Multiproxy data from Little Swift Lake, an alpine lake in southwestern Alaska, provide evidence for pronounced late glacial and Holocene environmental change. An alpine glacier upvalley of Little Swift Lake retreated following the Younger Dryas chronozone, as evidenced by sedimentological changes in the lake record. Glacier retreat was accompanied by local and regional vegetation changes, including the expansion of Betula and contraction of Cyperaceae, in response to climatic amelioration. Warm, moist conditions between ∼9800 and 8000 cal yr B.P. supported abundant Betula shrubs and high lake and watershed productivity. Alnus rapidly expanded near Little Swift Lake while the region cooled between 8000 and 7500 cal yr B.P. Environmental changes at Little Swift Lake appear to have been roughly synchronous with similar changes elsewhere in southwestern Alaska, but late glacial and Holocene changes in other parts of Alaska were different in nature and timing. The complex spatial and temporal patterns of late glacial and Holocene environmental change throughout Alaska point to the importance of local- and regional-scale factors, especially controls on moisture availability, as modulators of site-specific responses to hemispheric- and global-scale climate forcing.

A sediment core recovered in Lake Lyadhej-To at the northwestern edge of the Ural Mountains reflects the complete Holocene environmental history from ∼11,000 cal. yr B.P. Five limnological episodes are identified in the diatom and geochemical records. The initial lake stage, Episode I (∼11,000–10,850 cal. yr B.P.) is characterized by the absence of biogenic production and a high influx of clastic sediments. Episode II (∼10,850–8650 cal. yr B.P.) is characterized by ice-free conditions during summer, highest bioproductivity, strong growth of planktic diatoms and anoxic bottom waters. This period represents the Holocene climatic optimum. Deterioration of climatic conditions commenced in Episode III (∼8650–7000 cal. yr B.P.) as indicated by distinctly lower bioproductivity and longer persistence of winter ice on the lake. During Episode IV (∼7000–2500 cal. yr B.P.), the diatom and pollen records indicate that temperatures were cool and the growing season was short. Finally, in Episode V (∼2500 cal. yr B.P. to present), limnological conditions, indicated by increased organic carbon and diatom deposition, initially suggest improved conditions followed by a return to modern conditions beginning ∼500 cal. yr B.P. The pollen stratigraphy from Lake Lyadhej-To is consistent with other paleoclimatic records from northern Eurasia, confirming rapid postglacial warming, the presence of dense tree forests during the climatic optimum, and finally a gradual southward retreat of the treeline towards its modern location.

The concentration and fluorescence characteristics of dissolved organic carbon (DOC) from surface waters in glacial and nonglacial catchments were used to investigate the provenance of DOC and flow routing of runoff from glacial and nonglacial environments. Seasonal trends in DOC concentration and fluorescence in the Bow River indicate that DOC in nonglacial runoff originates primarily from soil and plant organic matter that is flushed to the stream by shallow subsurface flow at the onset of snowmelt. Snowmelt in ice-free areas of the glacial catchment also appears to be routed through the shallow subsurface, but this snowmelt runoff has much less contact with organic soils or litter, than snowmelt runoff from the nonglacial catchment. The fluorescence of DOC in the Glacial stream in summer (when most runoff originates from ice-covered areas), suggests that DOC from glaciated regions is more “microbial” in character than that derived from ice-free areas. Summer rainstorms in the Glacial catchment flushed DOC derived from catchment soils and plants by displacing concentrated pre-event waters from the shallow subsurface to the stream.

Pine latewood width, density, and stable carbon isotope ratios were measured at two sites, separated in altitude by 400 m, close to the forest limit on a south-facing slope in the western French Alps. The signal to noise ratio in the δ¹³C series from each site is higher than that of either of the growth proxies. When the sites are combined, the high-frequency climate signal in the δ¹³C series is enhanced, whereas in both the ring width and density series it is weakened. Because regional climate dominates over local site conditions, δ¹³C ratios from long pine chronologies will provide a better indicator of past climate than either ring widths or densities. At dry Alpine sites, δ¹³C values are controlled mainly by stomatal conductance, which is linked to summer moisture stress and thus antecedent precipitation.

