also due to the students who analyzed the permanent plots: M. van der Duim and F. Prins (1971), M. van der Duim (1972), R. Schwab and T. Schwab-Vos (1973), and G. Allersma (1974, 1975).     

Effects of mowing on the composition of Baltic salt-meadow communities

A moving experiment is carried out at eight sites, situated at different levels in a Baltic salt meadow. The plots have been analyzed and mown with a scythe each year in August since 1979. The response of the sites to mowing is expressed as qualitative and quantitative changes in composition of the vegetation. So far, the most distinct changes in composition have been changes in relative importance of species already present in the initial vegetation. The resistance is found to be highest in the upper parts of the geolittoral, and lowest in the Phragmites australis swamp.     

Effect of grazing on the vegetation of shore meadows along the Bothnian Sea,Finland

The objective of this study was to evaluate the effects of grazing on shoreline meadows. To accomplish this, five ungrazed and four grazed meadow transects (a total of 411 1 m2 plots) were studied on the west coast of Finland (61° 30–61° 33 N/21° 28–21° 41 E). The summed cover of all species was decreased by grazing. The abundances of annuals+biennials, perennials, dicots and pteridophytes were decreased while the cover of monocots was increased by grazing. This trend was similar in all elevation classes and mainly both in the seashore and the delta. In the seashore grazing decreased the cover of chamaephytes and therophytes and in delta it seemed to increase the cover of geophytes and hemicryptophytes, but these results were influenced by differences in elevation. The height of vegetation and the dry biomass were smaller in the grazed than in the ungrazed plots. Agrostis stolonifera, Carex nigra, Festuca rubra, Juncus gerardii, Leontodon autumnalis, Poa subcaerulea and Potentilla anserina were more abundant in grazed, while the abundances of Filipendula ulmaria, Galium palustre, Lathyrus palustris and Phragmites australis were greater in ungrazed plots. Shores are multi-stress environments in which the water level fluctuation narrows the species pool. Grazing cattle is a disturbance, which has varied effects on different vegetation zones and on different kinds of species. Overall, it appears that stress-tolerant perennial monocots and halophytes are favored by grazing in those shoreline communities.     

Vegetation changes following sheep grazing in abandoned mountain meadows

Abstract. Sheep grazing was investigated as an alternative to traditional management of meadows in the Krkono?e Mts. Until the second World War these meadows were mown in mid‐summer and grazed by cattle for the rest of the season. Subsequent abandonment of the meadows has resulted in decreasing species richness. Degradation phases of the former communities have been replacing the original species‐rich vegetation. Significant changes were apparent six years after the introduction of sheep grazing. In grazed plots the proportion of dominant herbs (Polygonum bistorta and Hypericum maculatum) decreased and grasses (Deschampsia cespitosa, Festuca rubra, Agrostis capillaris, Anthoxanthum alpinum) increased. The increase in grasses was positively correlated with an increase in several herbs. The proportion of some herbs increased despite being selectively grazed (Adenostyles alliariae, Melandrium rubrum, Veratrum lobelianum). Any losses caused by grazing of mature plants were probably compensated by successful seedling establishment. Cessation of grazing resulted in significant changes in vegetation within three years. The cover of nitrophilous tall herbs and grasses (e.g. Rumex alpestris, Holcus mollis, Deschampsia cespitosa, Geranium sylvaticum) increased in the abandoned plots. In the plots grazed for nine years cover of species‐rich mountain meadow species increased (e.g. fine‐leaved grasses, Campanula bohemica, Potentilla aurea, Viola lutea, Silene vulgaris). The main conservation risk is the expansion of a competitive species with low palatability, Deschampsia cespitosa. This species can be suppressed by a combination of grazing and mowing. In order for grazing to be effective, the number of sheep should be proportional to meadow production. This may be difficult to maintain as production is variable and is impossible to predict at the beginning of a growing season. A large part of the biomass may thus remain intact in some years. Negative effects of grazing may be, at least partly, eliminated by a combination of cutting and grazing.     

