Showing papers in "Arctic, Antarctic, and Alpine Research in 2006"
TL;DR: In this paper, a simple parameterization of the likely effects of the warming on the rate of snow melt suggests an increase across the Antarctic Peninsula ice sheet from 28 ± 12 Gt a−1 in 1950, to 54 ± 26 Gt A−1 by 2000.
Abstract: Long-term records from meteorological stations on the Antarctic Peninsula show strong rising trends in the annual duration of melting conditions. In each case, the trend is statistically significant and represents a major increase in the potential for melting; for example, between 1950 and 2000 the record from Faraday/Vernadsky Station showed a 74% increase in the number of positive degree-days (PDDs). A simple parameterization of the likely effects of the warming on the rate of snow melt suggests an increase across the Antarctic Peninsula ice sheet from 28 ± 12 Gt a−1 in 1950, to 54 ± 26 Gt a−1 by 2000. Given a similar rate of warming over the next 50 years this may reach 100 ± 46 Gt a−1. The majority of this increased meltwater does not drain into the sea but is refrozen in the ice sheet, and it is difficult to predict the fraction of ablation that will become runoff; however, a calculation based on an established criterion for runoff indicates that the contribution from the Antarctic Peninsula...
186 citations
TL;DR: In this paper, soil A horizons on alpine moraines of late-glacial (Satanta Peak) age in the Colorado Front Range were studied and the compositions of sand and silt fractions of the soils were compared to possible local source rocks, using immobile trace elements Ti, Nb, Zr, Ce, and Y.
Abstract: Surface horizons of many alpine soils on Quaternary deposits in high-mountain settings are enriched in silt. The origin of these particles has been debated, particularly in the Rocky Mountain region of North America. The most common explanations are frost shattering of coarser particles and eolian additions from distant sources. We studied soil A horizons on alpine moraines of late-glacial (Satanta Peak) age in the Colorado Front Range. Surface horizons of soils on these moraines are enriched in silt and have a particle size distribution that resembles loess and dust deposits found elsewhere. The compositions of sand and silt fractions of the soils were compared to possible local source rocks, using immobile trace elements Ti, Nb, Zr, Ce, and Y. The sand fractions of soils have a wide range of trace element ratios, similar to the range of values in the local biotite gneiss bedrock. In contrast, silt fractions have narrower ranges of trace element ratios that do not overlap the range of these ratios in biotite gneiss. The particle size and geochemical results support an interpretation that silts in these soils are derived from airborne dust. Eolian silts were most likely derived from distant sources, such as the semiarid North Park and Middle Park basins to the west. We hypothesize that much of the eolian influx to soils of the Front Range occurred during an early to mid-Holocene warm period, when sediment availability in semiarid source basins was at a maximum.
119 citations
TL;DR: In this paper, the influence of comparable unequal environmental conditions on primary vegetation succession in an alpine glacier valley by means of transects was assessed by measuring the progressions of alpha and beta diversity.
Abstract: The aim of this study was to assess the influence of comparable unequal environmental conditions on primary vegetation succession in an alpine glacier valley by the means of transects. Two longitudinal transects were established along the glacier foreland of the Rotmoosferner, Tyrol, Austria, and two transverse transects were established across the valley on the 1923 and 1858 moraines. The progressions of alpha- and beta-diversity were compared, and vegetation data within the glacier foreland were analyzed. Moraine age emerged as the primary factor within a canonical correspondence analysis (CCA), while the second axis separated the two valley sides. A clearly differentiated development of plant communities became obvious especially within the early development stages. Early development of vegetation cover and alpha diversity was further developed on the shaded valley side, and progression of beta diversity differed significantly among the valley sides. The results indicate two different successi...
112 citations
TL;DR: In this article, the root zone temperature and associated metabolism appear to determine tree growth at low elevation permafrost ground, regardless of shoot temperatures, and they showed that the low elevation study site resembles thermal conditions typical for the high elevation treeline.
Abstract: Trees have a common high elevation distribution limit at similar soil temperatures across the globe. Here we tested whether low temperature in the root zone alone can induce the well known dwarfing at the low temperature growth limit of trees by using a “natural experiment” with trees growing on low elevation permafrost ground. At the natural high elevation treeline, both air (shoot) and soil (root) temperature are low, while at the montane permafrost site in the Swiss Jura mountains, roots are cold, but not shoots. Soil temperature records confirmed that the low elevation study site resembles thermal conditions typical for the high elevation treeline. The warm air conditions have no ameliorating effect on tree growth. Irrespective of shoot temperatures, the root zone temperature and the associated metabolism appear to determine tree growth at this site. The test revealed a critical role of soil temperature, which by itself is sufficient to explain a growth limit of trees associated with a season...
