Classification and ordination of the mire vegetation of Stormyra near Tynset, S Norway

The vegetation of Stormyra, a flat fen at Tynset, in Hedmark province, Southern Norway is classified by cluster analyses into seven different plant communities, all of a nonfixed hierarchical, low rank as follows:
(1) Scorpidium scorpioides comm., (2) Campylium stellatum - Drepanocladus revolvers comm., (3) Carex rostrata - Calliergon giganteum comm., (4) Sphagnum papillosum - S. subfulvum comm., (5) Homalothecium nitens - Sphagnum warnstorfii comm., (6) Pinus sylvestris - Sphagnum angustifolium comm. and (7) Empetrum hermaphroditum - Sphagnum fuscum comm.
A DCA-ordination showed that the samples were distributed mainly along a hummock - mud-bottom vegetational gradient, reflecting the local groundwater level. The range of the plant communities in terms of the traditional poor - rich and mire expanse - mire margin vegetational gradients is also dealt with. The vegetation and its relationship to such environmental factors as the ground-water level, and its seasonal fluctuations, the supply or absence of running surface water, the pH and electrical conductivity, are also discussed.     

Vegetation changes of a Danish mire 1957–1981

A Danish mire influenced by culture until ca. 100 years ago and since then with incipient growth of Betula pubescens , was analyzed in 1957 and 1981 with regard to height of the Betula trees and cover percentage of plant species in the field layer. In 1957, every m2 along a 110 m transect was examined; in 1981 only 56 m2 representatively selected from the transect were examined. Betula showed considerable changes with a net intake of 10 trees (23%) and a net loss of 23 trees (52%), i.e. a net loss of 13 trees (30%). The mean height of the trees has, however, increased by 80 cm and the sum of the height of the trees per m2 by 29 cm. An increased total cover was found for Em–petrum nigrum, Molinia coerulea , and Erica tetralix , and a decreased total cover for Calluna, Sphagnum magellanicum, S. nemoreum, S. rubellum, Hypnum cupressi–forme, Pleurozium schreberi , and Aulacomnium palustre. An almost unchanged total cover was found for Eriophorum vaginatum, E. angustifolium, Sphagnum recurvum, Andromeda polifolia, Drosera rotundifolia , and Oxycoccus palustris. On the basis of quantitative changes in the individual plots, a specific index of change is calculated, decreasing in the order Empetrum > Sphagnum magellanicum > S. recurvum = Molinia > Calluna > Hypnum cupressiforme > Pleurozium schreberi> Oxycoccus palustre> Sphagnum nemoreum = S. rubellum = Eriophorum vaginatum = E. angustifolium > Aulacomnium palustre > Erica> Drosera > Andromeda. Analyses from 1981 demonstrate that usually the light conditions and/or the water content and rarely the bulk density of the soil is correlated with the change in cover of the individual species. For some species it is also shown that the change is correlated with the strongly increased cover of Empetrum in particular. The changes are finally illustrated by showing the position of the species along ecological gradients in 1981.     

Nutrient concentration in shape Sphagna at increased N-deposition rates and raised atmospheric CO2 concentrations

Sphagnum fuscum, S. magellanicum, S. angustifolium and S. warnstorfii were treated with N deposition rates (0, 10, 30 and 100 kg ha^-1 a^-1) and with four atmospheric CO₂ concentrations (350, 700, 1000 and 2000 ppm) in greenhouse for 71–120 days. Thereafter, concentrations of total N, P, K, Ca and Mg in the capitulae of the Sphagna were determined. The response of each species to N deposition was related to ecological differences. With increasing N deposition treatments, moss N concentrations increased and higher N:P-ratios were found, the increase being especially clear at the highest N load. Sphagnum fuscum, which occupies ombrotrophic habitats, was the most affected by the increased nitrogen load and as a consequence the other elements were decreased. Oligotrophic S. magellanicum, wide nutrient status tolerant S. angustifolium and meso-eutrophic S. warnstorfii tolerated better increased N deposition, though there were increased concentrations of Ca and Mg in S. warnstorfii and Mg in S. magellanicum. Nitrogen and P concentrations decreased with raised CO₂ concentrations, except for S. magellanicum. This seems to be the first time this kind of response in nutrient concentrations to enhanced CO₂ concentration has been shown to exist in bryophytes. The concentration of K clearly decreased in S. fuscum as did the concentration of Mg in the other Sphagna with increasing CO₂. Sphagnum angustifolium and S. magellanicum, which are the less specialized species, were the least affected by the CO₂ treatments.     