Restorative mowing on an abandoned semi‐natural meadow: short‐term and predicted long‐term effects

Abstract. When management, in the form of cattle grazing and mowing, ceases the abundance of competitively superior plant species tends to increase in abandoned semi‐natural meadows. Litter accumulation elevates the soil nutrient levels and hinders seedling recruitment. We surveyed changes in plant cover and species composition of a formerly grazed meadow in permanent plots for six years. Some plots were unmown, while others were mown and raked annually in August. The cover of grasses decreased and herb cover remained unchanged regardless of the treatment. Mowing and raking significantly reduced litter accumulation and increased the number of ground layer species. The expected long‐term effects of abandonment and restorative mowing were studied by calculating the transition probabilities for unmown and mown plots and simulating the course of succession as projected by the transition matrices. During a simulation period of 30 yr, abandonment led to (1) a decrease in the cover of small herbs, (2) a slight increase in the cover of tall herbs and (3) a slight decrease in the cover of grasses. In contrast, the cover of small herbs on the mown plots remained unchanged or slightly increased during the course of simulation. These results suggest that mowing late in the season is primarily a management tool for the maintenance of the existing species diversity and composition. However, it may not be an effective restorative tool to induce overall changes in the resident vegetation of abandoned grass‐dominated meadows. Grazing or mowing early in the season may be more effective in this respect. Consequently, mowing early or, alternatively, late in the season may provide management strategies for the maintenance and restoration of species diversity, respectively.     

THE FRIT FLY AND ALLIED STEM-BORING DIPTERA IN WINTER WHEAT AND HOST GRASSES

Sampling for stem-boring larvae was undertaken in 1954-56 on ley plots of Lolium perenne, Dactylis glomerata, Festuca arundinacea, F. rubra, Agrostis tenuis and Poa pratensis in randomized experiments at Hurley, Berks. The samples showed infestations by dipterous larvae, mainly species of Oscinella, Meromyza and Opomyza. The larvae showed preferences for specific grass hosts. More larvae were found where plots had been grazed throughout the season than where an early hay cut had preceded grazing. The total numbers of larvae varied between o and 688 per sq.yd. in November.
The larval populations of the leys were reflected in the populations in winter wheat which followed the plough-up of the leys. Populations of up to sixty-five larvae per sq.yd., mostly species of Oscinella , were found in the wheat in March. In 1956 a heavy larval infestation was associated with the death of considerable numbers of wheat plants.     

A hay meadow in western Norway-changes in the course of a growing season

Interference of management with groups of species/single species in a hay meadow is studied in a pilot project. Plant species are recorded 3 times during growing season from 10 permanent plots at intervals along 2 transects crossing the meadow. Hult-Sernander-Du Rietz scale is used for estimating cover, and phenological phases are estimated according to Dierschke.
The hay meadow is lightly fertilized in spring, mown once late in July and grazed lightly by calves in autumn. Until 7–8 years ago the meadow was more heavily grazed by sheep both in spring and autumn.
50 species are recorded, 44 within the permanent plots, 33 are indicators of agricultural management, 21 are indicators of traditional management, and 24 are adapted to grazing. The meadow belongs to Cardamino pratensis-Conopodietum majoris, subas-sociation campanuletosum. Luzula campestre, Campanula rotundifolia, Potentilla erecta, Hypochoeris radicata and Trifolium repens vary little in cover throughout the summer. Anthoxanthum odoratum, Leucanthemum vulgare, Trifolium pratense and Agrostis capillaris have a higher cover just before mowing than afterwards. Conopodium majus is not present above ground at all in August. Rumex acetosa and Achillea millefolium have their highest cover values in August. The time of flowering varied. At the spring analysis, Ajuga pyramidalis, Anthoxantum odoratum, Luzula campestre and Plantago lanceolata flowered. The main flowering took place at the end of June, when 20 species flowered. In August the flowers of Leontodon autumnalis, Hypochoeris radicata, Potentilla erecta and Hieracium vulgatum characterized the meadow. Several hypothesis and proposals for testing of the hypothesis are put forward.     

四种生态型芦苇叶中离子分布对生境的生理适应

采用X射线微区分析技术,测定了4种生态型芦苇(Phragmites australis (CaV.) Trin. exSteud.)叶的表皮泡状细胞、叶肉细胞和叶脉维管束鞘细胞离子的含量.结果表明:沼泽芦苇的鞘细胞内,K+、Na+、Ca2+、Mg2+和Cl-分布均较叶肉细胞和泡状细胞高.沙丘芦苇的泡状细胞中Ca2+分布较叶肉细胞和鞘细胞高,而Mg2+在其叶肉细胞,以及K+、Na+和Cl-在其鞘细胞内分布均较高.在轻度盐化草甸芦苇的叶肉细胞内分布较多的Na+和Mg2+,而在鞘细胞内K+、Ca2+ 和Cl-的分布均较叶肉细胞和泡状细胞为高.重度盐化草甸芦苇的泡状细胞内Na+和Mg2+的分布较多;同样,在叶肉细胞中K+、Ca2+和Cl-的分布也较多.最后,讨论了上述各种离子在不同生态型芦苇叶内分布的状况, 以及与其环境适应的生理意义.     

