Showing papers in "Arctic, Antarctic, and Alpine Research in 2004"
TL;DR: In this paper, biogeochemical characteristics of miniecosystems present in cryoconite holes and to determine links to other components (soils, streams, and lakes) of the dry valley landscape were examined.
Abstract: Once thought of as inert, ice has been increasingly recognized as a habitat suitable for life. The landscape of the MCMurdo Dry Valleys (MCM) of Antarctica is dominated by glaciers, and glacier melt is the primary water source for life in soils, streams, and lakes. The glaciers, despite their cold and lifeless appearance, offer functioning habitats for life. The major objective of this study was to examine biogeochemical characteristics of miniecosystems present in cryoconite holes and to determine links to other components (soils, streams, and lakes) of the dry valley landscape. We examined cryoconite holes from 5 glaciers spanning the length of Taylor Valley, one of many valleys in the MCM. Cryoconite biotic communities were composed of the same species observed in streams and lakes, namely, cyanobacteria (Chlorococcus, Chroococcus, Crinalium, Oscillatoria, Nostoc, and Sprirulina), rotifers (Philodina gregaria and Cephalodella catellina), tardigrades (Acutuncus antarcticus and Hypsibius spp.), ...
169 citations
TL;DR: In this article, the authors used tree-ring and ecological plot analysis to study conifer growth in upper elevation forests of the central Sierra Nevada, California, U.S.A. They found correlated multidecadal and century-long responses associated with climate.
Abstract: Four independent studies of conifer growth between 1880 and 2002 in upper elevation forests of the central Sierra Nevada, California, U.S.A., showed correlated multidecadal and century-long responses associated with climate. Using tree-ring and ecological plot analysis, we studied annual branch growth of krummholz Pinus albicaulis; invasion by P. albicaulis and Pinus monticola into formerly persistent snowfields; dates of vertical branch emergence in krummholz P. albicaulis; and invasion by Pinus contorta into subalpine meadows. Mean annual branch growth at six treeline sites increased significantly over the 20th century (range 130–400%), with significant accelerations in rate from 1920 to 1945 and after 1980. Growth stabilized from 1945 to 1980. Similarly, invasion of six snowfield slopes began in the early 1900s and continued into snowfield centers throughout the 20th century, with significantly accelerated mean invasion from 1925 to 1940 and after 1980. Rate of snowfield invasion decreased bet...
154 citations
TL;DR: In this paper, the authors analyzed the 20th-century fluctuations of glaciers in the Cordillera Blanca in Peru and found that the total ice coverage around 1990 was obtained using optical satellite data SPOT XS.
Abstract: The value of glacier fluctuations as indicators of climate change detection has been increasingly recognized in recent years. Tropical glaciers are of particular interest. The Cordillera Blanca in Peru (77°30′W, 9°S) is the largest glaciated area within the tropics. Its 20th-century fluctuations have been analyzed. The total ice coverage around 1990 was obtained using optical satellite data SPOT XS. Based on the 1990 results, inventories and estimates of the glaciation during the 20th century had to be corrected. The data in this paper illustrate the general ice retreat in the tropical Cordillera Blanca: 620 km2 in 1990, 660–680 km2 in 1970, and 800–850 km2 in 1930. The 1930 value documents the extent of glaciation shortly after an intense advance in the 1920s. The Little Ice Age extent is estimated as 850–900 km2. The ice recession during the 20th century was not constant but was concentrated in two periods. Strong ice retreat occurred in the 1930s and 1940s and intermediate retreat from the mid...
150 citations
TL;DR: In this paper, vegetation changes in the Nordic mountain birch forest in northern Norway, covering a period of more than 40 years, were investigated and a significant change in vegetation cover during the study period was registered in the whole study area.
Abstract: The study focuses on vegetation changes in the Nordic mountain birch forest in northern Norway, covering a period of more than 40 yr. The study area comprises the municipalities of Kautokeino and Karasjok on Finnmarkskvidda; it is predominantly covered by lichen and dwarf shrub vegetation. Sizes of various vegetation classes were estimated by the use of remote-sensing techniques and ground surveys. A significant change in vegetation cover during the study period was registered in the whole study area. Vegetation types dominated by bilberry (Vaccinium myrtillus), wavy hair-grass (Deschampsia fleuxuosa), the dwarf cornel (Cornus suecica), and mosses have tripled in abundance compared to 40 yr ago. In contrast, lichen-dominated heaths and woodland (forests), preferred by the reindeer stocks intensively utilizing these areas of Finnmarksvidda, have decreased by approximately 80% in abundance during the same period. Correspondingly, there has been a significant increase in the extent of birch forests ...
