Fellfield Site Research Articles

Diel activity patterns of alpine carabid beetles (Coleoptera: Carabidae) differ according to habitat type

In lowland areas, carabid beetles show diurnal or nocturnal activity patterns depending on habitat type. However, the diel activity patterns of carabid beetles in alpine areas are poorly understood. We conducted field studies in the alpine area of Mt. Hakusan in central Japan to determine the diel activity patterns of carabid beetles according to habitat type and ground surface temperature. Using baited pitfall traps, we collected samples every three hours over a 24-hour period in the summers of 2015 and 2016 in Pinus scrub, snowbed, and fellfield sites. In both years, the numerically dominant species were Pterostichus janoi Jedlicka, 1952 in the Pinus scrub, Bembidion sp. in the snowbed, and Bembidion sp. and Colpodes xestus (Bates, 1883) in the fellfield. Carabid beetles on alpine Hakusan showed activity patterns that varied depending on habitat type or ground surface temperature. Bembidion sp. showed diurnal activity patterns in the snowbed but nocturnal activity patterns in the fellfield when the diurnal temperature range was large. However, this species was active throughout the day and night in these habitats when the diurnal temperature range was small. By contrast, P. janoi in the Pinus scrub and C. xestus in the fellfield were mainly active nocturnally in both years, regardless of temperature fluctuations. Because alpine areas are generally characterized by harsh and changeable climates, some alpine carabids such as Bembidion sp. are probably adapted to show versatile activity patterns in response to changeable microclimatic conditions.

The importance of facilitative interactions on the performance of Colobanthus quitensis in an Antarctic tundra

AbstractAimsThe sign of interactions among plants in very harsh environments is under debate. The Antarctic tundra is one of the harshest environments on Earth and only two vascular plants (Deschampsia antarctica and Colobanthus quitensis) have successfully established natural populations. D. antarctica mostly establishes facilitative interactions with other species (mosses), but there is no information about the inter‐specific interactions established by C. quitensis. We assessed whether C. quitensis grows frequently associated with D. antarctica, and if D. antarctica neighbours have a positive effect on the survival, growth and photochemical efficiency of C. quitensis individuals.LocationKing George Island, Antarctic Peninsula.MethodsTo assess the spatial association among the two Antarctic vascular plants fifty 50 m × 50 cm quadrats were sampled on each of four different substrates: moss carpet areas; dead moss carpet areas dominated by D. antarctica; a transition zone between dead moss carpets and fellfields; and fellfields characterized by very poor vegetation cover. Infrared thermal images were taken to estimate whether growth associated with D. antarctica affected the foliar temperature of C. quitensis. The importance of D. antarctica neighbours on the growth, survival and photochemical efficiency of C. quitensis was evaluated with a neighbour removal experiment.ResultsThe number of C. quitensis individuals associated with D. antarctica was significantly higher than when growing alone in the moss carpet and the dead moss carpet, while in the transition zone there was a trend in that direction. C. quitensis individuals growing associated with D. antarctica were bigger than those growing alone in these three substrate types. In the fellfield site there were no significant differences, neither in the number nor the size of individuals when growing alone or associated with D. antarctica. Foliar temperature of C. quitensis individuals associated with D. antarctica was slightly (1.1°C) but significantly higher than in those growing alone. The growth, survival and photochemical efficiency of C. quitensis individuals with neighbours were higher than in individuals with neighbours removed.ConclusionsOur results indicate that D. antarctica has a facilitative effect on the growth, survival and photochemical efficiency of C. quitensis. Thus, facilitative interactions are present and are important in one of the harshest environments on Earth, although results from the fellfield site indicate that further research is needed.

Plant and Vegetation Dynamics on Disko Island, West Greenland: Snapshots Separated by Over 40 Years

We report on a revisit in 2009 to sites where vegetation was recorded in 1967 and 1970 on Disko Island, West Greenland. Re-sampling of the same clones of the grass Phleum alpinum after 39 years showed complete stability in biometrics but dramatic earlier onset of various phenological stages that were not related to changes in population density. In a fell-field community, there was a net species loss, but in a herb-slope community, species losses balanced those that were gained. The type of species establishing and increasing in frequency and/or cover abundance at the fell-field site, particularly prostrate dwarf shrubs, indicates a possible start of a shift towards a heath, rather than a fell-field community. At the herb-slope site, those species that established or increased markedly in frequency and/or cover abundance indicate a change to drier conditions. This is confirmed both by the decrease in abundance of Alchemilla glomerulans and Epilobium hornemanii, and the drying of a nearby pond. The causes of these changes are unknown, although mean annual temperature has risen since 1984.