Seasonal Abundance and Species Richness of Birds in Common Reed Habitats in Lake Erie

Abstract: Common reed (Phragmites australis) forms dense stands with deep layers of residual organic matter that negatively affects plant diversity and possibly habitat use by wetland birds. We sought to determine whether seasonal relative abundance and species richness of birds varied among 3 habitat types in Great Lakes coastal wetland complexes recently invaded by common reed. We used fixed-distance point counts to determine species relative abundances and species richness in edge and interior locales within common reed, cattail (Typha spp.), and meadow marsh habitats of various sizes during 2 summers (2001 and 2002) and 1 autumn (2001) at Long Point, Lake Erie, Ontario, Canada. We found that total relative abundance and species richness of birds were greater in common reed habitat compared to cattail or meadow marsh habitats. However, we also found that relative abundance of marsh-nesting birds was greater in meadow marsh habitat than in cattail and common reed during summer. Lastly, we found that, irrespective of habitat type, habitat edges had higher total relative abundance and species richness of birds than did habitat interiors. Our results show that common reed provides suitable habitat for a diversity of landbirds during summer and autumn but only limited habitat for many marsh-nesting birds during summer. Based on these results, we recommend restoration of meadow marsh habitat through reduction of common reed in Great Lakes wetlands where providing habitat for breeding marsh-nesting birds is an objective. Managers also might consider reducing the size of nonnative common reed stands to increase edge effect and use by birds, possibly including wetland birds.     

Sustaining recovered grasslands is not likely without proper management: vegetation changes after cessation of mowing

Grasslands recovered by sowing low diversity seed mixtures of local provenance are usually managed by mowing. Besides restoration success only a few studies have focused on the direct effects of post-restoration mowing on recovered grassland vegetation. In this study we followed vegetation changes in 13 successfully recovered grasslands in 5 × 5-m-sized sites with continuous and ceased mowing at Hortobágy National Park, East-Hungary. We asked the following questions: (i) What are the effects of cessation of mowing on the vegetation structure and diversity of recovered grasslands? (ii) What are the effects of cessation of mowing on the abundance of sown grasses, target and undesirable species? (iii) Is yearly mowing an appropriate management tool for the maintenance of recovered grasslands? Our results showed that the cessation of mowing caused litter accumulation, while diversity, total vegetation cover and the cover of sown grasses decreased compared to the mown sites. The cover of undesirable perennial species was significantly higher in unmown sites than in mown ones. The species composition of mown sites remained more similar to near-natural grasslands than the unmown ones. Our results suggest that without regular post-restoration mowing the favourable status of recovered grasslands can rapidly decline due to litter accumulation and by the expansion of undesirable species, even in the short-run. We also stress that while yearly mowing is enough to maintain grasslands recovered by low-diversity seed sowing, it cannot be considered to be enough to recover target vegetation composition.     

How is Regeneration of Plants after Mowing Affected by Shoot Size in Two Species-Rich Meadows with Different Water Supply?

Mowing a meadow is an example of an equalizing process that reduces differences among species by removing aboveground biomass approximately 5 cm above ground. This regular disturbance that affects all plants prevents competitive exclusion of small species and thus allows coexistence of numerous species differing in shoot size. In this paper we search for the mechanism behind this by comparing the shoot biomass of 41 common species in dry and wet species-rich meadows in mown and recently abandoned plots in June (before mowing) and in October. We asked the following questions: i) Do the plants differ in proportion of biomass lost by mowing? ii) Are the mown plants able to compensate for biomass lost by mowing? iii) Is the compensatory ability of mown plants related to their size? iv) Is the compensatory ability of plants related to severity of disturbance (removed biomass)? v) Does water availability in meadows affect these features? Our results revealed that the earlier explanation of equalization of meadow plants after mowing due to the proportionally larger biomass loss in larger plants than small plants does not represent the entire mechanism. Even when larger plants in the wet meadow lost more biomass, the proportion of lost biomass was not dependent on plant size, and compensation ability (growth of mown in comparison with unmown plants) was not related to the lost biomass in this meadow type. On the contrary, the observed pattern could be explained by different compensation abilities of small versus tall plants. In addition, according to our expectations, the compensation for lost biomass in the wet meadow was higher than in the dry one.     

