A selective review of lichenometry as used to date Holocene moraines in five diverse regions of Alaska and in southeastern Kamchatka suggests that growth curves for this North Pacific area may be improved by attention to several factors. These included lichen identification, control point number and distribution, radiocarbon calibration, alternative curve models, and compatibility of lichen growth rate with climate. Support for control points presented for Kamchatka and published for Alaska areas will benefit from supplementary control at and beyond the break from the great growth curve segments of the last centuries. With regard to alternative—linear, logarithmic, and composite curve—models drawn for the published lichenometric data, the composite (logarithmic and linear composite models) appear the best fit for the Brooks Range and Wrangell–St. Elias areas of slow growth and continental interior climates. Calibration of ¹⁴C ages make minor changes in well-controlled curves, but differences may be marked where a single age supports the long-term portion of growth curves.

Lichen subgenus Rhizocarpon section Geographicum and section Alpicola should, and usually can be, differentiated in North Pacific areas. Nevertheless, growth curves that may represent both yellow-green Rhizocarpons (e.g., central Brooks Range and southeastern Kamchatka) appear to allow derivation of reasonable surface dating where the taxa distribution is similar to that of the curves. Chronologies of glaciation based on lichenometry of moraines over the last millennium in these two areas across the Bering Sea are strikingly similar to each other and to more precisely dated tree-ring-based glacial chronologies in southern Alaska.

We tested the hypothesis that foliar nitrogen and phosphorus concentrations are correlated with estimates of soil nutrient supply, a common assumption in studies of plant nutrient relations. This hypothesis was tested in an alpine ecosystem characterized by a wide range of soil nutrient availabilities using 3 herbaceous plants with widespread distributions. Rates of soil N and P supply were estimated using ion exchange resin bags deployed during the first half of the growing season, when the majority of plant nutrient uptake occurs. Measurements were made at 3 to 5 landscape positions (vegetation types) at 3 sites: a valley bottom that was glaciated until 12,000 yr ago and 2 ridgetop sites, 1 with deposits of Tertiary age and 1 that was not glaciated during the Pleistocene. Foliar N and P concentrations generally were not correlated with rates of soil N and P supply. We present several hypotheses to explain the lack of a correlation between soil N and P supply and foliar N and P concentrations, most notably the probable buffering between soil nutrient supply and foliar nutrient concentrations by belowground nutrient storage in plants and the use of organic N by plants. Foliar N:P ratios reflected the specific nutrient limitation of production for 1 of the 3 study species. Rates of soil N supply were associated with landscape position, indicating that microclimatic and/or plant species effects were the most important controls over spatial variation in N supply. Rates of P supply differed significantly among valley and ridge locations, but not with landscape position. Soil age and eolian deposition of dust probably differ between these collection sites and may explain the differences in soil P supply. These results suggest that caution should be used in estimating soil fertility and specific nutrient limitations of growth based on foliar nutrient concentrations in herbaceous communities.

Remote sensing provides a viable alternative for mapping vegetation in the Arctic because it allows for the mapping of discontinuous distribution of cover types over different spatial scales. In this paper we present a statistical method to map the distribution of important cover types for the reindeer Rangifer tarandus during summer in northernmost Sweden using IRS 1D-LISS satellite imagery. We exemplify our method with modeling of the distribution of snowbed vegetation, the cover type used most intensively by the reindeer in the study area. An autologistic regression model that incorporates the spatial structure of the data is used to combine the field data and the satellite image data. The terrain effects in the satellite image are accounted for in the regressions using a digital elevation model (DEM). We produced a fine-scaled coverage depicting the probability of occurrence of snowbed vegetation as a continuous variable at the pixel level. The accuracy of mapping snowbed vegetation was 69–77%, depending on the data used. We conclude that small-scale, pixel-wise classification modeling may be useful for depicting sparsely occurring cover types, some of which may be important determinants of range quality for reindeer.