Habitat-Specific Responses of Alpine Plants to Climatic Amelioration: Comparison of Fellfield to Snowbed Communities

Because of the contrastive differences in environment and species composition, climatic amelioration may affect alpine vegetation differently between fellfield and snowbed communities. To test this prediction, the effects of warming on plant growth and vegetation structure were studied in two fellfield and two snowbed communities in northern Japan over 7 years using open-top-chambers (OTCs). OTCs increased the temperature by 1.1–1.8 °C, but the effects on snowmelt time and soil moisture were small. Vegetation height and canopy volume increased substantially at both fellfield sites as a result of the use of OTCs. Deciduous shrubs increased substantially at the lower fellfield and graminoids increased at the upper fellfield. In contrast, the responses of snowbed plants to OTCs were not significant. Because snowbed plants are snow-covered until mid-summer, climatic amelioration during the snow-free period may influence plant growth only slightly if the snow-free period does not change. Species richness and diversity were not changed by OTCs at any of the sites, indicating that the effect of warming alone may not be strong enough to change the species composition and diversity over several years. These results indicate significant variation in the response among alpine communities to warming.

Responses of springtail and mite populations to prolonged periods of soil freeze-thaw cycles in a sub-arctic ecosystem

The effect of temperature changes on soil communities is an important aspect when estimating the effects of a predicted climate change. The aim of this investigation was to increase knowledge on how freeze-thaw cycles alter the soil microarthropod community in the sub-arctic. The abundance of springtails and mites was investigated after three seasons of prolonged periods of freeze-thaw cycles in the field, and the presence or absence of migration barriers, at two different field sites. Dome shaped transparent plastic greenhouses were successfully used as a novel method to increase freeze-thaw cycle frequencies in the soil. At a fellfield site, freeze-thaw treatment did not lead to significant differences in the five main soil faunal groups, but increased abundance were seen in a number of separate taxa. There was no freeze-thaw treatment effect on soil microbial biomass or soil nutrients, although treatments interacted as inorganic N increased in the separate freeze-thaw and migration barrier treatments. By contrast, at a glade site responses were strong due to more pronounced increases in the number of freeze-thaw cycles. The highest numbers of Collembola after 2 years of treatment were found in the freeze-thaw plots, in combination with migration barriers. The freeze-thaw treatment here also resulted in more Oribatida, microbial biomass C and dissolved organic C. A common hypothesis is that an increased number of freeze-thaw cycles would result in elevated winter mortality in microarthropods due to increased risk of inoculative freezing. However, we observed no increased mortality due to freeze-thaw events. Rather, there was a stimulation of soil microarthropods and microbial biomass, perhaps due to a prolonged period of microbial and faunal activity when the soil is repeatedly frozen and thawed compared to a constantly frozen soil.

The biology of Bothrometopus elongatus (Coleoptera, Curculionidae) in a mid-altitude fellfield on sub-Antarctic Marion Island

Bothrometopus elongatus is one of four Ectemnorhinus-group species restricted to the epilithic biotope on the Prince Edward Islands. Here we examine the biology of this species over a full year at Kerguelen Rise, a mid-altitude fellfield site on Marion Island. B. elongatus adults eclose from April onwards, reaching maximum densities (ca. 17 individuals m−2) in September. Females mature approximately three eggs at a time and these commence hatching in July. Larval eclosion reaches a peak in November, during which time larval densities are also highest (ca. 153 individuals m−2). The larvae develop through six instars, which is within the range found for other Ectemnorhinus-group species. The high densities of B. elongatus in fellfield habitats, and its single, virtually discrete annual generation, make this species unusual among insects indigenous to the sub-Antarctic. The latter generally have low densities compared to other micro-arthropods, prolonged life-cycles, and flexible life-histories. We suggest that the diversity of life-histories found amongst the indigenous insects at Marion Island presents considerable potential for testing environmental effects on insect life-histories. An overview of sub-Antarctic insect life-history data suggests that the indigenous species, with generally prolonged life-cycles, are at a disadvantage relative to introduced species that have more rapid cycles and often complete several generations per year. This is reason for concern given rapid climate change at these islands.

