Showing papers in "Arctic, Antarctic, and Alpine Research in 2007"
TL;DR: In this paper, the authors studied the effect of glacial retreat on the hydrological processes in the Tibetan Plateau and surrounding regions, and found that the retreat is relatively small in the interior of the Tibetan plateau and increases to the margins of the plateau with the greatest retreat around the edges.
Abstract: Glacial retreat on the Tibetan Plateau and surrounding regions is characteristic since the 1960s and has intensified in the past 10 yr. The magnitude of glacial retreat is relatively small in the interior of the Tibetan Plateau and increases to the margins of the plateau, with the greatest retreat around the edges. Glacial retreat in this region is impacting the hydrological processes in the Tibetan Plateau and surrounding regions. The glacial retreat has caused an increase of more than 5.5% in river runoff from the plateau. In some areas, such as the Tarim River basin, the increase in river runoff is greater. Glacial retreat has also caused rising lake levels in the areas with large coverage of glaciers, such as the Nam Co Lake and Selin Co Lake areas. Rising lake levels are devastating grasslands and villages near the lakes.
388 citations
TL;DR: In this paper, the ecosystems of alpine snowbed habitats are reviewed with emphasis on ecosystem functioning and capability to adapt to current and predicted global change, and several ecosystem services which snowbeds provide to the alpine landscape are identified.
Abstract: The ecosystems of alpine snowbed habitats are reviewed with emphasis on ecosystem functioning and capability to adapt to current and predicted global change. Snowbeds form in topographic depressions that accumulate large amounts of snow during the winter months, and the final snowmelt does not occur until late in the growing season. Many species preferentially grow in snowbed habitats and some of these are even restricted to these habitats. In this review we identify several ecosystem services which snowbeds provide to the alpine landscape. For instance, snowbeds provide a steady water and nutrient supply to adjacent plant communities and offer newly emerged high-quality food for herbivores late in the growing season. We also propose that alpine snowbeds are much more productive than earlier thought, especially when the very short growing season and often high grazing pressure are taken fully into account. Furthermore, we propose that bryophytes and graminoids (grasses, sedges, and rushes) probab...
197 citations
TL;DR: It is suggested that microclimatic modifications associated with cushion plants could be important for the establishment and survival of other plant species, both native and non-native, in the high alpine communities of central Chile.
Abstract: Cushion plants are one of the most common growth forms in alpine habitats. Their low stature, dense canopy, and compact form allow them to decouple their microclimate from the surrounding environment, mitigating the effect of low temperatures and drought, enhancing the survival of other species. In this study, we evaluated the modifications on soil temperature and moisture over an entire growing season by two cushion species (Laretia acaulis and Azorella monantha) in alpine communities located at two different elevations in the central Chilean Andes. Additionally, w ep erformed seedling survival experiments with two native herbaceous species (Hordeum comosum and Erigeron andicola) and the non-native forb Cerastium arvense to assess if seedling survival is higher within cushions than outside them. Our results indicated that cushions ameliorated extreme low and high substrate temperatures, improved soil moisture, and enhanced seedling survival of the three herbaceous plant species evaluated. Our results suggest that microclimatic modifications associated with cushion plant sc ould be important for the establishment and survival of other plant species, both native and non-native, in the high alpine communities of central Chile.
194 citations
TL;DR: In this article, historical climate data and repeat photographs were used to assess and document changes in alpine treeline and glacial recession in northwestern Yunnan, China, showing that mean annual temperature in the last two decades of the 20th century has been increasing locally at a rate of 0.06 °C yr−1 (p < 0.001).
Abstract: Historic climate data and repeat photographs were used to assess and document changes in alpine treeline and glacial recession in northwestern Yunnan, China. Results show that mean annual temperature in the last two decades of the 20th century has been increasing locally at a rate of 0.06 °C yr−1 (p < 0.001). Furthermore, the annual trend is a result of both summer- and wintertime warming (0.037 °C yr−1, p < 0.001; and 0.036 °C yr−1, p < 0.001, respectively). Additionally, a local drying trend (−3.80 mm yr−1; p < 0.001) was observed during the period 1955–1995. Repeat photos and supplemental measurements show that this warming is causing the retreat of glaciers and contributing to the elevational advance of alpine treeline. Fire, a traditional management tool used to halt the advance of woody species, has been suppressed since 1988. One consequence of these interactions is the encroachment of woody vegetation into alpine meadows, which will have negative impacts on plant species diversity and Tib...