99 citations
TL;DR: In this paper, the authors studied the responses of seven alpine vascular plant species during 2001 and found that the start of the reproductive development was not directly linked with the date of snowmelt, but rather with the cumulative energy input.
Abstract: Low temperatures and the short growing season in high altitude snow patches in temperate mountains constrain life cycles and reproduction of snowbed species. This leads to a highly adapted timing of sexual reproduction. Winter precipitation and temperature, the main factors determining growing season length, are predicted to change with global warming. To understand their impacts on plant phenology, we studied the responses of seven alpine vascular plant species during 2001. Temperature had a clear impact on phenological patterns. The start of the reproductive development was not directly linked with the date of snowmelt, but rather with the cumulative energy input. In addition, photoperiodism may also contribute to the control of plant development through an increasing temporal adjustment of phenology until flowering.
94 citations
TL;DR: In this article, the authors measured N-fixation of plant-soil cores by the acetylene reduction technique at different topographic positions in an upland tundra watershed, Imnavait Creek, through two growing seasons.
Abstract: Atmospheric nitrogen (N) fixation is a key N input to arctic ecosystems, but relatively few estimates of annual N-fixation rates are available. We measured N-fixation of plant-soil cores by the acetylene reduction technique at different topographic positions in an upland tundra watershed, Imnavait Creek, through two growing seasons in order to evaluate spatial and temporal variation in N-fixation. We also examined the effects of light and temperature on N-fixation to estimate annual N-fixation rates of surface soil in this watershed using field meteorological data. Surface soil at Imnavait Creek had significant acetylene reduction potential throughout the watershed (generally 6 to 10 μmol C2H4 m−2 h−1), indicating that N-fixing organisms were present everywhere. Although acetylene reduction potential was roughly constant through the growing season, moisture, temperature and light intensity strongly affected the measured acetylene reduction rates in laboratory incubations. In addition, the relativ...
83 citations
TL;DR: In this paper, the authors assess whether increased anthropogenic nitrogen (N) deposition from distant sources is contributing to directional changes in the biogeochemistry and ecology of two remote lakes on Baffin Island in the eastern Canadian Arctic.
Abstract: Although arctic lakes rank among the most pristine ecosystems remaining on Earth, widespread paleoecological analyses have revealed rapid recent changes in lake ecology that largely surpass Holocene natural variability and that are generally attributed to climate warming since the end of the Little Ice Age. However, the possibility that climate is only one dimension of these unprecedented ecological shifts remains an untested possibility, especially given that current warming may not yet exceed maximum, naturally mediated, postglacial warmth. In this paper, we assess whether increased anthropogenic nitrogen (N) deposition from distant sources is contributing to directional changes in the biogeochemistry and ecology of two remote lakes on Baffin Island in the eastern Canadian Arctic. Paleolimnological analyses, including diatom assemblages and a suite of biogeochemical proxies (total organic matter, biogenic silica, organic N and C contents, and stable isotopic ratios) reveal a complex suite of pr...
80 citations
TL;DR: In this article, a new GIS-based glacier inventory was produced using a combination of ASTER and Landsat remotely sensed images and paper maps, with a total of 150 glaciers were digitized, with 19 of these (12.6%) being classified as surge-type.
Abstract: Surge-type glaciers experience cyclic flow instabilities characterized by alternating periods of slow and fast flow. The geographical distribution of surge-type glaciers has been shown to be distinctly non-random in that they are clustered in some regions yet are completely absent from others. In order to identify factors that influence glacier surging, a number of environmental and glacial attributes were examined for an area in the Karakoram Himalaya, Central Asia. A new GIS-based glacier inventory was produced using a combination of ASTER and Landsat remotely sensed images and paper maps. A total of 150 glaciers were digitized, with 19 of these (12.6%) being classified as of surge-type. Attribute data for 10 glacial and environmental attributes were recorded either during the digitization phase or extracted automatically from the GIS. Simple data visualization techniques revealed a positive correlation between glacier surging and glacier length, area, perimeter size, average width, debris cove...
79 citations
TL;DR: A 2.2 km-long, 4 m-high snow fence was constructed east of the coastal village of Barrow, Alaska as discussed by the authors, and the results of the 6-yr study indicate that soil temperatures beneath the drift are 2 to 14°C warmer than the control in winter due to the insulting effects of the snow.