Competition between Sphagnum magellanicum and Eriophorum angustifolium as affected by raised CO2 and increased N deposition

The competition between peat mosses ( Sphagnum ) and vascular plants as affected by raised CO₂ and increased N deposition was studied in a glasshouse experiment by exposing peat monoliths with monocultures and mixtures of Sphagnum magellanicum and Eriophorum angustifolium to ambient (350 ppmv) or raised (560 ppmv) atmospheric CO₂ concentrations, combined with low (no N addition) or high (5 g m⁻² yr⁻¹ added) N deposition. Growth of the two species was monitored for three growing seasons.
The presence of Eriophorum did not affect Sphagnum biomass, because Eriophorum density did not become high enough to severely shade the moss surface. In contrast, Sphagnum had a negative effect on Eriophorum biomass, particularly on the number of flowering stems. Possibly, the presence of a living Sphagnum layer decreased nutrient availability to Eriophorum by immobilising nutrients mineralised from the peat.
Raised CO₂ and/or increased N deposition did not change these competitive relationships between Sphagnum and Eriophorum , but had independent effects. Raised CO₂ had a positive effect both on Sphagnum and Eriophorum biomass, though on Eriophorum the effect was transient, probably because of P limitation. Nitrogen addition had a direct negative effect on Sphagnum height growth in the first growing season, but by the third year an increased shoot density had cancelled this out, so no N effect on Sphagnum biomass was present at the end of the experiment. The response of Eriophorum to N addition was small; N availability appeared not to limit its growth.     

Long‐term effects of drainage and initial effects of hydrological restoration on rich fen vegetation

Questions: What vegetational changes does a boreal rich fen (alkaline fen) undergo during a time period of 24 years after drainage? How is plant species richness affected, and what are the changes in composition of ecological groups of species? Is it possible to recover parts of the original flora by rewetting the rich fen? Which are the initial vegetation changes in the flora after rewetting? What are the major challenges for restoration of rich fen flora after rewetting? Location: Eastern central Sweden, southern boreal vegetational zone. Previously rich fen site, drained for forestry purposes during 1978–1979. The site was hydrologically restored (rewetted) in 2002. Method: Annual vegetation survey in permanent plots during a period of 28 years. Results: There were three successional stages in the vegetational changes. In the first stage there was a rapid (< 5 years) loss of rich fen bryophytes. The second step was an increase of sedges and early successional bryophytes, which was followed by an increase of a few emerging dominants, such as Molinia caerulea, Betula pubescens and Sphagnum spp. After rewetting, there are indications of vegetation recovery, albeit at slow rates. Depending on, for instance, initial species composition different routes of vegetation change were observed in the flora after drainage, although after 24 years, species composition became more homogenous and dominated by a few species with high cover. Conclusion: Major changes have occurred after changes in the hydrology (drainage and rewetting) with a severe impact on the biodiversity among vascular plants and bryophytes. Several rich fen bryophytes respond quickly to the changes in water level (in contrast to vascular plants). The recovery after rewetting towards the original rich fen vegetation is slow, as delayed by substrate degradation, dispersal limitation and presence of dominant species.     