178 citations
TL;DR: In this article, the authors examined the carbon and nutrient dynamics in a sub-arctic heath and a birch forest with high temporal resolution from March until snowmelt at both ambient and experimentally increased snow depths.
Abstract: Recent evidence suggests that biogeochemical processes in the Arctic during late winter and spring-thaw strongly affect the annual cycling of carbon and nutrients, indicating high susceptibility to climate change. We therefore examined the carbon and nutrient dynamics in a sub-arctic heath and a birch forest with high temporal resolution from March until snowmelt at both ambient and experimentally increased snow depths. Ecosystem respiration (ER) from mid-March to snowmelt at ambient snow was high, reaching 99 ± 19 (birch) and 67 ± 1.4 g C m−2 (heath). Enhanced snow depth by about 20–30 cm increased ER by 77–157% during late winter but had no effects during spring-thaw. ER rates at the birch site were poorly described by classic first-order exponential models (R2 = 0.06–0.10) with temperature as a single variable, but model fit improved considerably by including the supply of dissolved organic carbon (DOC) or nitrogen (DON) in the model (R2 = 0.40–0.47). At the heath, model fit with temperature a...
126 citations
TL;DR: This article examined elemental chemistry and 87Sr/86Sr of streams and sequential and total digests of soils, permafrost, and soil parent materials from seven glacial deposit surfaces of varying geomorphic ages in arctic Alaska in the vicinity of the Philip Smith Mountains quadrangle (69°N, 150°W).
Abstract: Climate change may bring about geochemical changes in arctic regions as a result of increasing thaw depth. In order to better understand current watershed geochemistry and mineral weathering and provide a basis for predicting the geochemical effects of active-layer thickness increase, we examined elemental chemistry and 87Sr/86Sr of streams and sequential and total digests of soils, permafrost, and soil parent materials from seven glacial deposit surfaces of varying geomorphic ages in arctic Alaska in the vicinity of the Philip Smith Mountains quadrangle (69°N, 150°W). We found overall greater exchangeable K concentrations, exchangeable and acid digestible P and Ca concentrations, acid digestible and total Ca/Na and Ca/Sr, and lower acid digestible 87Sr/86Sr in permafrost than in active-layer mineral soil. Of the surfaces with similar parent material, stream and soil data suggest that weathering has progressively depleted calcium carbonate in the active layer with increasing surface age. Our resu...
98 citations
TL;DR: In this paper, a wide range of tropical treelines were studied at seven sites in the tropical and subtropical Andes (Argentina, Bolivia, Ecuador and Venezuela) and on a Hawaiian volcano (Haleakala, Maui).
Abstract: Alpine treeline ecotones can be gradual transitions, abrupt boundaries, or patchy mosaics, and these different patterns may indicate important processes and dynamic properties. We present observed spatial patterns of a wide range of tropical treelines and try to explain these patterns. Treelines were studied at seven sites in the tropical and subtropical Andes (Argentina, Bolivia, Ecuador, and Venezuela) and on a Hawaiian volcano (Haleakala, Maui). Treeline vegetation structure was described using transects perpendicular to the treeline, and air and soil temperatures were measured above and below the forest boundary. Temperature fluctuations were much larger and the average temperature was higher in alpine vegetation than in forest. Most treelines were abrupt, with surprisingly similar patterns across a wide geographical range. This abruptness could result from positive feedback processes
89 citations
TL;DR: In this article, a novel method is presented that applies spatial analysis software to digital photo-pairs, allowing vegetation change to be categorized and quantified, in order to detect landscape change over decadal timescales.
Abstract: Repeat photography is a powerful tool for detection of landscape change over decadal timescales. Here a novel method is presented that applies spatial analysis software to digital photo-pairs, allowing vegetation change to be categorized and quantified. This method is applied to 12 sites within the alpine treeline ecotone of Glacier National Park, Montana, and is used to examine vegetation changes over timescales ranging from 71 to 93 years. Tree cover at the treeline ecotone increased in 10 out of the 12 photo-pairs (mean increase of 60%). Establishment occurred at all sites, infilling occurred at 11 sites. To demonstrate the utility of this method, patterns of tree establishment at treeline are described and the possible causes of changes within the treeline ecotone are discussed. Local factors undoubtedly affect the magnitude and type of the observed changes, however the ubiquity of the increase in tree cover implies a common forcing mechanism. Mean minimum summer temperatures have increased b...