Abstract: In autumn 1997, a 2.2 km-long, 4 m-high snow fence was constructed east of the coastal village of Barrow, Alaska. A large drift develops each winter on the downwind side of the fence, and a smaller drift forms upwind. To monitor the thermal impact on ice-rich permafrost, nine monitoring sites were installed near the fence in 1999 to measure soil temperature at 5, 30, and 50 cm; an additional three sites were located in the undisturbed tundra as a control. Maximum thaw and snow depth were measured annually. The results of the 6-yr study indicates that soil temperatures beneath the drift are 2 to 14°C warmer than the control in winter due to the insulting effects of the snow. Since the drift persists 4 to 8 wk after snow has disappeared from the undisturbed tundra, soil thaw is delayed and soil temperatures in summer are 2 to 3°C cooler than the control. The mean soil temperature over the 6-yr period of record has warmed 2 to 5°C, and the upper permafrost has thawed. The ground surface has experien...
74 citations
TL;DR: In this article, the authors investigated soil changes (primarily on the basis of soil types) in the proglacial area Morteratsch to derive time trends that can be used as a basis for spatial modeling.
Abstract: Proglacial areas in the Alps usually cover a time span of deglaciation of about 150 years (time since the end of the “Little Ice Age” in the 1850s). In these proglacial areas soils have started to develop. In view of the foreseeable climate change, the time factor is of growing interest with respect to the landscape and consequently the soil development. We investigated soil changes (primarily on the basis of soil types) in the proglacial area Morteratsch (Swiss Alps) to derive time trends that can be used as a basis for spatial modeling. Differences in the soil development could be primarily interpreted in view of the time scale and topography (landscape shape, slope, aspect). Data was managed with GIS and regression analyses. Input data sets were the digital soil map, the glacial states, and the digital elevation model. The calculations were done raster based (GRID, 20 m resolution). After about 20 years the first signs of soil development could be found. Around 25% of the area of the valley fl...
74 citations
TL;DR: In this paper, the impacts of early spring snow cover extent and temperature during the growing season on the annual radial growth in arctic willow (Salix arctica Pallas) in the Zackenberg valley, High Arctic Northeast Greenland were analyzed.
Abstract: Using a combination of microscopic examination and electronic scanning and printing, we analyzed the impacts of early spring snow cover extent and temperature during the growing season on the annual radial growth in arctic willow (Salix arctica Pallas) in the Zackenberg valley, High Arctic Northeast Greenland. So far, only little dendroclimatological research has been conducted on Salix arctica, and the species constitutes a yet-untapped resource for climate reconstruction in the Arctic. We obtained reliable annual radial growth measurements from a total of 43 Salix arctica stem samples and analyzed these in a mixed model to determine the limiting climatic factors. We found that early spring snow cover extent impacted the annual growth significantly, whereas variable temperature regimes seemed unimportant. Following the building of a site chronology for the Zackenberg valley, the early spring snow cover extent during the last century was reconstructed.
TL;DR: In this paper, the abundance and fluorescence characteristics of dissolved organic carbon (DOC) were investigated at John Evans Glacier and Outre Glacier, Canada, and Victoria Upper Glacier, Antarctica.
Abstract: The biogeochemical cycling of organic carbon (OC) has important implications for aquatic system ecology because the abundance and molecular characteristics of OC influence contaminant transport and bioavailability, and determine its suitability as a substrate for microbial metabolism. There have been few studies of OC cycling in glacier systems and questions remain regarding the abundance, provenance, and biogeochemical transformations of OC in these environments. To address these questions, the abundance and fluorescence characteristics of dissolved organic carbon (DOC) were investigated at John Evans Glacier and Outre Glacier, Canada, and Victoria Upper Glacier, Antarctica. These systems are characterized by different thermal and hydrological regimes, and have different potential DOC sources. Where possible, samples of supraglacial runoff, glacier ice and basal ice, and subglacial meltwater were collected. The DOC concentration in each sample was measured (high-temperature combustion and non-di...
TL;DR: In this article, a simple wind model was used to simulate topographic effects on the surface wind field and calculated spatially variable sensible and latent turbulent heat fluxes for a small (63 km2) research catchment dominated by open tundra vegetation.
Abstract: Turbulent sensible and latent heat exchanges play an important role in melting snow covers, contributing 30–40% of overall melt energy with daily values reaching over 50% on warm, cloudy days (Morris, 1989). The spatial variability of these turbulent fluxes across a basin and the relative importance of the differences is not well known. This paper specifically addresses small-scale variabilities in sensible and latent energy fluxes related to topographically induced wind speed variations. A simple wind model was used to simulate topographic effects on the surface wind field. Hourly wind observations were areally distributed by the model and used to calculate spatially variable sensible and latent turbulent heat fluxes for a small (63 km2) research catchment dominated by open tundra vegetation. Simulations showed that, even though the study area is characterized by relatively low relief (average slope 3°), the small-scale sensible and latent heat fluxes varied considerably throughout the basin. Th...