The relationships of vegetation to surface water chemistry and peat chemistry in fens of Alberta,Canada

The relationships between vegetation components, surface water chemistry and peat chemistry from 23 fens in boreal Alberta, Canada, substantiate important differences along the poor to rich fen gradient. Each of the three fen types have their own characteristic species. The extreme-rich fens are characterized by Calliergon trifarium, Drepanocladus revolvens, Scirpus hudsonianus, S. cespitosus, Scorpidium scorpioides, and Tofieldia glutinosa. Moderate-rich fens are characterized by Brachythecium mildeanum, Carex diandra, Drepanocladus vernicosus, D. aduncus, and D. polycarpus. Poor fens are characterized by Carex pauciflora, Drepanocladus exannulatus, Sphagnum angustifolium, S. jensenii, and S. majus. Moderate-rich fens have fewer species in common with poor fens than with extreme-rich fens, while species richness is highest in the moderate-rich fens and lowest in poor fens. Variation in vascular plant occurrence appears to be more associated with nutrient levels, while bryophytes are more affected by changes in acidity and mineral elements. Based on chemical criteria, the three fen types are clearly separated by surface water pH, calcium, magnesium, and conductivity, but are less clearly differentiated by the nitrogen and phosphorus components of the surface waters. Moderate-rich fens are chemically variable both temporally and spatially, whereas poor fens and extreme-rich fens are more stable ecosystems. Whereas components of alkalinity-acidity are the most important factors that distinguish the three fen types in western Canada, nutrient concentrations in the surface waters generally do not differ appreciably in the three fen types.     

Moss Regeneration for Fen Restoration: Field and Greenhouse Experiments

Fen bryophytes are an important component of natural fens and should be included in fen restoration projects. The goal of this study was to examine the regeneration capabilities of nine bryophytes common to moderate-rich and poor fens in North America. A greenhouse experiment was carried out to examine the limitations and optima for the regeneration of fen bryophytes under different light and water regimes. A field experiment tested these same bryophytes in the presence of three potential nurse-plants. In the greenhouse experiment, the presence of shade increased regeneration success for eight out of nine species. A high water level was ideal for the regeneration of the majority of species tested. In the field experiment, Sphagnum species had the highest regeneration, and all species had higher regeneration under a dense canopy of herbaceous plants. Fen bryophytes show good potential for use in restoration projects because the tested bryophytes regenerated well from fragments.     

Impact of climate change on alpine vegetation of mountain summits in Norway

Climate change is affecting the composition and functioning of ecosystems across the globe. Mountain ecosystems are particularly sensitive to climate warming since their biota is generally limited by low temperatures. Cryptogams such as lichens and bryophytes are important for the biodiversity and functioning of these ecosystems, but have not often been incorporated in vegetation resurvey studies. Hence, we lack a good understanding of how vascular plants, lichens and bryophytes respond interactively to climate warming in alpine communities. Here we quantified long-term changes in species richness, cover, composition and thermophilization (i.e. the increasing dominance of warm-adapted species) of vascular plants, lichens and bryophytes on four summits at Dovrefjell, Norway. These summits are situated along an elevational gradient from the low alpine to high alpine zone and were surveyed for all species in 2001, 2008 and 2015. During the 15-year period, a decline in lichen richness and increase in bryophyte richness was detected, whereas no change in vascular plant richness was found. Dwarf-shrub abundance progressively increased at the expense of lichens, and thermophilization was most pronounced for vascular plants, but occurred only on the lowest summits and northern aspects. Lichens showed less thermophilization and, for the bryophytes, no significant thermophilization was found. Although recent climate change may have primarily caused the observed changes in vegetation, combined effects with non-climatic factors (e.g. grazing and trampling) are likely important as well. At a larger scale, alpine vegetation shifts could have a profound impact on biosphere functioning with feedbacks to the global climate.     

