Glacial recession is a major process in terrestrial ecosystems of the world and an obvious result of global warming. Here we describe the alpine (above tree line) and subalpine forested and wetland/peatland vegetation chronosequences in Glacier Bay National Park and Preserve, Alaska. We derived the results from three products: (1) deglaciation map of 50,000-, 13,000-, and 1- to 246-year-old (Neoglacial) surfaces; (2) a landcover map; and (3) a plant association classification. For the alpine chronosequence, Neoglacial surfaces are dominated by the tall shrub (>1.5 m) (Alnus and Salix), dwarf shrub (<0.1 m) (Salix and Dryas), and mesic herbaceous landcover classes. These landcover classes also dominate the 13,000- and 50,000-year-old surfaces but dwarf shrub dominance changes to ericaceous. The subalpine forested chronosequence consists of Populus balsamifera ssp. trichocarpa and Picea sitchensis classes dominating the mid- and late-seral Neoglacial surfaces, then Tsuga mertensiana and Picea sitchensis classes dominating the 13,000- and 50,000-year-old surfaces. Wetlands/peatlands are rare on the Neoglacial and 13,000-year-old surfaces but common on the 50,000-year-old surface. Alnus is rare on the 50,000-year-old surface yet common on the 13,000-year-old surface and, we speculate, is a relict from the end of the Pleistocene.

Bacterial strains isolated from Antarctic environments were used to assess the role of carotenoid pigments as cryo- and solar radiation protectants. Isolates were subjected to one hundred 12-hr freeze-thaw cycles and exposed to ambient simulated solar radiation (300 Wm⁻²) with growth recovery evaluated after pre-set time intervals. Differences in survival were observed between carotenoid pigmented and non-pigmented strains in response to the different stresses based upon the enumeration of colony forming units. On average carotenoid pigmented strains were more resistant to freeze-thaw cycles as compared to the non-pigmented strains. Survival for non-pigmented strains decreased precipitously from 2 × 10⁷ to 1.5 × 10⁴ cells mL⁻¹, on average, within the first 20 cycles. Similar results were found in the solar radiation experiments. After 2 hrs of solar radiation exposure, 61% of the pigmented organisms survived versus 0.01% for the non-pigmented isolates. We applied an additive mixed model to estimate differences between the carotenoid pigmented and non-pigmented bacterial groups. Modeled results confirmed a positive effect of pigmentation on survivability and provide evidence that carotenoid pigmentation in heterotrophic bacteria isolated from Antarctic environments increases resistance to environmental stressors.

Rapid climate change in arctic environments is leading to a widespread expansion in woody deciduous shrub populations. However, little is known about the reproductive, dispersal, and establishment mechanisms associated with shrub expansion. It is assumed that harsh environmental conditions impose limitations on plant sexual reproduction in the Arctic, such that population survival and expansion is predominately a function of clonal recruitment. We present contrary evidence from microsatellite genetic data suggesting the prevalence of recruitment by seed. Further, we present a conceptual model describing modes of recruitment in relation to the abiotic environment. Climate change may be alleviating abiotic stress so that resources are available for more frequent recruitment by seed. Such changes have widespread implications for ecosystem structure and functioning, including species composition, wildlife habitat, biogeochemical cycling, and surface energy balance.

Snow avalanches can exert considerable erosive forces on soils. If a snow avalanche flows directly over bare ground, basal shear forces may scrape away and entrain soil. Soil material entrained by the avalanche is transported to the deposition zone, changing the chemical composition of the soils and potentially contributing to unique landforms. The quantity of soil material eroded and accumulated depends on avalanche characteristics and on morphological features, as well as soil properties and vegetation cover.