133 citations
TL;DR: A 1977 tundra fire burned a hillslope where pre-fire soils and vegetation ranged from poorly drained moist tussock-shrub tundras on the lower slopes to well-drained dwarf shrub Tundra on the back slope and very poorly drained wet sedge meadow on the flat crest as discussed by the authors.
Abstract: A 1977 tundra fire burned a hillslope where prefire soils and vegetation ranged from poorly drained moist tussock-shrub tundra on the lower slopes to well-drained dwarf shrub tundra on the back slope and very poorly drained wet sedge meadow on the flat crest. We sampled the vegetation on this slope before the fire and at 8 sites following the fire at irregular intervals from 1 yr to 25 yr. During the first decade after the fire, short-term recovery was dominated by bryophytes, sedges, and grasses from both regrowing sedge tussocks and seedlings. However, during the second and third decade, and by 24 yr after the fire, evergreen (Ledum palustre) and deciduous shrubs (mainly Salix pulchra willow) expanded dramatically so that shrub cover was generally higher than before the fire. Labrador tea has increased by vegetative means on the poorly drained lowest 3 tussock-shrub tundra sites. Upslope on the better-drained and more severely burned tussock-shrub and dwarf shrub tundra sites, willows became es...
112 citations
TL;DR: This paper assess the impact of winter climate on the population dynamics of an isolated herd of Svalbard reindeer near Ny-Alesund with a retrospective analysis of past winter snowpack.
Abstract: Winter climate is a key factor affecting population dynamics in high-arctic ungulates, with many studies showing a strong negative correlation of winter precipitation to fluctuations in population growth rate. Terrestrial ice crust or ground-ice can also have a catastrophic impact on populations, although it is rarely quantified. We assess the impact of winter climate on the population dynamics of an isolated herd of Svalbard reindeer near Ny-Alesund with a retrospective analysis of past winter snowpack. We model landscape-scale snowpack and ground-ice thickness using basic temperature and precipitation data in a simple degree-day model containing four adjustable parameters. Parameter values are found that lead to model snow and ground-ice thicknesses which correlate well with three different model targets: reindeer population growth rates; April snow accumulation measurements on two local glaciers; and a limited number of ground-icing observations. We explain a significant percentage (80%) of th...
110 citations
TL;DR: In this paper, the authors examined three ecotypes associated with roads and found that the dominant exotic found in these ecotypes was Achillea millefolium (yarrow), which had significantly higher soil pH and exchangeable levels of calcium and potassium than natural areas.
Abstract: The construction and maintenance of roads in the Australian Alps has caused profound disturbance to the natural existing soil and vegetation, as well as the introduction and proliferation of exotic plant species. This study examined three ecotypes associated with roads. These ecotypes were tested for differences in soil characteristics and occurrence of different plant species. Differences in chemical and physical soil properties were found between road verges and adjacent native vegetation areas. Soils from natural areas had higher humus levels, less gravel and sand, higher levels of nutrients, and higher pH and electrical conductivity than road verges. A relationship was found between soil properties and the occurrence of different exotic plant species along roadsides. Exotics dominated in areas along the road verge and road drainage lines. The dominant exotic found in these ecotypes was Achillea millefolium (yarrow). These ecotypes were characterized by high water and sediment wash off, which had significantly higher soil pH and exchangeable levels of calcium and potassium than natural areas and disturbed areas without yarrow.
101 citations
TL;DR: A network of 14 meteorological stations was installed across the Annapurna Range in central Nepal in 1999 and expanded in subsequent years to 19 stations in order to measure snow depths and water equivalents in high-altitude sites as mentioned in this paper.
Abstract: Knowledge of spatial and altitudinal variations in precipitation in high mountains is integral to quantifying alpine climates and to calibrating interactions between climate and surface processes. To date, however, few meteorological networks exist in alpine settings. A network of 14 meteorological stations was installed across the Annapurna Range in central Nepal in 1999 and expanded in subsequent years to 19 stations. In order to measure snow depths and water equivalents in high-altitude sites, a combination of look-down distance rangers and gamma-ray loggers was installed at 5 sites. The data from this network delineate a strong south-to-north gradient in monsoonal precipitation. Precipitation peaks at 5032 mm yr−1 at about 3000 m altitude on the southern side, which is also approximately the lowest altitude of winter snow in the area. Annual precipitation decreases to ∼1100 mm yr−1 in the rain shadow to the north of the Himalayan crest. Although snow depth and snow water equivalent content ar...
