Arctic-alpine Research Articles

Arctic Alpine Ecosystems and People in a Changing Environment

Because of my own interest in this topic, Arctic Alpine Ecosystems and People in a Changing Environment immediately caught my attention. However, upon opening the book and reviewing the contents, I felt somewhat misguided by the title (as most potential buyers would be), given the actual topics addressed.

Integrated long-term responses of an arctic–alpine willow and associated ectomycorrhizal fungi to an altered environment

We evaluated ectomycorrhizal (ECM) colonization and morphotype community composition together with growth response and biomass distribution in the arctic–alpine, prostrate willow Salix herbacea L. × Salix polaris Wahlenb. after 11 seasons of shading, warming, and fertilization at a fellfield in subarctic Sweden. The aim was to assess responses of the integrated plant–fungal system to long-term field experiments simulating expected environmental changes. Warming more than doubled aboveground S. herbacea × S. polaris biomass and shoot growth, whereas shading and nutrient addition had less influence on these variables. In shaded plants, adjustments at leaf level probably buffered major changes in plant biomass allocation. Fertilization increased the root mass fraction and changed root system morphology by decreasing the number of root tips per unit root mass. While no long-term changes in total ECM colonization (%ECM root tips) in response to the treatments were identified, ECM colonization in June just after snowmelt was positively correlated with root density. Changes in densities of potential host plants may therefore be of great importance for ECM colonization intensity in this ecosystem type. The ECM morphotype community changed through the season, and frequencies of some ECM morphotypes ( Cortinarius saturninus and Clavulina spp.) changed more with season than with the treatments. Warming only slightly affected ECM morphotype frequencies, which implies a balanced increase in root tip numbers of most ECM morphotypes in warmed plants. Fertilization changed ECM morphotype community composition mainly because of a decrease in Cenococcum geophilum frequency and an increase in Tomentella stuposa frequency. We hypothesize that a shift from drought stress-tolerant fungi towards a dominance of minerogenic fungi may take place if nutrient availability increases substantially because of anthropogenic disturbances.

Incipient weathering rind development on introduced machine‐polished granite discs in an Arctic alpine environment, northern Scandinavia

AbstractWeathering rinds, zones of alteration on the exterior surfaces of rock outcrops and coarse unconsolidated surficial debris are widely used by geomorphologists and Quaternary geologists as indicators of the relative age of landforms and landscapes. Additionally they provide unique insights into the earliest stages of rock and mineral weathering, yet the origin of these alteration zones is relatively poorly understood. This lack of understanding applies especially to the initial stages of rind formation. The study reported in this paper has two principal objectives. The first is to use lightly polished granite discs inserted in soil profiles under several different plant communities in an Arctic alpine environment for a period of four or five years to investigate the nature of incipient weathering rind development. The second is to investigate the factors responsible for spatial variability in the nature and rates of rind formation.Incipient weathering rind development on the outer edges of the granite discs is observable and measurable over a period of time as short as four years in the mild Arctic alpine environment of Swedish Lapland. The earliest stages of rind development involve the development of a porous structure consisting of a combination of pits and fractures which have been solutionally enlarged and modified. Solution appears to be preferentially concentrated on the surfaces of feldspars and, to a lesser extent, quartz. In addition, iron oxides are present along grain boundaries and in grain interiors and are interpreted to have been derived from the oxidation of ferromagnesian minerals. Spatial variability in weathering rind development appears to be particularly driven by differences in moisture but is not related to soil pH. Copyright © 2005 John Wiley & Sons, Ltd.

Genetic and morphological variation of Saxifraga caespitose L. from Spitsbergen (Svalbard): a preliminary study

Saxifraga caespitose is a taxonomically difficult and poorly studied circumpolar arctic–alpine species. Two different phenotypes with distinct growth habits were collected at two shared localities in Spitsbergen. The natural genetic variation of both phenotypes was tested by AFLPs in order to investigate whether the differences at the phenothypical level are reflected at the genetic level. Low level of molecular variability between “tall” and “short” plants may suggest that the morphological variation could be due to phenotypic plasticity rather than genetic background.

