Tidewater glaciers have coalesced to advance through Icy Bay, Alaska, three times during the past 3800 yr. Radiocarbon ages show that the first of these expansions was underway by 3750 cal yr B.P. and culminated at the outer coast between 3505 and 3245 cal yr B.P. Subsequent recession and readvance brought the ice margin back to the outer coast by 1525 cal yr B.P. (cal a.d. 425) where it remained for about 650 yr before retreating. Tree-ring cross-dates of glacially killed trees show that the most recent ice advance was underway through the inner bay by the a.d. 1640s and reached into the outer bay in the 1810s. Historical data support ice expansion through the outer bay in the early 19th century and show a late 19th century maximum prior to 20th century retreat. These results are a significant revision and extension of previous studies of the Holocene glacial history of Icy Bay. Average advance rates for the most recent expansion were typical of modern tidewater glaciers in the inner bay but much faster in the outer bay; shallow water here may have been important to this latter phase of unusually rapid advance.

The biogeochemical cycling of organic carbon (OC) has important implications for aquatic system ecology because the abundance and molecular characteristics of OC influence contaminant transport and bioavailability, and determine its suitability as a substrate for microbial metabolism. There have been few studies of OC cycling in glacier systems and questions remain regarding the abundance, provenance, and biogeochemical transformations of OC in these environments. To address these questions, the abundance and fluorescence characteristics of dissolved organic carbon (DOC) were investigated at John Evans Glacier and Outre Glacier, Canada, and Victoria Upper Glacier, Antarctica. These systems are characterized by different thermal and hydrological regimes, and have different potential DOC sources. Where possible, samples of supraglacial runoff, glacier ice and basal ice, and subglacial meltwater were collected. The DOC concentration in each sample was measured (high-temperature combustion and non-dispersive IR detection), and emission and/or synchronous fluorescence spectroscopy were used to characterize the DOC from each environment. DOC exists in detectable quantities (0.06–46.6 ppm) in all of these glacier systems. The fluorescence characteristics of DOC vary between glaciers, between environments at the same glacier, and over time within a single environment. These results suggest that quality of available OC and glacier hydrological flow routing influence the characteristics of DOC, and that microbial cycling of OC may be active in glacier systems.

Heavy, increasing recreation on Colorado's high peaks has created numerous social trails requiring restoration. We studied success of turf transplants 3 yr after transplanting on Mount Belford in the Sawatch Range, and Humboldt Peak in the Sangre de Cristo Range. Based on point-intercept data, sum of all vascular species' covers was 12% to 31% lower in transplanted plots than in control areas. We found no differences in canopy density and height between transplant and control plots on Mount Belford, while both were about 40% lower in transplants on Humboldt Peak. Species richness adjusted for plot size was slightly greater in transplant plots on Mount Belford and slightly lower on Humboldt Peak. On both peaks, we found greater absolute cover of grasses in transplant plots, while forb cover was lower. After 3 yr, turf transplants effectively established vegetation cover and maintained high species richness in these communities. Whenever turf is available, e.g., new trail construction, it should be used to restore closed social trails and campsites, and turf transplants can be considered in other ecosystems for small disturbances in high-value areas where restoration would otherwise be slow.

Environmental factors associated with deep chlorophyll maximum (DCM) layers were examined in five lakes of the McMurdo Dry Valleys, Antarctica, to test the hypothesis that DCM are more closely associated with resource limitations than water density. Because data could not be transformed to meet the assumption of normal distribution, distance matrices were constructed from vectors of observed chlorophyll-a (CHL), photosynthetic active radiation intensity (PAR), soluble reactive phosphorous (SRP), dissolved inorganic nitrogen (DIN), dissolved oxygen (DO), water density (DEN), and incremental change in water density/depth (DEL). Multiple regression analyses then were based on permutation evaluations of the relationships between distance matrices (partial Mantel analyses). Results indicated that resource availability (PAR and DIN) was most frequently related to chlorophyll-a, although DEN and DEL often were significant within individual lakes. Hence, resource relationships were strongest across lakes and seasons whereas density relationships also were important within individual lakes. Moreover, DCM appeared sensitive to threshold levels of DEN and PAR, suggesting that controls may exist as both discrete (threshold) and continuous functions of both resource availability and water density.