93 citations
TL;DR: In this paper, the authors measured pine latewood width, density, and stable carbon isotope ratios at two sites, separated in altitude by 400 m, close to the forest limit on a south-facing slope in the western French Alps.
Abstract: Pine latewood width, density, and stable carbon isotope ratios were measured at two sites, separated in altitude by 400 m, close to the forest limit on a south-facing slope in the western French Alps. The signal to noise ratio in the δ13C series from each site is higher than that of either of the growth proxies. When the sites are combined, the high-frequency climate signal in the δ13C series is enhanced, whereas in both the ring width and density series it is weakened. Because regional climate dominates over local site conditions, δ13C ratios from long pine chronologies will provide a better indicator of past climate than either ring widths or densities. At dry Alpine sites, δ13C values are controlled mainly by stomatal conductance, which is linked to summer moisture stress and thus antecedent precipitation.
90 citations
TL;DR: In this paper, the authors measured snow depth and density from groomed ski pistes (runs) with compacted snow and their effects on ground temperatures and timing of snowmelt, and analyzed groomed pistes with and without artificial snow (10 each) as well as adjacent ungroomed off-piste control plots beside the piste.
Abstract: Increasing production of artificial snow in ski resorts is controversially discussed, but only few investigations have been carried out systematically to specify the environmental impacts. We measured snow depth and density from groomed ski pistes (runs) with compacted snow and their effects on ground temperatures and timing of snowmelt. We analyzed groomed pistes with and without artificial snow (10 each) as well as adjacent ungroomed off-piste control plots beside the piste. On pistes with natural snow, the thin and compacted snow cover led to severe and long lasting seasonal soil frost. On pistes with artificial snow, soil frost occurred less frequently because of increased insulation due to the greater snow depth. However, due to the greater snow mass, the beginning of the snow-free season was delayed by more than 2 wk. Average winter ground temperatures under a continuous snow cover were decreased by approximately 1°C on both piste types compared with off-piste control plots. The results sug...
84 citations
TL;DR: In this article, a tree-ring-based avalanche chronology for three scree slope stands in the northern Gaspe Peninsula (Quebec) was provided, which indicated that high-magnitude avalanches occurred seven times during the period from 1860 to 1997, i.e., in 1871, 1898, 1952, 1956, 1966, 1977, and 1996, with 5- to 15-yr return intervals for the period between 1939 and 1997.
Abstract: In eastern Canada, snow avalanches are a common phenomenon, but their occurrences remain poorly documented. In the last 30 yr, they were responsible for deaths and damage to property and forests in avalanche-prone areas in northern and eastern Quebec. This study provides tree-ring–based avalanche chronologies for three scree slope stands in the northern Gaspe Peninsula (Quebec). Tree-ring records indicated that high-magnitude avalanches occurred seven times during the period from 1860 to 1997, i.e., in 1871, 1898, 1952, 1956, 1966, 1977, and 1996, with 5- to 15-yr return intervals for the period between 1939 and 1997. High-magnitude avalanches occurred during snowy winters, with total snowfall well above average (330 cm). According to the size of past runout zones established from damaged trees at the main study stand, snow avalanches were greater in 1956 and 1966 than in 1996. The 1996 avalanche area was about 16,600 m2 of which 60% (10,000 m2) was covered with mature trees. It caused a ∼200-m r...
TL;DR: In this article, the authors investigated the provenance of dissolved organic carbon (DOC) from surface waters in glacial and nonglacial catchments and investigated the flow routing of runoff from both environments.