Distribution of Mycorrhizal Types among Alpine Vascular Plant Families on the Beartooth Plateau, Rocky Mountains, U.S.A., in Reference to Large-Scale Patterns in Arctic–Alpine Habitats

Mycorrhizal symbiosis is critical to plant establishment and survival, influences plant community structure and function, and could be particularly important in harsh environments such as the alpine tundra. An examination of 53 vascular plant species in 21 families from alpine areas of the Beartooth Plateau (Rocky Mountains) revealed most were mycorrhizal (68%) and four distinct types of symbioses were present. They differ in fungal groups involved, plant taxa, physiology, ecology, morphology, and resource acquisition. Betula, Dryas, Salix, and Polygonum viviparum consistently form ectomycorrhizae (ECT) with basidiomycete fungi. Phyllodoce, Kalmia, and Vaccinium (Ericaceae) form ericoid mycorrhizae with ascomycete fungi, and Arctostaphylos an arbutoid type with basidiomycetes. Eight families (18 species) had only arbuscular mycorrhizae (AM) of glomalean fungi: Apiaceae, Asteraceae, Campanulaceae, Fabaceae, Hydrophyllaceae, Onagraceae, Poaceae, Ranunculaceae. Nonmycorrhizal (NM) families were Brassicaceae, Caryophyllaceae, Crassulaceae, Cyperaceae, Gentianaceae, and Juncaceae. Split families included Polygonaceae (NM/AM/ECT), Portulacaceae (NM/AM), Rosaceae (AM/ECT), and Scrophulariaceae (NM/AM). This is the first report of mycorrhizae for 25 alpine plant species, and most others are new reports for the Rocky Mountains. The distribution of mycorrhizal types among plant families is reasonably consistent across the arctic-alpine biome (reviewed here) with exceptions. The patchy distribution of mycorrhizal types associated with large-scale perennial vegetation mosaics suggests microbial functioning is not uniform across tundra landscapes.

Seasonal trends in usnic acid concentrations of Arctic, alpine and Patagonian populations of the lichen Flavocetraria nivalis

The widespread secondary metabolite usnic acid, a dibenzofuran derivative, is the principal acetone-soluble compound in the lichen Flavocetraria nivalis. Seasonal variation in concentrations were studied in four populations of this lichen, three from Arctic–alpine habitats in the Northern Hemisphere, and one from Patagonian heathland in the Southern Hemisphere. Usnic acid is produced in large amounts, making up between 4% and 8% of thallus dry weight. Large seasonal variation is seen, with a trend towards peak levels in late spring and early summer, and generally low levels during autumn and winter. However, at an Arctic steppe in Central West Greenland, remarkably high levels were also detected during late autumn and early winter. Comparisons with environmental data using model selection procedures show that usnic acid levels of three of the populations are positively correlated with time of season, as measured by the proximity in time to nearest summer solstice, solar radiation levels, and temperature conditions. All these three variables are intercorrelated, thus indicating the same overall trend. For the three driest sites, precipitation rates are included in the models that best explain the variation in usnic acid. However, the explanatory powers of the models are generally low, partly due to high variation between thalli growing together and sampled at the same time. This is the first attempt to compare statistically seasonal variation in usnic acid concentrations and environmental variables, and thus also the first time it is shown that the concentration in various populations of the same lichen species shows different types of correlation with seasonal climatic changes.

Physical and Chemical Characteristics of Soils Forming on Boulder Tops, Kärkevagge, Sweden

Recent pedologic studies in Karkevagge, Swedish Lapland, have characterized soil distribution and confirmed the importance of chemical weathering in this arctic–alpine environment. However, these studies have overlooked soils that are forming on the uppermost surface of the boulders that give Karkevagge its name, “Valley of the Boulders.” The physical and chemical characteristics of the soils forming on boulder tops are therefore examined herein. Soil samples were collected from 20 large boulder tops and analyzed according to standard procedures. The boulder-top soils were weakly developed, Mg > K > Na in the soils, albeit the values are substantially lower overall in the boulder-top soils than for the rest of the soils in Karkevagge. Although the boulder-top soils were weakly developed, there was incipient pedogenesis as exemplified by the presence of pedogenic Fe. The boulder-top soils were classified as loamy-skeletal, micaceous, acid Lithic Cryorthents. Results illustrated that, like the rest of Karkevagge, chemical weathering is an important contributing process in boulder-top soil formation, and that the boulder-tops provided a unique opportunity to evaluate incipient pedogenesis in an arctic–alpine setting.