We monitored a channeled avalanche path in the Aosta Valley of NW Italy in order to assess the contribution of avalanche debris to the formation of soils in the runout zone. Sediment concentration estimates and measurements of the avalanche deposit volumes were used to estimate the total sediment load. The collected sediments were separated into fine sediments (<2 mm) and large (>2 mm) organic and mineral fractions. Results, obtained from the winter seasons of 2006, 2007, and 2008, showed that the amount of sediment deposited on the preexistent soil at the foot of the avalanche path was mainly the fine sediments fraction. The total carbon and nitrogen content in the fine sediment fraction ranged respectively from 6.6 to 9.0% and 0.37 to 0.42%. The total sediment load transported out of the 3.5 km² basin was estimated to be 7585 kg in 2006, 27,115 kg in 2007, and 2323 kg in 2008. This mass transport resulted in basin averaged denudation rates ranging from 0.67 g m⁻² event⁻¹ in 2008 to 7.77 g m⁻² event⁻¹ in 2007. Annual accumulation in the runout zone was 240 Mg ha⁻¹ in 2006, 38 Mg ha⁻¹ in 2007 and 10 Mg ha⁻¹ in 2008. The inorganic N concentration of the snow in the runout zone was significantly greater than in the starting zone and was correlated with the organic fraction accumulated by the avalanche.

By redistributing snow, avalanches not only redistribute water but also nutrients that can be available for plants in the growing season. Moreover, avalanche paths are places where soil accumulates in some areas and erodes in others, contributing to potentially unique pedo-environmental conditions.

The Collembola succession was studied in the Hardangerjøkulen glacier foreland in south-central Norway. Twenty sampling plots 30 to 230 years of age were distributed along a chronosequence where a glacier snout had been receding since 1750. Also, five plots 10,000 years of age were sampled. All soil samples were taken in Salix herbacea vegetation, in order to standardize the microhabitat. The youngest zone (30–50 years) contained 14 springtail species, mainly large, surface active generalists. Additional pitfall catches here revealed considerable surface activity of several species, also on vegetation-free areas. Even a three-year-young moraine contained at least three springtail species. Most pioneers also occurred in older soils. The cumulative number of species increased rapidly up to about 70 years, at which age 72% of all species had been recorded. Only five species in low numbers were confined to 10,000-year-old soil. A high density of Folsomia quadrioculata and F. brevicauda was noted at 50–70 years of age, and of Tetracanthella brachyura at about 100 years. Compared to oribatid mites, a higher number of springtail species colonized pristine ground. While the two pioneer oribatids were parthenogenetic, the dominant springtail pioneers were bisexual. Springtails are among the earliest colonizers along receding glaciers.

The sink-limitation hypothesis postulates that suppression of meristematic activity can limit growth at low temperatures (direct-cold-limitation) in situations where photosynthesis is not restricted. In accordance with this hypothesis, high concentrations of non-structural carbohydrates (NSC) have been found, in several studies, in plants at high altitudes or latitudes. However, high concentrations of NSC could also be due to nutrient deficiency. This study aimed to differentiate between nutrient- and direct-cold-limitation by comparing the growth and NSC concentrations of Abies veitchii saplings at two altitudes (high/low) and with two fertilization treatments (N-rich/N-poor).

N-rich saplings grew better at the low than the high site, but N-poor saplings were suppressed to similar degrees at both altitudes. Among N-rich saplings, the leaf nitrogen concentration was lower at the high site than the low site. Leaf NSC concentrations were higher in N-poor than N-rich saplings. However, NSC concentrations were higher at the high site than the low site in leaves with the same nitrogen concentrations. These results indicate that direct-cold and nutrient-limitation may occur simultaneously at high altitude, causing restricted growth and NSC accumulation. Therefore, NSC concentration should be interpreted in terms of both direct-cold and nutrient-limitation.

Because of the contrastive differences in environment and species composition, climatic amelioration may affect alpine vegetation differently between fellfield and snowbed communities. To test this prediction, the effects of warming on plant growth and vegetation structure were studied in two fellfield and two snowbed communities in northern Japan over 7 years using open-top-chambers (OTCs). OTCs increased the temperature by 1.1–1.8 °C, but the effects on snowmelt time and soil moisture were small. Vegetation height and canopy volume increased substantially at both fellfield sites as a result of the use of OTCs. Deciduous shrubs increased substantially at the lower fellfield and graminoids increased at the upper fellfield. In contrast, the responses of snowbed plants to OTCs were not significant. Because snowbed plants are snow-covered until mid-summer, climatic amelioration during the snow-free period may influence plant growth only slightly if the snow-free period does not change. Species richness and diversity were not changed by OTCs at any of the sites, indicating that the effect of warming alone may not be strong enough to change the species composition and diversity over several years. These results indicate significant variation in the response among alpine communities to warming.