Abstract: The concentration and fluorescence characteristics of dissolved organic carbon (DOC) from surface waters in glacial and nonglacial catchments were used to investigate the provenance of DOC and flow routing of runoff from glacial and nonglacial environments. Seasonal trends in DOC concentration and fluorescence in the Bow River indicate that DOC in nonglacial runoff originates primarily from soil and plant organic matter that is flushed to the stream by shallow subsurface flow at the onset of snowmelt. Snowmelt in ice-free areas of the glacial catchment also appears to be routed through the shallow subsurface, but this snowmelt runoff has much less contact with organic soils or litter, than snowmelt runoff from the nonglacial catchment. The fluorescence of DOC in the Glacial stream in summer (when most runoff originates from ice-covered areas), suggests that DOC from glaciated regions is more “microbial” in character than that derived from ice-free areas. Summer rainstorms in the Glacial catchment...
TL;DR: In this article, the authors experimentally warmed patches of High Arctic tundra with infrared heating in Northeast Greenland and found that experimental warming significantly increased green cover, for example, at the time of peak cover, the total green cover was enhanced from 59.1 to 67.3%.
Abstract: Lengthening of the growing season at high latitudes, observed by satellites with the Normalized Difference Vegetation Index (NDVI), has been ascribed to climate warming. To test this assumption, and to verify whether changes in vegetation greenness are quantitative or qualitative, we experimentally warmed patches of High Arctic tundra with infrared heating in Northeast Greenland. By analyzing digital images of the vegetation, changes in cover were distinguished from changes in senescence. During the season, experimental warming significantly increased green cover, for example, at the time of peak cover, the total green cover was enhanced from 59.1 to 67.3%. The dominant wavelength (hue) reflected by our tundra plots shifted from yellow-green to yellow. Experimental warming with 2.5°C delayed this hue-shift by 15 d. The results demonstrate that higher summer temperatures do not only promote plant growth at these latitudes but also retard and/or postpone the senescence process, contrary to indicati...
TL;DR: The cell volume biomass and diversity index are relatively smaller on the Patagonian glacier than those in algal communities on Alaskan and Himalayan glaciers.
Abstract: We quantitatively investigated a snow algal community on Tyndall Glacier of the Southern Patagonia Icefield, Chile, at an elevation from 300 to 1500 m a.s.l. We observed 7 species of snow and ice algae (Chlorophyta and cyanobacteria) on the glacier. These species were Mesotaenium (M.) berggrenii, Cylindrocystis (Cyl.) brebissonii, Ancylonema sp., Closterium sp., Chloromonas sp., Oscillatoriaceae cyanobacterium, and an unknown alga. The spatial distribution of these algae differed among the species. M. berggrenii, Cyl. brebissonii, Ancylonema sp., and Closterium sp. appeared mainly in the lower-elevation area (370–770 m a.s.l.), the unknown alga in the higher-elevation area (900–1500 m a.s.l.), and Chloromonas sp. and Oscillatoriaceae cyanobacterium in the middle part of the glacier. The mean cell concentration and total cell volume biomass ranged from 0 to 9.2 × 104 (mean: 1.8 × 104) cells mL−1, from 0 to 327 (mean: 63) μL m−2, respectively. The cell volume biomass generally decreased with altitu...
TL;DR: Using a simulation model, the accuracy of age estimates was shown to vary with temporal variation in plant growth rate and plant size, and the model remains a valuable tool for estimating plant ages in an environment where many related techniques can not be applied.
Abstract: Plant species with morphological features that enable the age of individuals to be estimated are potentially useful for understanding past environmental conditions. Here, the size and growth rate of the cushion plant, Azorella selago Hook. (Apiaceae), are examined to determine if an accurate and reliable age can be assigned to individual plants using the phytometric model detailed by Frenot et al. (1993). Plant size, growth rate, epiphyte load, nearest-neighbor characteristics, and spatial position (used as a surrogate, to encompass a range of abiotic conditions to which plants were exposed) were measured at three sites. Additionally, variation in some of these variables was quantified across three altitudinal transects. Relationships were examined using regression, trend surface and partial regression approaches. Growth rate was independent of plant size, differed between sites, and was related to abiotic as well as other biotic factors. As a result, the phytometric model's age estimates may be ...
TL;DR: In this paper, all obtained data have been summarized and analyzed in order to review possible temporal trends for selected atmospheric contaminants at Svalbard, and only those organochlorines exhibiting significant statistically confirmed temporal trends were chosen for the present comparison.