Wetland development in early stages of volcanic succession

Abstract. Wetland vegetation developed in the crater of Mount Usu, northern Japan, soon after the 1977–1978 eruptions which destroyed the vegetation. The cover of each species was measured in 1994 in 118 50 cm × 50 cm plots situated in transects and related to environmental factors (elevation, water depth, soil texture, soil compaction, soil organic matter, and soil pH) to clarify vegetation development. Five vegetation types were recognized dominated by Eleocharis kamtschatica, Equisetum arvense, Lythrum salicaria, Juncus fauriensis and Phragmites australis respectively. Sedge/grass marsh and reed swamp dominated deep-water sites; willow swamp and wet meadow vegetation characterized shallow-water sites, indicating that vegetation zonation developed soon after the eruption. Since those wetland plants were derived neither from seed banks nor from vegetative propagules, they had to immigrate from outside the summit areas. However, except for willows, most species lack the ability for long-distance dispersal. Late successional species, such as P. australis established in the early stages of the primary succession. The water depth varied by 27.5 cm among the plots. Coarse soil particles accumulated, and pH (5.22–6.55) was low on the elevated sites. Organic matter ranged from 2.8 % to 19.1 %, and was high on the elevated sites. Water depth was responsible for the establishment of large-scale vegetation patterns, while edaphic factors, i.e. soil compaction, pH, and organic matter, were determinants of small-scale vegetation patterns. Among the edaphic factors, soil compaction appeared to have a strong influence on vegetation development.     

Leaving uncut refuges during meadow harvesting increases the functional diversity of Orthoptera

In the past, insect species richness was high in Central European seminatural grasslands, which were characterized by low‐intensity land use. Currently, however, the hay in most of these grasslands is mechanically harvested, which negatively impacts insect biodiversity. One way to reduce this negative effect is to leave unmown patches as refuges. In the current research we evaluated the short‐term effects of leaving an unmown patch on the taxonomic and functional diversity of the Orthoptera assemblage in a meadow. We found that orthopteran species richness and abundance were significantly reduced by mowing, whether or not a patch was left uncut. In contrast, functional evenness, indicating distribution of species abundances in a niche space, was reduced by mowing only if the plot lacked an uncut refuge. Functional richness, indicating the amount of niche space occupied by species, was elevated if the plot had an uncut refuge. Larger species were negatively affected by mowing, while habitat specialists, mobile species and soil‐ovipositing species benefitted from it. We infer that the presence of an uncut patch increased the diversity of habitats available to orthopterans and maintained even distribution of species among niche space. In summary, leaving an unmown refuge in grasslands could increase the functional diversity of orthopterans, even if it does not preserve taxonomic diversity.     

Genetic survey on a reed-bed in Central Italy showing early die-back symptoms

Phragmites australis die-back is a well known phenomenon in Central Europe and rather recently observed also in some Mediterranean wetlands. In this study we analyze the genetic structure of a reed-bed in a protected wetland in N-W Tuscany (Italy) recently showing some clear symptoms of die-back, in particular the clumped growth-form, searching for any possible relationships with the ecological condition or the health status of common reed stands. After a diachronic analysis of vegetation maps (from 1988 to 2013) and a field survey, we have sampled four temporarily emerged and four permanent submerged reed stands, being the submersion regime a crucial trigger of reed die-back. Aquatic plots showed two clear conditions, with the presence of clumped and non-clumped stands. Emerged stands have been sampled in areas showing temporarily stable, increasing and decreasing reed-bed surface. In order to investigate the genetic structure of the population, the AFLP technique was applied on 69 individuals. The total reedbed surface showed a decrease in the observed time, partly due to the human activities and partly attributable to the RDBS. In several areas of the Lake the reed-bed appeared clumped and fragmented. The genetic analysis put in evidence a rather high level of genetic diversity, compared to the results of previous international studies on other populations of the same species. No significant differences between temporarily and permanently submerged stands were found. The major portion of genetic variation appeared within sampling sites rather than between sampling sites, indicating the absence of isolation between the different reed stands of the lake and a negligible role of genetic diversity in the occurrence of die-back symptoms.     

Initial establishment of vegetation in a man-made coastal area in Denmark

A man-made coastal area (8 km long, 300 m wide), constructed from seed-free, marine sand was investigated from 1978 to 1983 as regards relief, soil properties, and establishment of vegetation.
The following developments were apparent:

• 1. 

  The outer shore zone changed from a Cakile -dominated vegetation to a sparse and less diverse vegetation.
• 2. 

  The inner shore zone maintained spontaneous Ammophila as dominant and developed into a mobile dune with changing species.
• 3. 

  The outer dune slope with planted Ammophila developed into a mobile dune dominated by vigorous Ammophila.
• 4. 

  The dune zone with planted Ammophila: The outer part developed towards a somewhat fixed dune with increasing diversity. The inner part developed into a diverse and more fixed dune community with mainly Festuca rubra.
• 5. 