76 citations
TL;DR: In this paper, the impact of penguin rookeries on vegetation patterns and diversity was examined by descriptive and quantitative methods along a transect from a rookery to areas distant from penguin impact.
Abstract: Breeding penguins are the major source of nutrients for terrestrial ecosystems in the Maritime Antarctic. The impact of penguin rookeries on vegetation patterns and diversity was examined by descriptive and quantitative methods along a transect from penguin rookeries to areas distant from penguin impact. Several vegetation zones related to varying degrees of rookery impact have been recognized: (1) areas under the immediate influence of fresh penguin guano and trampling support little or no vegetation; (2) the adjacent zone is covered with nitrophilous green algae, locally also cyanobacteria; (3) the next zone is dominated by the Antarctic hair-grass; (4) further on, a zone dominated by mosses is formed; (5) finally, the zone least affected by penguin impact is dominated by lichens. With increasing distance from penguin rookeries, vegetation zones become less distinct and more complex; along consecutive zones vegetation richness and diversity increase and dominance decreases. Change in species co...
68 citations
TL;DR: In this article, a study of permafrost along the Qinghai-Tibet (Xizang) Highway shows that there is a large difference in the response of permaffrost to climate change and to engineering construction.
Abstract: Monitoring of permafrost along the Qinghai-Tibet (Xizang) Highway shows that there is a large difference in the response of permafrost to climate change and to engineering construction. The change in cold (<−1.5°C) permafrost is greater than that in warm (≥−1.5°C) permafrost under the effect of climate change, while the cold permafrost is less sensitive to the disturbances from engineering activities. However, warm permafrost is very sensitive to both climate warming and the impacts from engineering construction. This is because engineering construction has more immediate and direct impacts on the thermal and moisture regimes of underlying permafrost, and consequently greater influence than climate change during the first few years after engineering construction. Assuming constant annual rates of warming, the surface of cold permafrost would approach the warming due to engineering construction in 50 yr, while it would take about 20 yr in areas with warm permafrost. At a depth of 6 m, the temperat...
68 citations
TL;DR: This article conducted two case studies at documented avalanche tracks in the Swiss Alps to determine the most valuable dendroecological indicators for reconstructing past avalanche events, including reaction wood formation, changes in stem eccentricity, and presence of traumatic resin canals among sectors.
Abstract: Avalanche records are important for land-use planning and risk management in mountainous areas. Written records on dates, disturbed area, and pressure patterns of past snow avalanches are scarce. Tree rings can be used to complement written records on past avalanche activity. We conducted two case studies at documented avalanche tracks in the Swiss Alps to determine the most valuable dendroecological indicators for reconstructing past avalanche events. Both tracks were impacted by avalanche events in 1951 and 1999, the two most exceptional avalanche years in recent Swiss history. The difference in tree age among the track, border, run-out, and control sectors was a valuable indicator of the area impacted by past avalanches, but not a useful tool to establish dates of avalanche occurrences. Comparisons of reaction wood formation, changes in stem eccentricity, and presence of traumatic resin canals among sectors showed significantly larger values of these indicators after the 1999 event in the trac...
TL;DR: In this paper, the authors evaluated the vegetation and soil dynamics of ski runs constructed above timberline and hydroseeded 4, 6, 10, and 12 years ago, respectively, at the Monterosa ski resort in Aosta, Italy.
Abstract: Construction of ski runs has a very heavy impact on alpine ecosystems since it results in total destruction of the existing vegetation and profound alteration of the soil. Restoration work must thus set out to develop a protective plant cover immediately and promote re-establishment of a functional plant-soil system in the long term. The aims of the present study, conducted at the Monterosa ski resort (Val d'Ayas, Aosta, Italy) were to evaluate (1) how disturbance related to ski run construction at high altitude (2200–2600 m a.s.l.) has affected vegetation and soil properties compared to undisturbed sites, and (2) how vegetation and soil properties change in machine-graded ski runs with increasing time after hydroseeding. Herbaceous cover and specific composition, root density, physico-chemical soil properties, and aggregate stability were evaluated to determine the vegetation and soil dynamics of four runs constructed above timberline and hydroseeded 4, 6, 10, and 12 years ago, respectively, and...
TL;DR: In this paper, the authors used tree-ring data from Qilian juniper (Sabina przewalskii Kom) in the middle Qilian Mountains to reconstruct the temperature variations in the last 1000 yr.
