The second largest concentration of glaciers in the U.S. Rocky Mountains is located in Glacier National Park (GNP), Montana. The total glacier-covered area in this region decreased by ∼35% over the past 50 years, which has raised substantial concern about the loss of the water derived from glaciers during the summer. We used an innovative weather station design to collect in situ measurements on five remote glaciers, which are used to parameterize a regional glacier melt model. This model offered a first-order estimate of the summer meltwater production by glaciers. We find, during the normally dry month of August, glaciers in the region produce approximately 25 × 10⁶ m³ of potential runoff. We then estimated the glacier runoff component in five gaged streams sourced from GNP basins containing glaciers. Glacier-melt contributions range from 5% in a basin only 0.12% glacierized to >90% in a basin 28.5% glacierized. Glacier loss would likely lead to lower discharges and warmer temperatures in streams draining basins >20% glacier-covered. Lower flows could even be expected in streams draining basins as little as 1.4% glacierized if glaciers were to disappear.

The mesophyll cells of four species of Poaceae flowering plants growing in polar regions were studied—Deschampsia antarctica Desv. from the region of the Admiralty Bay on King George Island (West Antarctica) and D. alpina (L.) Roem. Sch., Poa alpina L. var. vivipara and P. arctica R. Br. var. vivipara from the Hornsund region of Spitsbergen island (Arctic). Ultrastructural changes were analyzed in the organelles of plants growing in Arctic and Antarctic habitats and plants grown in greenhouse, including plants exposed to short-term cold stress. The cell organelles were characterized by structural dynamics. Their morphological plasticity was manifested by elongation, formation of protrusions in the direction of adjacent organelles, as well as cytoplasm-filled pockets and invaginations that increase the contact area and reduce the distance between cell compartments. D. antarctica and P. alpina var. vivipara plants were characterized by highly dynamic cell nuclei with invaginations of the nuclear membrane filled with cytoplasm and organelles, high morphological plasticity, and conformational dynamics of chloroplasts and mitochondria, manifested by variations in the electron-optical density of matrix, membranes, and envelopes. The above could suggest that the studied taxa and their metabolic mechanisms had adapted to severe climates and changing conditions of the polar regions.

Warming temperatures in the Arctic are resulting in greater plant growth, particularly deciduous shrubs, in a phenomenon termed the “Greening of the Arctic.” Local expansion of deciduous shrubs is most likely resulting from vegetative growth, while the contribution of recruitment from seed is unknown. Here we compare seeds dispersed from plant communities created by experimental nutrient addition for 5 or 22 years with those from a community of sedges, deciduous shrubs, and evergreen shrubs at ambient soil nutrients. Nutrient addition decreased species richness and diversity and shifted the plant community toward dominance by dwarf birch, Betula nana, and a forb, Rubus chamaemorus. Generally, the composition of the seed rain resembled the adjacent plant community for deciduous shrubs, but not for other growth forms. Total seed abundance and proportion and total abundance of deciduous shrub seeds were greater adjacent to plots fertilized for 22 years. The deciduous shrub seed response was driven by a dramatic increase in seeds dispersed by Betula, resulting in lower taxa diversity, but not richness, of seed rain. These results suggest that increased shrub abundance will affect local seed dispersal, providing additional propagules for germination and increasing opportunities for reproduction by seed to be an important factor in the Greening of the Arctic.

Few studies provide experimental data to support the role of permafrost thaw on changes in arctic freshwater chemistry. We designed an incubation experiment to look at rapid nutrient release from permafrost soils and active layer soils under different warming scenarios, changes in redox environment, and microbial activity. Permafrost soil tended to immediately release more nutrients than active layer soils, especially under warmer conditions; suggesting the active layer is depleted in nutrients and the water column may be resupplied with these ions from thawing permafrost. The release of micronutrients (Ca, Fe, Mg, S, Si) from incubated permafrost soils responded strongly to increased temperature; however, temperature alone was not necessarily the primary driver of macronutrient (N, P) release from permafrost. Other physicochemical parameters influenced by temperature, such as oxidation-reduction potential (ORP), microbial activity, dissolved organic carbon (DOC), and Fe played an additional role in nutrient release from permafrost. These experiments suggest nutrient release via thaw of permafrost soils is able to contribute ample essential nutrients to arctic aquatic ecosystems, even within one day of warming. Further warming of the Arctic is likely to result in substantial changes to nutrient availability and cycling in these dominant habitats.

