Ice elevation changes since 1975 and ice areal changes since 1945 of glaciers in the southeastern part of the Southern Patagonia Icefield (SPI) are presented. Comparison of digital elevation models, GPS, and optical survey data revealed high thinning rates for all the ablation areas of the glaciers, with average values between 1.4 and 3.4 m a⁻¹ and maximum ice thinning of 7.6 m a⁻¹. Ice elevation changes for the glacier accumulation areas were smaller than the estimated errors, and no significant trends could be detected. All the glaciers are retreating and shrinking considerably, with a total areal loss of 62.2 km², which represents 8% of the total ice area of 1945. This trend is in agreement with other similar measurements carried out during recent decades for several glaciers of the SPI. The high thinning rates for the ablation areas of the SPI have been primarily interpreted as a result of the increase in temperature observed in the region, however, this warming trend is not large enough to account for all the ice thinning, indicating that dynamic factors could be important, especially in glaciers which have been thinning dramatically, allowing frontal calving fronts to reach nearly floating conditions. More measurements are needed to test and validate dynamic hypotheses related to glacier behavior in Patagonia.

Lengthening of the growing season at high latitudes, observed by satellites with the Normalized Difference Vegetation Index (NDVI), has been ascribed to climate warming. To test this assumption, and to verify whether changes in vegetation greenness are quantitative or qualitative, we experimentally warmed patches of High Arctic tundra with infrared heating in Northeast Greenland. By analyzing digital images of the vegetation, changes in cover were distinguished from changes in senescence. During the season, experimental warming significantly increased green cover, for example, at the time of peak cover, the total green cover was enhanced from 59.1 to 67.3%. The dominant wavelength (hue) reflected by our tundra plots shifted from yellow-green to yellow. Experimental warming with 2.5°C delayed this hue-shift by 15 d. The results demonstrate that higher summer temperatures do not only promote plant growth at these latitudes but also retard and/or postpone the senescence process, contrary to indications from previous research that late-season phenology in the High Arctic is governed by photoperiod.

We examined soil microbial activities, i.e., biomass, respiration rate, and temperature dependence of the respiration on a glacier foreland in Ny-Ålesund, Svalbard, Norway. We collected soil samples from 4 study sites that were set up along a primary succession (Site 1, the youngest, to Site 4, the oldest). Microbial biomass measured with the SIR method increased with successional age (55 to 724μg C_biomass g⁻¹ soil d.w. from Site 1 to Site 4). The microbial respiration rate of the soil was measured in a laboratory with an open-flow infrared gas-analyzer system, changing the temperature from 2° to 20°C at 3–4° intervals. The microbial respiration rate increased exponentially with the temperature at all sites. The temperature dependence (Q₁₀) of the microbial respiration rate ranged from 2.2 to 4.1. The microbial respiration rates at a given temperature increased with succession as a step change (0.48, 0.43, 1.26, and 1.29μg C g⁻¹soil h⁻¹ at 8°C from Site 1 to Site 4, respectively). However, the substrate-specific respiration rate (respiration rate per gram soil carbon) decreased with successional age (0.034 to 0.006μg C mg⁻¹C_soil h⁻¹ from Site 1 to Site 4). A comparison of these respiratory properties with other ecosystems suggested that soil microorganisms in arctic soils have a high potential for decomposition when compared to those of other temperate ecosystems.