Vegetation dynamics following trampling in grassland and heathland in Sølendet Nature Reserve, a boreal upland area in Central Norway

Trampling is recognised as a cause of disturbance in grassland and heathland vegetation along two public nature trails in Sølendet nature reserve in central Norway. The effects of trampling by visitors and of controlled trampling were monitored over a period of 5–7 years in permanent plots. A retrogressive development was recorded as vegetation cover and height were reduced and a substantial loss of species richness and biomass took place. Some species, mainly graminoids such as Agrostis capillaris and Carex vaginata , initially appeared to be more tolerant, but were eventually reduced as well. Low, geophytic and prostrate habits of growth and hardy leaf tissues seemed to be beneficial for tolerance to trampling. Moist grassland and lichen-dominated heathland were more vulnerable to trampling than dry grassland. Even though 350–1500 visitors walked through the permanent plots along the trails each summer, effects on the soil surface remained moderate and only a minor furrow was visible on the ground.     

Ozone effects on the ultrastructure of peatland plants: Sphagnum mosses, Vaccinium oxycoccus, Andromeda polifolia and Eriophorum vaginatum

BACKGROUND AND AIMS: Ozone effects on peatland vegetation are poorly understood. Since stress responses are often first visible in cell ultrastructure, electron microscopy was used to assess the sensitivity of common peatland plants to elevated ozone concentrations. METHODS: Three moss species (Sphagnum angustifolium, S. magellanicum and S. papillosum), a graminoid (Eriophorum vaginatum) and two dwarf shrubs (Vaccinium oxycoccus and Andromeda polifolia), all growing within an intact canopy on peat monoliths, were exposed to a concentration of 0, 50, 100 or 150 ppb ozone in two separate growth chamber experiments simulating either summer or autumn conditions in central Finland. After a 4- or 5-week-long exposure, samples were photographed in a transmission electron microscope and analysed quantitatively using image processing software. KEY RESULTS: In the chlorophyllose cells of the Sphagnum moss leaves from the capitulum, ozone exposure led to a decrease in chloroplast area and in granum stack thickness and various changes in plastoglobuli and cell wall thickness, depending on the species and the experiment. In E. vaginatum, ozone exposure significantly reduced chloroplast cross-sectional areas and the amount of starch, whereas there were no clear changes in the plastoglobuli. In the dwarf shrubs, ozone induced thickening of the cell wall and an increase in the size of plastoglobuli under summer conditions. In contrast, under autumn conditions the cell wall thickness remained unchanged but ozone exposure led to a transient increase in the chloroplast and starch areas, and in the number and size of plastoglobuli. CONCLUSIONS: Ozone responses in the Sphagnum mosses were comparable to typical ozone stress symptoms of higher plants, and indicated sensitivity especially in S. angustifolium. The responses in the dwarf shrubs suggest stimulation of photosynthesis by low ozone concentrations and ozone sensitivity only under cool autumn conditions.     

Long‐term vegetation changes in bogs exposed to high atmospheric deposition,aerial liming and climate fluctuation

Questions: Is vegetation composition of ombrotrophic bogs with an undisturbed water regime resistant or sensitive to ongoing high atmospheric deposition and climatic changes? Location: The Sudeten Mountains (Czech Republic). Methods: Species composition of bryophytes and vascular plants was sampled in 25 permanent plots in suboceanic bogs of the Jizerské hory Mountains and in 26 permanent plots in subcontinental bogs of the Hrubý Jeseník Mountains. The permanent plots were established and first sampled in 1991. These plots were re‐sampled after 14 and 17 years, respectively. We also used historical vegetation plots (1947–1949; 1980) from the same localities in order to reveal possible changes that might start earlier. Water chemistry was analysed annually, usually three times a year. Compositional changes were analysed by PERMANOVA, β‐diversity changes by PERMDISP and other changes by t‐test and Fisher's exact test. Results: At the community level, no statistically significant changes were detected in permanent plots (PERMANOVA, PERMDISP), either in hollows or in hummocks, but the vegetation composition changed between the oldest (historical) and the newest data sets. At the level of functional groups, cover of Cyperaceae significantly decreased and cover of other herbs (excluding graminoids) and Sphagna increased in the Hrubý Jeseník Mountains, whereas no changes were detected in the Jizerské hory Mountains. Cover of ericoid dwarf shrubs has not changed in either area. At the level of particular species, the frequency of Sphagnum magellanicum, Carex limosa, Scheuchzeria palustris and Vaccinium myrtillus decreased, while the frequency of Straminergon stramineum, Sphagnum recurvum agg., Eriophorum angustifolium and Luzula sylvatica increased. These changes were more evident when recent and historical data were compared. Conclusions: When water regime is not affected, the bog vegetation seems to be rather resistant to high atmospheric deposition and climate fluctuation. A significant change of the species composition occurs only in the long‐term perspective. Particular species could, however, decrease or increase their frequencies more rapidly. For some of these species a positive or negative response to nitrogen availability was also found in other studies, whereas for other species further research is needed in order to separate the effects of atmospheric deposition and internal ecosystem dynamics.     