Effects of enhanced UV-B radiation in the field on the concentration of phenolics and chlorophyll fluorescence in two boreal and arctic–alpine lichens

Lichens constitute a prominent part of the vegetation at high latitudes and altitudes, but the effects of UV-B radiation on these symbiotic organisms are not well known. In a northern boreal site (Abisko, northern Sweden), the usnic acid-producing lichens Flavocetraria nivalis and Nephroma arcticum were exposed to enhanced UV-B radiation, corresponding to 25% ozone depletion, for two and one growing seasons, respectively. They were compared with lichens grown under ambient UV-B and harvested fresh from the field. The treated thalli of F. nivalis had been transplanted from a site 24 km from the treatment site. From this source locality, untreated thalli were also harvested. Enhanced UV-B did not affect concentrations of usnic acid and the two depsides phenarctin and nephroarctin. A gradual decline of usnic acid, probably coupled to unusually long periods of dry, sunny weather, was observed both under enhanced and ambient UV-B and in untreated thalli. Photosystem II efficiency in both species was slightly reduced by enhanced UV-B. However, differences between seasons were larger than differences between treatments, which indicate that UV-B effects are minor in comparison to other climatic variables. Concentrations of UV-B-absorbing phenolics in lichens do not show a simple relationship to UV-B dose and therefore cannot be used as bioindicators of UV-B levels.

The impact of short‐term predator removal on vole dynamics in an arctic‐alpine landscape

During 1991–95, mammalian predators (weasel, Mustela nivalis, stoat, M. erminea, mink, M. vison, and red fox, Vulpes vulpes) were excluded in late summers from a 2 ha piece of a north Norwegian mountain slope. The exclosure extended from an outpost of luxuriant sub‐arctic birch forest to a typical arctic–alpine habitat complex, including productive willow scrublands, tundra heaths, dry ridges and snow‐beds. The exclosure thus encompassed the entire range of habitat conditions encountered in a typical north Fennoscandian mountain and tundra landscapes. During 1991–95, the exclosure was predator‐proof from late July to late September. In wintertime and in early summer, the exclosure was accessible to mammalian predators. Vole dynamics in the short‐term exclosure were compared to dynamics in five reference areas with similar habitat conditions.In 1991, when vole densities were rising in the area, neither collective vole densities nor densities of individual vole species differed significantly between the exclosure and the replicated controls. Spring densities of voles were never significantly different between the exclosure and the controls. With respect to autumnal densities of voles, however, the exclosure was a statistical outlier in the peak year 1992 and throughout the gradual decline phase of 1993–95. In the peak year, the difference in collective vole densities was modest (30%), but increased to two‐fold during the first two decline years and was almost four‐fold in the crash year of 1995. The strongest response was displayed by field voles (Microtus agrestis), hypothesized to be the pivotal prey species of weasels, especially by females and young individuals, i.e. by the functional categories especially sensitive to mammalian predation. These results are consistent with the hypothesis that predation plays a pivotal role for the regulation of herbivorous mammals in relatively productive arctic–alpine habitats.

Importance of large and small mammalian herbivores for the plant community structure in the forest tundra ecotone

Both theoretical arguments and empirical evidence suggests that herbivory in general and mammalian winter herbivory in particular is important in arctic–alpine ecosystems. Although knowledge of the effect of herbivores on specific plants and communities is quite extensive, little is known about the relative impact of large and small vertebrate herbivores and how it might vary among different habitats. To address this key issue, we established exclosures with two different mesh sizes in forest and nearby tundra at three different sites in four contrasting locations in the forest–tundra ecotone in northernmost Sweden and Norway. Plant community composition was recorded annually in three permanent plots within each exclosure and an unfenced control. Local densities of vertebrate herbivores were estimated in spring and autumn from 1998 to 2002.Reindeer (Rangifer tarandus) were the most abundant large vertebrate while Norwegian lemmings (Lemmus lemmus) and grey‐sided voles (Clethrionomys rufocanus) were the most common small vertebrates. The study reveals that voles and lemmings have larger effects on the vegetation than reindeer in both habitats in all four locations, even though densities of reindeer differ between locations and only two locations experienced lemming peaks during the period of the experiment. The relative abundance of five of the fifteen most common species was significantly influenced by voles and lemmings whereas only a single species was significantly influenced by reindeer. Different analyses give contrasting results on the importance of herbivory in forest versus open heathlands. A principal component analyses revealed that herbivory influenced the vegetation more in open heathlands than in forests. However, an importance index of herbivores did not differ between forest and open heathlands. Moreover, none of the plant species responded differently in the two habitats, when herbivores were removed. Our results suggest that intense and localised selective foraging by small mammals may have a more marked effect on vegetation than transient feeding by reindeer.

