This paper presents the results of a distributed surface energy balance model which is used to calculate season-long patterns of melt on a small valley glacier, Haut Glacier d'Arolla, Valais, Switzerland, under different summer meteorological conditions and winter snow depth distributions. The model uses a Digital Elevation Model of the glacier and the surrounding topography, together with meteorological data collected at a site in front of the glacier to determine hourly totals of the surface energy balance components, and hence melt, over the entire glacier surface throughout a melt season, with a spatial resolution of 20 m. From these results, the spatially averaged mass-balance/elevation profile for the glacier can be calculated. A cubic relationship with elevation gives the best fit to the calculated mass-balance curve. The shape of this profile varies with the imposed change in meteorological conditions, however, becoming increasingly “S” shaped for warmer or less snowy conditions. These mass-balance profile changes are due to the complex interplay between albedo variations due to different snow depths over the glacier surface (and eventual removal of the snow cover), the variations in solar energy receipts caused by slope and aspect variation over the glacier and the changing patterns of shading by the surrounding topography. The changes in mass-balance profile lead to maximum calculated mass-balance sensitivity to imposed change occurring at intermediate elevations on the glacier; the calculated equilibrium-line altitude (ELA) occurs at the upper end of this zone, resulting in very large calculated changes in the ELA for different climatic conditions.

The acclimation response of the chloroplast was studied in the green marine microalga Koliella antarctica exposed to a simulated austral night of 90 d. On the basis of the micro- and submicroscopic aspects observed, the photosynthetic pigment patterns monitored spectrophotometrically, and the course of the assembly of the PSII chlorophyll-protein complexes evaluated microspectrofluorimetrically in vivo on single living cells, it was established that the alga tolerates the stress of light absence when cultured in the laboratory. During the treatment, the organism undergoes substantial structural and functional reorganization of the plastid, resulting in the formation of a chlorochromoplast-like structure, suitable for the storage, in different times and in specialized structures, of the products coming from the breakdown of the pre-existing plastid constituents. On the whole, the dark acclimation occurs in two different steps: a first acclimation, quickly realized, during the first 6 d and maintained up to 20 d of darkness, and a second acclimation period, starting from the 21st day, maintained up to the end of the experiment.

We collected ground-penetrating radar data at 10 sites along the Kuparuk River and its main tributary, the Toolik River, to detect unfrozen water beneath river ice. We used 250 MHz and 500 MHz antennas to image both the ice-water interface and the river channel in late April 2001, when daily high temperatures were consistently below freezing and river ice had attained its maximum seasonal thickness. The presence of water below the river ice appears as a strong, horizontal reflection observed in the radar data and is confirmed by drill hole data. A downstream transition occurs from ice that is frozen to the bed, called bedfast ice, to ice that is floating on unfrozen water, called floating ice. This transition in ice type corresponds to a downstream change in channel size that was detected in previously conducted hydraulic geometry surveys of the Kuparuk River. We propose a conceptual model wherein the downstream transition from bedfast ice to floating ice is responsible for an observed step change in channel size due to enhanced bank erosion in large channels by floating ice.

A 10-yr (1993–2003) geodetic survey was conducted at the Besiberris rock glacier, a tongue-shaped, glacigenic rock glacier, located in the eastern-central Spanish Pyrenees (42°35′48″N, 0°49′20″E). Displacement measurements were made on three traverse lines across the rock glacier. Surface horizontal velocity increases from the head to the toe sectors (average values: traverse line A = 8.72 cm yr⁻¹; line B = 10.65 cm yr⁻¹; line C = 13.35 cm yr⁻¹). Velocities are greater at the axis of the rock glacier compared to its lateral margins. In terms of vertical movement, the rock glacier has shown clear thinning of an ice-core. In all three traverse lines, surface lowering has been detected (average values: line A = 5.00 cm yr⁻¹; line B = 7.10 cm yr⁻¹; line C = 5.27 cm yr⁻¹). This general lowering is interpreted as the adjustment of the rock glacier to the climatic amelioration (higher temperature, drier conditions, and reduced snowfall) observed in the Pyrenean region since the end of the Little Ice Age and accentuated in the last few decades.