Abstract: Using long-lived Qilian juniper (Sabina przewalskii Kom.) in the middle Qilian Mountains, the temperature variations in the last 1000 yr were reconstructed. We find that the annual growth ring width and δ13C series mainly reflect variations in regional temperature. Except in May, warmer temperatures indicate greater growth over the period from December to April, and δ13C values in tree-rings are higher for years with higher temperature. The notable features in the temperature reconstruction are the occurrence of the Little Ice Age from A.D. 1600 to 1880 and the abrupt warming over the end of past millennia. The comparison of our chronology to a Northern Hemispheric temperature proxy shows that our tree-ring data will facilitate intercontinental differentiation of large-scale synoptic climate variability.
TL;DR: In this article, surface microrelief, permafrost table configuration, ground-ice, and soil organic-matter contents are described for three sites near Inuvik, N.W.T., that are characterized by collapsed, poorly developed and well-developed earth hummocks, respectively.
Abstract: Surface microrelief, permafrost table configuration, ground-ice, and soil organic-matter contents are described for three sites near Inuvik, N.W.T., that are characterized by collapsed, poorly developed, and well-developed earth hummocks, respectively. The diameters of collapsed earth hummocks were significantly greater than those of well-developed vegetated hummocks. Hummock relief and interhummock distance increased along the continuum of forms, with the widest spacing and greatest relief measured at the site with well-developed vegetated hummocks. A bowl-shaped permafrost table mirrored the surface relief of most hummocks, but the collapsed hummocks were underlain by a planar or domed permafrost table. Segregated ice lenses parallel to the permafrost table, and small bodies of intrusive ice, were observed beneath the developing and well-developed hummocks. The configuration of the permafrost table and hummock relief, long-term observations of active-layer and hummock change, and hummock respon...
TL;DR: In this article, the stable carbon isotope composition (δ13C) of modern and subfossil grasses and sedges (graminoids) from Eastern Beringia was investigated.
Abstract: The nature of vegetation cover present in Beringia during the last glaciation remains unclear. Uncertainty rests partly with the limitations of conventional paleoecological methods. A lack of sufficient taxonomic resolution most notably associated with the grasses and sedges restricts the paleoecological inferences that can be made. Stable isotope measurements of subfossil plants are frequently used to enhance paleoenvironmental reconstructions. We present an investigation of the stable carbon isotope composition (δ13C) of modern and subfossil grasses and sedges (graminoids) from Eastern Beringia. Modern grasses from wet habitats had a mean δ13C of −29.1‰ (standard deviation [SD] = 2.1‰, n = 75), while those from dry habitats had a mean of −26.9‰ (SD = 1.19, n = 27). Sedges (n = ~50) from dry, wet, marsh, and sand dune habitats had specific habitat ranges. Four modern C4 grasses had δ13C values typical of C4 plants. Analyses were also conducted using subfossil graminoid remains from several sedim...
TL;DR: In this paper, a new hypothesis was proposed that debris-covered glaciers served as Pleistocene biological refugia, based on detailed studies of vascular plant growth on six debris-mantled glaciers.
Abstract: This study proposes a new hypothesis: Debris-covered glaciers served as Pleistocene biological refugia. This is based on detailed studies of vascular plant growth on six debris-mantled glaciers, literally around the world, as well as many casual observations also across the globe. We find that such glaciers are quite common and are distributed globally. Using Carbon Glacier, Mount Rainier, U.S.A., as a type locality and case study, we show aspects of the floristic and structural diversity as well as spatial patterns of plant growth on the glacier surface. Migration strategies, root characteristics, and origin and dispersal strategies for vascular plant species are documented. Also reported are special microclimatic conditions in these areas allowing for this remarkable plant ecology. We find that alpine taxa can grow considerably below their usual altitudinal niche due to the cooler subsurface soil temperatures found on glacial debris with ice underneath, and that may have significantly altered t...
TL;DR: It is suggested that late-summer temperatures might have a non-linear negative threshold effect on recruitment rather than a linear effect, which may imply limited range shifts of these populations in response to climate warming.