Pollen and macrofossils were analyzed at two sites above today's treeline (or tree limit) in the Swiss Central Alps (Gouillé Loéré, 2503 m a.s.l., and Lengi Egga, 2557 m a.s.l.) to test two contrasting hypotheses about the natural formation of timberline (the upper limit of closed forest) in the Alps. Our results revealed that Pinus cembra–Larix decidua forests near timberline were rather closed between 9000 and 2500 B.C. (9600–4000 ¹⁴C yr BP), when timberline fluctuations occurred within a belt 100–150 m above today's tree limit. The treeline ecocline above timberline was characterized by the mixed occurrence of tree, shrub, dwarf-shrub, and herbaceous species, but it did not encompass more than 100–150 altitudinal meters. The uppermost limit reached by timberline and treeline during the Holocene was ca. 2420 and 2530 m, respectively, i.e., about 120 to 180 m higher than today. Between 3500 and 2500 B.C. (4700–4000 ¹⁴C yr BP) timberline progressively sank by about 300 m, while treeline was lowered only ca. 100 m. This change led to an enlargement of the treeline-ecocline belt (by ca. 300 m) after 2500 B.C. (4000 ¹⁴C yr BP). Above the treeline ecocline, natural meadows dominated by dwarf shrubs (e.g., Salix herbacea) and herbaceous species (e.g., Helianthemum, Taraxacum, Potentilla, Leontodon t., Cerastium alpinum t., Cirsium spinosissimum, Silene exscapa t., and Saxifraga stellaris) have been present since at least 11,000 cal yr ago. In these meadows tree and tall shrub species (>0.5 m) never played a major role. These results support the conventional hypothesis of a narrow ecocline with rather sharp upper timberline and treeline boundaries and imply that today's treeless alpine communities in the Alps are close to a natural stage. Pollen (percentages and influx), stomata, and charcoal data may be useful for determining whether or not a site was treeless. Nevertheless, a reliable and detailed record of past local vegetation near and above timberline is best achieved through the inclusion of macrofossil analysis.

Ice flow speeds were measured at Glaciar Soler in northern Patagonia during the middle of the melt season (November–December) in 1998 and compared to data from 1985. In 1998 the surface flow speed was greater at all survey points, yet the ice was about 40 m thinner; the greater melt rate in 1998 probably explains these differences because of the effect of melt rate on basal sliding speed. Multiday variations in surface speed were well correlated with daily variations in surface water input, which is the sum of melt rate and rainfall. Although the basal sliding speeds vary from place to place, we obtained similar linear relationships between basal sliding speed and surface water input. This result indicates the possibility of taking account of basal sliding as a function of surface water input.

During the Last Glacial Maximum (LGM), ice thickened considerably and expanded toward the outer continental shelf around the Antarctic Peninsula. Deglaciation occurred between >14 ka BP and ca. 6 ka BP, when interglacial climate was established in the region. Deglaciation of some local sites was as recent as 4–3 ka BP. After a climate optimum, peaking ca. 4–3 ka BP, a distinct climate cooling occurred. It is characterized at a number of sites by expanding glaciers and ice shelves. Rapid warming during the past 50 yr may be causing instability of some Antarctic Peninsula ice shelves. Detailed reconstructions of the glacial and climatic history of the Antarctic Peninsula since LGM are hampered by scarcity of available archives, low resolution of many datasets, and problems in dating samples. Consequently, the configuration of LGM ice sheets, pattern of subsequent deglaciation, and environmental changes are poorly constrained both temporally and spatially.

Dendroecological analysis is often used in animal ecology to infer population fluctuations. In this study, we used scars produced by caribou hooves on superficial roots of conifers to evaluate the recent activity of the George River caribou herd (GRCH). In 1999 and 2000, we sampled a minimum of 300 trampling scars at each of 31 lichen woodland sites distributed over the summer habitat of the GRCH. Among the 31 selected sites, 18 had been previously sampled in 1992–1993 and showed a good agreement in trends inferred in caribou activity with the 1999–2000 data set at the same sites. We evaluated the recent activity pattern of the GRCH using mean values of pooled scar-age data from the 31 sites. We inferred two major trends from the tree-ring data: that the GRCH experienced an important increase from 1975 to the late 1980s, and that this growth was followed by a major decline that began in the early 1990s. Radio-collar data from 1991 to 1998 also support the decline as no major change was found in the geographical distribution of the GRCH during this period.

Tree-ring analysis from Abies densa growing at the treeline in the Eastern Himalayan region reveals that temperature during late summer (July–September) plays a significant role in controlling the growth of this tree. Mean temperature of each year for these three months has been reconstructed based on this ring-width data. This record goes back to A.D. 1507; however data prior to A.D. 1757 are questionable because they are based on only one sample. The reconstructed temperature series for the last 237 yr shows annual to multiyear fluctuations punctuated with cool and warm periods. The warmest and coolest 10-yr periods of the entire span occurred in 1978–1987 ( 0.25°C) and 1801–1810 (−0.31°C), respectively.