Abstract: As a part of the national Norwegian monitoring program, long-term surveys of contaminants have been carried out at the Zeppelin atmospheric research station (Ny-Alesund, Svalbard ) since the early 1990s In the present study, all obtained data have been summarized and analyzed in order to review possible temporal trends for selected atmospheric contaminants at Svalbard The following heavy metals were determined in aerosols: Pb, Cd, Hg, Cu, Zn, Cr, Ni, Co, Mn, V, and As Only Ni showed a decreasing trend in the concentrations over the past decade Organochlorine compounds in combined gaseous phase and aerosol samples evaluated were the following: α-HCH (hexachlorocyclohexane), γ-HCH, HCB (hexachlorobenzene), and sum-DDT (dichlorodiphenyltrichloroethane) Only those organochlorines exhibiting significant statistically confirmed temporal trends were chosen for the present comparison Thus, although polychlorinated biphenyls (PCBs) as well as chlordanes are routinely monitored at the Zeppelin statio
TL;DR: Both Andean and Antarctic plants increased soluble sugars with increasing acclimation time, but it did not differ between populations, and the mechanistic basis of the higher survival to freezing of Antarctic plants was not elucidated.
Abstract: Colobanthus quitensis is one of only two vascular plant species that occur in the Antarctic islands. We evaluated morphological and physiological traits and survival after freezing in individuals of C. quitensis collected in two populations: one from the Andes of central Chile and the other from the maritime Antarctic. We addressed whether these populations are ecotypes in terms of shoot morphology and physiology, and cold resistance. We also evaluated genetic differentiation at the internal transcribed spacer (ITS) regions. Under controlled growing conditions, Andean plants had longer and narrower leaves and longer peduncles. However, shoot biomass was similar in both populations. There was a 1.17% sequence divergence of ITS regions between populations. Survival to freezing at temperatures from 0° to −16°C was not different in nonacclimated plants. After cold-acclimation at 4°C, freezing tolerance was greater in Antarctic plants. Both Andean and Antarctic plants increased soluble sugars with inc...
TL;DR: In this paper, the authors show that patch structures in high mountain Mediterranean vegetation are a consequence of facilitative and competitive interactions in a very harsh environment which ultimately involve strong localized effects on soil properties.
Abstract: Vegetation in high Mediterranean mountains usually consists of patchy communities. Patch structures have been interpreted as a result of the prevalence of facilitation phenomena in highly stressful environments. Several mechanisms have been proposed in order to explain the factors that control the existence of these clumped structures. However, they have not been evaluated in these mountains. Our hypothesis is that patchy structure in high mountain Mediterranean vegetation is a consequence of facilitative and competitive interactions in a very harsh environment which ultimately involve strong localized effects on soil properties. Our results show that levels of soil nutrients were higher under vegetation patches than in bare ground areas, confirming the hypothesis of an amelioration of soil resources under canopies. Pairwise associations and repulsions suggest the existence of two contrasting composition stages. Contrasting models relating patch species composition (cover and biomass) and soil resources indicated a weak relationship between species features and soil nutrient levels. Finally, structural modeling showed that patch size has a relevant but indirect effect on soil resource levels through grass and total biomass. We conclude that patch structure and dynamics in high Mediterranean mountain communities may be partly controlled by an endogenous process involving facilitation and competition for soil key resources. These interactions may operate through some community traits related to patch size but not to composition.
TL;DR: In this paper, a digital elevation model (DEM) of the ice cap surface was used to delineate interior ice divides allowing patterns of change to be investigated at the drainage basin scale, and strong correlation between the hypsometric characteristics of drainage basins and the observed changes in ice-cap geometry suggests that these changes reflect interbasin differences in the inherent sensitivity of glacier mass balance to...
Abstract: Image data from the years 1959/1960 and 1999/2000 reveal a 2.4% decrease in the surface area of the Devon Ice Cap, Nunavut, over the last 40 yr. This has resulted primarily from extensive retreat of tidewater glacier margins on the eastern side of the ice cap, and shrinkage of its near-stagnant southwestern arm. Thinning of the ice cap has also increased bedrock exposure in the ice cap interior. However, since 1960 the northwestern margin of the ice cap has advanced slightly. Volume loss associated with these changes was estimated at −67 ± 12 km3 as calculated from two independent techniques. A digital elevation model (DEM) of the ice cap surface was used to delineate interior ice divides allowing patterns of change to be investigated at the drainage basin scale. Strong correlation between the hypsometric characteristics of drainage basins and the observed changes in ice-cap geometry suggests that these changes reflect interbasin differences in the inherent sensitivity of glacier mass balance to ...