Megafossil wood remnants (trunks and roots) of mountain birch (Betula pubescens ssp. tortuosa) were retrieved from the alpine tundra of the southern Swedish Scandes (the Sylarna Mountains). The samples have recently become exposed by rapid recession of glaciers and snow patches at three sites located 630 to 350 m higher than the present-day birch tree-limit and 350 to 80 m higher than the early Holocene pine limit. Radiocarbon dating yielded ages ranging between 8700 and 6200 B.P. (9700–7000 cal B.P.). This is the first direct evidence of past tree growth at such high elevations in the Scandes, relative to the modern tree-limit. The overall situation with uniquely high tree-limits and absence of glaciers suggests a climate with generally drier and warmer summers than during any later part (secular-millennial scale) of the Holocene. Corrected for glacioisostatic land-uplift, summers around 8700 B.P. may have been about 3°C warmer than at present. This inference is compatible with the Milankovitch model of orbital climate forcing during the course of the Holocene, implying a gradually increasing maritime climate (less seasonal), with a heavier snowpack. As a consequence, alpine snowfields started to develop over the period 8700–6200 B.P., causing demise and burial of the highest metapopulations of mountain birch. At lower elevations, where snow accumulation had previously been suboptimal for birch, this species could now benefit from a deeper and more persistent snow cover. Since about 7000 B.P., a distinct mountain birch belt has been a characteristic feature in this part of the Scandes. The exposure of mountain birch megafossils relates to substantial 20th-century warming, reaching a peak in the past few years. Evidently, this is an exceptional occurrence in the context of several past millennia.

Four independent studies of conifer growth between 1880 and 2002 in upper elevation forests of the central Sierra Nevada, California, U.S.A., showed correlated multidecadal and century-long responses associated with climate. Using tree-ring and ecological plot analysis, we studied annual branch growth of krummholz Pinus albicaulis; invasion by P. albicaulis and Pinus monticola into formerly persistent snowfields; dates of vertical branch emergence in krummholz P. albicaulis; and invasion by Pinus contorta into subalpine meadows. Mean annual branch growth at six treeline sites increased significantly over the 20th century (range 130–400%), with significant accelerations in rate from 1920 to 1945 and after 1980. Growth stabilized from 1945 to 1980. Similarly, invasion of six snowfield slopes began in the early 1900s and continued into snowfield centers throughout the 20th century, with significantly accelerated mean invasion from 1925 to 1940 and after 1980. Rate of snowfield invasion decreased between 1950 and 1975. Meadow invasion and vertical leader emergence showed synchronous, episodic responses. Pinus contorta invaded each of ten subalpine meadows in a distinct multidecadal pulse between 1945 and 1976 (87% of all trees) and vertical release in five krummholz P. albicaulis sites also occurred in one pulse between 1945 and 1976 (86% of all branches). These synchronies and lack of effect of local environments implicate regional climate control. Composite weather records indicated significant century-long increases in minimum monthly temperature and multidecadal variability in minimum temperature and precipitation. All ecological responses were significantly correlated with minimum temperature. Significant interactions among temperature, precipitation, Pacific Decadal Oscillation (PDO) indices, and multiyear variability in moisture availability further explained episodic ecological responses. Four multidecadal periods of the 20th century that are defined by ecological response (<1925; 1925–1944; 1945–1976; >1976) correlate with positive and negative PDO phases, as well as with steps in the rate of temperature increase. These diverse factors in spatially distributed upper-montane and treeline ecosystems respond directionally to century-long climate trends, and also exhibit abrupt and reversible effects as a consequence of interdecadal climate variability and complex interactions of temperature and moisture.

The construction and maintenance of roads in the Australian Alps has caused profound disturbance to the natural existing soil and vegetation, as well as the introduction and proliferation of exotic plant species. This study examined three ecotypes associated with roads. These ecotypes were tested for differences in soil characteristics and occurrence of different plant species. Differences in chemical and physical soil properties were found between road verges and adjacent native vegetation areas. Soils from natural areas had higher humus levels, less gravel and sand, higher levels of nutrients, and higher pH and electrical conductivity than road verges. A relationship was found between soil properties and the occurrence of different exotic plant species along roadsides. Exotics dominated in areas along the road verge and road drainage lines. The dominant exotic found in these ecotypes was Achillea millefolium (yarrow). These ecotypes were characterized by high water and sediment wash off, which had significantly higher soil pH and exchangeable levels of calcium and potassium than natural areas and disturbed areas without yarrow.

The growth, longevity, and decay of mineral-cored palsas at an altitudinal treeline site in the southern Yukon all appear to be significantly affected by the activities of beaver (Castor canadensis). The palsas are composed of stratified, fine-grained, organic-rich, frost-susceptible deposits, which are interpreted as originating from sedimentation in beaver ponds. Peat development, which is a precondition for mound formation, takes place in the adjacent wetland, in part due to poor drainage because of dams. Palsa degradation over the past 55 yr preferentially followed flooding due to dam construction. Drainage of ponds by dam breach was succeeded by mound formation in aggrading permafrost. Unlike previous studies, therefore, it is impossible to infer a clear climate signal from palsa dynamics at this location.