Several environmental indicators show that climate changed dramatically at the turn of the 19th century, with global warming throughout the 20th century. Among the most used proxies to evaluate long-term changes in climate are trees located at their northern range limit. Several studies have shown enhanced tree regeneration at treeline caused by recent warming, but no data are available on height growth performance of forest trees at treeline before and during the 20th century warmth. In this study, we examined the long-term growth performance of black spruce (Picea mariana [Mill.] B.S.P.) trees located in a lichen-spruce woodland, near the arctic treeline in eastern Canada. The study woodland is an old-growth stand that has escaped fire approximately during the past two millennia. We performed stem analysis on normally developed trees which grew in the woodland over the last centuries. The sampled trees are ramets from long-lived, self-regenerating black spruce clones that are forming small tree islands within the woodland. The co-occurrence of living and dead tree stems inside clones gives the opportunity to evaluate the growth performance of the same genets through time. Height and radial growth of 60 tree stems from 15 old-growth clones were evaluated for a period spanning the last 400 yr. Sampling included the two tallest living stems and the two tallest dead stems of randomly selected clones. No differences in height and radial growth were found among the 30 living stems nor among the 30 dead stems within clones. Living stems were 2 m taller and radial growth was 1.6 times greater than dead stems. Vertical development of stems was divided into two parts according to position of snow cover. Growth of dead and living stems was similar below the snowpack line. However, significant differences were found for growth above snowpack for the two types of stems. Growth above snow cover for all dead stems occurred between the 17th and 19th centuries. In contrast, growth of living stems above snow cover started during the late 19th century. Our data indicate that stems of the same genotype responded directly to climate change, in conjunction with climatic conditions prevailing at the time when they were protruding above the snowpack. Compared to extant trees, significantly smaller trees grew in the woodland during the Little Ice Age. Potential causal factors of differential growth performance through time are discussed.

A calibrated Rhizocarpon spp. lichen growth curve spanning the last 680 yr was developed for the Bella Coola and Mount Waddington areas, southern Coast Mountains of British Columbia (Canada). It is based on 18 control surfaces whose ages were determined using radiocarbon dates, tree-ring dated moraines, and ice front positions derived from historical air photographs. Population distribution statistics were used to assess the validity of each control lichen measurement. The relationship is characterized by logarithmic growth during the first 100 yr following surface stabilization, and is described as linear for the successive 600 yr. Application of the curve at Tiedemann Glacier revealed evidence for six periods of late-Neoglacial moraine formation in ca. AD 620, 925, 1118, 1392, 1575, and 1621. The study confirms the importance of incorporating a multisite approach and a lichen population dynamic assessment. Large samples sizes and replication are also noted as necessary in order to adequately assess any dating errors.

Increasing production of artificial snow in ski resorts is controversially discussed, but only few investigations have been carried out systematically to specify the environmental impacts. We measured snow depth and density from groomed ski pistes (runs) with compacted snow and their effects on ground temperatures and timing of snowmelt. We analyzed groomed pistes with and without artificial snow (10 each) as well as adjacent ungroomed off-piste control plots beside the piste. On pistes with natural snow, the thin and compacted snow cover led to severe and long lasting seasonal soil frost. On pistes with artificial snow, soil frost occurred less frequently because of increased insulation due to the greater snow depth. However, due to the greater snow mass, the beginning of the snow-free season was delayed by more than 2 wk. Average winter ground temperatures under a continuous snow cover were decreased by approximately 1°C on both piste types compared with off-piste control plots. The results suggest that the heat balance of alpine soils is changed by both piste types, either by an extensive heat loss on pistes with natural snow or by prolonged snow cover on pistes with artificial snow.

We examined the impact of Salix lapponum canopies on plant community structure in five sites along a climatic gradient in a glacier foreland in alpine south Norway. Species richness is lower inside canopies compared to outside in climatically relatively benign communities, while species richness is not affected by canopies in the most severe communities closest to the glacier. Differences in species composition inside and outside canopies, as judged by detrended correspondence analysis, are greater in the benign communities compared to the severe communities. Variation in the differences in species richness or composition outside and inside canopies within a community is related to differences in the reduction of photosynthetically active radiation (PAR) by canopies in only one community. Canopy size does not explain differences in species richness or composition between outside and inside canopies in any except one benign community. Our results suggest that species responses to canopies are individualistic, and that at the whole-community level negative and positive impacts of canopies on species occurrences cancel each other out in severe communities, whereas in benign communities negative effects dominate slightly over positive ones in their effects on species persistence inside canopies.