Impact of rewetting on the vegetation of a cut‐away peatland

Abstract. We tested whether rewetting improved environmental conditions during peatland restoration and promoted colonization and development of mire vegetation. Vegetation change was monitored in a cut‐away peatland one year before, and four years after, rewetting. Colonizers before rewetting were perennials, mostly typical of hummocks or bare peat surfaces. The main variation in vegetation was related to variation in the amounts of major nutrients and water table level. The wettest site with the highest nutrient level had the highest total vegetation cover and diversity, as well as some species typical of wet minerotrophic mires. Raising the water table level above, or close to, the soil surface promoted development of wet minerotrophic vegetation. Diversity initially decreased because of the disappearance of hummock vegetation but started to recover in the third year. Eriophorum vaginatum and Carex rostrata were both favoured, and bryophytes typical of wet habitats colonized the site. Moderate rewetting promoted the development of Eriophorum vaginatum seedlings and an increase in the cover of tussocks. Bryophytes typical of disturbed peat surfaces spread. In the control site development continued slowly towards closed hummock vegetation. The study showed that raising the water level to, or above, soil surface promotes conditions wet enough for a rapid succession towards closed mire vegetation.     

Experimental trampling and vegetation recovery in some forest and heathland communities

Abstract. Over the past decades outdoor recreation has become progressively more important and as a result human‐induced potential damage has increased. In this study, short‐term effects – a 2‐yr period – of human trampling on some common forest and heath communities in Central Belgium were studied experimentally. Vulnerability to disturbance was compared among plant communities in terms of resistance, resilience and tolerance, which are based on cover measurements. The herb layer of the examined mesophilous forest communities appeared to be more sensitive than the heath and dry forest community, which were dominated by more resistant graminoid (Molinia caerulea, Deschampsiaflexuosa) and dwarf‐shrub species (Vaccinium myrtillus, Calluna vulgaris, Erica tetralix). The analysis showed that site structure and vegetation were already affected by low intensities of trampling, while vegetation recovery during the first year after trampling was limited in most plant communities. Recovery during the second year in vegetation cover as well as height was most pronounced in mesophilous forest communities. Occasional trampling clearly can lead to increased visual evidence of previous use and continued recreational disturbance. Therefore management plans should discourage hiking activity off paths and restrict recreation activities to the least vulnerable communities.     

Root decomposition and soil nutrient and carbon cycling in two temperate fen ecosystems

Although root litter contributes to a large extent to soil organic matter accumulation in peatlands, decomposition of root litter is often neglected in studies on litter decomposition and carbon and nutrient cycling in these ecosystems. In this study, decomposition of root and rhizome litter of Carex diandra and Carex lasiocarpa was determined in two temperate fens, one dominated by Sphagnum species ( Sphagnum fen; soil pH=4.4) and one without a Sphagnum cover ( Carex fen; soil pH=5.7). One-year mass loss increased in the order: roots Carex diandra 相似文献   

