Metals in some dominant vascular plants, mosses, lichens, algae, and the biological soil crust in various types of terrestrial tundra, SW Spitsbergen, Norway

Arctic environments are commonly considered to be relatively pristine because of minimal local human activity. However, these areas receive air pollution from lower latitude regions. Our goal was to determine concentrations of metals (Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, and Zn) in dominant species of vascular plants, mosses, lichens, algae, and in the biological soil crust (BSC), and topsoil (0–3 cm) from various types of tundra in the southwestern part of Spitsbergen, Norway. Results indicate that mosses are more efficient bioaccumulators of Cd, Co, Cr, Cu, Fe, Mn, and Zn than lichens. The highest levels of Co, Cr, Cu, Fe, Hg, Mn, Ni, and Pb were found in the BSC, and the moss species Racomitrium lanuginosum, Sanionia uncinata, and Straminergon stramineum from the polygonal tundra, initial cyanobacteria-moss wet tundra, snow bed cyanobacteria-moss tundra, and flow water moss tundra alimented by melting ice or snow. The observed higher concentrations of Cu and lower concentrations of Hg in mosses, lichens, and vascular plants compared with values observed 20 years earlier were apparently associated with changes in the atmospheric deposition of contaminants over Spitsbergen due to changes in the long-distance transport of anthropogenic emissions from industrialized areas. Prasiola crispa and Salix polaris may be useful bioindicators of Cd and Zn, and the BSC, R. lanuginosum, S. uncinata, and S. stramineum as bioindicators of Co, Cr, Cu, Fe, Hg, Mn, Ni, and Pb. These results may be extrapolated across other areas of Spitsbergen with similar climates.     

Utilization of lichens in the arctic and subarctic

Economic Botany - The principal economic importance of lichens lies in their providing sustenance for hundreds of thousands of reindeer in circumpolar regions, animals upon which the Eskimos, Lapps...     

Comparative study of dark respiration in plants inhabiting arctic (Wrangel Island) and temperate climate zones

Comparative analysis of dark respiration was carried out for 18 plant species inhabiting arctic zone (Wrangel Island, lat. 71° N) and temperate zone (Leningrad oblast, lat. 59° N). For 15 pairs of species examined, the Stocker’s rule was proved valid; i.e., respiration rates of identical species were equal at average temperatures of their natural habitats. The concept of respiratory features in boreal and mountain plants is described in its historic development. The possible causes for controversial data are explained. It is concluded that gas exchange measurements in natural plant habitats are the only valid means for characterizing plant respiration. Only such measurements should provide the basis for the discussion of global climate changes.     

Acidobacteria in microbial communities of the bog and tundra lichens

Bacterial communities of the lichens from a Sphagnum bog (Karelia) and tundra (Vorkuta oblast) were investigated. Members of the phylum Acidobacteria were numerous in the thallus of living and decaying lichens (3.8 × 10⁸ cells/g), constituting 6 to 32% of the total bacterial number. Pure cultures of acidobacteria were isolated from the samples of living and decaying lichen thallus. Ten of them were identified and classified as members of subgroup 1 of the Acidobacteria. The hydrolytic activity of two strains isolated from the living and decomposing zones of the thallus was investigated. They were capable of growth on xylan, starch, pectin, laminarin, and lichen extract. Acidobacteria were shown to be a stable and numerous component of microbial communities of the bog and tundra lichens.     

Seasonal geochemistry of an arctic tundra drainage basin

The snow melt food at Imnavait Creek takes place sometime between 12 May and 2 June and constitutes the single most important hydrological and geochemical event. Three years of study indicate this event spans 7 to 10 days and that peak discharge can be expected to be between 0.6 and 0.9 cu. mes. Ion concentrations peak during the first 15% of the event while pH is at a minimum. In all cases, ion concentrations in the spring runoff are 4 to 9 times those of the snow pack, Precipitaion, including dryfall, contributes significant amounts of Ca, Mg, K, Na, Cl and SO₄. Postassium is present in surface waters only during melt-off and for a short time after. Calcium. Mg. suspended solids and electrical conductivity all reach broad, poorly defined peaks in mid-summer. Only pH shows a significant relationship to discharge. On a seasonal basis a substantial charge imbalance favoring cations occurs. It seems probable that the, as yet, unmeasured negative charge is associated with organic anions. No seasonal trends were recorded for Mg, K or Mn in subsurface flow in the surrounding slopes. Calcium. Fe and Al showed a late season peak, and the concentration of Na and Si decreased as the melt season progressed.     