Response of Arctic ecosystems to climate change: results of long-term field experiments in Sweden and Alaska

Long-term field experiments at Abisko, Sweden, and Toolik Lake, Alaska, reveal both similarities and differences in response of contrasting Arctic ecosystems to changes in temperature, light, and nutrient availability. Five different ecosystems were manipulated for 5–15 years by increasing air temperature with greenhouses, by decreasing light with shading, and by increasing available N and P with fertilizers. The ecosystems at Abisko included evergreen-dominated heath and fellfield sites; at Toolik Lake they included wet sedge tundra, moist tussock tundra, and dry heath tundra. In all ecosystems, fertilizer treatment increased plant growth, production, and/or biomass. Plant responses to warming were smaller and occasionally nonsignificant, Responses to shading were generally nonsignificant after 3–6 years, although after 9 years the tussock tundra showed significant decreases in biomass. In general, the ecosystems at Abisko were less responsive to nutrients and more responsive to temperature than the ecosystems at Toolik Lake. Overall, though, the sites were quite similar in their responses to the perturbations, increasing our confidence in predictions of response to climate change over large areas based on small-area studies.

Nitrogen uptake by rhizomes of the clonal sedge Carex bigelowii: a previously overlooked nutritional benefit of rhizomatous growth

Studies on the rhizomatous clonal sedge Carex bigelowii, at a fellfield site in subarctic Swedish Lapland examined the ecological potential of rhizomes as nitrogen uptake systems. Direct application of a solution of 15NH415NO3 to the rhizomes of C. bigelowii significantly enriched the 15N content of the plant tissue. The pattern of enrichment indicated movement of labelled nitrogen into rhizomes and adjoining tissue (including roots and shoots), showing both uptake and translocation via the rhizome system. There was a gradient of decreasing 15N enrichment with increasing distance from the point of labelling, and estimation of the total mass of nitrogen taken up via labelled rhizomes showed low levels and rates of uptake. Quantification of the size of rhizome and root systems of C. bigelowii at the study site indicates that 80% of the living biomass may be below ground, and that the surface area of the rhizome system of C. bigelowii is approx. two‐thirds that of the roots. The rhizome system of C. bigelowii can therefore act as a route for nitrogen uptake, with the potential to exploit almost as great a volume of soil as the root system. This mechanism of nitrogen uptake may play an important role in the Arctic, where many species have a clonal, rhizomatous growth form. In addition, plant growth in many arctic ecosystems is limited by low soil nutrient availability, a result of low temperatures (leading to slow soil decomposition rates) and patchy resource distribution. Nitrogen uptake via rhizomes may provide plants with the capacity to take advantage of transient nutrient supplies, and may partly compensate for the cost of developing and maintaining persistent rhizome networks in ecosystems where nutrient resources are in short supply.

Response of Arctic ecosystems to climate change: results of long-term field experiments in Sweden and Alaska

Long-term field experiments at Abisko, Sweden, and Toolik Lake, Alaska, reveal both similarities and differences in response of contrasting Arctic ecosystems to changes in temperature, light, and nutrient availability. Five different ecosystems were manipulated for 5–15 years by increasing air temperature with greenhouses, by decreasing light with shading, and by increasing available N and P with fertilizers. The ecosystems at Abisko included evergreen-dominated heath and fellfield sites; at Toolik Lake they included wet sedge tundra, moist tussock tundra, and dry heath tundra. In all ecosystems, fertilizer treatment increased plant growth, production, and/or biomass. Plant responses to warming were smaller and occasionally nonsignificant, Responses to shading were generally nonsignificant after 3–6 years, although after 9 years the tussock tundra showed significant decreases in biomass. In general, the ecosystems at Abisko were less responsive to nutrients and more responsive to temperature than the ecosystems at Toolik Lake. Overall, though, the sites were quite similar in their responses to the perturbations, increasing our confidence in predictions of response to climate change over large areas based on small-area studies.

Soil nematode fauna of a subarctic heath: potential nematicidal action of plant leaf extracts

Dwarf shrub heaths are common vegetation types of the Arctic and Subarctic. Some of the dominant plants in these communities release toxic substances which can affect neighbouring plants. We investigated the effects of leaf extracts from two dwarf shrubs, Cassiope tetragona and Empetrum hermaphroditum, and from mountain birch, Betula pubescens spp. tortuosa, on nematode community structure and reproduction in a pot and an agar culture experiment. In pots two graminoids, Carex bigelowii and Festuca viuipara, were grown in previously sterilized or non-sterilized soil. Soil was collected from a subarctic heath, and plants from a fellfield site, near Abisko, northern Swedish Lapland. The naturally occurring nematode community at the heath site is also described. A total of 34 nematode taxa were observed at the field site and 32 taxa in the pot experiment. Most species, especially frequent taxa, occurred in both soils. Potted soil was strongly dominated by bacterial feeders and showed a shift towards a more colonizer controlled population. These changes were presumably due to the establishment of residual species after freezing and/or sterilization of the soil prior to incubation in the laboratory. Direct exposure of the nematode Aphelenchoides saprophilus to the leaf extracts in agar cultures resulted in a lower reproduction rate. Leaf extract treatment in potted soil altered nematode species composition and dominance structure, and generally reduced species number and maturity index. The diversity of genera was decreased by all extract treatments in pots with Carex. Nematode population density was not affected, except after application of Betula extracts, where significantly higher densities occurred. Nematode data were related to respiration and active fungal biomass in the soil, indicating that rather than allelochemicals with nematicidal properties, carbohydrates in the leaf extracts promoting a beneficial microflora may have affected the nematode community.