We examined the effects of snow avalanche on stand structure and the subsequent regeneration of subalpine Abies mariesii Mast forest in northern Japan, and discussed whether gap formation after avalanche disturbance leads to immediate seedling establishment or not. Tree size and age, tree-ring chronology, and seedling density were compared between, on, and around a relatively large avalanche path, which was created in the mid-1980s within Hachimantai National Park. On the avalanche path, only smaller and younger trees (height <5 m, 50–100 yr old) escaped the mechanical damage of avalanche by leaning into the remaining snowpack, and old canopy trees were mostly killed by stem breakage. Tree size structure of the avalanche path, including both living and dead individuals, was relatively similar to that of nearby undisturbed forest, indicating that a mature stand (>ca. 200 yr old) had been previously developed on the avalanche slope without large-scale disturbances in the past. Most of the surviving, younger trees showed abrupt growth release during the few years (1987–1989) after the avalanche event. However, densities of both post-avalanche (<15 yr old) and pre-avalanche (≥15 yr old) seedlings were much lower on the avalanche path than in the nearby forest, especially at microsites covered with dense dwarf bamboo (Sasa kurilensis) shrub. The pre-avalanche seedlings on the avalanche path sharply increased annual height growth rates after the mid-1980s avalanche, but such positive growth response did not continue longer than 6 to 7 yr. These findings suggested that gap formation following the infrequent, large-scale avalanche disturbance did not necessarily lead to immediate seedling recruitment and/or further growth release of pre-avalanche seedlings. The constraint of seedling establishment was primarily explained by the lack of potential seed supply, and shading effect of the dwarf bamboo bush. Consequently, post-avalanche regeneration of the subalpine fir forest was likely to depend on the smaller individuals (2–5 m in height) that were able to avoid both the mechanical damage of avalanche and mortality from shading by the dwarf bamboo.

Modern chironomid assemblages consisting of 68 taxa were extracted from the sediments of 39 lakes in southwest Yukon and northern British Columbia, Canada. Important factors accounting for the distribution of the chironomid taxa include sediment organic matter (LOI; weight-loss-on-ignition), total phosphorus, bottom water temperature, and lake alkalinity. The results show the importance of organic matter, which is associated with water depth and lake productivity, in affecting chironomid community composition. Tanytarsus sp. C, Tanytarsus pallidicornis type, Allo/Mesopsectrocladius, Polypedilum, and Procladius were associated with lakes having high LOI values and shallow lake depths, while Paratanytarsus, Sergentia, and Corynocera oliveri type were more prevalent in deeper lakes with more minerogenic sediments. Surprisingly, Chironomus was most abundant in deeper lakes with low LOI values, which might be partially explained by low oxygen levels. Contrary to some findings, Tanytarsus lugens group was common in shallow, productive lakes in this region.

Carbon dioxide fluxes in a dry subarctic heath were examined after 10 and 11 yr of experimental manipulations of temperature, light, and nutrients. The aim was to investigate how growing season carbon (C) balance was affected by the major climatic factors that are expected to change in the future. Carbon flux was measured in closed chambers as uptake through gross ecosystem production (GP), release through ecosystem respiration (ER), and as net ecosystem production (NEP). Diurnal NEP through a day with clear skies at peak growing season was consistently negative through all treatments the first year of measurement, and day-time NEP varied around zero at eight days across the growing season the second year, implying that a net release of C from the ecosystem to the atmosphere may take place during the growing season. Our results suggest that respiration was the main determinant of C balance, and that variations in light levels and temperature could alter the balance between C uptake and C loss. Fertilization strongly enhanced both ER and GP whereas temperature enhancement changed neither ER nor GP. Shading decreased both ER and GP. After harvest of the aboveground plant biomass, the belowground respiration was 72 to 93% of the ER before harvest. The significant treatment effects on belowground respiration after harvest were similar to the effects on ER before harvest. These results suggest that the ER were mainly from belowground respiration, and that the treatments affected the belowground respiration more than the respiration above ground.

Positive interactions in alpine plant communities have been reported to increase in importance with increasing altitude and exposure. Positive and negative interactions between plants might occur simultaneously, so the net plant-plant interaction is determined by the balance between positive and negative effects. I investigated the relative effect of facilitation and resource competition by surrounding dwarf shrubs on Carex bigelowii in two contrasting arctic-alpine tundra heathlands. Carex bigelowii was positively associated with dwarf shrubs on an exposed mountain ridge but negatively associated with dwarf shrubs on a protected heath. A removal experiment indicated that positive associations at the exposed site are the result of facilitation of C. bigelowii by the dwarf shrub canopy. Our understanding of arctic and alpine plant communities can be enhanced by regarding plant interactions as combinations of positive and negative components.