The distribution of arctic lichens and thoughts concerning their origin

The distribution of many Arctic lichens is well known but their place and time of origin is still conjectural. Land bridges are often suggested but continental drift suggests a possible tie to Gondwanaland and Pangaea. This review suggests consideration of the available evidence for such ideas and emphasizes the need for more exact data from molecular studies of living and amber materials to determine the antiquity of the lichen species involved.     

Microfaunal response to fertilization of an arctic tundra stream

1. As part of a whole-system study, the response of the heterotrophic microfaunal community colonizing artificial substrata (polyfoam units) to fertilization of an arctic tundra stream was followed for 6 weeks during the summer. 2. Dominant heterotrophic microfauna observed included amoebae (approximately 40% of colonizing biomass), rotifers (36% of biomass) and ciliates (25% of biomass). 3. Biomass of heterotrophic microfauna on artificial substrata was not significantly different in a control reach and an experimental reach fertilized with phosphorus (loading rate ten times ambient), but in a reach fertilized with both phosphorus and nitrogen (loading rates ten times ambient) biomass was double that of the control and phosphorus-fertilized reaches. The lack of response in the phosphorus reach was probably due to greater insect grazing as a result of previous phosphorus fertilization of this reach. 4. Abundance of microfauna on epilithic surfaces in the river was higher on rocks from pools than on rocks from riffle areas, but abundance on the artificial substrata was higher than on the natural rocks. 5. The results suggest that microfauna of arctic tundra streams are regulated by grazers and that their importance in transfers among trophic levels is greater in pools than in riffles.     

Population dynamics of tundra voles in relation to configuration of willow thickets in southern arctic tundra

The areal extent and configuration of thickets of willow shrubs are currently changing in the Arctic both as an effect of global warming and changed browsing pressure of reindeer. These changes have been predicted to impact the distribution and abundance of wildlife species relying on willow thickets as habitat. We assessed the relation between variables quantifying willow thicket configuration and population dynamics of tundra voles (Microtus oeconomus) in three riparian regions in Finnmark, northern Norway, which were subject to intense browsing by semi-domesticated reindeer. The tundra vole, which exhibits 5-year population cycles in Finnmark, is the dominant small rodent species in riparian landscape elements in southern arctic tundra. In the course of a 4-year trapping study, tundra vole populations went through the cyclic phases of increase, peak and crash, however, with distinct differences between the three regions in the population dynamics. Within regions, the occupancy pattern during the increase phase was positively related to willow thicket configuration (in particular edge density and willow height) only in the region attaining the highest abundance and occupancy. However, local abundance was not clearly related to habitat features within any regions. The lack of consistency in the response of tundra vole populations to willow thicket configuration, as well as the positive relation between the degree of thicket shredding and tundra vole habitat occupancy in one of the regions, indicates that tundra voles will not be much affected by climate or browsing induced changes in the shrubbiness of the tundra in the future.     

Maximum CO2-assimilation rates of vascular plants on an Alaskan arctic tundra slope

Light-saturated CO₂-assimilation rates of 19 vascular plant species were measured on a tundra slope in the foothills of the Brooks Range, Alaska. Maximum assimilation capacities on a leaf area basis ranged from 20.3 μmol m⁻² s⁻¹ for the forb, Bistorta plumosa , to 6.0 μmol m⁻² s⁻¹ for the evergreen, Empetrum hermaphroditicum . Graminoids, deciduous shrubs, and forbs fell within a similar range of maximum photosynthetic rates on a leaf area basis. Evergreens had the lowest rates. On a leaf weight basis, maximum assimilation rates were greatest for forbs, followed by deciduous shrubs, graminoids, and evergreens. Rates of evergreens were less than half those of all other growth forms. Cassiope tetragona had the lowest rates per unit leaf weight of any species tested; mean maximum rates of C. tetragona were only 14% of those of B. plumosa , the species with the highest rates. When the data were subjected to canonical analysis, only a partial correspondence was found between species growth form and photosynthetic characteristics.     