TL;DR: In this article, a survey of the distribution of natural water isotope abundances within the well-defined dry valley hydrologic system in Taylor Valley, which extends 20 km inland from McMurdo Sound, is presented.
Abstract: The hydrologic system of the coastal McMurdo Dry Valleys, Antarctica, is defined by snow accumulation, glacier melt, stream flow, and retention in closed-basin, ice-covered lakes. During the austral summers from 1993–1996 and 1999–2000 to 2002–2003, fresh snow, snow pits, glacier ice, stream water, and lake waters were sampled for the stable isotopes deuterium (D) and 18O in order to resolve sources of meltwater and the interactions among the various hydrologic reservoirs in the dry valleys. This data set provides a survey of the distribution of natural water isotope abundances within the well-defined dry valley hydrologic system in Taylor Valley, which extends 20 km inland from McMurdo Sound. The three major Taylor Valley lakes are not connected to one another hydrologically, and their levels are maintained by glacial meltwater inflow and perennial ice-cover sublimation. At the valley scale, glacial ice, snow, stream, and lake waters become more depleted in δD with increasing distance from McMur...
TL;DR: In this article, the authors used retrospective analysis of the widespread evergreen dwarf-shrub, Cassiope tetragona, to reconstruct average summer air temperature for Alexandra Fiord, Ellesmere Island, Canada.
Abstract: We used retrospective analysis of the widespread evergreen dwarf-shrub, Cassiope tetragona, to reconstruct average summer air temperature for Alexandra Fiord, Ellesmere Island, Canada. Retrospective analysis is a technique based on dendrochronological methods. In this study, chronologies are based on the morphological characteristics of the plant stems. Two growth and two reproduction chronologies, ranging from 80 to 118 years long, were developed from each of two populations at the High Arctic site. We used multiple regression models to develop a 100-year-long (1895–1994) reconstruction of July–September average air temperature that explained 45% of the climatic variance in the instrumental record. The reconstruction revealed an increase in summer temperature from ∼1905 to the early 1960s, a cooling trend from the mid-1960 to the 1970s, and an increase in temperature after 1980. These historical temperature patterns correspond well with those from other climate proxies from sites on Ellesmere an...
TL;DR: In this article, a simple model of soil microbial CO2 production during the cold season was developed for tussock tundra, moss tundras, and wet meadow Tundra in the Alaskan Arctic.
Abstract: Microbial activity in arctic tundra soils has been evaluated through both lab incubations and field flux measurements. To determine whether these different measurement approaches can be directly linked to each other, we developed a simple model of soil microbial CO2 production during the cold season in tussock tundra, moss tundra, and wet meadow tundra in the Alaskan Arctic. The model incorporated laboratory-based estimates of microbial temperature responses at sub-zero temperatures with field measurements of C stocks through the soil profile and daily temperature measurements at the sites. Estimates of total CO2 production overestimated in situ cold season CO2 fluxes for the studied sites by as much as two- to threefold, suggesting that either CO2 produced in situ does not efflux during the cold season or that microbial respiration potentials are constrained by some other factor in situ. Average estimated winter CO2 production was near 120 g C m−2 in moist tundra and 60 g C m−2 in wet meadow tun...
TL;DR: The 154-year (1850-2004) chronosequence of the Forni Glacier foreland has been studied by sampling ant, centipede, ground beetle, and spider species assemblages.
Abstract: The 154-year (1850–2004) chronosequence of the Forni Glacier foreland has been studied by sampling ant, centipede, ground beetle, and spider species assemblages. Species numbers increase with terrain age along the chronosequence from 2 to 26 on the oldest soils. Thirty-nine species were collected; species richness and diversity (Shannon's Index) of communities are correlated to the year of soil deglaciation. Shannon Index values increase with sites deglaciated between 1 and 61 years ago; sites deglaciated between 61 and 78 years ago produce similar values, and those deglaciated 78 to 154 years ago show a further increase in diversity. Ground beetles and spiders are found at all sites, while ants and centipedes were associated with mature forest soils. On the glacier surface, pioneer species such as the wolf-spider Pardosa saturatior and the ground beetle Oreonebria castanea permanently inhabit the supraglacial detritus surviving on trophic resources. Wingless ground beetle species are associated ...