Low-elevation glaciers in coastal regions of Alaska, the Canadian Arctic, individual ice caps around the Greenland ice sheet, and the Patagonia Ice Fields have an aggregate glacier area of about 332 × 10³ km² and account for approximately 42% of all the glacier area outside the Greenland and Antarctic ice sheets. They have shown volume loss, especially since the end of the 1980s, increasing from about 45% in the 1960s to nearly 67% in 2003 of the total wastage from all glaciers on Earth outside those two largest ice sheets. Thus, a disproportionally large contribution of coastal glacier ablation to sea level rise is evident. We examine cumulative standardized departures (1961–2000 reference period) of glacier mass balances and air temperature data in these four coastal regions. Analyses indicate a strong association between increases in glacier volume losses and summer air temperature at regional and global scales. Increases in glacier volume losses in the coastal regions also coincide with an accelerated rate of ice discharge from outlet glaciers draining the Greenland and West Antarctic ice sheets. These processes imply further increases in sea level rise.

The effect on photosynthetic capacity, photochemical efficiency of photosystem II (PSII), and frost resistance to environmental changes during winter in the evergreen alpine cushion plant Saxifraga paniculata were investigated at different altitudes. S. paniculata was more resistant to cold induced photoinhibition during midwinter than other evergreen subalpine species. Photochemical efficiency (F_v/F_m) was only reduced to 0.62. Photosynthetic capacity was only reduced if weekly mean leaf temperatures dropped below 5°C and remained positive during the entire investigation period. Growth cessation was accompanied by low values of photosynthetic capacity to maintain photostasis, i.e., the balance between energy input through photochemistry and subsequent energy utilization through metabolism. Even in January after night temperatures down to −22°C, photosynthetic capacity still averaged 4.0 ± 0.8 μmol CO₂ m⁻² s⁻¹. Initial frost damage did not commence until leaf temperatures dropped below −27.6°C. This was sufficient to survive absolute air temperature minima. As an evergreen species, the sustained high efficiency of PSII in winter potentially enables S. paniculata to immediately utilize periods with moderate temperature conditions for photosynthesis, particularly at the end of winter when there is sufficient water on rocks due to melting snow.

This study is presented against the background that climate warming is predicted to continue in much of the Arctic through the next century and that small greenhouse chambers have been used widely to warm tundra communities in order to forecast climate-related changes. It reports results from up to 8 years of experimental warming with ∼1 m² open-top chambers (OTCs) at four tundra communities near Barrow (71°18′N, 156°40′W) and Atqasuk (70°29′N, 157°25′W) in northern Alaska. Between 1994 and 2002 the OTCs increased the mean growing season air temperature by between 0.6 and 2.2°C, depending on the site and year. The change in average July soil temperature recorded over 3 years at 10 cm depth due to the OTCs varied between −0.8 and 0.7°C, depending on the site. Changes in soil temperature did not result in detectable differences in thaw depth at any site. This is interpreted to be the result of the small size of the OTCs and possibly changes in vegetation. The differences in warming profiles between sites are important for the biological interpretation of manipulative warming experiments. These profiles also illustrate that vertical heat exchange varies according to plant community type and that this may be an important consideration as the region undergoes climatic change.

On Axel Heiberg Island, Nunavut, Canada, a banded vegetation pattern occurred on a hillside where patterned ground and unidirectional abiotic fluxes, such as downslope water flow or wind, were not present. The parent material was the obvious source of the plant pattern, as the soils occurred on five distinct types of alluvial deposits. To examine the observed pattern, plants were inventoried and soils were sampled in July 1999. Twelve vascular species of plants, but no non-vascular species, were present at the site. Neither water, often thought to limit plant distribution in the High Arctic, nor any of the other measured soil variables, predicted plant abundance. The best predictor of plant abundance, based on regression tree analysis, was total soil nitrogen; however, higher plant density was associated with lower nitrogen. The five soil types differed in plant density and soil properties. Even though the sand soil always had soil nutrients equal to or lower than the blocky clay soil, the sand and clay soils had the highest plant density and the blocky clay soil the lowest. Although the vegetation pattern is obvious, the underlying mechanism creating the pattern is not.