Controls on production of bryophytes in an arctic tundra stream

1. Two bryophyte taxa (Hygrohypnum spp. and, to a lesser extent, Fontinalis neomexicana) were abundant in riffles within phosphorus-fertilized reaches of the Kuparuk River (North Slope, Alaska), but were much less common in fertilized pools and virtually absent in unfertilized reaches of the river. We conducted field experiments using stems and clumps of both species and artificial bryophytes to test the hypotheses that bryophyte growth was strongly limited by low phosphorus concentrations in unfertilized reaches, and limited by epiphytes in fertilized pools. 2. Stem tips of Hygrohypnum spp. did not elongate when grown in unfertilized pool and riffle environments. In fertilized reaches, Hygrohypnum elongated significantly, although there was no significant difference in elongation of stem tips placed in pools [2.5 ± 0.9 cm (SD)] as opposed to riffles (2.8 ± 0.9 cm) for 32 days. 3. Stem tips of F. neomexicana elongated significantly in all sites. There was a significant difference in elongation of stem tips in control and fertilized riffles (2.1 ± 1.1 and 4.7 ± 0.1 cm, respectively) but not in tips grown in control and fertilized pools (2.8 ± 0.8 and 2.7 ± 0.9 cm, respectively). 4. Biomass increments in clumps of these same species followed similar patterns except in fertilized pools. Hygrohypnum spp. lost weight in control riffle environments and did not grow in pools, but accumulated 181 ± 44 and 335 ± 200% of initial biomass in fertilized riffles in 1992 (over 32 days) and 1993 (over 44 days), respectively. F. neomexicana accumulated 38 ± 39 and 98 ± 47% of initial biomass in 1992 in unfertilized and fertilized riffles, respectively. Total phosphorus concentrations of both bryophytes in 1992 were significantly greater when grown in fertilized riffles than control riffles. 5. Artificial mosses (untwisted, natural fibre rope) and clumps of Hygrohypnum spp. were used to assess effects of flow regime on derrital and epiphyte accumulation in the fertilized zone. Epiphyte and detrital mass was 4–4.5 times greater on average on artificial mosses in slow-flowing pool environments than in fast-flowing riffle environments. Epiphyte chlorophyll a was 4 times greater on Hygrohypnum clumps in pools than in riffles. This difference was probably brought about by increased detrital deposition and reduced grazing by invertebrates in pools. It is likely that both Hygrohypnum spp. and F. neomexicana could grow throughout the river, but are limited strongly by low phosphorus concentrations in unfertilized reaches and secondarily by detritus accumulation and interference competition with epiphytic algae in fertilized pools.     

Landscape patterns of free amino acids in arctic tundra soils

Concentrations of free amino acids were measured in soils from four major ecosystem types in arctic Alaska. Total free amino acid concentrations were several-fold higher than ammonium (the major form of inorganic nitrogen) in water extracts of soils. The dominant free amino acids in these soils were glycine, aspartic acid, glutamic acid, serine, and arginine. Concentrations of total amino acids ranged 5-fold across communities, being highest in tussock tundra and lowest in wet meadows. Incubation experiments indicate that the turnover of amino acids is rapid, which suggests high rates of gross nitrogen mineralization in these soils. The high concentrations and dynamic nature of soil free amino acids suggest that this nitrogen pool is a significant component of nitrogen cycling in these tundra ecosystems.     