TL;DR: In the Central Greater Caucasus Mountains, Georgia, Betula litwinowii (birch) occurs on north-facing slopes of east-west ridgelines that extend upward to high mountain peaks, forms the alpine timberline at higher elevation, and reaches its highest treeline limit only when associated with the broadleaf evergreen shrub, Rhododendron caucasicum.
Abstract: In the Central Greater Caucasus Mountains, Georgia, Betula litwinowii (birch) occurs on north-facing slopes of east-west ridgelines that extend upward to high mountain peaks, forms the alpine timberline at higher elevation, and reaches its highest treeline limit only when associated with the broadleaf evergreen shrub, Rhododendron caucasicum. This association might generate an ecological facilitation of either temperatures or sky exposure, both of which have been related to the altitudes at which timberlines/treelines occur. At the lowest site (2072 m) the greatest abundance of birch seedlings (up to 2.3 seedlings/m2) occurred at shaded microsites beneath the B. litwinowii overstory and along shaded north-facing walls of polyhedral soil depressions just beyond this treeline. These seedling microsites also had substantially colder air and soil temperature regimes than more sun-exposed microsites. Similarly, at the highest elevation site (2512 m) the second greatest seedling abundance (0.73 seedlin...
TL;DR: A 35-year chronology from 1965 to 2000 of the deposition of wind-blown sediment from snowpits for coastal southern Victoria Land, Antarctica was constructed in this article, where meteorology, eolian sedimentation, and mineralogy confirm a Victoria Valley provenance, while the presence of volcanic tephra is ascribed to an Erebus volcanic province source.
Abstract: A 35 year chronology from 1965 to 2000 of the deposition of wind-blown sediment is constructed from snowpits for coastal southern Victoria Land, Antarctica. Analysis of local meteorology, contemporary eolian sedimentation, and mineralogy confirm a Victoria Valley provenance, while the presence of volcanic tephra is ascribed to an Erebus volcanic province source. Winter foehn winds associated with anticyclonic circulation are considered responsible for transporting fine-grained sediment from the snow- and ice-free Victoria Valley east toward the coast, while cyclonic storms transport tephra north along the Scott Coast. No trend could be identified in the occurrence of either tephra or wind-blown sediments sourced from the Victoria Valley and retrieved from the snowpits excavated on the Victoria Lower and Wilson Piedmont Glaciers. We infer this to indicate that the region has not undergone a significant change in weather patterns for at least the last 35 years. Our results also confirm the McMurdo ...
TL;DR: In this article, the authors report results from up to 8 years of experimental warming with ∼1 m2 open-top chambers (OTC) at four tundra communities near Barrow (71°18′N, 156°40′W) and Atqasuk (70°29′N and 157°25′W), in northern Alaska.
Abstract: This study is presented against the background that climate warming is predicted to continue in much of the Arctic through the next century and that small greenhouse chambers have been used widely to warm tundra communities in order to forecast climate-related changes. It reports results from up to 8 years of experimental warming with ∼1 m2 open-top chambers (OTCs) at four tundra communities near Barrow (71°18′N, 156°40′W) and Atqasuk (70°29′N, 157°25′W) in northern Alaska. Between 1994 and 2002 the OTCs increased the mean growing season air temperature by between 0.6 and 2.2°C, depending on the site and year. The change in average July soil temperature recorded over 3 years at 10 cm depth due to the OTCs varied between −0.8 and 0.7°C, depending on the site. Changes in soil temperature did not result in detectable differences in thaw depth at any site. This is interpreted to be the result of the small size of the OTCs and possibly changes in vegetation. The differences in warming profiles between...
TL;DR: In this paper, the authors measured nitrogen fixation, denitrification, and ecosystem pools of nitrogen in three subarctic ecosystem types differing in soil frost-heaving activity and vegetation cover.
Abstract: Nitrogen (N) fixation, denitrification, and ecosystem pools of nitrogen were measured in three subarctic ecosystem types differing in soil frost-heaving activity and vegetation cover. N2-fixation was measured by the acetylene reduction assay and converted to absolute N ecosystem input by estimates of conversion factors between acetylene reduction and 15N incorporation. One aim was to relate nitrogen fluxes and nitrogen pools to the mosaic of ecosystem types of different stability common in areas of soil frost movements. A second aim was to identify abiotic controls on N2-fixation by simultaneous measurements of temperature, light, and soil moisture. Nitrogen fixation rate was high with seasonal input estimated at 1.1 g N m−2 on frost-heaved sorted circles, which was higher than the total plant N content and exceeded estimated annual plant N uptake several-fold but was lower than the microbial N content. Seasonal fixation decreased to 0.88 g N m−2 on frost-heaved moss-covered surfaces and to 0.25 ...