The extremely high level of solar radiation on the Qinghai-Tibet Plateau may induce photoinhibition and thus limit leaf carbon gain. To assess the effect of high light, we examined gas exchange and chlorophyll fluorescence for two species differing in light interception: the prostrate Saussurea superba and the erect-leaved Gentiana straminea. In controlled conditions with favorable water and temperature, neither species showed apparent photoinhibition in gas exchange measurements. In natural environment, however, their photosynthetic rate decreased remarkably at high light. Photosynthesis depression was aggravated under high leaf temperature or soil water stress. Relative stomatal limitation was much higher in S. superba than in G. straminea and it remarkably increased in the later species at midday when soil was dry. F_v/F_m as an indicator for photoinhibition was generally higher in S. superba than in the other species. F_v/F_m decreased significantly under high light at midday in both species, even when soil moisture was high. F₀ linearly elevated with the increment of leaf temperature in G. straminea, but remained almost constant in S. superba. Electron transport rate (ETR) increased with photosynthetically active photon flux density (PPFD) in S. superba, but declined when PPFD was high than about 1000 μmol m⁻² s⁻¹ in G. straminea. Compared to favorable environment, the estimated daily leaf carbon gain at PPFD above 800 μmol m⁻² s⁻¹ was reduced by 32% in S. superba and by 17% in G. straminea when soil was moist, and by 43% and 53%, respectively, when soil was dry. Our results suggest that the high radiation induces photoinhibition and significantly limits photosynthetic carbon gain, and the limitation may further increase at higher temperature and in dry soil.

This study investigated the relationship of seed bank and field seedlings on the structure of standing vegetation. We also studied the roles in sexual regeneration of seed size, diaspore morphology, and the ability to regenerate vegetatively. Seed banks, field seedlings, and standing vegetation were sampled in 8 subarctic plant communities in Kilpisjärvi, Finland, in, 1995–1998. The seed bank densities varied from 99 to, 1109 viable seeds m²⁻¹ and decreased toward higher altitudes. The seed bank densities were significantly larger than the field seedling densities in the closed vegetation of the lower slopes, whereas the differences were smaller in the open, late-melting snowbeds on higher slopes. The species that occurred only in the seed bank had small seeds or appendaged diaspores. The field seedling densities were high in plant communities dominated by species with ineffective vegetative reproduction or by species with diaspores and with pappus. The floristic similarity was low between the seed bank, field seedlings, and standing vegetation. The nonmetric multidimensional scaling revealed that the species diversity was lower in the seed banks than in standing vegetation and field seedlings. The results indicate that all transitions equally constrain the sexual regeneration of vegetation. Clonality, very small and very large seed sizes, appendaged diaspores, and possibly narrow first leaves in seedlings are traits that limit the transition of plants from standing vegetation to the phase of field seedlings via seed bank. Persistent seed bank has a minor role compared to clonal growth in the regulation of vegetation structure.

Mycorrhizal symbiosis is generally advantageous for plants in nutrient-poor soils, but this advantage may be low in arcto-alpine conditions. While the relative coverage of nonmycorrhizal plant species has been found to increase along an altitudinal gradient, the within-species patterns of mycorrhizal colonization in arctic and alpine plants are not well known, and different results have been obtained in relation to altitude. We investigated arbuscular mycorrhizal (AM) and dark-septate endophytic (DSE) root colonization in six subarctic herbaceous plants Ranunculus glacialis L., Saxifraga aizoides L., Sibbaldia procumbens L., Solidago virgaurea L., Trientalis europaea L., and Viola biflora L. along an altitudinal gradient (0–1400 m a.s.l.) at Mt. Paras, North Norway. We did not find any consistent decline in the different types of fungus colonization along the entire gradient. There was no statistically significant shift in coarse AM or DSE colonization with altitude. However, fine endophyte type AM colonization showed a statistically significant, positive relationship with altitude. These results suggest that root colonization of any particular mycorrhizal species may yield different gradient patterns with altitude than the relative coverages of mycorrhizal and nonmycorrhizal plant taxa. Because of its positive association with altitude, fine endophyte colonization may have a specific role in the nutrition of arctic and alpine plants.