Modelling carbon balances of coastal arctic tundra under changing climate

Rising air temperatures are believed to be hastening heterotrophic respiration (R_h) in arctic tundra ecosystems, which could lead to substantial losses of soil carbon (C). In order to improve confidence in predicting the likelihood of such loss, the comprehensive ecosystem model ecosys was first tested with carbon dioxide (CO₂) fluxes measured over a tundra soil in a growth chamber under various temperatures and soil‐water contents (θ). The model was then tested with CO₂ and energy fluxes measured over a coastal arctic tundra near Barrow, Alaska, under a range of weather conditions during 1998–1999. A rise in growth chamber temperature from 7 to 15 °C caused large, but commensurate, rises in respiration and CO₂ fixation, and so no significant effect on net CO₂ exchange was modelled or measured. An increase in growth chamber θ from field capacity to saturation caused substantial reductions in respiration but not in CO₂ fixation, and so an increase in net CO₂ exchange was modelled and measured. Long daylengths over the coastal tundra at Barrow caused an almost continuous C sink to be modelled and measured during most of July (2–4 g C m^?2 d^?1), but shortening daylengths and declining air temperatures caused a C source to be modelled and measured by early September (～1 g C m^?2 d^?1). At an annual time scale, the coastal tundra was modelled to be a small C sink (4 g C m^?2 y^?1) during 1998 when average air temperatures were 4 °C above normal, and a larger C sink (16 g C m^?2 y^?1) during 1999 when air temperatures were close to long‐term normals. During 100 years under rising atmospheric CO₂ concentration (C_a), air temperature and precipitation driven by the IS92a emissions scenario, modelled R_h rose commensurately with net primary productivity (NPP) under both current and elevated rates of atmospheric nitrogen (N) deposition, so that changes in soil C remained small. However, methane (CH₄) emissions were predicted to rise substantially in coastal tundra with IS92a‐driven climate change (from ～20 to ～40 g C m^?2 y^?1), causing a substantial increase in the emission of CO₂ equivalents. If the rate of temperature increase hypothesized in the IS92a emissions scenario had been raised by 50%, substantial losses of soil C (～1 kg C m^?2) would have been modelled after 100 years, including additional emissions of CH₄.     

Diurnal patterns of gas‐exchange and metabolic pools in tundra plants during three phases of the arctic growing season

Arctic tundra plant communities are subject to a short growing season that is the primary period in which carbon is sequestered for growth and survival. This period is often characterized by 24‐h photoperiods for several months a year. To compensate for the short growing season tundra plants may extend their carbon uptake capacity on a diurnal basis, but whether this is true remains unknown. Here, we examined in situ diurnal patterns of physiological activity and foliar metabolites during the early, mid, and late growing season in seven arctic species under light‐saturated conditions. We found clear diurnal patterns in photosynthesis and respiration, with midday peaks and midnight lulls indicative of circadian regulation. Diurnal patterns in foliar metabolite concentrations were less distinct between the species and across seasons, suggesting that metabolic pools are likely governed by proximate external factors. This understanding of diurnal physiology will also enhance the parameterization of process‐based models, which will aid in better predicting future carbon dynamics for the tundra. This becomes even more critical considering the rapid changes that are occurring circumpolarly that are altering plant community structure, function, and ultimately regional and global carbon budgets.     

Plant responses to fertilization and exclusion of grazers on an arctic tundra heath

This study investigated the impacts of fertilization and grazing by Norwegian lemmings (Lemmus lemmus), grey‐sided voles (Clethrionomys rufocanus), and reindeer (Rangifer tarandus) on a diverse tundra plant community dominated by deciduous shrubs. Four out of eight study areas, having a size of 2500 m² each, were fertilized with a N‐P‐K fertilizer and four areas served as unfertilized controls. Two types of exclosures were used within each study area, one to exclude solely reindeer, and one to exclude both rodents and reindeer. Open, grazed plots served as controls. During 5 years following the fertilization event the changes in vegetation inside and outside the exclosures were monitored using a point frequency method. The densities of rodents on the fertilized and unfertilized areas were investigated by live trapping and by counting nests of overwintering individuals. Reindeer do not graze on the study area during the growing season but migrate through this area in autumn and spring. Fertilization increased the abundance of vascular plants while grazing by reindeer and rodents decreased the abundance of vascular plants significantly on both fertilized and unfertilized areas. Rodents preferred clearly the fertilized areas during winter, decreasing the abundance of Vaccinium myrtillus and Vaccinium vitis‐idaea, while very little grazing occurred during summer. Graminoids showed the strongest positive response to fertilization and dominated the plant community on ungrazed plots, while winter grazing by both reindeer and rodents significantly decreased the abundance of graminoids. Deciduous shrubs (Betula nana, Vaccinium myrtillus) increased slightly but significantly due to fertilization and evergreen dwarf shrubs showed no response to fertilization. However, the use of functional growth forms for predicting the responses of nutrient enrichment and grazing must be questioned, as responses to fertilization as well as preferences by herbivores were shown to be species‐specific rather than uniform within functional groups based on plant growth forms.