The summer diets of a natural population of white-tailed ptarmigan (Lagopus leucurus), an herbivorous alpine grouse, in the Rocky Mountains and an introduced population in the Sierra Nevada were compared to determine if differences in alpine tundra plant communities affected nutritional intake. Foraging selections of 28 adult ptarmigan were recorded regarding number, amount, availability, nutritional, mineral and energy content of plant species eaten. The average diet of the Rocky Mountain ptarmigan was composed of nine plant species (99% g dry wt), while the average diet of the Sierra Nevada ptarmigan was composed of only two plant species, Salix anglorum and Carex jonesii (99% g dry wt). Although plant species eaten differed between the populations, the energy and lipid content of the diets were nearly identical. The diet of Sierra Nevada ptarmigan was 28% higher in protein and 13% lower in carbohydrate than the diet of Rocky Mountain ptarmigan, likely due to high consumption of Salix leaves and low consumption of flowers by the Sierra Nevada ptarmigan. Both populations exhibited sampling behavior (ingesting occasional bites from many species), which would allow ptarmigan to track changing resources in the highly variable alpine environment and may have enabled the introduced ptarmigan to identify a suitable diet.

Mycorrhizal symbiosis is critical to plant establishment and survival, influences plant community structure and function, and could be particularly important in harsh environments such as the alpine tundra. An examination of 53 vascular plant species in 21 families from alpine areas of the Beartooth Plateau (Rocky Mountains) revealed most were mycorrhizal (68%) and four distinct types of symbioses were present. They differ in fungal groups involved, plant taxa, physiology, ecology, morphology, and resource acquisition. Betula, Dryas, Salix, and Polygonum viviparum consistently form ectomycorrhizae (ECT) with basidiomycete fungi. Phyllodoce, Kalmia, and Vaccinium (Ericaceae) form ericoid mycorrhizae with ascomycete fungi, and Arctostaphylos an arbutoid type with basidiomycetes. Eight families (18 species) had only arbuscular mycorrhizae (AM) of glomalean fungi: Apiaceae, Asteraceae, Campanulaceae, Fabaceae, Hydrophyllaceae, Onagraceae, Poaceae, Ranunculaceae. Nonmycorrhizal (NM) families were Brassicaceae, Caryophyllaceae, Crassulaceae, Cyperaceae, Gentianaceae, and Juncaceae. Split families included Polygonaceae (NM/AM/ECT), Portulacaceae (NM/AM), Rosaceae (AM/ECT), and Scrophulariaceae (NM/AM). This is the first report of mycorrhizae for 25 alpine plant species, and most others are new reports for the Rocky Mountains. The distribution of mycorrhizal types among plant families is reasonably consistent across the arctic-alpine biome (reviewed here) with exceptions. The patchy distribution of mycorrhizal types associated with large-scale perennial vegetation mosaics suggests microbial functioning is not uniform across tundra landscapes.

A study of shoot populations of Carex curvula subspecies (Carex curvula ssp. rosae and C. curvula ssp. curvula) compared predictions from a 3-year observation period with renewed observations after 10 years. The study sites were located in the Dolomites (Mount Latemar), Italy, at 2390–2580 m a.s.l. The first observation period (1990–1992) produced findings on shoot numbers in different plots at five sites. These shoot numbers allowed the finite rates of population increase λ (characterizing the dynamic state of the populations) to be calculated. The values of λ varied modestly within and among populations. The long-term rates of population increase remained close to the equilibrium value of 1.0. The spatial pattern was calculated by means of the patchiness index and patch occupancy. The smaller the plot population, the higher the patchiness and the lower the proportion of occupied patches. To some extent, patchiness can serve as a measure of a population's dynamic state. A correlation between the structural measures (patchiness, patch occupancy) and the rate of population increase λ showed that strongly aggregated populations were small and also decreasing in size. The extinction risks for the next 50 years were found to be very low for populations on the pioneer grassland stand whereas most other populations will decrease and probably reach critical thresholds.

We derived and implemented two spatial models of May snow water equivalent (SWE) at Lee Ridge in Glacier National Park, Montana. We used the models to test the hypothesis that vegetation structure is a control on snow redistribution at the alpine treeline ecotone (ATE). The statistical models were derived using stepwise and “best” subsets regression techniques. The first model was derived from field measurements of SWE, topography, and vegetation taken at 27 sample points. The second model was derived using GIS-based measures of topography and vegetation. Both the field- (R² = 0.93) and GIS-based models (R² = 0.69) of May SWE included the following variables: site type (based on vegetation), elevation, maximum slope, and general slope aspect. Site type was identified as the most important predictor of SWE in both models, accounting for 74.0% and 29.5% of the variation, respectively. The GIS-based model was applied to create a predictive map of SWE across Lee Ridge, predicting little snow accumulation on the top of the ridge where vegetation is scarce. The GIS model failed in large depressions, including ephemeral stream channels. The models supported the hypothesis that upright vegetation has a positive effect on accumulation of SWE above and beyond the effects of topography. Vegetation, therefore, creates a positive feedback in which it modifies its environment and could affect the ability of additional vegetation to become established.