TL;DR: In this article, the authors examined the underside of 950 opaque rocks in sixteen locations in the Arctic for hypolithic colonization by photosynthetic microorganisms and found that greater than 90% of the rocks were colonized.
Abstract: The colonization of the underside of rocks normally requires that the material is sufficiently translucent to allow the penetration of photosynthetically active radiation. We examined the underside of 950 opaque rocks in sixteen locations in the Arctic for hypolithic colonization by photosynthetic microorganisms. Greater than 90% of rocks were colonized. The mean width of the bands of colonization was 3.1 ± 1.9 cm on Devon Island, and 3.0 ± 1.6 cm on Cornwallis Island. The width of the bands of colonization was less in the interior of frost-sorted polygons compared to their edges (in the arctic location, 0.7 ± 0.8 and 3.6 ± 1.4 cm in the interior and at the edges, respectively), suggesting the importance of frost sorting in enhancing the penetration of light around the edges of rocks to their undersides, and thus allowing colonization by photosynthetic organisms. We observed a similar pattern of colonization in antarctic polygons. The hypolithic habitat provides protection from environmental extremes. We show that within the hypolithic habitat organisms are protected from UV radiation. From radiolabeled carbon uptake measurements we estimate the productivity of the arctic communities to be approximately 0.8 g m−2 a−1, potentially as high as above-ground productivity. We discuss the potential implications of climate change for these communities.
TL;DR: A comparative analysis of physical, chemical, and biological characteristics of five of the Ellesmere ice shelves including geographic information system (GIS) mapping of ice types was conducted in this article.
Abstract: Over the course of the last century, the 9000-km2 Ellesmere Ice Shelf (82–83°N, 64–90°W) fragmented into six main ice shelves now totaling 1043 km2. This ensemble of thick ice environments lies along the northern coast of Ellesmere Island in the Canadian High Arctic and provides a cryohabitat for microbial communities that occur in association with eolian and glacially entrained sediments on the ice surface. We undertook a comparative analysis of physical, chemical, and biological characteristics of five of the remnant ice shelves including geographic information system (GIS) mapping of ice types. Each of these remnants is a thick (>20 m) mass of ice with substantial sediment overburden that promotes the formation of oligotrophic meltwaters in the summer. Microbiota occurred in all sampled sediment, forming a continuum of abundance from sparse to loosely cohesive and pigmented microbial mats. Using digital images from over-flight transects we determined that 8% of the combined ice-shelf area was ...
TL;DR: In this article, the authors reconstructed thermokarst formation and vegetation change in central Yakutia, eastern Siberia, based on newly obtained AMS radiocarbon data and pollen records from four typical thermokarast depressions (alases).
Abstract: Thermokarst formation and vegetation change in central Yakutia, eastern Siberia, were reconstructed based on newly obtained AMS radiocarbon data and pollen records from four typical thermokarst depressions (alases). Radiocarbon ages of wood fragments, which are good indicators of the development of thermokarst depressions, suggest that they formed during the early Holocene. The result of dating at various locations implies that thermokarst in central Yakutia developed synchronously, at a time that regional paleoclimate records indicate warm and moist conditions prevailed. Major trends in pollen records from the four thermokarst deposits were similar. The predominant vegetation type during the thermokarst active phase was open larch and birch forest with herbaceous taxa. Grassland developed on areas exposed by a decrease in water levels of thermokarst lakes during the late Holocene.
TL;DR: This study characterized the microclimatic modifications made by the cushion plants Azorella monantha and Laretia acaulis and examined their role as microClimatic shelters for two species of high Andean coleopterans: Eriopis connexa and Hippodamia variegata.
Abstract: High mountain environments are highly stressful for insect survival. It has been suggested that small microtopographic variations generating less stressful microclimatic conditions than the surrounding environment would provide more suitable sites for insect development. Cushion plants represent one of the life forms best adapted to the extreme alpine habitats. Cushion plants can modify microclimatic conditions within and under their canopy, generating less severe microsites than the surrounding environment. In this study, we characterized the microclimatic modifications made by the cushion plants Azorella monantha and Laretia acaulis and examine their role as microclimatic shelters for two species of high Andean coleopterans (Coccinelidae): Eriopis connexa and Hippodamia variegata at 3200 m a.s.l. in the Andes of central Chile. Results showed that the cushion species create microhabitats with higher availability of water and less oscillating temperatures. However, the intensity of modifications was higher in A. monantha compared to L. acaulis. The abundance of the two ladybird beetle species was higher within cushions than outside, although E. connexa showed higher abundances compared to H. variegata. However, a habitat selection experiment in a greenhouse showed that under milder temperature conditions ladybird beetles species do not prefer cushions. This suggests that in the harsh alpine climate, cushion plants may act as microclimatic shelters since they reduce stressful environmental conditions, allowing greater abundances of coleopterans than in the surrounding environment.