Abstract: To infer future changes in the distribution of tree species in response to climatic variability, we need an understanding of the recruitment dynamics and their climatic controls at the species' distribution limit. We studied the recruitment processes in an isolated population of Pinus uncinata Ram. located at the southwestern limit of the species' distribution in Europe (Iberian System, NE Spain). We assessed (1) the temporal patterns of pine recruitment, and (2) how climate influenced recruitment. To reconstruct the recent recruitment episodes and to assess the climatic influence on recruitment and radial growth we employed dendrochronological methods. We mapped, measured the size, and estimated the age of all P. uncinata individuals located within a 50 m × 40 m plot. Additional age data were obtained from individuals located in four nearby 20 m × 20 m plots. The main episodes of tree establishment (early 1960s, late 1980s) coincided with low radial growth during a period with reduced grazing pr...
TL;DR: In this article, the NDVI derived from NOAA AVHRR Global Vegetation Index (GVI) for Lhasa area in the central Tibetan Plateau from 1985 to 1999 and its relationship with climate conditions (precipitation and temperature) are established.
Abstract: The Normalized Difference Vegetation Index (NDVI) derived from NOAA AVHRR Global Vegetation Index (GVI) for Lhasa area in the central Tibetan Plateau from 1985 to 1999 and its relationship with climate conditions (precipitation and temperature) are established in this study. Climate data from the Lhasa meteorological station provided by the Tibet Climate Data Center are used for this analysis. The NDVI-derived vegetation growth patterns show very strong seasonal cycles and interannual variations. The growing season length varies between years. The correlation between NDVI and precipitation (r = 0.75, P < 0.01) in Lhasa area is higher than the correlation between NDVI and temperature (r = 0.63, P < 0.01), suggesting that NDVI is more sensitive to precipitation than temperature in this semiarid climate zone. Furthermore, the time series of NDVI demonstrate a positive trend from 1985 to 1999, which means that the vegetation biomass present on land surface is increasing. This trend is strongly correl...
TL;DR: In this paper, observations at the Shiquanhe and Gaize meteorological stations provide data for analysis of δ18O and δD variations in precipitation for the Ngari (Ali) region, western Tibetan Plateau Temperature controls δ 18O in precipitation in this area.
Abstract: Observations at the Shiquanhe and Gaize meteorological stations provide data for analysis of δ18O and δD variations in precipitation for the Ngari (Ali) region, western Tibetan Plateau Temperature controls δ18O in precipitation in this area δ18O in precipitation positively correlates with air temperature at the Shiquanhe and Gaize stations, especially for precipitation weighted monthly mean δ18O The δ18O – T correlation gradually strengthens from south to north across the western Tibetan Plateau and adjacent regions, with gradual weakening of southwest monsoon activity The strongest correlation is found at Hetian There is a poor correlation between δ18O and air temperature in the south at New Delhi because the moisture derives predominantly from the Indian Ocean in summer The Ngari region exhibits a close relation between δD and δ18O in precipitation samples, similar to stations in adjacent regions and the global meteoric water line The summer seasonal averaged deuterium excess (d) values
TL;DR: In this paper, the authors combined genetic, morphological, and long-term monitoring data on Dryas from a High Arctic hybrid zone of D. integrifolia and D. octopetala to assess whether climate variation influenced flowering differently in areas of early and late snowmelt, and whether this could have a genetic origin.
Abstract: The extreme seasonality of the High Arctic creates very different flowering conditions for plants in areas of early and late snowmelt. Therefore, future reproductive responses to climate change may be dependent on the timing of snowmelt. We combined genetic, morphological, and long-term monitoring data on Dryas from a High Arctic hybrid zone of D. integrifolia and D. octopetala to assess whether climate variation influenced flowering differently in areas of early and late snowmelt, and whether this could have a genetic origin. We found a non-linear relationship between timing of snowmelt and flowering. The duration of the period between snowmelt and the onset of flowering (pre-floration interval) varied with the date of snowmelt. Shorter pre-floration intervals were associated with warmer average temperature during the pre-floration intervals in both early and late melting plots. However, the pre-floration interval was much shorter in early than in late plots at the same average temperature. Like...
TL;DR: In this article, the authors analyzed thaw strain and thaw depth data from soil cores distributed across the central Beaufort Coastal Plain to evaluate potential thaw settlement at landscape and regional scales in connection with various oilfield studies during the period 1998-2003.