Data for Rhizocarpon agg. thalli at the Illecillewaet Glacier in British Columbia were used to see whether a single growth curve could provide accurate age estimates on either side of the Continental Divide, to determine whether modern and historical growth rates are similar, and to test a published model that estimates lichen age from short-term radial growth rates. A lichen growth curve was developed for Rhizocarpon agg. using thallus-size data from 14 tree-ring and historically dated substrates. Comparison of this curve with one developed on similar materials 250 km north of this location found similar growth rates for the first 150 yr but slightly faster growth over the next 150 yr at the Illecillewaet site. Radial growth was also measured annually at an average of five points at 105 Rhizocarpon agg. thalli to see if direct-measurement data could be used to reliably estimate lichenometric ages. Radial growth from 1996–2000 ranged between 0.262 and 0.412 mm yr⁻¹and showed large variation within and between thalli. Mathematical analysis found that radial growth was not a positive function of the radius, and linear regression incorrectly predicted that growth rates increase with thallus size. Ages estimated by linear extrapolation of the 4-yr mean growth rate were ca. 10 yr less than those estimated by the indirectly calibrated growth curve on surfaces <200 yr old. Progressively less accurate minimum estimates were obtained using linear extrapolation of radial growth rates for old surfaces and thalli >60-mm diameter. These findings lend support to the assumption that modern growth rates of Rhizocarpon lichens averaged over several years can potentially provide close estimates of lichenometric age.

Populations of the only two flowering plants native to the Antarctic have recently increased in number and size possibly due to climate warming. We have undertaken a preliminary study of the population genetics of one of these species by surveying variation in amplified fragment length polymorphisms (AFLP) within the Antarctic Hairgrass, Deschampsia antarctica. Populations of D. antarctica from two widely separated regions of the maritime Antarctic, namely Signy Island in the north and Léonie Islands 1350 km farther south, were characterized by low genetic diversity (only 15.95% of total genetic variation found within populations). Populations from the northern and southern maritime Antarctic were genetically distinct from each other (F_CT = 37.10%), and low levels of historical gene flow occurred among them (Nm = 0.05). This genetic structure suggests that new populations of D. antarctica are founded by one or few individuals, which mainly reproduce by self-fertilization and/or vegetative propagation. Vegetative reproduction and selfing are, therefore, likely to have been key factors in the establishment of D. antarctica at new sites in the Antarctic during recent years.

The extent of the Last Glacial Maximum (LGM) and the timing of deglaciation around the Northwest Peninsula of Iceland are poorly understood. To provide information on these issues, we report sedimentological, foraminiferal, isotopic, and chronological data from marine piston cores B997-322PC, -323PC, -326PC1, and -326PC2 from a transect along Reykjafjardaáll/Húnaflóaáll, a large trough that extends from the north Iceland coast toward the shelf break, ca. 66.8°N and 20°W. Cores B997-322PC, -323PC, and -326PC1 recovered diamictons (stiff, pebbly muds) overlain by fine-grained, postglacial muds, with intermittent occurrences of iceberg-rafted clasts and volcanic shards. No glacial con-structional features (moraines) were noted on the seismic profiles. In the outermost cores (B997-322PC and 323PC) the diamictons contained small but persistent numbers of foraminifera which gave dates between 25 and 44 ka B.P.; foraminifera are absent in the diamicton at the base of core B997-326PC1. ¹⁴C dates immediately above the diamictons have ages of ca. 13 ka B.P., which we take to represent the date of deglaciation of Húnaflóaáll and the withdrawal of the ice margin to the adjacent Strandir coast. Foraminifera are used to construct a bio- and isotope stratigraphy of cores B997-322PC and 323PC. In the diamictons, the fauna is dominated by cold-water benthic foraminifera including Elphidium excavatum and Cassidulina reniforme; Cassidulina neoteretis is also a persistent component. In B997-322PC and -323PC the deglacial sequence is interrupted by an interval of IRD deposition, a dramatic reduction in foraminiferal numbers, and heavy δ¹⁸O values; we equate this interval with the Younger Dryas cold event. Alternative working hypotheses are advanced for the origin of the diamictons and their importance to mapping the LGM ice extent. The 12-ky hiatus between the diamictons and the overlying marine muds indicates that the sequence is not conformable. The diamictons probably represent glacial-marine sediments overrun by late Weichselian ice streaming down the trough. The absence of a thick, deglacial sequence of glacial-marine sediments indicates a dramatic retreat of the ice cap to the present coast by ∼13 ka B.P.

The formation of calcium phosphate rock coating and its influence in geomorphic processes were investigated on the Yalour Islands (Antarctica). amples of coating on the metamorphosed andesitic rock are composed of a ∼25 μm-thick, white, shiny, relatively hard layer of hydroxylapatite (Hp) with traces of calcite and quartz. Scanning electron micrographs, X-ray diffractograms, Fourier Transform Infrared (FTIR) spectra, and in situ analysis of the chemical composition of the coatings suggest that the calcium phosphate coating is formed mainly through the decomposition of penguin excrement from nearby penguin rookeries and subsequent precipitation of Hp in micropits on the surface of the rock from solutions containing high amounts of calcium and phosphorus. These coatings undergo abiotic and biotic weathering processes that lead to the accumulation of secondary Hp as “flakes” and infillings in microcracks. The coatings give the dark, metamorphosed andesitic rock a shiny, light-colored surface. The coatings can decrease the permeability and increase the albedo of the rock, thereby limiting moisture infiltration (into the rock) and changing the rock's temperature. Based on theoretical estimates, a change of albedo from 0.2 to 0.3 significantly decreases the radiative heating of the rock during the summer months. These changes to rock properties will influence geomorphic processes such as freeze-thaw, thus affecting rock weathering and hence the evolution of the local landscape.