Polyploid origins in a circumpolar complex in Draba (Brassicaceae) inferred from cloned nuclear DNA sequences and fingerprints

Polyploid evolution has been of major importance in the arctic flora, but rarely addressed on the full circumpolar scale. Herein we study the allopolyploid Draba lactea and its close allies, which form a taxonomically intricate arctic–alpine complex including diploids, tetraploids, and hexaploids. Based on samples from the entire circumpolar area, we inferred the origins of polyploids in this complex using cloned DNA sequences from two nuclear regions (one intron from a gene encoding a second largest subunit in the RNA polymerase family, RPD2, and the ribosomal internal transcribed spacer region, ITS) and DNA fingerprints (random amplified polymorphic DNAs, RAPDs). Although D. lactea and all other polyploids examined in Draba are genetic alloploids showing fixed heterozygosity, the data obtained in the present study suggest that each of the polyploids analyzed here may have originated from a single diploid lineage: hexaploid D. lactea via tetraploid D. lactea from the D. palanderiana lineage (not from the D. fladnizensis and D. nivalis lineages as previously hypothesized), the tetraploid D. turczaninovii from the D. fladnizensis lineage, the tetraploid D. porsildii from the D. lonchocarpa lineage, and a tetraploid here named Draba spB from the D. nivalis lineage. Draba lactea has probably originated several times in the Beringian area, and it is not necessary to invoke complex origins based on a combination of different species lineages as previously suggested.

Polyploid origins in a circumpolar complex in Draba (Brassicaceae) inferred from cloned nuclear DNA sequences and fingerprints

Polyploid evolution has been of major importance in the arctic flora, but rarely addressed on the full circumpolar scale. Herein we study the allopolyploid Draba lactea and its close allies, which form a taxonomically intricate arctic–alpine complex including diploids, tetraploids, and hexaploids. Based on samples from the entire circumpolar area, we inferred the origins of polyploids in this complex using cloned DNA sequences from two nuclear regions (one intron from a gene encoding a second largest subunit in the RNA polymerase family, RPD2, and the ribosomal internal transcribed spacer region, ITS) and DNA fingerprints (random amplified polymorphic DNAs, RAPDs). Although D. lactea and all other polyploids examined in Draba are genetic alloploids showing fixed heterozygosity, the data obtained in the present study suggest that each of the polyploids analyzed here may have originated from a single diploid lineage: hexaploid D. lactea via tetraploid D. lactea from the D. palanderiana lineage (not from the D. fladnizensis and D. nivalis lineages as previously hypothesized), the tetraploid D. turczaninovii from the D. fladnizensis lineage, the tetraploid D. porsildii from the D. lonchocarpa lineage, and a tetraploid here named Draba spB from the D. nivalis lineage. Draba lactea has probably originated several times in the Beringian area, and it is not necessary to invoke complex origins based on a combination of different species lineages as previously suggested.

Local population dynamics are important to the conservation of metapopulations in highly fragmented landscapes

Summary 1. Population viability analyses (PVA) are extremely useful tools for the management of endangered species at the landscape scale. Two main families of spatially explicit models are available to perform PVA: (i) presence–absence models, in which local populations are either existing or extinct at each generation, and (ii) structured population models, in which the dynamics of each local population are modelled. In this study we compared the usefulness of both approaches for the prediction of the persistence of a species living in a highly fragmented landscape. 2. The cranberry fritillary Boloria aquilonaris is an arctic–alpine relict species in western Europe. It lives in landscapes where altitude or the proximity of oceans provide the high humidity conditions required for the formation of peat bogs, the only habitat of the butterfly. In such landscapes, the distribution of the butterfly is fragmented, following the natural distribution of peat bogs; this fragmentation is increased by human‐induced peat bog destruction. 3. The study of the dynamics of a highly fragmented metapopulation of the cranberry fritillary in a network of 14 habitat patches totalling 26·23 ha revealed that: (i) the density at the equilibrium was c. 700 butterflies ha−1; (ii) local population dynamics in small populations were negative; and (iii) six estimates of the growth rate Rt showed large variations even in a large population. Both local extinctions and recolonization events are likely to occur, and two sites (one of 7 ha) unoccupied during two generations were recolonized in the third year. 4. We conclude that the future of this metapopulation is not guaranteed, given its large spatial scale and unbalanced, erratic local population dynamics. We hypothesize that global warming could explain the instability of local population dynamics detected here in addition to the decline of this arctic–alpine relict species, which is currently reported in all its refuge localities in the Netherlands. 5. Presence–absence models based on metapopulation structure and habitat characteristics should provide relatively safe predictions, as the population network (14 patches) is just below the minimum amount of suitable habitat (MASH) for the long‐term persistence of a viable metapopulation. However, careful investigation of local population dynamics showed a high instability in the network, which is confirmed by population extinction at a large site. 6. Synthesis and applications. We urge conservation biologists to consider the local population dynamics of endangered species for the management of metapopulations in fragmented landscapes. In the case of the cranberry fritillary, continuing site protection is essential.