Field studies of nitrogen fixation of Australian alpine plants and soils

Alpine grassland areas in Victoria and New South Wales have been subjected to summer grazing by cattle and sheep for well over a hundred years. Legumes other than a few species of shrubs, which provide a very small percentage of the vegetation cover in the grasslands, are absent. Other alpine communities include Sphagnum ‘mossbeds’ in the valleys and areas of snowgum woodland and shrubland. Virtually nothing is known of the mineral status of these communities and nothing of their nitrogen economy. On the Bogong High Plains, enclosure of grassland and of Sphagnum mossbeds from grazing and trampling has resulted, in the last few decades, in considerable changes in both cover and composition of the vegetation. A portable gas chromatogram was used to carry out determinations of the capacity of samples of the grassland and Sphagnum to support acetylene reduction to ethylene, by convention equated to a capacity to fix nitrogen. There appears to be a substantial capacity for acetylene reduction associated with the rhizosphere of the grasses (Poa australis agg.). The capacity of the Sphagnum for acetylene reduction is even greater and appears to be due to facultative anaerobes, abundant only in the upper, living part of the Sphagnum. These organisms may depend in part on leakage of photosynthate from the living Sphagnum. Associations of Sphagnum with blue-green algae appear to be unusual in contrast with work on Swedish subarctic mosses, which is discussed. The only non-leguminous Australian alpine plant so far examined for nitrogen fixation is Podocarpus lawrencei. A capacity for acetylene reduction was found for neither the nodules of the roots of this plant nor the associated soils.     

Revegetation following experimental disturbance in a boreal old-growth Picea abies forest

Abstract. We studied revegetation patterns after experimental fine-scale disturbance (e.g. uprooting) in an old-growth Picea abies forest in southeastern Norway. An experimental severity gradient was established by manipulation of the depth of soil disturbance; two types of disturbed areas were used. Species recovery was recorded in the disturbed patches in three successive years after disturbance. The cover of vascular plants and, even more so the cover of bryophytes and lichens, recovered slowly after disturbance. The least severe treatments (removal of vegetation and removal of vegetation and the litter layer) was followed by the fastest recovery. The mean number of vascular plant species was usually higher three years after disturbance than before disturbance, while the opposite was true for bryophytes. Several vascular plant species that were abundant in intact forest floor vegetation (Vaccinium myrtillus, V. vitis-idaea and Deschampsia flexuosa) recovered during a three-year period primarily by resprouting from intact rhizomes and clonal in-growth. Other important recovery mechanisms included germination from a soil-buried propagule bank (e.g. Luzula pilosa, Plagiothecium laetum agg., Pohlia nutans and Polytrichum spp.) and dispersal of propagules into the disturbed patches (e.g. Betula pubescens and Picea abies). Microsite limitation seemed to occur in several species that were abundant in the soil propagule bank (e.g. the ferns Athyrium filix-femina, Gymnocarpium dryopteris and Phegopteris connectilis) but which did not appear in disturbed patches. Disturbance severity influenced revegetation patterns, recorded both as trajectories of vegetation composition in a DCA ordination space and as change in floristic dissimilarity. The length of the successional path (compositional change measured in β-diversity units) increased with increasing disturbance severity, and was also influenced by the area of the disturbed patch and the distance to intact vegetation. The rate of succession depended on the method by which it was measured; decreasing year by year in floristic space, while first decreasing and then increasing in ordination space. The reason for this difference is explained.     

Vegetation-Environment Relationships in Peatlands Dominated by Sphagnum fallax in Western Poland

We investigated species composition and relative abundance of Sphagnum fallax dominated peatlands in relation to measured environmental variables on the basis of 26 sites in the Wielkopolska region. Most studied plots were characterized by soft waters, poor in Ca²⁺ but rich in nutrients, especially N-NH₄ ⁺ and P-PO₄ ^3-, with high electrolytic conductivity and high DOC (dissolved organic carbon) concentration. Six of the 19 measured variables of surface water chemistry (DOC, pH, SO₄ ^2-, P-PO₄ ^3-, Na⁺ and Ca²⁺) significantly explained 23% of the variation in floristic composition. In 65 vegetation plots, 107 species were observed. Cluster analysis revealed four types of vegetation in the studied mires. Sphagnum fallax was the most abundant species and formed plant communities in a wide range of habitats: in floating mats, with the plants usually adjoining the mineral basin edge (e.g. E. vaginatum, Andromeda polifolia and Ledum palustre) as well as it occupied central parts of Sphagnum lawn (e.g. Eriophorum angustifolium) and rich fen habitats (e.g. Carex rostrata or Phragmites australis). In Wielkopolska terrestrializating peatlands, four variables determine the poor-rich gradient: conductivity, DOC, SiO₂ dissolved, Ca²⁺ and alkalinity. This study provides new data on the ecology and typology of Sphagnum peatlands in western Poland.     