Tree-ring chronologies for tamarack (Larix laricina (Du Roi) K. Koch) growing in four stand types covering a dry-to-wet gradient were developed to investigate the association between radial growth and climate as well as evidence of larch sawfly (Pristiphora erichsonii Hartig) herbivory near Churchill, subarctic Manitoba. The chronologies, produced using both living and subfossil material, were well replicated for the period 1800 to 2000. Our results indicated that climate explained more than 60% of the growth variation in tamarack with temperature from May to July of the growing season being most important. This was unusual considering that other studies showed a weak radial growth-climate association in tamarack because of signal contamination due to severe larch sawfly defoliation. Potential outbreak episodes were investigated by looking at pointer years and by contrasting the variance within the tamarack tree-ring series with that observed in climate and in nonhost species. A weak correspondence was observed among pale latewood rings, growth suppression period, and incomplete rings. Comparison of host and nonhost chronologies revealed synchronized growth suppression periods in tamarack during 1818–1824, 1857–1864, 1891–1892, 1903–1912, and 1959–1964, with seldom more than 25% of the trees being affected. The 20th-century suppressions corresponded to known outbreaks identified in Manitoba. However, they also corresponded to periods of little residues in the climate model suggesting that they may be due to short-term changes in site hydrology. This study stresses the difficulties to use dendrochronology to identify what may be low severity or “subepidemic” defoliation events. It also stresses the potential differences in the larch sawfly dynamics between the boreal forest and the forest-tundra. Further studies using an extended network of chronologies will be needed to decipher the short-term impacts of climate from those of low severity defoliation episodes.

This paper describes the structural glaciology of Haut Glacier d'Arolla, a small valley glacier fed by two distinct accumulation basins in the Swiss Alps. A considerable body of field data is presented alongside observations from ground and aerial photographs. Suites of structures identified in the field and from aerial photographs are first described in nongenetic terms before being assigned regular structural terms. Haut Glacier d'Arolla is dominated by primary stratification, which is progressively folded and eventually transposed into longitudinal foliation as it moves into the glacier tongue. Crevasses and crevasse traces cross-cut and in places displace primary stratification and longitudinal foliation. Crevasse traces are formed by the closure of crevasses or may represent tensional veins. On their journey downglacier, crevasse traces become increasingly rotated. Close to the snout, some crevasse traces become reactivated as thrust faults. Strain ellipses, derived from the velocity field, show progressive deformation downglacier (cumulative strain). The shapes of the strain ellipses agree with inferences made concerning the orientation and magnitude of strain from observations of structures in the field. Independent modeling of cumulative strain shows good agreement with the development of longitudinal foliation in a simple shear regime. However, there are inconsistencies in the relationship between modeled cumulative strain and other structures.

Morphological and physiological variation of four geographically separated European populations of Oxyria digyna (L.) Hill (Polygonaceae) ranging from 45 to 78°N latitude were studied in controlled environments. Characters such as the presence of rhizomes, variable stamen number, few inflorescence branches, and low leaf length/width ratio were found to be common to northern populations. Perennating buds were formed under short day (SD) conditions in all populations across the temperature range (9–21°C), while induction of dormancy required the combination of SD and low temperature. Dormancy release of dormant buds required long day (LD) conditions only. The species was found to be a short-long-day plant for flowering control, the SD requirement being quantitative while the subsequent LD requirement is obligatory. Both the SD flowering response and the fecundity of flowering decreased clinally with increasing latitude of population origin, while the critical daylength for secondary floral induction showed a parallel increase. With some minor modifications, these results agree with earlier findings with North American populations. It is concluded that the obligatory LD requirement for flowering has been a limiting factor for the southward geographic distribution of the species, and that the photoperiodic control of flowering and winter dormancy renders Oxyria particularly well adapted to resist potential negative effects of rising global temperature.