TL;DR: Active layer thickness was monitored along three ephemeral streams in the Taylor Dry Valley of Antarctica during the 1997-1998 summer season as discussed by the authors, and the thickness of the active layer was measured every 1.5 m over intervals ranging from 2 to 30 days.
Abstract: Active layer thickness was monitored along three ephemeral streams in the Taylor Dry Valley of Antarctica during the 1997–1998 summer season. Five to seven cross sections were established on each stream, and the thickness of the active layer was measured every 1.5 m over intervals ranging from 2 to 30 days. Active layer depths ranged from a minimum of 3 cm in early November to a maximum of 60 cm in late January, and the depth of the active layer increased rapidly as summer temperatures climbed above freezing. While there were significant differences in the thickness of the active layer among the three streams, the timing of rapid thaw was similar for all cross sections. Changes in active layer thickness were responsive to both daily and seasonal changes in air temperature. There was more rapid thaw under the areas with flowing water, suggesting a transfer of heat from meltwater into the underlying sediments, and some evidence of an insulating effect during cold periods. Active layer thickness was...
TL;DR: In this article, a hierarchical approach was used to test whether reindeer responded to spatial heterogeneity during the plant growing season (divided into three distinct periods) in a mountainous subarctic environment in northern Sweden.
Abstract: Reindeer, Rangifer tarandus, live in subarctic and alpine environments with spatially and temporally heterogeneous resource distribution. In this study, we used a hierarchical approach to test whether reindeer responded to spatial heterogeneity during the plant growing season (divided into three distinct periods) in a mountainous subarctic environment in northern Sweden. A reindeer herd in northern Sweden was surveyed using radio-telemetry (8 female reindeer) and the selection of feeding habitats by observing individuals/groups (135 observations) using laser range-finding binoculars. Reindeer selected feeding areas (evaluated at 5-km grid size), as well as feeding habitats (evaluated at 0.5- and 1-km grid size) during spring, in response to high terrain ruggedness and habitat heterogeneity. Reindeer switched during summer to select against terrain ruggedness and habitat heterogeneity at the level of feeding habitats, while preferring southward facing habitats. During autumn, a broader spectrum of...
TL;DR: In this paper, small (1 ≤ m diameter) sorted patterned ground features were studied on the Little Ice Age forelands of three Jotunheimen glaciers, showing that vegetation and soil development are negligible within recent patterns.
Abstract: Small (1 ≤ m diameter) sorted patterned ground features were studied on the Little Ice Age forelands of three Jotunheimen glaciers. Patterned ground appears to be most active near the ice margins, declining in intensity of activity with distance from the glaciers. Vegetation and soil development are negligible within patterned ground that is “Recent” (decadal time frame). Significant (P < 0.05) fine scale differences in vegetation and soil development occur within patterned ground on terrain ∼70 yr in age, with patterned ground borders having higher values of vegetation cover and thicker soils than that in patterned ground centers. With increasing age of terrain and patterned ground, soil development and vegetation encroach inward toward patterned ground centers, implying that a short-term, active periglacial zone exists near the ice margin, decaying with time and glacier retreat. Specifically, terrain that has been deglaciated for ∼70 years and is approximately ∼350–500 m from the ice margin sho...
TL;DR: Ozenda et al. as discussed by the authors described the historical development of a particular approach to the study of mountains, their environment, biology, and ecology, which was highly successful and widespread during the past century.