Arctic foxes are evaluated as seed dispersal vectors for Greenlandic plant species through a feeding experiment with subsequent scat analysis and germination test. Seeds of 22 common species with different morphology were tested. Passage time ranged between 4 and 48 h. No significant differences were detected in passage time for seeds with different morphology. Cerastium alpinum and Stellaria longipes had higher germination after passage through the fox's digestive tract when compared to controls. Sibbaldia procumbens, Oxyria digyna, and Silene acaulis were favored by passage when shorter than 10 h. Salix glauca ssp. callicarpaea, Veronica alpina, Gnaphalium norvegicum, Papaver radicatum, Ranunculus hyperboreus, Chamaenerion latifolium, Luzula parviflora, and bulbils of Polygonum viviparum and Saxifraga cernua were inhibited by passage, whereas the remaining species had germination percentage too low to allow for evaluation. Species with adaptations to wind dispersal seemed particularly vulnerable to gut passage. Arctic foxes are able to provide long-distance dispersal of seeds lacking morphological adaptations to dispersal, but for most species seeds need to be defecated within 12 h to remain viable.

We analyzed attributes of tree encroachment on montane meadows and subalpine grasslands on the North Rim of Grand Canyon National Park. Species composition, age, density, height, diameter, condition class, and patterns of tree establishment were examined on belt transects at 12 meadow sites. Of the 3481 live and dead trees sampled, 52% of all trees were Populus tremuloides, 20% were Picea spp., 11% were Abies lasiocarpa, 10% were Abies concolor, and 7% were Pinus ponderosa. Tree densities averaged 4703 trees ha⁻¹. Sixty-two percent of the trees sampled were less than 20 yr of age, although some species established in the early and mid-1800s. Ninety-one percent of all trees, however, established after the mid-1930s, with the greatest establishment occurring after the early 1970s. Of this 91%, Populus tremuloides composed the majority (90%) of recent tree recruitment, with a mean establishment date of 1983–1984. A general pattern of progressively younger trees from the closed forest toward the meadow interiors was detected for some species, and together with little evidence of historical tree occurrence (e.g., large standing dead, downed logs, etc.) on the transects, indicated that trees had been encroaching on these meadows since the 1800s. These trends suggest a loss of important meadow habitat and landscape biodiversity within Grand Canyon National Park during the past century.

Colobanthus quitensis is one of only two vascular plant species that occur in the Antarctic islands. We evaluated morphological and physiological traits and survival after freezing in individuals of C. quitensis collected in two populations: one from the Andes of central Chile and the other from the maritime Antarctic. We addressed whether these populations are ecotypes in terms of shoot morphology and physiology, and cold resistance. We also evaluated genetic differentiation at the internal transcribed spacer (ITS) regions. Under controlled growing conditions, Andean plants had longer and narrower leaves and longer peduncles. However, shoot biomass was similar in both populations. There was a 1.17% sequence divergence of ITS regions between populations. Survival to freezing at temperatures from 0° to −16°C was not different in nonacclimated plants. After cold-acclimation at 4°C, freezing tolerance was greater in Antarctic plants. Both Andean and Antarctic plants increased soluble sugars with increasing acclimation time, but it did not differ between populations. Shoot water content decreased with acclimation time in both populations, but Antarctic plants maintained slightly higher water contents after cold exposure. Shoot growth did not differ during acclimation. The studied populations of C. quitensis represent different morphological and cold resistant ecotypes despite their genetic similarity. However, the mechanistic basis of the higher survival to freezing of Antarctic plants was not elucidated.

We evaluated fecal pellet counts as an index of hoary marmot (Marmota caligata) social group size in order to develop a simple, inexpensive method for monitoring population change of a widely distributed, but poorly studied alpine mammal. Fecal pellet counts were conducted in three separate seasons along several 2 m × 100 m transects located parallel to and 10, 20, and 30 m from the edge of alpine boulderfields (talus) occupied by marmots. Marmot activity and location relative to talus was also determined to assess the proportion of time spent foraging as a function of distance from refuge. Marmots spent 74% of their activities in meadows at a mean distance of 11.6 m from talus, and activity in meadows declined with increasing distance from talus, as did fecal pellet counts. Fecal counts at 10 m from the edge of talus were strongly and linearly related (r² = 0.89) to marmot abundance. The functional equation of marmot abundance predicted marmot abundance in five independent social groups within 17% of the observed group size. Fecal pellet counts appear to provide a precise index of marmot group size suitable for long-term monitoring of population change.