Vegetation change in Southeast Greenland? Tasiilaq revisited after 40 years

Questions: Are there changes in species composition of the oceanic, Low‐Arctic tundra vegetation after 40 years? Can possible changes be attributed to climate change? Location: Ammassalik Island near Tasiilaq, Southeast Greenland. Methods: Species composition and cover of 11 key vegetation types were recorded in 110 vegetation survey plots in 1968–1969 and in 11 permanent plots in 1981. Recording was repeated in 2007. Temporal changes in species composition and cover between the surveys were tested using permutation tests linked with constrained ordinations for vegetation types, and Mann–Whitney tests for individual species. Changes in vegetation were related to climate change. Results: Although climate became warmer over the studied period, most of the vegetation types showed minor changes. The changes were most conspicuous in mire and snowbed vegetation, such as the Carex rariflora mire and Hylocomium splendens snowbed. In the C. rariflora mire, species number and cover of vascular plants and cover of bryophytes increased, whereas in the H. splendens snowbed species numbers of vascular plants, bryophytes, and also lichens increased. Lichen richness increased in the Carex bigelowii snowbed and cover of bryophytes in the Salix herbacea snowbed. No such changes occurred in the Alchemilla glomerulans meadow, Alchemilla alpina snowbed and Phyllodoce coerulea heath. There was no change of species composition within the Salix glauca scrub, A. alpina snowbed, lichen grassland and the Empetrum nigrum and Phyllodoce coerulea heaths. Most changes resulted from increasing frequency or cover of some species; there were very few decreasing species. Most of the increasing species indicate drier substrate conditions. Conclusions: Only minor changes in species composition and cover were detected in the vegetation types studied. These changes were probably caused by milder winters and warmer summers during the years before the 2007 sampling. Climate warming may have reduced the duration of snow cover and soil moisture, particularly in snowbed and mire habitats, where species composition change was most pronounced. However, its magnitude was insufficient to cause a major change in species composition. Thus, on the level of plant community types, tundra vegetation near Tasiilaq was rather stable over the last 40 years.     

Bryophytes of Zhelania Cape,Severny Island,Novaya Zemlya Archipelago in the Russian Arctic

We present the results of a revsion of an extensive set of collections of bryophytes from the Novaya Zemlya Archipelago northern extremity, the northern‐most sector of polar deserts, which until now has been poorly explored in terms of the bryophyte flora. The checklist produced includes 24 liverwort and 135 moss species. Thirteen species, viz. Lophoziopsis propagulifera, Scapania degenii, Brachytheciastrum collinum, Bryoerythrophyllum cf. rubrum, Bucklandiella microcarpa, Campylium laxifolium, C. longicuspis, Dicranum schljakovii, Drepanium recurvatum, Flexitrichum gracile, Grimmia longirostris, Hamatocaulis vernicosus and Pseudocalliergon angustifolium are reported for the first time from the polar desert region. Though in number of species known the area loses only to the more intensively studied NE Land of Svalbard, a comparative analysis suggests that our study area is still incompletely known and suffers from ‘phytosociological sampling’ which underestimates the number of small pioneer mosses. A comparative analysis based on published data on other areas of the polar desert region is presented but the results does not confirm previously proposed floristic subdivisions of the polar desert region and may be strongly influenced by incomplete and biased sampling. Some species have a higher share in the vegetation cover of the polar desert region than elsewhere, thus contributing to its segregation and among these are mostly calciphilous/basiphilous species.