In this study, we apply temperature, precipitation, and other data from 66 Chinese meteorological stations including Xining and Lhasa to analyze the extreme climate events and their impacting factors over the Qinghai-Tibet Plateau during the period 1961–2007. We focus on the spatial and temporal features of extreme climate events and their long-term changes over five climate zones of alpine grassland, meadow, and desert areas.

Results show that, during the past decades, the changes in climate over the Qinghai-Tibet Plateau present trends towards warm and wet conditions. These changes in temperature and precipitation are evident in both seasonal means and extreme events, and the changes in precipitation are apparent in both precipitation amount and number of precipitation days. Clearly, warm and wet events increase, but cold and dry events decrease over the plateau region. Features of the warming climate are relatively consistent in spatial and seasonal distributions, with the most significant changes in winter and autumn and at nighttime. Northern Qinghai exhibits the greatest and most significant decrease in the frequency of extremely low-temperature events. However, the wetting trend shows more distinctive spatial features and is more seasonally dependent. While the trends in both precipitation amount and the number of precipitation days are positive in all climate zones for winter and spring, both positive and insignificant negative trends appear in summer and autumn. The largest decrease in the frequency of severely dry events is found over southeastern Tibet and western Sichuan.

We describe changes in vascular plant richness on 13 high mountain summits based on a historical study performed approximately 40 years ago. A summit is defined as the uppermost 30 m of the mountain tops. The altitudes of the summits range from 1512 to 1814 m. Data from neighboring climatologic stations showed higher mean values for July temperature ( 0.7 °C) and January temperature ( 1.5 °C), and mean annual precipitation had increased from 714 to 764.7 mm (7.1%) for the period from 1970 until 2009 compared with average data for the normal period (1961–1990). The total “top flora” had during this period increased by 19 taxa. On average, the increase in taxa richness was 18.9 ± 8.4 per summit, representing an average increase of 90.2%. Woody species had an average upward movement of 7.3 m during the study period. The ongoing upward shift of common, ubiquitous alpine species has resulted in a floristic homogenization of the mountain summits, and thus increasing α-diversity was accompanied by decreasing β-diversity. The use of recorded plants as temperature indicators showed that average summer temperatures had increased by approximately 1.3 °C during this period. Several of the newly established species indicate that the climate has become more humid. We assume that the recorded floristic changes are the result of ongoing climatic changes.

Dendroclimatological reconstructions may be influenced by intraspecific variation in radial growth caused by plant gender and ecotypic differentiation. We examined the growth response of the High Arctic Salix arctica to interannual variation in snow precipitation in Zackenberg, NE Greenland. Tree ring examinations revealed a consistent response of annual radial growth in this dwarf shrub to variation in the amount of snow precipitation across gender and across three distinct vegetation types. Annual growth, however, differed between vegetation types. These results are discussed with respect to an improved understanding of the factors limiting the growth of S. arctica, which can be used for future reconstructions of climatic conditions, especially in remote High Arctic regions.

We studied sexual segregation in an endangered alpine ungulate, Sierra Nevada bighorn sheep (Ovis canadensis sierrae) in the Sierra Nevada, California, U.S.A., during winter 2005–2006. We tested hypotheses for sexual segregation to better understand that phenomenon and to obtain information critical for the conservation of these rare mammals. Females foraged in larger groups that were closer to escape terrain than did males. Areas used by males had higher biomass of vegetation and were less open than areas used by females. Males foraged more efficiently in larger groups, whereas females foraged more efficiently when close to escape terrain. Females exhibited a higher bite rate than did males. Males traveled farther per day and in more open terrain than did females. Sexes of bighorn sheep also differed in their dietary niches. Those niches differed most where sexes of bighorn sheep overlapped more in spatial distribution, and differed less where spatial separation was more pronounced. These outcomes are most parsimoniously explained by the gastrocentric and predation hypotheses. In addition, sexes of bighorn sheep behaved as if they were separate species by exhibiting avoidance on one niche axis (space) when there was overlap on another axis (diet). Management and conservation plans must consider the disparate requirements of males and females to help assure the viability of these endangered mountain ungulates.