This paper presents observations of summertime anti-winds monitored under ideal conditions in the Lake Tekapo hydro-catchment situated in the central Southern Alps, New Zealand. Onset and cessation of anti-winds was observed to coincide with the change in phase of the surface limbs of thermally generated valley and mountain winds under settled anti-cyclonic conditions. Anti-winds were best developed in the early morning before surface heating and associated convective mixing of the valley atmosphere began to mask the boundaries between the surface based limb of the mountain-valley wind and the corresponding anti-wind. By mid-day, the anti-valley wind exceeded the height of the surrounding ridgeline and became embedded in the topographically channeled gradient wind. Observations presented here have both theoretical and applied implications with regard to the development of thermally generated wind systems in deep alpine valleys, and their role in the dispersion of air pollution.

A complex sequence of sawtooth moraines occurs on the proglacial foreland at Lambatungnajökull, southeast Iceland. These features reflect the pattern of deglaciation of a highly crevassed ice margin. The whole sequence documents a period of overall glacier recession exceeding 450 m. Dates have been interpolated for the formation of these moraines through the examination of aerial photographs and the application of lichenometry. The moraines formed annually between AD ∼1932 and 1950. Retreat rates were greatest between 1933 and 1939 and slowest between 1942 and 1944, as reflected by the spacing of annual moraine ridges. Differences in glacier recession rate from year to year are related to variations in mean summer air temperature. A rise in mean summer temperature of 1°C results in a retreat rate of ∼30 m yr⁻¹. It is shown that annual moraine spacings are a suitable geomorphological proxy for annual net glacier balance and a potentially valuable source of paleoclimatic information.

Plant species with morphological features that enable the age of individuals to be estimated are potentially useful for understanding past environmental conditions. Here, the size and growth rate of the cushion plant, Azorella selago Hook. (Apiaceae), are examined to determine if an accurate and reliable age can be assigned to individual plants using the phytometric model detailed by Frenot et al. (1993). Plant size, growth rate, epiphyte load, nearest-neighbor characteristics, and spatial position (used as a surrogate, to encompass a range of abiotic conditions to which plants were exposed) were measured at three sites. Additionally, variation in some of these variables was quantified across three altitudinal transects. Relationships were examined using regression, trend surface and partial regression approaches. Growth rate was independent of plant size, differed between sites, and was related to abiotic as well as other biotic factors. As a result, the phytometric model's age estimates may be biased by environmental variables. The results of the phytometric model, albeit in the absence of support for one assumption, estimated mean plant age at 30 yr, with some plants estimated as older than 80 yr. Using a simulation model, the accuracy of age estimates was shown to vary with temporal variation in plant growth rate and plant size. Nonetheless, even a conservative approach suggested these estimates to be accurate to within 2 to 15 yr. While further development of the phytometric model would improve its reliability, the model remains a valuable tool for estimating plant ages in an environment where many related techniques can not be applied.

Vegetation in high Mediterranean mountains usually consists of patchy communities. Patch structures have been interpreted as a result of the prevalence of facilitation phenomena in highly stressful environments. Several mechanisms have been proposed in order to explain the factors that control the existence of these clumped structures. However, they have not been evaluated in these mountains. Our hypothesis is that patchy structure in high mountain Mediterranean vegetation is a consequence of facilitative and competitive interactions in a very harsh environment which ultimately involve strong localized effects on soil properties. Our results show that levels of soil nutrients were higher under vegetation patches than in bare ground areas, confirming the hypothesis of an amelioration of soil resources under canopies. Pairwise associations and repulsions suggest the existence of two contrasting composition stages. Contrasting models relating patch species composition (cover and biomass) and soil resources indicated a weak relationship between species features and soil nutrient levels. Finally, structural modeling showed that patch size has a relevant but indirect effect on soil resource levels through grass and total biomass. We conclude that patch structure and dynamics in high Mediterranean mountain communities may be partly controlled by an endogenous process involving facilitation and competition for soil key resources. These interactions may operate through some community traits related to patch size but not to composition.