TL;DR: In this paper, a comparison of digital elevation models, GPS, and optical survey data revealed high thinning rates for all the ablation areas of the glaciers, with average values between 1.4 and 3.4 m a−1 and maximum ice thinning of 7.6 m a −1.
Abstract: Ice elevation changes since 1975 and ice areal changes since 1945 of glaciers in the southeastern part of the Southern Patagonia Icefield (SPI) are presented. Comparison of digital elevation models, GPS, and optical survey data revealed high thinning rates for all the ablation areas of the glaciers, with average values between 1.4 and 3.4 m a−1 and maximum ice thinning of 7.6 m a−1. Ice elevation changes for the glacier accumulation areas were smaller than the estimated errors, and no significant trends could be detected. All the glaciers are retreating and shrinking considerably, with a total areal loss of 62.2 km2, which represents 8% of the total ice area of 1945. This trend is in agreement with other similar measurements carried out during recent decades for several glaciers of the SPI. The high thinning rates for the ablation areas of the SPI have been primarily interpreted as a result of the increase in temperature observed in the region, however, this warming trend is not large enough to a...
TL;DR: In this article, the authors examined soil microbial activities, i.e., biomass, respiration rate, and temperature dependence of the respiration on a glacier foreland in Ny-Alesund, Svalbard, Norway.
Abstract: We examined soil microbial activities, i.e., biomass, respiration rate, and temperature dependence of the respiration on a glacier foreland in Ny-Alesund, Svalbard, Norway. We collected soil samples from 4 study sites that were set up along a primary succession (Site 1, the youngest, to Site 4, the oldest). Microbial biomass measured with the SIR method increased with successional age (55 to 724μg Cbiomass g−1 soil d.w. from Site 1 to Site 4). The microbial respiration rate of the soil was measured in a laboratory with an open-flow infrared gas-analyzer system, changing the temperature from 2° to 20°C at 3–4° intervals. The microbial respiration rate increased exponentially with the temperature at all sites. The temperature dependence (Q10) of the microbial respiration rate ranged from 2.2 to 4.1. The microbial respiration rates at a given temperature increased with succession as a step change (0.48, 0.43, 1.26, and 1.29μg C g−1soil h−1 at 8°C from Site 1 to Site 4, respectively). However, the su...
TL;DR: The response of testate amoebae to nitrogen and phosphorus addition in an Arctic fen, at Toolik Lake Long-Term Experimental Research (LTER) Station, Alaska, suggests that testates respond to nutrient manipulations in the Arctic
Abstract: There are few data on the effect of long-term manipulations on soil protozoa, and almost nothing is known about soil protozoa in Alaska. I studied the response of testate amoebae to nitrogen and phosphorus addition in an Arctic fen, at Toolik Lake Long-Term Experimental Research (LTER) Station, Alaska. Testate amoebae were extracted from Sphagnum mosses in control and fertilized plots. Of the 35 testate amoebae taxa recorded, 7 are first observations for the Arctic (excluding Russia) and 14 for Alaska. The total density and biomass of testate amoebae were significantly reduced, by 77% and 84%, in the fertilized plots. The structure of testate amoebae communities was also modified in those plots, although for most taxa the changes were not significant. Four taxa (Amphitrema flavum, Assulina muscorum, Placocista spinosa ssp. hyalina, and Hyalosphenia papilio) accounted for over half of the population in the control plots but only for 11% in the N and P plots. The densities of A. muscorum and Difflu...
TL;DR: It is suggested that root colonization of any particular mycorrhizal species may yield different gradient patterns with altitude than the relative coverages of mycor Rhizal and nonmycorrhIZal plant taxa.
Abstract: Mycorrhizal symbiosis is generally advantageous for plants in nutrient-poor soils, but this advantage may be low in arcto-alpine conditions. While the relative coverage of nonmycorrhizal plant species has been found to increase along an altitudinal gradient, the within-species patterns of mycorrhizal colonization in arctic and alpine plants are not well known, and different results have been obtained in relation to altitude. We investigated arbuscular mycorrhizal (AM) and dark-septate endophytic (DSE) root colonization in six subarctic herbaceous plants Ranunculus glacialis L., Saxifraga aizoides L., Sibbaldia procumbens L., Solidago virgaurea L., Trientalis europaea L., and Viola biflora L. along an altitudinal gradient (0–1400 m a.s.l.) at Mt. Paras, North Norway. We did not find any consistent decline in the different types of fungus colonization along the entire gradient. There was no statistically significant shift in coarse AM or DSE colonization with altitude. However, fine endophyte type ...