Abstract: On the Beaufort Coastal Plain of northern Alaska, thaw settlement in permafrost soils occurs whenever natural or human disturbances result in an increase in the depth of seasonally thawed soil (the active layer). Knowledge of the potential magnitude of thaw settlement is important for assessing the long-term recovery of disturbed land and for developing rehabilitation plans and performance standards. To address this need, we analyzed thaw strain and thaw depth data from soil cores distributed across the central Beaufort Coastal Plain to evaluate potential thaw settlement at landscape (e.g. terrain units) and regional (e.g. ecodistricts) scales in connection with various oilfield studies during the period 1998–2003. Mean thaw strain values ranged from 1% for meander active channel deposits to 55% for delta inactive overbank deposits, and tended to be highest at 1–2 m below the ground surface. The potential thaw settlement of specific terrain units was evaluated based on thaw strain of soils and th...
TL;DR: In this article, the relative importance of major hydrological processes on thaw season 2003 lakewater balances in the Slave River Delta, NWT, Canada, was characterized using water isotope tracers and total suspended sediment (TSS) analyses.
Abstract: The relative importance of major hydrological processes on thaw season 2003 lakewater balances in the Slave River Delta, NWT, Canada, is characterized using water isotope tracers and total suspended sediment (TSS) analyses. A suite of 41 lakes from three previously recognized biogeographical zones—outer delta, mid-delta, and apex—were sampled immediately following the spring melt, during summer, and in the fall of 2003. Oxygen and hydrogen isotope compositions were evaluated in the context of an isotopic framework calculated from 2003 hydroclimatic data. Our analysis reveals that flooding from the Slave River and Great Slave Lake dominated early spring lakewater balances in outer and most mid-delta lakes, as also indicated by elevated TSS concentrations (>0.01 g L−1). In contrast, the input of snowmelt was strongest on all apex and some mid-delta lakes. After the spring melt, all delta lakes underwent heavy-isotope enrichment due to evaporation, although lakes flooded by the Slave River and Great...
TL;DR: The vegetation composition of four contiguous permanent plots was analyzed during 37 of 42 years between 1959 and 2001 to evaluate successional processes following the cessation of human trampling in alpine tundra as mentioned in this paper.
Abstract: The vegetation composition of four contiguous permanent plots was analyzed during 37 of 42 years between 1959 and 2001 to evaluate successional processes following the cessation of human trampling in alpine tundra. The plots were established adjacent to the Rock Cut parking lot at ~3658 m elevation along Trail Ridge Road in Rocky Mountain National Park, Colorado. Due to limitations in the original study design, the lack of true replication required that the plots be treated individually when subject to indirect ordination analysis to follow trends in overall plant composition and cover. The three most abundant species in the study plots were Artemisia scopulorum, Acomastylis rossii, and Kobresia myosuroides. At the beginning of the study in 1959, total cover ranged from 20 to 55% in the four plots. By 1961, three of the four plots achieved total canopy cover values of at least 100%. Vascular plant species richness (number of taxa per plot) averaged 20 in 1959, but by 1967 had nearly doubled to 37...
TL;DR: In this article, the authors collected fresh snow samples following seven snow accumulation events along an altitudinal transect of the Robertson valley and analyzed them for 18O isotopic gradients.
Abstract: Fresh snow samples were collected following seven snow accumulation events along an altitudinal transect of the Robertson Valley. This glacierized valley is on the eastern slopes of the Canadian Rockies at the Continental Divide and receives precipitation from both westerly (Pacific) air masses and from easterly (upslope) systems. Snow samples were collected over two winter seasons and were analyzed for δ18O, revealing altitudinal gradients that ranged from −0.3‰/100 m to +1.8‰/100 m. Five of seven snow events had positive (inverse) isotopic gradients with altitude: 18O enrichment at higher altitudes. Surface and upper-air meteorological data were analyzed to classify the type of weather systems bringing precipitation to the area for each accumulation event. Three storm classifications were developed: westerly, upslope, and mixed/northwesterly systems. Positive δ18O-elevation gradients were found under strong westerly and northwesterly flow, when the Robertson Valley acts as a leeward slope, whil...
TL;DR: In this paper, the authors provide an accurate, complete account of rock glacier locations in a digital format, to compare topographic variables of rock glaciers form and activity classes, and to evaluate glacier and rock glacier topographic information.