Soil organic matter distributions, reservoirs, and mineralization rates in tundra soils are important factors for understanding biogeochemical carbon cycling. This study focuses on spatial trends and environmental controls of soil carbon distribution and microbial soil respiration in 4 tundra vegetation communities in an arctic valley in NE-Greenland (74°N), including Dryas and Cassiope heaths, Salix snow bed, and fen vegetation. Measured total soil organic carbon in the upper 50 cm averaged (±SD) 11.0 ± 1.5 kg C m⁻² with spatial variations strongly affected by vegetation, hydrology, and buried organic layers. Observed soil CO₂ concentrations and effluxes were simulated with a steady-state diffusion model using laboratory measured CO₂ productions as input. Simulated CO₂ profiles and CO₂ effluxes (up to 3 μmol CO₂ m⁻² s⁻¹) agreed with field observations and revealed the importance of both vegetation- and depth-specific CO₂ production and CO₂ diffusion for understanding the spatial variation in near-surface soil CO₂ gas dynamics. These results confirm that molecular diffusion dominates gas transport in the studied soils; but also that the complexity of CO₂ production/transport coupled to soil heterogeneity (in particular the litter layer) complicates the application of soil-diffusion models to estimate seasonal trends of soil gas effluxes.

A simple method is presented which demonstrates the use of continuously injected Rhodamine WT dye to provide automated around-the-clock estimates of flow during the spring breakup. Dye of a known concentration is injected at a constant rate upstream from a sampling point, and the dilution of the dye in the sampled downstream water is a measure of discharge. Field trials conducted in and around Inuvik, Northwest Territories in two small snow-choked streams during spring breakup of 1995 to 1999 suggest that some dye is adsorbed to suspended sediment in the stream channel, resulting in an overestimate of discharge. However, there is still a strong linear relationship between the discharge as estimated by the dye method and that determined by conventional current metering. Correcting the dye values by a linear regression equation line results in a reasonable estimate of streamflow. This method's most promising application is in the monitoring of small basins where much of the annual discharge occurs during the spring melt. Given the occurrence of rapid changes in discharge in these basins due to both diurnal variations in snowmelt and changing runoff source area, and the excessive manpower required to carry out a sufficient number of current meterings needed to properly observe this changing discharge, the dye dilution method often provides a more accurate estimate of discharge.

In eastern Canada, snow avalanches are a common phenomenon, but their occurrences remain poorly documented. In the last 30 yr, they were responsible for deaths and damage to property and forests in avalanche-prone areas in northern and eastern Québec. This study provides tree-ring–based avalanche chronologies for three scree slope stands in the northern Gaspé Peninsula (Québec). Tree-ring records indicated that high-magnitude avalanches occurred seven times during the period from 1860 to 1997, i.e., in 1871, 1898, 1952, 1956, 1966, 1977, and 1996, with 5- to 15-yr return intervals for the period between 1939 and 1997. High-magnitude avalanches occurred during snowy winters, with total snowfall well above average (330 cm). According to the size of past runout zones established from damaged trees at the main study stand, snow avalanches were greater in 1956 and 1966 than in 1996. The 1996 avalanche area was about 16,600 m² of which 60% (10,000 m²) was covered with mature trees. It caused a ∼200-m recession of the tree line. Causal factors of snow avalanches including weather conditions and stand characteristics were also examined.

We performed a spatiotemporal analysis of a network of 21 Scots pine (Pinus sylvestris) ring-width chronologies in northern Fennoscandia by means of chronology statistics and multivariate analyses. Chronologies are located on both sides (western and eastern) of the Scandes Mountains (67°N–70°N, 15°E–29°E). Growth relationships with temperature, precipitation, and North Atlantic Oscillation (NAO) indices were calculated for the period 1880–1991. We also assessed their temporal stability. Current July temperature and, to a lesser degree, May precipitation are the main growth limiting factors in the whole area of study. However, Principal Component Analysis (PCA) and mean interseries correlation revealed differences in radial growth between both sides of the Scandes Mountains, attributed to the Oceanic-Continental climatic gradient in the area. The gradient signal is temporally variable and has strengthened during the second half of the 20th century. Northern Fennoscandia Scots pine growth is positively related to early winter NAO indices previous to the growth season and to late spring NAO. NAO/growth relationships are unstable and have dropped in the second half of the 20th century. Moreover, they are noncontinuous through the range of NAO values: for early winter, only positive NAO indices enhance tree growth in the next growing season, while negative NAO does not. For spring, only negative NAO is correlated with radial growth.