High mountain environments are highly stressful for insect survival. It has been suggested that small microtopographic variations generating less stressful microclimatic conditions than the surrounding environment would provide more suitable sites for insect development. Cushion plants represent one of the life forms best adapted to the extreme alpine habitats. Cushion plants can modify microclimatic conditions within and under their canopy, generating less severe microsites than the surrounding environment. In this study, we characterized the microclimatic modifications made by the cushion plants Azorella monantha and Laretia acaulis and examine their role as microclimatic shelters for two species of high Andean coleopterans (Coccinelidae): Eriopis connexa and Hippodamia variegata at 3200 m a.s.l. in the Andes of central Chile. Results showed that the cushion species create microhabitats with higher availability of water and less oscillating temperatures. However, the intensity of modifications was higher in A. monantha compared to L. acaulis. The abundance of the two ladybird beetle species was higher within cushions than outside, although E. connexa showed higher abundances compared to H. variegata. However, a habitat selection experiment in a greenhouse showed that under milder temperature conditions ladybird beetles species do not prefer cushions. This suggests that in the harsh alpine climate, cushion plants may act as microclimatic shelters since they reduce stressful environmental conditions, allowing greater abundances of coleopterans than in the surrounding environment.

We used retrospective analysis of the widespread evergreen dwarf-shrub, Cassiope tetragona, to reconstruct average summer air temperature for Alexandra Fiord, Ellesmere Island, Canada. Retrospective analysis is a technique based on dendrochronological methods. In this study, chronologies are based on the morphological characteristics of the plant stems. Two growth and two reproduction chronologies, ranging from 80 to 118 years long, were developed from each of two populations at the High Arctic site. We used multiple regression models to develop a 100-year-long (1895–1994) reconstruction of July–September average air temperature that explained 45% of the climatic variance in the instrumental record. The reconstruction revealed an increase in summer temperature from ∼1905 to the early 1960s, a cooling trend from the mid-1960 to the 1970s, and an increase in temperature after 1980. These historical temperature patterns correspond well with those from other climate proxies from sites on Ellesmere and Devon Islands. As well, the similarity between our model and an arctic-wide proxy temperature time series suggests that the Cassiope-based reconstruction contains a large-scale temperature signal. There is great potential for the development of proxy climate data using Cassiope tetragona from sites throughout the Arctic.

Human use of arctic and alpine environments can result in damage to the natural vegetation and soils. Restoration of the damage can have limited success due to the severity of the environment, which restricts plant germination and growth and increases the potential for soil erosion. In this study, we evaluated the success of restoration of a closed track in the alpine area around continental Australia's highest mountain, Mount Kosciuszko. Vegetation and soils along a 4 km walking track (that was closed and rehabilitated more than 15 yr ago) were compared with the adjacent undisturbed vegetation and soils. There was limited success in restoration with clear differences in soil nutrients, extent of vegetation cover, plant species composition, and height of vegetation between the track and adjacent natural vegetation sampled using 1 m² quadrats. The study highlights the need for limiting disturbance in such environments, and for ongoing rehabilitation in areas that have been disturbed. It also indicates that when non-native species are used in rehabilitation, they may not necessarily be succeeded by natives, particularly if soil conditions do not return to a state similar to undisturbed areas.

Microbial activity in arctic tundra soils has been evaluated through both lab incubations and field flux measurements. To determine whether these different measurement approaches can be directly linked to each other, we developed a simple model of soil microbial CO₂ production during the cold season in tussock tundra, moss tundra, and wet meadow tundra in the Alaskan Arctic. The model incorporated laboratory-based estimates of microbial temperature responses at sub-zero temperatures with field measurements of C stocks through the soil profile and daily temperature measurements at the sites. Estimates of total CO₂ production overestimated in situ cold season CO₂ fluxes for the studied sites by as much as two- to threefold, suggesting that either CO₂ produced in situ does not efflux during the cold season or that microbial respiration potentials are constrained by some other factor in situ. Average estimated winter CO₂ production was near 120 g C m⁻² in moist tundra and 60 g C m⁻² in wet meadow tundra. Production was strongly seasonal, with most of the winter CO₂ production happening early in the winter, before soils froze completely through. Roughly two-thirds of the total estimated CO₂ production was from deep soils, largely mineral soils, in contrast to growing season CO₂ dynamics.

Using a combination of microscopic examination and electronic scanning and printing, we analyzed the impacts of early spring snow cover extent and temperature during the growing season on the annual radial growth in arctic willow (Salix arctica Pallas) in the Zackenberg valley, High Arctic Northeast Greenland. So far, only little dendroclimatological research has been conducted on Salix arctica, and the species constitutes a yet-untapped resource for climate reconstruction in the Arctic. We obtained reliable annual radial growth measurements from a total of 43 Salix arctica stem samples and analyzed these in a mixed model to determine the limiting climatic factors. We found that early spring snow cover extent impacted the annual growth significantly, whereas variable temperature regimes seemed unimportant. Following the building of a site chronology for the Zackenberg valley, the early spring snow cover extent during the last century was reconstructed.