Knowledge of spatial and altitudinal variations in precipitation in high mountains is integral to quantifying alpine climates and to calibrating interactions between climate and surface processes. To date, however, few meteorological networks exist in alpine settings. A network of 14 meteorological stations was installed across the Annapurna Range in central Nepal in 1999 and expanded in subsequent years to 19 stations. In order to measure snow depths and water equivalents in high-altitude sites, a combination of look-down distance rangers and gamma-ray loggers was installed at 5 sites. The data from this network delineate a strong south-to-north gradient in monsoonal precipitation. Precipitation peaks at 5032 mm yr⁻¹ at about 3000 m altitude on the southern side, which is also approximately the lowest altitude of winter snow in the area. Annual precipitation decreases to ∼1100 mm yr⁻¹ in the rain shadow to the north of the Himalayan crest. Although snow depth and snow water equivalent content are strongly dependent on station altitude, snow depth shows little spatial variation at a given altitude, partly due to the surprisingly low local wind speeds. Based on extrapolation of mean monthly summer lapse rate of air temperature, only snow precipitates above 5883 m.

We analyze errors in several digital elevation models (DEMs) of part of Axel Heiberg Island, Nunavut, Canada. We define total error as the sum of map-reading error, which measures the fidelity of the DEM to the map, and mapping error, which measures the fidelity of the map to the terrain. Three of the DEMs derive from estimates made by eye on maps prepared for research purposes and having scales of 1:10,000 (“10K”), 1:50,000 (“50K”) and 1:100,000 (“100K”), while two are based on spatial interpolation from published topographic maps of scale 1:250,000 (“250K”) and 1:1 000,000 (“1M”). Map-reading errors are reduced markedly by proofreading, and are unbiased but not normally distributed. They are also moderately correlated, with decorrelation distances of 1 to 3 DEM resolution elements. Replicate readings from maps 10K and 50K have rms differences of about 20 m, a figure which shrinks to 12 m when gross errors are identified and excluded. These differences represent the mapping errors. Total error in the 10K DEM may range from ∼1 m up to, at worst, ∼19 m, while for the 50K DEM the total error may reach 20 m. Excluding gross errors, the worst-case estimates of total error decrease to 11–12 m. Total error is estimated as 90 m for 250K and 158 m for 1M. We show that map-reading error is small in comparison with mapping error. However there are three obstacles to formal description of total DEM error. First, there is no objective basis for partitioning the mapping error between the two maps of a comparison pair. Second, gross errors cannot be accommodated satisfactorily. Third, because the usual statistical assumptions are violated the errors define confidence regions narrower than the usual 68% by some unknown amount. Maps of larger scale have steeper slopes. Differences in the frequency distribution of slopes are such that a simple additive correction would worsen, not improve, the gentle-slope bias of the smaller-scale DEMs. Elevation errors are roughly equal to one half of the contour interval of the parent map. It is not obvious why this should be so, but as a practical rule of thumb it should perform well.

Image data from the years 1959/1960 and 1999/2000 reveal a 2.4% decrease in the surface area of the Devon Ice Cap, Nunavut, over the last 40 yr. This has resulted primarily from extensive retreat of tidewater glacier margins on the eastern side of the ice cap, and shrinkage of its near-stagnant southwestern arm. Thinning of the ice cap has also increased bedrock exposure in the ice cap interior. However, since 1960 the northwestern margin of the ice cap has advanced slightly. Volume loss associated with these changes was estimated at −67 ± 12 km³ as calculated from two independent techniques. A digital elevation model (DEM) of the ice cap surface was used to delineate interior ice divides allowing patterns of change to be investigated at the drainage basin scale. Strong correlation between the hypsometric characteristics of drainage basins and the observed changes in ice-cap geometry suggests that these changes reflect interbasin differences in the inherent sensitivity of glacier mass balance to recent climate forcing. Response time calculations indicate that most of the ice cap is responding to recent climate warming, whereas the northwestern region is likely still responding to cooler conditions that prevailed during the Little Ice Age (LIA).

Glacier-climate relationships in the Canadian Rockies have been documented previously through mass-balance studies of individual glaciers and local meteorological parameters. In terms of regional significance, however, the relationship between the areal distribution of glaciers and regional climate is perhaps more important in evaluating large-scale responses to climate forcings. The purpose of the current study is to establish which climate variables are responsible for the observed distribution of glaciers. Using a 1:50,000 digitized coverage of glaciers in the Canadian Rockies, a 1-km resolution Digital Elevation Model (DEM) and climate normals from 88 stations throughout the study area, the authors examine the correlation between climate variables and the distribution of glacial ice in the Canadian Rockies. Through the construction of climatic lapse rates, sea-surface interpolation, and subsequent extrapolation based on the DEM, simple cell climatologies that reflect both the altitudinal and regional variations in temperature and precipitation are developed for the study area. Normalized Ice Coverage values prescribed for the study cells from the digitized coverage are then examined through a statistical framework which suggests that spring precipitation, annual temperatures, and winter precipitation are the strongest predictors of glacier distributions in the Canadian Rockies.