As glacier length fluctuations provide useful information about past climate, we derived historic fluctuations in the equilibrium-line altitude (ELA) on the basis of 19 glacier length records from different parts of the world. We used a model that takes into account the geometry of the glacier, the length response time and the mass balance–surface height feedback. The results show that all glaciers of the data set experienced an increase in the ELA between 1900 and 1960. Between 1910 and 1959, the average increase was 33 ± 8 m. This implies that during the first half of the 20th century, the climate was warmer or drier than before. The ELAs decreased to lower elevations after around 1960 up to 1980, when most of the ELA reconstructions end. These results can be translated into an average temperature increase of 0.8 ± 0.2 K and a global sea-level rise of about 0.3 mm a⁻¹ for the period 1910–1959.

An ecological study of the freshwater testate amoebae (Protozoa, Rhizopoda) on the subantarctic island Île de la Possession (Crozet Archipelago) revealed 85 taxa, belonging to 21 genera. Twenty-two taxa belonged to the genus Difflugia, typical for freshwater habitats whereas the genus Trinema showed the highest relative abundance. A cluster analysis revealed two communities: a Difflugiella crenulata assemblage and a Trinema lineare–T. enchelys assemblage. These communities, together with the results of a RDA analysis, represented a clear geographical separation on the island. The Difflugiella crenulata assemblage typified locations, with a high specific conductance and neutral to alkaline pH values, on the western part of the island. Aquatic habitats in the larger valleys on the eastern side of Île de la Possession, with a low conductivity and slightly acid pH values, were characterized by the Trinema assemblage. Weighted averaging and calibration were used to develop a statistical transfer function to infer the pH of freshwater bodies from the testate amoebae assemblages. The model is usable over a pH range of 5 to 9.

Snowbanks are characteristic for many alpine areas and add considerably to the great variability of growth conditions in high mountain systems. We studied the long-term (5- to 9-yr) growth response of two alpine forbs, Pedicularis recutita and Cirsium spinosissimum, to the environmental conditions in the center and at the periphery of a snowbank in the Swiss Alps. For that we analyzed the growth increments (annual rings) in the roots or rhizomes of the plants. While for both species there were no considerable size differences (number of shoots) between individuals growing in the center of the snowbank and those at the periphery, the growth patterns differed depending on species, temporal variations in growth conditions, and growth position. There were synchronous fluctuations in the width of the annual growth increments that were more pronounced in C. spinosissimum than in P. recutita and were restricted to plants growing in the center of the snowbank. These were apparently related to interannual variations in climatic conditions. In addition, C. spinosissimum plants growing at the periphery of the snowbank showed initially wide but strongly declining growth increments whereas plants growing in the center of the snowbank showed initially narrower but relatively stable growth increments. These patterns were only weakly reflected in P. recutita. Our results suggest that effects of climatic fluctuations on plant growth can be amplified in snowbanks and that there may be favorable growth conditions initially at the periphery of the snowbank that are compensated for in the center of the snowbank, in the long run, by continuously low-competition growth conditions.

A long-term proxy record of glacier mass balance was developed for Colonel Foster and Septimus glaciers on Vancouver Island, British Columbia, Canada. This was accomplished by analyzing the radial growth characteristics of climatically-sensitive mountain hemlock trees (Tsuga mertensiana), and by comparing this response with mass balance records from four glaciers in the Pacific Northwest. A strong (negative) relationship between the two records for the period 1966–1994 provides the basis for a mass balance reconstruction extending back to 1600. The reconstruction is in general agreement with information derived from dated moraine sequences at the two glaciers on Vancouver Island, and it has potential applicability to glaciers in adjacent areas of coastal Pacific North America. Our results highlight the likely influence of the Pacific Decadal Oscillation (PDO) on glacier dynamics during the mid- to late-Little Ice Age (LIA) and provide the groundwork for long-term glaciohydrologic studies.