Nitrogen (N) fixation, denitrification, and ecosystem pools of nitrogen were measured in three subarctic ecosystem types differing in soil frost-heaving activity and vegetation cover. N₂-fixation was measured by the acetylene reduction assay and converted to absolute N ecosystem input by estimates of conversion factors between acetylene reduction and ¹⁵N incorporation. One aim was to relate nitrogen fluxes and nitrogen pools to the mosaic of ecosystem types of different stability common in areas of soil frost movements. A second aim was to identify abiotic controls on N₂-fixation by simultaneous measurements of temperature, light, and soil moisture.

Nitrogen fixation rate was high with seasonal input estimated at 1.1 g N m⁻² on frost-heaved sorted circles, which was higher than the total plant N content and exceeded estimated annual plant N uptake several-fold but was lower than the microbial N content. Seasonal fixation decreased to 0.88 g N m⁻² on frost-heaved moss-covered surfaces and to 0.25 g N m⁻² in stable heath vegetation, both lower than the plant and microbial N content. Yet fixation was estimated to correspond to about 2.7 times the annual plant N demand on the moss-covered surfaces but less than the plants' demand on the heath. Surprisingly, we found no denitrification on any surface.

Climatic changes in the Arctic will generate a warmer climate and change precipitation patterns. A warmer, drier environment will decrease N₂-fixation and thereby N availability to plants and microorganisms, while wetter conditions probably will increase N₂-fixation and thereby N supply to the surroundings.

To determine if canopy gaps offer “safe sites” for recruitment and persistence of arctic-alpine plants, we compared seedling densities in frost boils and closed vegetation, and examined persistence of Diapensia lapponica within frost boils. Seedling density was greater within frost boils, and D. lapponica numbers increased in resurveyed frost boils, suggesting persistence. Lower seed bank size combined with higher seedling numbers confirmed that frost boils represent favorable sites for germination.

Nine late Miocene glacier advances are identified in the Lago Cardiel region (49°S, 72°15′W in southern South America), a region that until now has been assumed to be unglaciated. Several dating results indicate a minimum age of 6.4 Ma for four advances of the Monte San Lorenzo lobe terminating east of Lago Cardiel and 6.6 Ma for the three oldest glaciations of the San Martín lobe terminating south of this lake. Two further advances have a minimum age of 5.4 Ma. Eleven to 14 m.y. old basaltic lava, which partly covers Patagonian Gravel, indicates the maximum age of these advances. The two oldest terminal moraines of the San Martín glacier are only modestly incised into the Patagonian Gravel suggesting an age of 9 to 10.5 Ma. These age estimates are especially accurate for both meseta glaciations of the San Lorenzo lobe. These glaciers were about 240 km long during their Miocene maximum, which is four times their length during the Last Glacial Maximum. Hence, the late Miocene glacier advances require colder and/or more humid conditions that were considerably longer lasting than the Pleistocene glaciations. Due to glacial meltwater, Lago Cardiel was significantly larger and served as a regional catchment area during these early glaciations in southern South America. The erratic boulders of the southeastern lake terraces at more than 350 m above modern lake level may be attributed to the oldest late Miocene moraine or outwash plain.

Critical revision is presented of taxa comprising 27 verified species of Rhagidiidae from the Alps. Assemblages of endemic, Palearctic, and Holarctic Rhagidiidae inhabiting montane stony debris in the Ötztal Alps, North Tyrol, Austria, consist of 2 to 9 species, and Poecilophysis pseudoreflexa is the most abundant and widely distributed species. The highest species richness and endemism are in the mid-alpine zone (2400–2600 m a.s.l.) and the high alpine zone (2600–2800 m a.s.l.). A particular assemblage of rhagidiids of low diversity occurred in voids of a bare scree slope. Cluster and numerical multivariate analyses revealed that (1) the different altitudinal niches of a majority of common species overlap, but some species become rare with increasing altitude; (2) additional species of rhagidiid mites might be expected to be found in special, previously uncollected microhabitats; (3) rhagidiid mites having some affinities to specific environmental factors can be distinguished; (4) the altitudinal gradient proved to be the significant complex environmental factor influencing the occurrence of mites; (5) moisture proved to influence abundance of mites but has no direct relation to species identity; and (6) in contrast, dryness proved to be bound with the occurrence of particular species of rhagidiid mites.