Abstract: In the Colorado Front Range, rock glacier distribution has been noted on U.S. Geological Survey maps and in several publications; however, a comprehensive account of distribution is not available. When analyzed in a Geographic Information System (GIS), Digital Elevation Model variables (elevation, slope, or aspect) could reveal unique topographic characteristics of rock glaciers. The objectives of this study are to provide an accurate, complete account of rock glacier locations in a digital format, to compare topographic variables of rock glacier form and activity classes, and to evaluate glacier and rock glacier topographic information. Rock glacier locations were obtained from previous studies and were re-digitized on high-resolution digital orthophotos. Glacier distribution was determined through classification of a satellite image. Topographic information for rock glacier form and activity classes as well as for glaciers was obtained through zonal overlay in a GIS. Results indicate that tongu...
TL;DR: In this paper, the authors present a Perspective on Environmental Study of Response to Climatic and Land Cover/Land Use Change over the Qinghai-Tibetan Plateau: an Introduction.
Abstract: (2007). Perspectives on Environmental Study of Response to Climatic and Land Cover/Land Use Change over the Qinghai-Tibetan Plateau: an Introduction. Arctic, Antarctic, and Alpine Research: Vol. 39, No. 4, pp. 631-634.
TL;DR: The effects of microclimate change on the growth of fast and slow-growing glacier foreland species were analyzed from 1996 to 2004 to test the following hypotheses: (1) plant growth and cover will increase due to experimental warming; (2) fast-growing species will respond the most; and (3) asexually and sexually reproducing forms of Poa alpina react differently.
Abstract: The effects of microclimate change on the growth of fast- and slow-growing glacier foreland species were analyzed from 1996 to 2004 to test the following hypotheses: (1) plant growth and cover will increase due to experimental warming; (2) fast-growing species will respond the most; and (3) asexually and sexually reproducing forms of Poa alpina react differently—the asexually produced plantlets will respond the most due to their growth advantages in contrast to seedlings. Temperatures were increased with open top chambers (OTCs) by 1 ± 0.01 °C (soil surface) and 0.7 ± 0.03 °C (soil) during the growing seasons using a modified ITEX approach. Juvenile plants of Artemisia genipi (pioneer species), Trifolium pallescens (mid-successional species), Anthyllis vulneraria ssp. alpestris (late-successional species), Poa alpina, and Poa alpina ssp. vivipara (ubiquitous species) were planted into plots with OTCs and adjacent control plots and harvested after three, four, and five years, respectively. The Art...
TL;DR: In this paper, the authors modeled the soil thermal regime of the Tibetan Plateau by applying a one-dimensional heat transfer model with phase change, and simulated daily fields of active layer depth (ALD) for the period January 1980 through December 2001.
Abstract: The soil thermal regime of the Tibetan Plateau is modeled by applying a one-dimensional heat transfer model with phase change. The two main forcing variables are surface air temperature, from the ERA-40 reanalysis, and snow depth, derived from passive microwave satellite data. Daily fields of soil temperature are simulated, ranging from the soil surface down to 30 m depth, and the horizontal grid cell resolution is 25 km × 25 km. Results are presented for three different soil moisture regimes. The trend analysis is based on daily fields of active-layer depth (ALD) for the period January 1980 through December 2001. Significant positive ALD trends for all Tibetan permafrost regions are simulated in response to positive air temperature trends, with the strongest trend for the northern Tibetan Plateau (+1.4 cm yr−1). Significant trends can reach +4 cm yr−1 locally. The day of year when ALD was reached shows strong interannual variation, and significant trends occur for smaller areas than for ALD. As ...
TL;DR: In this article, three fen sites differing in water balance and plant community, as well as one dry meadow site, were used to study the importance of soil temperature, water table, and plant biomass as controlling factors for net methane emission in the Eastern Alps, Europe, during a period of 24 months.
Abstract: Although the contribution of methane emission to global change is well recognized, analyses of net methane emissions derived from alpine regions are rare. Therefore, three fen sites differing in water balance and plant community, as well as one dry meadow site, were used to study the importance of soil temperature, water table, and plant biomass as controlling factors for net methane emission in the Eastern Alps, Europe, during a period of 24 months. Average methane emissions during snow-free periods in the fen ranged between 19 and 116 mg CH4 m−2 d−1. Mean wintertime emissions were much lower and accounted for 18 to 59% of annual flux. The alpine dry meadow functions as a methane sink during snow-free periods, with mean flux of −2.1 mg CH4 m−2 d−1 (2003) and −1.0 mg CH4 m−2 d−1 (2004). Seasonal methane emissions of the fen were related to soil temperature and groundwater table. During the snow-free periods the water table was the main control for seasonal methane emission. The net methane flux r...