Paleoecological analyses were carried out from two sediment cores from lake sites at the alpine treeline on Pyhäkero mountain, the northernmost peak of an isolated mountain range, Pallastunturi-Ounastunturi, south of the polar forestline in western Finnish Lapland. Plant macrofossils, supported by pollen data, show presence of pine (Pinus sylvestris) and birch (Betula pubescens) on the top of the mountain from 9500 cal yr BP (birch) and 8300 cal yr BP (pine) up to 2000 cal yr BP (pine) and 1500 cal yr BP (birch). However, the major floristic elements of the modern alpine vegetation, as evidenced by plant macrofossils of a number of typical alpine taxa, including Salix cf. polaris, show persistence through the warmer periods of the Holocene, and indicate that the scattered pine-birch forest never completely replaced the low-alpine plant communities. The current low-alpine vegetation on the mountain top has therefore long continuity from the time of regional deglaciation. Dispersal of these alpine species took place primarily during the deglaciation phase and it is unnecessary to invoke dispersal of the arctic-alpine plants from the arctic regions of Fennoscandia during the mid- or late-Holocene to explain the origin of the alpine flora of the mountain range.

Ice wedges are common in the Mackenzie Delta, although troughs may be filled by sediments and obscured by growth of vegetation. At four sites in eastern Mackenzie Delta, over 85% of the trees within 1 m of ice-wedge troughs leaned towards these troughs. The mean angle of lean was 12° from the vertical, with some trees leaning by more than 25°. The angle of tree tilt varied inversely with distance from the ice-wedge trough and most of the trees over 1 m from an adjacent trough leaned away from the ice-wedge. Trees near the troughs are susceptible to toppling because their root systems trail away from the troughs. Reaction-wood rings in cross-sectional disks from trees leaning towards troughs indicated that progressive tilting has been sustained for decades to centuries. Long-term rates of tree tilting are estimated to be between 0.1 and 0.4° a⁻¹. Progressive, unidirectional tilting may eventually destroy the spruce trees. In Mackenzie Delta, where forest fire is infrequent, earth movements associated with ice-wedge polygons may be one mechanism driving forest change in old-growth stands.

Variations of the diatom distribution in a lake sediment core of Lake Lama, Central Siberia, were used to reconstruct paleotemperatures during the Holocene. The changes of the diatom assemblages revealed a strong association to climatic changes during this period. A transfer function based on weighted averaging partial least squares regression (WA-PLS), derived from a calibration dataset from northwestern Finnish Lapland, was used to infer July air temperatures for the area around Lake Lama. The prediction accuracy of the diatom-temperature model was 0.89°C. The analysis of the modern vs. core assemblages showed the suitability of the model for the lake sediment core. The reconstruction yielded a rapid increase in temperature at the beginning of the early Holocene. There was a period between 8000 and 6500 cal. yr BP with slightly higher temperatures, which were assigned to the Holocene thermal optimum (Hypsithermal), followed by a short and distinct temperature decrease. The period between 4000 and 2800 cal. yr BP again revealed higher temperatures. The inferred temperatures are consistent in their trends with a pollen-based paleotemperature reconstruction of the same core. The range of the diatom-based temperatures was 1.6°C, which is low compared to that of the pollen-based temperatures. This discrepancy may be explained by over- and underestimation of temperatures at the edges of the temperature range by our diatom-based model, and by the large size of this water body which could have moderated the response of diatoms to the temperature signal. The inferred temperature trends from the diatom assemblages at Lake Lama show the potential of aquatic organisms for paleoclimatic reconstructions. This is one of the very few quantitative paleoclimate reconstructions in arctic Russia. Previous research was limited mainly due to the lack of available calibration datasets. Our results also imply that, although this lack might be a drawback, an ecologically sound and reliable reconstruction is still possible and needs to be carried out in other parts of the arctic regions in order to obtain a more detailed knowledge about past regional climate and environmental changes.