Aerial dispersal of lichen soredia in the maritime Antarctic

SUMMARYAn aerobiological monitoring programme was carried out for over a year on Signy Island, South Orkney Islands, Antarctica. Collections were made using arrays of rotorod samplers at three sites. Lichen soredia were found to be the most abundant air borne propagules, more so than ascospores, the sexual propagules of lichen fungi. The dominance of soredia over ascospores appeared to decrease with increasing maturity of fellfield sites. No correlations were found with temperature, relative humidity or wind speed. Collections at 1 m above ground level were shown not to be significantly different to those at 0·15 m at two of the sites. Size range distribution also differed at two of the sites. Soredial clumps in excess of 100 μm in diameter were collected at 1 m above ground level and at some distance from potential source plants, though most fell in the range 30–60 μm. Peaks in numbers of air borne soredia were found after winter snow melt, demonstrating that soredial production continues at subzero temperatures.

Response of pioneer soil microalgal colonists to environmental change in Antarctica

There is increasing evidence of climate change in Antarctica, especially elevated temperature and ultraviolet B (UVB) flux within the ozone "hole." Its origins are debatable, but the effects on ice recession, water availability, and summer growth conditions are demonstrable. Light-dependent, temperature-sensitive, fast-growing organisms respond to these physical and biogeographical changes. Microalgae (cyanobacteria and eukaryotic algae), which are pioneer colonists of Antarctic mineral fellfield soils, are therefore highly suitable biological indicators of such changes. In frost-heaved soil polygons containing naturally sorted fine mineral particles, microalgal growth is restricted to a shallow zone of light penetration. By virtue of this light requirement, microalgae are exposed to extreme seasonal fluctuations in temperature (air and black-body radiation), photosynthetically active radiation, UV radiation, and desiccation. Dominance of conspicuous autofluorescent indicator species with distinctive morphology allowed quantification of responses using epifluorescence microscopy, and image analysis of undisturbed, unstained communities. However, the physical changes in climate, although significant in the long term, are gradual. The changes were therefore amplified experimentally by enclosing the communities at a fellfield site on Signy Island, maritime Antarctica, in cloches (small greenhouses). These were made of polystyrene of either UV transparent or UV opaque acrylic plastic, with or without walls. During a 6-year period, statistically significant changes were observed in microalgal colonization of the soil surface and in the morphology of filamentous populations. Evidence of community succession correlated with measured changes in local environment was found. Results from Signy Island and at continental sites on Alexander Island suggested that rates of microalgal colonization and community development might change significantly during current climate changes in Antarctica.

Precipitation nitrogen at maritime Signy Island and continental Cape Bird, Antarctica

The mineral nitrogen (NH4-N + NO3-N) in precipitation occurring at continental and maritime Antarctic sites has been determined. Precipitation at sites remote from animal activity contained much less mineral N than that occurring at sites influenced by such activity. Estimates for nitrogen input at two contrasting fellfield sites, one at continental Cape Bird (dry site), the other at maritime Signy Island (wet site) are presented. At both sites precipitation N represented the major N input to fellfield biota than did wind blown particulate matter containing organic nitrogen or ammonia volatilized from adjacent guano soils and becoming absorbed by moist artificial soils traps.