  The inner dune slope developed into a vegetation comprising few species.
• 1. 

  The grassland zone, initially sown with Festuca rubra and Lolium perenne , changed into a grass-herb-vegetation dominated by Festuca rubra , with a slowly increasing number of immigrating species, changing from annuals to perennials, in particular species of Fabaceae and Hippophaë.

     

Restoration of a Landfill Site in Berlin, Germany by Spontaneous and Directed Succession

We report on spontaneous and directed succession on a dry sandy landfill site of low fertility at Berlin‐Malchow, Germany. Changes in species composition and cover were followed on unmown and mown permanent plots of 2 × 2 m size through 5 years of vegetation development. Species richness on unmown plots was relatively constant during the time of observation, with 20 to 25 species per 4 m². Total cover of unmown plots continuously increased from approximately 10% in the first year to 80% in the fifth year. There are no clearly discernible sequential successional stages until present. The species composition includes species of all life forms, which colonized the site immediately after the initiation of the succession process representing the initial floristic composition type of vegetation development. However, perennial grasses and herbs gradually increased in cover up to approximately 40%. Woody plants were also present from the first year of succession and increased up to more than 20% cover in the fifth year, forming a shrub layer (>0.5 m) after the second year. Mowing significantly increased species richness, which was evident from the third year onward. This effect was mainly due to the reduction of the tall perennial grass Calamagrostis epigejos. Solidago canadensis and woody species were also significantly affected (lower cover and height), whereas short perennial herbs like Plantago lanceolata and Trifolium repens benefited from mowing.     

Rotational fallows as overwintering habitat for grassland arthropods: the case of spiders in fen meadows

Regular mowing of grassland is often necessary for plant conservation, but uncut vegetation is needed by many arthropods for overwintering. This may lead to conflicting management strategies for plant and arthropod conservation. Rotational fallows are a possible solution. They provide a spatio-temporal mosaic of mown and unmown areas that may combine benefits to both plants and arthropods. We tested if rotational fallows enhance spider overwintering in fen meadows. Rotational fallows consisted of three adjoining strips 10 m wide and 35–50 m long. Each year, one of these strips was left unmown (fallow) in an alternating manner so that each strip was mown two out of three years. Spiders were sampled during spring with emergence traps in nine pairs of currently unmown fallow strips and completely mown reference plots. Fallows significantly enhanced orb-weavers (Araneidae), sac spiders (Clubionidae) and ground spiders (Gnaphosidae). However, only 4.7% of the total variation in community composition was attributable to fallows. Community variation was larger between landscapes (34.5%) and sites (38.2%). Also β diversity was much higher between landscapes (45 species) and sites (22 species) than between fallows and mown reference plots (10 species). We conclude that the first priority for spider conservation is to preserve as many fen meadows in different landscapes as possible. Locally, rotational fallows enhance overwintering of the above-mentioned spider families, which are sensitive to mowing in other grassland types as well. Thus, rotational fallows would probably foster spider conservation in a wide range of situations. However, stronger effects can be expected from larger and/or older fallow areas.     

Management impacts on vegetation dynamics of hyper‐eutrophicated fields at Berlin,Germany

Abstract. This paper reports on vegetation dynamics on terrestrial, temperate grassland sites at the upper range of the productivity scale, i.e. on abandoned sewage fields (fields once used for waste water disposal) at Berlin‐Blankenfelde, Germany. I studied regeneration and the influence of different management practices (removal of top soil and mowing in late summer). Changes in species composition and cover were followed on permanent plots of 2m × 2m size through five years of vegetation development. At the outset of the experiment the abandoned fields were dominated by dense Urtica dioica /Elymus repens stands. Species richness was 7 species/ 4m², and it remained low on unmanaged plots during the time of observation (7.6 species/plot in year 5). Removal of 20 cm of top soil caused a severe decline of Urtica and a large increase in species richness (21 species in year 1 after disturbance). Mowing was slightly higher compared with unmown plots on both initially excavated and unexcavated plots. Total cover was always near 100 % (except immediately after top soil removal). Colonization of bare soil was very rapid and in late summer of the first year after disturbance cover already increased towards 100%. On all plots the vegetation was mostly dominated by perennial herbs and grasses. Winter season gaps are occupied by Galium aparine, a large‐seeded annual scrambling climber. Monocarpic perennials behaved as winter annuals in most cases. Woody species were inhibited by dense above‐ground biomass and litter cover. The paper questions whether succession on abandoned sewage fields may proceed towards a woodland stage and advises how vegetation of such hyper‐eutrophicated sites can be managed towards higher diversity.