TL;DR: In this paper, the authors investigated the relationship of the vegetation in Karkevagge, an alpine ecosystem in the subarctic, to soil properties and found that at the lowest elevations, on stable portions of the landscape dominated by Betula and Empetrum, Spodosols developed in glacio-fluvial sediments, and Cryosaprists occur in scattered bedrock depressions with bog-type vegetation.
Abstract: Karkevagge, an alpine ecosystem in the subarctic, has been the subject of scientific study for half a century. We investigated the relationship of its vegetation to soil properties. At the lowest elevations, on stable portions of the landscape dominated by Betula and Empetrum, are found Spodosols developed in glacio-fluvial sediments. Cryosaprists occur in scattered bedrock depressions with bog-type vegetation. Cryofluvents are found in flood-prone areas covered by dwarf-willow thickets. Intermediate elevations have meadow-type vegetation with Cryofluvents on floodplains and on lower colluvial slopes, Cryaquents in wetter areas, and Cryorthents on steeper soliflucted slopes. Above that, on steep, west-facing Dryas-covered colluvial slopes, soils are Ca-rich Eutrocryepts and Haplocryolls. The highest-elevation soils are infertile with poor horizonation, despite their possible antiquity, and vegetation that is largely cryptogams. Dystrocryepts occur on more stable alpine locations; Cryorthents on s...
TL;DR: In this paper, the effect of a 2.5°C temperature increment, induced by controlled infrared irradiation, on various components of the carbon balance of a High Arctic tundra ecosystem at Zackenberg in Northeast Greenland (74°N, 21°W) over the 1999 growing season was studied.
Abstract: Tundra ecosystems constitute large stocks of carbon and might therefore, if climate warming releases CO2, induce positive feedback and amplify temperature increase. We studied the effect of a 2.5°C temperature increment, induced by controlled infrared irradiation, on various components of the carbon balance of a High Arctic tundra ecosystem at Zackenberg in Northeast Greenland (74°N, 21°W) over the 1999 growing season. Gross photosynthesis (Pgross), belowground respiration (Rsoil), and canopy respiration (Rcanopy) were regularly determined with closed dynamic CO2 exchange systems, and the whole-growing season C-balance was reconstructed by relating these components to potentially controlling factors (green cover, soil moisture, radiation, soil and canopy temperature, and thawing depth). Thawing depth and green cover increased in heated plots, while soil moisture was not significantly affected. Pgross increased 24.2%, owing to both a green cover and a physiological influence of warming. Belowgroun...
TL;DR: In this article, the authors investigated how growing season carbon (C) balance was affected by the major climatic factors that are expected to change in the future, and found that respiration was the main determinant of C balance, and that variations in light levels and temperature could alter the balance between C uptake and C loss.
Abstract: Carbon dioxide fluxes in a dry subarctic heath were examined after 10 and 11 yr of experimental manipulations of temperature, light, and nutrients. The aim was to investigate how growing season carbon (C) balance was affected by the major climatic factors that are expected to change in the future. Carbon flux was measured in closed chambers as uptake through gross ecosystem production (GP), release through ecosystem respiration (ER), and as net ecosystem production (NEP). Diurnal NEP through a day with clear skies at peak growing season was consistently negative through all treatments the first year of measurement, and day-time NEP varied around zero at eight days across the growing season the second year, implying that a net release of C from the ecosystem to the atmosphere may take place during the growing season. Our results suggest that respiration was the main determinant of C balance, and that variations in light levels and temperature could alter the balance between C uptake and C loss. Fertilization strongly enhanced both ER and GP whereas temperature enhancement changed neither ER nor GP. Shading decreased both ER and GP. After harvest of the aboveground plant biomass, the belowground respiration was 72 to 93% of the ER before harvest. The significant treatment effects on belowground respiration after harvest were similar to the effects on ER before harvest. These results suggest that the ER were mainly from belowground respiration, and that the treatments affected the belowground respiration more than the respiration above ground.
TL;DR: The relative effect of facilitation and resource competition by surrounding dwarf shrubs on Carex bigelowii in two contrasting arctic-alpine tundra heathlands was investigated to improve understanding of arctic and alpine plant communities.