Strategies of Survival in Plants of the Fenoscandian Tundra

Many arctic species originated outside the Arctic and some of their physiological responses are similar to those in temperate latitudes. Unique adaptations to the Arctic have rarely been found. The recent influx of other species has, however, broken down reproductive barriers and gene flow has been stimulated. In extreme arctic environments, selection forces driving evolution are mainly of the physical environment and plant interactions are positive. Elsewhere, biotic factors, such as herbivory, are important and plant interactions become negative through competition. Physical selective forces operate in winter and summer. Low winter temperatures rarely affect arctic plants, but snow depth and duration influence species distributions. Deep and persistent snow deforms plants and limits the period of resource acquisition. Cryptogams are common in such snow beds. Little or no snow cover exposes plants to abrasion by wind-blown particles and desiccation. In such fell-field sites, deciduous species and xerophytes, such as evergreen cushion plants, are common. Arctic summers are short and developmental processes are extended beyond one growing season, with perennials predominating. Cushion plants efficiently increase their temperatures above ambient, while evergreen and deciduous ericaceous dwarf shrubs coexist and have complementary strategies for intercepting radiation in a low canopy. Tundra soils are generally infertile and may be disturbed by freeze/thaw cycles. Nutrients are conserved by cycling within shoots and between ramets within clones. Vegetative proliferation enhances the survival of young ramets, while physiological integration between ramets enables young ramets to forage across patchy environments. Negative plant-animal relationships are particularly important in the Subarctic. Periodic infestation of moth caterpillars defoliate large areas of mountain birch and stimulate increases in populations of their predators. Periodic population peaks of small rodents graze or kill much vegetation and they may moderate the dynamic structure of plant communities, as the plant species have different abilities to regenerate.Key words: arctic plants, tundra, winter, snow, frost

THE EFFECT OF SLOPE-ASPECT ON TURBULENT TRANSFER IN AN ALPINE FELLFIELD: NIWOT RIDGE, FRONT RANGE, COLORADO

This study investigates the impact of local convergence and divergence of air on turbulent transfer at a mid-latitude alpine fellfield site. Pairs of simultaneous wind and temperature profile measurements on a knoll crest and primary slope (aspect =0, 90, 180, and 270°) are analyzed assuming the logarithmic law. Friction velocity (u*) and roughness length (z0) vary systematically from windward to leeward slopes. General relationships of the form u* = f(u) are derived for conditions of westerly flow with wind speed (u) ranging between 2 and 24 m s-1. Coefficients in the empirical equations for estimating u* at sites on the knoll from wind speed measurements on the crest vary in a consistent manner with respect to local convergence and divergence. Large differences in z0 values between windward and leeward sites correspond with contrasts in surface temperature.

Experimental Ecology of Dryas Octopetala Ecotypes: I. Ecotypic Differentiation and Life-Cycle Stages of Selection

SUMMARY (1) Natural populations of Dryas octopetala show large site-specific variations in phenotype. The genetic and environmental basis for this variation was examined in common-garden and reciprocal-transplant experiments. Morphological characters were examined in seedlings grown from seed in a 'common garden' in controlled growth chambers at the Duke University Phytotron. Adult plants of three D. octopetala populations were transplanted reciprocally at three sites along a snowbank gradient in mountains of interior Alaska. (2) Several factors capable of maintaining genetic differentiation between adjacent snowbed and fellfield populations were studied. Restrictions on pollen flow by phenological and spatial isolation were determined. Barriers to gene flow, selection between ecotypes, and site effects within an ecotype were investigated experimentally by measuring survival of reciprocal transplants at the pollination, seed, seedling, and adult stages. (3) Seedlings raised under common conditions showed differences in leaf size parallel to those observed in the field. Differences in leaf pubescence, used to distinguish two D. octopetala subspecies, were also maintained. The two most prevalent forms were therefore termed ecotypes. (4) Leaf morphology was measured to assess phenotypic effects of reciprocal transplants of adults. Analysis of leaf traits suggested that greater morphological plasticity in the snowbed ecotype accounts for the bulk of the observed phenotypic differences between populations. (5) Pollen flow was greatly reduced by separation of flowering times of the two ecotypes. More than 99% of pollen movement was between flowers of the same ecotype. Neither ecotype was apomictic or auto-fertile; both were self-incompatible. There were apparently no breeding system barriers to gene flow. (6) Selection, measured as survival, favoured seedlings of the snowbed ecotype over those of the fellfield ecotype at the snowbed site (selection coefficient 0 55). At the fellfield site, selection favoured the fellfield ecotype at the adult stage (selection coefficient 0.50). No significant selection was demonstrated at any other life-cycle stage, although 10 of 11 stage-specific selection coefficients indicated a trend toward selection against an alien ecotype at both sites. (7) Seed germination was higher and seedling survival lower at the fellfield site than at the snowbed site for both ecotypes. Therefore, the 'home' site was not always the 'better' site at all life-cycle stages; ecotypes were not perfectly matched with the environment. Therefore, selection at present acts only to give a relative advantage to native ecotypes.