Abstract: This is a curious little book, and is rather unclassifiable in today’s diversified fields of environmental sciences. The book is worthwhile for the useful compiled historical information and ideas that it presents, but is also highly frustrating in form and substance, even for a French reader. Indeed, the primary drawback for many non-French readers will be that the text is primarily in French. Only short, albeit informative, abstracts in English are found at the beginning of each chapter. The author, Professor Paul Ozenda, now retired, had a distinguished and productive career as a geobotanist, for lack of a better word, spanning over half of the twentieth century. He was a pioneer and leader in the disciplines of plant and vegetation ecology in Europe during that period. It is remarkable that, at an age when some North American ecologists might be content to play golf, Professor Ozenda still exhibits knowledge of and passion for his profession. Indeed, the book is a largely personal reflection on the vast field of mountain biogeography and ecology, in the widest sense of these two terms. The contributions of this book that may be of interest to today’s practitioners fall into three broad categories. First, the book describes the historical development of a particular approach to the study of mountains, their environment, biology, and ecology, which was highly successful and widespread during the past century. It is extremely advantageous to recognize how past advances in this area have led to contemporary approaches to scientific issues. Second, it contains useful information (interpretations, data, maps, citations) that a younger generation of scientists not taught in the fields covered may find difficult to access elsewhere, since many aspects of these materials are no longer part of modern curricula. Third, it contains ideas and concepts that are of use during the present period of large-scale production of maps, monitoring schemes, and interdisciplinary approaches to ecological issues. In essence, the book makes us aware that there is nothing really new in our self-described innovative approaches to ecology and that, successful or not, our predecessors also considered that only integration and synthesis would yield full knowledge and understanding of mountain ecosystems at multiple spatial and temporal scales. Unfortunately, the book suffers from serious weaknesses. Many portions of the text contain arcane jargon that few modern students of the field will feel enthusiastic about and that, in this reviewer’s opinion, has lost its interest and relevance. This is regrettable because the concepts hidden behind the jargon can be interesting and relevant. Furthermore, the author compounds this problem by lengthy discussions of issues that, again in this reviewer’s opinion, can be perceived as sterile refinements of obsolete systems of ideas. This is even more unfortunate, because buried under rather unexciting discussions in what seems to be a foreign language (no pun intended), some significant problems are explored: the distributions of species in response to large geologic phenomena, climatic variability over large areas and multiple temporal scales, and the potential responses of mountain ecosystems to climatic and land use changes, among other topics. The book is well organized to achieve objectives that are clearly formulated in the ‘‘Avant-propos’’ or preamble (pp. V–VII). The ten chapters are articulated in three parts. The first part (chapters 1–3) defines the object of the book, i.e., the mountain systems, their spatial scales, their geographic distributions, and climatic complexity. It also includes a short discussion of the alpine-subalpine ecotone. The second part (chapters 4–6) tackles different dimensions of biodiversity in mountains with a special focus on species richness and withincommunity diversity. The third part (chapters 7–10) attempts a synthesis through integration to explain the vegetation and its floristic composition in mountain systems all over the world. The author presents a conceptual model of vegetation distributions for the European Alps and endeavors to expand it to the rest of the world. This attempt exemplifies both the contributions and weaknesses noted earlier. On one hand, a tremendous amount of useful information is presented. On the other hand, the lengthy discussion of obscure systems of classification borders on the tedious and the frivolous. The book would have benefited from de-emphasizing the typology of mountain systems and expanding the section on the dynamics of vegetation patterns. In summary, this is a really difficult book to review fairly. As the reflection of a European scientist who has contributed to his field of study, it has noteworthy dimensions, especially for students of the Alps. It can be used today to provide background information on integrated mountain ecology. However, it is of limited use for generating new ideas. The choice of citations limits its value as a reference book. For example, this reviewer does not understand the rationale for excluding major North American references on the topic (e.g., Daubenmire, Billings, Peet) while other less relevant references are included. This is also true for the omission of important European references. Still, this book provides some remarkable insights into past work that has influenced the field during the mid-twentieth century.
TL;DR: In this article, the success of restoration of a closed track in the alpine area around continental Australia's highest mountain, Mount Kosciuszko, was evaluated with 1 m2 quadrats.
Abstract: Human use of arctic and alpine environments can result in damage to the natural vegetation and soils. Restoration of the damage can have limited success due to the severity of the environment, which restricts plant germination and growth and increases the potential for soil erosion. In this study, we evaluated the success of restoration of a closed track in the alpine area around continental Australia's highest mountain, Mount Kosciuszko. Vegetation and soils along a 4 km walking track (that was closed and rehabilitated more than 15 yr ago) were compared with the adjacent undisturbed vegetation and soils. There was limited success in restoration with clear differences in soil nutrients, extent of vegetation cover, plant species composition, and height of vegetation between the track and adjacent natural vegetation sampled using 1 m2 quadrats. The study highlights the need for limiting disturbance in such environments, and for ongoing rehabilitation in areas that have been disturbed. It also indicates that when non-native species are used in rehabilitation, they may not necessarily be succeeded by natives, particularly if soil conditions do not return to a state similar to undisturbed areas.