Many alpine/arctic flowering plant species have presumably evolved the ability to self-pollinate as a reproductive assurance mechanism under harsh abiotic environmental conditions that restrict insect flower visitation. We compared self-pollination, pollen limitation, insect flower visitation, and dichogamy of low- and high-elevation populations of Cerastium alpinum, a species in established alpine communities, and Cerastium cerastoides, a pioneer species in disturbed habitats. Cerastium alpinum has large showy flowers, while C. cerastoides has smaller and paler flowers. The temporal separation of pollen release and stigma receptivity within a flower (dichogamy) was smallest in C. cerastoides, which was also more highly self-compatible. No pollen limitation on seed set occurred in any species, possibly due to their high selfing ability. Despite a substantially higher pollinator visitation to C. alpinum compared to C. cerastoides, the latter had the higher seed set. Pollen limitation, autogamy, and pollinator visitation did not differ between altitudes for either species. Differences in habitat and flower size, color, and development between the species are consistent with their different selfing ability.

New Zealand's alpine region is populated by many (∼613) species of vascular plants with a high endemism (∼93%). To investigate the potential impact of climate warming, we used species-area relations to estimate current and projected vascular plant floras and tested model sensitivity scaling from the whole world to small alpine regions.

Within their limitations, these models show that if the present mean temperature of ∼0.6°C higher than in 1900 were maintained, together with a large pool of exotic species, 40–70 species of native plants could become at risk. With a rise of 3°C, an approximate expectation for the following 100 yr, the total New Zealand alpine vascular flora could reach ∼550–685 species and lose 200–300 indigenous alpine species, the rest being exotic. Fragmentation of alpine areas could, over millennia, favor speciation, but in the short term, the loss of ∼80% of existing alpine islands will severely increase extinction risks.

These model projections will be modified by downward extension of species through unplanned vegetation destruction, or following deliberate vegetation clearance to create habitats favorable to alpine species, as well as through a number of other as yet unquantified factors. These projections are not predictions of extinctions but rather broad probabilities of risk to a whole flora.

In studying the response of alpine glaciers to climate warming, the study of debris-covered glaciers is important in order to demonstrate that a negative feedback exists in the temperature-ablation relationship that is introduced by the increase in debris cover. In this paper, variations in the Belvedere Glacier tongue volume and thickness were quantified through a comparison of large-scale maps for 1957 and 1991. A volume increase of 22.7 million m³ was revealed, and there was a mean increase of 15 m in thickness. Thickening was greatest above 1830 m, and thinning occurred at the glacier front (1830–1770 m). The glacier terminus advanced only slightly. This particular evolution of the Belvedere tongue has been attributed to positive balances of the glacier created by favorable climatic conditions (increase in winter precipitation between the early 1970s and mid-1980s and lower summer temperatures in the 1960s and 1970s). After the mid-1980s, reduced precipitation and a simultaneous increase in temperatures led to a slight retreat of the glacier front in the early 1990s. However, these climatic conditions were not sufficient to bring about a significant reduction of the thickness of the glacier, partly owing to the debris cover, which reduced the role of ablation.

The ice masses of Svalbard cover an area of ca. 36 600 km², and are thus among the largest glaciated areas in the Arctic. Annual mass balance measurements have been carried out on several Svalbard glaciers over up to 30 yr. However, these glaciers extend over only 0.5% of the total ice-covered area. The measured mean net balance has been negative and no changing trend has been observed. On some glaciers and larger ice caps, the mean net balance has also been measured at different altitudes by detecting radioactive reference layers from nuclear fallouts in 1963 and 1986 in shallow ice cores. The net balance/altitude curves have been estimated for thirteen different regions in Svalbard, and combined with digital elevation models of all Svalbard ice masses used to calculate the net balance in each 100-m altitude interval. The net loss of mass through iceberg calving was estimated and appears to be an important component of the net mass loss from Svalbard ice masses. The overall total net balance is slightly negative, −4.5 ± 1 km³ yr⁻¹, giving a specific net balance of ca. −120 ± 30 mm yr⁻¹ over the archipelago. The contribution of ice caps and glaciers on Svalbard to global sea-level change is, therefore, close to 0.01 mm yr⁻¹ as an average value over the last 30 years, which is less negative than former estimates.