Seed bank size and composition of Betula nana, Vaccinium uliginosum, and Campanula rotundifolia habitats in Svalbard and northern Norway

The rare thermophilous species in the arctic archipelago of Svalbard are probably relicts from previous warmer periods and may be unable to reproduce sexually under the present climatic conditions. Germination of seeds, seed banks, and vegetative sprouts were studied in one Betula nana L., one Vaccinium uliginosum L., and two Campanula rotundifolia L. habitats in Svalbard. For comparison, one islet and three alpine habitats in northern Norway were studied. In each habitat, 50 soil cores (9.6 cm2) were collected and placed in a phytotron for germination tests. In Svalbard, no germinable seeds or seed bank of the three species were observed, whereas vegetative sprout densities were 83, 1060, and 21–1060/m2 for B. nana, V. uliginosum, and C. rotundifolia, respectively. In northern Norway, germination percentages of the collected seeds were 59, 10–27, and 15–40%, seed bank densities of seedlings 21–2765, 21–187, and 21–374/m2, and vegetative sprouts densities 94–206, 56–674, and 94–711/m2 for B. nana, V. uliginosum, and C. rotundifolia, respectively. Less thermophilous plant species produced germinable seeds in Svalbard, as 1247–5405 seedlings/m2 of 26 species germinated from the soil cores. In comparison, 5322–9626 seedlings/m2 of 43 species germinated in soil cores from the alpine habitats and 3534 seedlings/m2 of 26 species from the islet habitat. The results suggest that the most thermophilous species in Svalbard rarely produce germinable seeds under the present climatic conditions.Key words: arctic–alpine, Betula nana, Campanula rotundifolia, seed bank, sexual reproduction, thermophily, Vaccinium uliginosum.

Biodiversity of rust fungi in the Šumava (Bohemian Forest) and in the Krkonoše (Giant Mountains), Czech Republic

The occurrence and seasonal dynamics of rust fungi (Uredinales) on wild growing plants was investigated on eleven localities in the Bohemian Forest (Šumava Mts.) and on three localities in the Giant Mountains (Krkonoše Mts.). All studied localities are situated in the most strictly protected areas of the Czech National Parks (ecosystems of the mires, the glacial corries, and the arctic alpine tundra) that are considered the primary centres of biodiversity. The frequency of occurrence of the rust species is linked with the host plant diversity. It is also influenced by the human activity in specific places. The occurrence and the distribution of rusts are compared with available historical data. Several rust species are regular inhabitants of the natural ecosystems. The others follow the invasive host plant species.

Near–surface ground temperature regime variability in selected microenvironments, kärkevagge, swedish lapland

The importance of topographic microvariability in influencing shallow (10–50 cm depths) soil temperature regimes in arctic–alpine Kärkevagge, northern Sweden, from August 1999 to July 2000 is demonstrated using six sites. The ground microclimate on the tops of very large boulders forming an extensive boulder field in the central valley bottom is more comparable to that at an alpine ridge–crest site 300 m higher than it is to the microclimate at the base of one of the boulders. The boulder crests also differ substantially from the more generalized valley–bottom conditions outside the boulder field. Assuming that chemical processes may be active at temperatures at or above 0°C, sites in the valley experience favorable conditions from 159 to 324 days of the year. Aside from the annual cycle, freeze–thaw cycles are infrequent within Kärkevagge.