We studied the fossil remains of the common Antarctic oribatid mites, Alaskozetes antarcticus and Halozetes belgicae, in sediment cores from two lakes in adjacent catchments on Signy Island, South Orkney Islands, maritime Antarctic. The aim was to examine the response of these species to 7000 yr of documented environmental change. Mites colonized the island shortly after the ice sheet retreated and habitats became available. A temperate period in the Holocene (c. 3800–1400 cal. yr BP) led to population expansion by factors of 7 (both species) in one catchment and 5.1 and 2.3 for both species in the other. This mid-Holocene hypsithermal is thought to have involved increases in habitat size, productivity, temperature, and moisture availability. Mite populations went into decline as conditions cooled. A period of short cold summers from c. 1400 cal. yr BP persisting to the middle of this century continued to impose restrictions on the biota. These results suggest that mite populations will respond positively to the recent rapid regional warming documented in the maritime Antarctic. However, on Signy Island this prediction is complicated by a similarly recent and rapid expansion of the populations of Antarctic fur seals (Arctocephalus gazella), which has not occurred previously since deglaciation, damaging the mites' habitats and exerting a new set of ecological constraints.

The mapping of air temperature in the Qinghai-Tibet Plateau is of practical importance because the meteorological stations are sparse and unevenly distributed in the region. The spatial interpolation methods of inverse distance weight, ordinary kriging, ordinary cokriging, and a combined method were used to estimate the spatial distribution of the 1961–1990 January mean air temperature in the Qinghai-Tibet Plateau. The combined method is a combination of ordinary kriging and correction of altitude effect by using lapse rate of air temperature. Comparison of results showed that the problem of mapping air temperature in the Qinghai-Tibet Plateau cannot be resolved by the simple geometric interpolation method as the inverse distance weight. Ordinary kriging can manifest some spatial pattern but the performance was not improved too much. Cokriging to a certain extent was an improvement of kriging but due to the limited altitude information included in the co-variable, the interpolation results were also not in agreement with the actual situation. The combined method was superior to the other methods. The interpolation result from it was reasonable, proved by both the subjective analysis and by many previous works. The comparison of the four methods leads to the conclusion that for regions with sparse meteorological stations, such as the Qinghai-Tibet Plateau, stochastic interpolation methods must be combined with the altitude-effect correction for estimating the spatial distribution of climatic variables.

The evolution of snow depth in the central Spanish Pyrenees was analyzed using measurements from 106 snow stakes over a period of 14 yr (1985–1999). Relationships were considered between the regional series of snow depths at the end of winter and in the middle of spring with respect to precipitation and temperature in previous months. Both variables explained a large percentage of the interannual variability in snowpack. The high correlation between climate parameters and snow depth series may help to better understanding snow evolution at different times of the year and to obtain a predicted series of snow depths for the period 1950–1999 from longer climate series. Snow depth decreased significantly during the second half of 20th century, probably because there was less precipitation from January to March. The decrease in winter precipitation seemed to be related with the positive trend of the North Atlantic Oscillation (NAO) index during the same period.

This is the first time that the soil arthropod community composition along a high-altitude gradient (3,837, 4,105, and 5,050 m a.s.l.) has been investigated in eastern Tibet, China. Five soil samples of 50 cm² were taken from each site and extracted for 7 days in Berlese/Tullgren funnels without heating. Acari was the dominant group of arthropods at all three elevations (79%, 53%, and 54%, respectively, from the lower site to the upper site). Prostigmata and Oribatida were more abundant than Mesostigmata and Astigmata at all three elevations. Mesostigmata and Oribatida were most abundant at the upper elevation (about 8,300 and 29,000 individuals/m², respectively). Prostigmata and Astigmata were most abundant at the lower elevation (about 170,000 and 20,000 individuals/m², respectively). Collembola was most abundant at the middle elevation (about 68,000 individuals/m²). The insect taxa were most abundant at the lower elevation. Diptera larvae, Protura, and Homoptera were the most abundant taxa along the elevation gradient, while Hemiptera, Thysanoptera, and Protura occurred only at the lower elevation. A multivariate redundancy analysis (RDA) shows that 64% of the variance can be explained by altitude. A change in dominant mite taxa along the elevation gradient could be seen. From the lower to upper sites, the dominant taxa changed from Prostigmata to Prostigmata and Oribatida, and then to Oribatida. About 33 genera in 24 families of oribatid mites were found. The numbers of genera from the lower, middle, and upper elevation were 14, 20, and 19, respectively.