Abstract: Positive interactions in alpine plant communities have been reported to increase in importance with increasing altitude and exposure. Positive and negative interactions between plants might occur simultaneously, so the net plant-plant interaction is determined by the balance between positive and negative effects. I investigated the relative effect of facilitation and resource competition by surrounding dwarf shrubs on Carex bigelowii in two contrasting arctic-alpine tundra heathlands. Carex bigelowii was positively associated with dwarf shrubs on an exposed mountain ridge but negatively associated with dwarf shrubs on a protected heath. A removal experiment indicated that positive associations at the exposed site are the result of facilitation of C. bigelowii by the dwarf shrub canopy. Our understanding of arctic and alpine plant communities can be enhanced by regarding plant interactions as combinations of positive and negative components.
TL;DR: Arctic foxes are able to provide long-distance dispersal of seeds lacking morphological adaptations to dispersal, but for most species seeds need to be defecated within 12 h to remain viable.
Abstract: Arctic foxes are evaluated as seed dispersal vectors for Greenlandic plant species through a feeding experiment with subsequent scat analysis and germination test. Seeds of 22 common species with different morphology were tested. Passage time ranged between 4 and 48 h. No significant differences were detected in passage time for seeds with different morphology. Cerastium alpinum and Stellaria longipes had higher germination after passage through the fox's digestive tract when compared to controls. Sibbaldia procumbens, Oxyria digyna, and Silene acaulis were favored by passage when shorter than 10 h. Salix glauca ssp. callicarpaea, Veronica alpina, Gnaphalium norvegicum, Papaver radicatum, Ranunculus hyperboreus, Chamaenerion latifolium, Luzula parviflora, and bulbils of Polygonum viviparum and Saxifraga cernua were inhibited by passage, whereas the remaining species had germination percentage too low to allow for evaluation. Species with adaptations to wind dispersal seemed particularly vulnerabl...
TL;DR: In order to learn more about the true nature of infiltration pathways into alpine soils, dye tracer experiments were set up at 2 locations in southern Switzerland: at Hannigalp (2100 m) and at Gd St Bernard (200 m) as mentioned in this paper.
Abstract: Snowmelt infiltration into alpine soils can be severely reduced and even impeded by soil frost. In order to learn more about the true nature of infiltration pathways into alpine soils, dye tracer experiments were set up at 2 locations in southern Switzerland: at Hannigalp (2100 m) and at Gd St Bernard. Over the course of two winters (2000–2001 and 2001–2002) we excavated vertical soil profiles during snowmelt to examine the distribution of a dye tracer (Brilliant Blue FCF) that had been applied on the surface of a 7-m2 plot at the beginning of the winter. Soil conditions varied between the winters, with the soils remaining unfrozen during the first and a significant frozen layer forming during the second. With this method the dominant infiltration processes at these 2 sites were identified. During the first winter the water infiltration at Hannigalp showed a pronounced preferential behavior, whereas at Gd St Bernard we found a more homogeneous front-like infiltration. During the second winter the...
TL;DR: In this paper, the authors examined carbon dioxide exchange and nitrogen cycling over two consecutive years (winter and summer) in a grazed alpine grassland and in an embedded long-term grazing exclosure to ascertain whether grazing history had resulted in divergent soil carbon attributes, CO2 exchange rates, and different vegetation C and N and soil N processes.
Abstract: Our study examined carbon dioxide exchange and nitrogen cycling over two consecutive years (winter and summer) in a grazed alpine grassland and in an embedded long-term grazing exclosure to ascertain whether grazing history had resulted in divergent soil carbon attributes, CO2 exchange rates, and different vegetation C and N and soil N processes. Soil C and N concentrations and masses were significantly higher in the grazed than in the ungrazed area, though grass leaf N was higher in the ungrazed area, as was vegetation biomass. Detectable amounts of CO2 were lost from the grazed and ungrazed areas of this grassland during the winters of 1998, 1999, and 2000, and at 6 of 15 winter flux sample dates, CO2 efflux was greater in the grazed area than in the ungrazed area. The ungrazed area consistently gained more C during the summer months than the grazed area, with net CO2 exchange peaking in mid-July 1998 at nearly 5 μmol m−2 s−1 in the ungrazed area compared to <2 μmol m−2 s−1 in the grazed area. ...