Weathering rinds and rock coatings from an Arctic alpine environment, northern Scandinavia

Coarse rock debris exposed in the subaerial environment of northern Sweden displays the development of a wide variety of surface coatings. These include weathering rinds as well as a great diversity of geochemical coatings, including those dominated by Ca, Fe, Si, and Al. Each of these types of rock coatings displays a high degree of geochemical complexity. The weathering rinds exhibit both geochemical and morphologic changes to the parent rock cores, including extensive dissolution, oxidation, and hydration as well as disaggregation, fracturing, and cementation by secondary geochemical coatings. Chemical breakdown of the rock to form weathering rinds includes loss of K, Si, Mg, and Ca and buildup of Fe. Weathering rinds are fundamentally the result of dissolution, as no clay minerals were identified in the rinds. Rock coatings are distinguished from rinds by their clear accretionary nature. Despite the distinction made between weathering rinds and rock coatings, it is important to note that often the two are intimately related. The presence of rock coatings as well as weathering rinds on rock surfaces amplifies the important role played by geochemical processes in the Arctic alpine climate of northern Sweden in particular, as well as its significance in landscape evolution in such environments in general.

The chemical weathering regime of Kärkevagge, arctic–alpine Sweden

Kärkevagge is a valley located in Swedish Lapland at approximately 68°N and represents an arctic–alpine landscape. It is a presently periglacial, glaciated trough incised into essentially horizontal metamorphic rocks, some of which are presumably pyrite-rich. A set of coordinated studies was undertaken to investigate the nature of chemical weathering and pedogenesis in the valley and upon the abutting ridges. August 1996 water quality measures reveal considerable spatial variation in solute totals with the highest Total Dissolved Solute abundances being correlated with high sulfate abundances. Ridge-crest soils exhibited poor horizonation, but more extensive development of secondary clay minerals developed in situ than was found in valley-flank and valley-bottom soils. Valley soils exhibited multiple thin horizons, many of which were buried, and are taken to reflect great paraglacial and periglacial instability. Favorable microenvironments in the valley permit significant development of Spodosols. Coarse debris along and across the valley bears both weathering rinds and rock coatings. Rock coatings in the valley include several types of iron films, sulfate crusts, carbonate skins, and heavy metal skins. Kärkevagge represents a mild arctic environment, which does not preclude substantial chemical weathering in locations where abundant pyrite-rich bedrock and water coincide. This weathering follows pathways which are eminently expectable given that weathering of the pyrite-rich rock permits generation of sulfuric acid which, in turn, weathers muscovite mica and calcite in local schists and marble, respectively. Zones of intense chemical weathering also generate clearly visible deposits of gypsum and iron sulfate deposits such as jarosite. Not all arctic and/or alpine environments are likely to be so active chemically, but the results from Kärkevagge clearly show that dismissal of chemical weathering in cold regions on the basis of presumed first principles is erroneous. Consequently, chemical weathering in such environments merits substantially more attention than it has hitherto received.

Weathering rates of fine pebbles at the soil surface in Kärkevagge, Swedish Lapland

In 1994, nylon mesh bags containing ∼6.2-mm diameter fragments of either freshly crushed dolomite or granite were placed on meadow, solifluction meadow, birch, heath and alpine tundra vegetation that cover surfaces within Kärkevagge, a glaciated arctic–alpine valley in Swedish Lapland. Each vegetation category contained three replicate sites comprising one bag of each rock type. In 1995, the study was extended to Dryas heath and willow (two sites only) surfaces. Percentage annual weight loss was used as a metric of chemical weathering rates. One site in each of the 1994 categories was measured in 1995. All sites were measured in 1999. Two dolomite and granite standards stored in the laboratory and subjected to identical cleaning and weighing regimes to the field samples, exhibited no more than a 0.24% total weight loss after 5 years. The percentage weight loss in the subgroup examined after 1 year (dolomite 0.54%/year; granite 0.41%/year) significantly exceeded the average annual loss for the subsequent 4 years in all cases (dolomite 0.40%/year; granite 0.07%/year). Ten sites with a 5-year record had a mean annual loss of 0.326±0.115%/year (two standard errors) for dolomite and 0.121±0.020%/year for granite. Assuming an exponential decay model, a 0.326%/year rate of loss produces a ‘half-life’ of approximately 212 years and a 0.121%/year loss rate, a half-life of approximately 570 years. Kruskal–Wallis one-way ANOVA on rank-ordered data determined significant differences in dolomite pebble mass loss between the Dryas heath and willow plus meadow microenvironments, as well as between the birch forest and the willow plus meadow microenvironments. The underpinning factor behind these differences appears to be moisture differences. A similar test failed to determine statistically significant differences for the granite pebbles. Dolomite appears to be a viable medium for determining mass loss rates over quite modest time periods providing that the number of samples is sufficiently large.

Arctic alpine fungi of the English Lake District

Arctic alpine fungi of the English Lake District