Subarctic peatlands are rich sources of organic carbon for freshwater ecosystems. Where those peatlands are underlain by permafrost, permafrost thaw may cause an initial release of bioavailable dissolved organic carbon (DOC) to surrounding freshwaters. In this study, we measured icebound and potentially leachable (extracted) DOC quantities and indices of DOC quality in active layer and permafrost layers from two subarctic peat mires, Stordalen and Storflaket. Most of the permafrost layers did not contain more organic matter or exportable DOC (as g kg^-1 dry soil) than the overlying active layer, and there was no difference in aromaticity, molecular weight, or the ratio between labile and recalcitrant DOC extracted from the permafrost and active layer. However, DOC held in segregated ice of the near-surface permafrost had relatively low aromaticity compared to extracted DOC from the same depth. Total icebound and potentially leachable DOC in the Stordalen mire permafrost that is predicted to experience active layer deepening during each of the next 50 years corresponded to about 0.1% of the current annual aquatic export of DOC from the mire. We conclude that the pool of potentially leachable DOC currently stored in permafrost layers is small. We also highlight differences in permafrost organic material between the two studied mire systems, which has an effect on the pool and properties of leachable DOC that is potentially available for export during thaw. Moreover, the geomorphological form of permafrost thaw will influence future hydrological connectedness and DOC production, in turn determining future DOC export from the mires.

Characterizing the above- and belowground carbon stocks of ecosystems is vital for a better understanding of the role of vegetation in carbon cycling. Yet studies on forest ecosystems at high altitudes remain scarce. We examined above- and belowground carbon partitioning in trees growing in mixed montane/upper montane forest ecosystems in the French Alps. Field work was performed in three forests along a gradient of both altitude (1400 m, 1700 m, and 2000 m) and altitude-induced species composition (from lower altitude Abies alba and Fagus sylvatica to higher altitude Picea abies and Pinus uncinata). We performed forest inventories and root sampling along soil wall profiles, so that the stand basal area (SBA, in m² ha^-1) and root cross-sectional area (RCSA, in m² ha^-1) were estimated at each altitude. To characterize the carbon allocation trend between the above-and belowground compartments, the ratio of RCSA to SBA was then calculated. We found that both SBA and RCSA of coarse roots (diameter > 2 mm) were significantly different among the three altitudes. No significant difference in RCSA of fine roots (diameter ≤ 2 mm) was found among altitudes. The ratio of RCSA of fine roots to SBA augmented with increasing elevation, suggesting that forest ecosystems at higher altitudes allocate more carbon from above- to belowground organs. This increased allocation to fine roots would allow trees to scavenge nutrients more efficiently throughout the short growing season. Furthermore, this work highlighted the interest of using easy to measure area-based indicators as proxies of root and stem biomass when investigating carbon partitioning in highly heterogeneous montane/upper montane forests.

This study describes and compares soil organic matter (SOM) quantity and characteristics in two areas of continuous permafrost, a mountainous region in NE Greenland (Zackenberg study site) and a lowland region in NE Siberia (Cherskiy and Shalaurovo study sites). Our assessments are based on stratified-random landscape-level inventories of soil profiles down to 1 m depth, with physico-chemical, elemental, and radiocarbon-dating analyses. The estimated mean soil organic carbon (SOC) storage in the upper meter of soils in the NE Greenland site is 8.3 ± 1.8 kg C m^-2 compared to 20.3 ± 2.2 kg C m^-2 and 30.0 ± 2.0 kg C m^-2 in the NE Siberian sites (95% confidence intervals). The lower SOC storage in the High Arctic site in NE Greenland can be largely explained by the fact that 59% of the study area is located at higher elevation with mostly barren ground and thus very low SOC contents. In addition, SOC-rich fens and bogs occupy a much smaller proportion of the landscape in NE Greenland (∼3%) than in NE Siberia (∼20%). The contribution of deeper buried C-enriched material in the mineral soil horizons to the total SOC storage is lower in the NE Greenland site (∼13%) compared to the NE Siberian sites (∼24%–30%). Buried SOM seems generally more decomposed in NE Greenland than in NE Siberia, which we relate to different burial mechanisms prevailing in these regions.

Water scarcity is a growing issue for high altitude arid countries like Bolivia, where serious water resource concerns exist because of climate change and population growth. In this study we use a recent Bolivian rock glacier inventory (Rangecroft et al., 2014) to estimate the water equivalent storage of these understudied cryospheric reserves. This paper shows that Bolivian rock glaciers currently store between 11.7 and 137 million cubic meters of water. Rock glacier water equivalents are compared to corresponding ice glacier water equivalent to allow an assessment of the hydrological importance of rock glaciers as water stores in this water scarce region. It can be seen that in the densely glaciated Cordillera Real (15°–16°S) rock glaciers form a small component of mountain water stores; however, along the Cordillera Occidental (17°–22°S), where ice glaciers are absent, rock glaciers are a more important part of the cryospheric water store, suggesting that they could be important for local water management. This is the first time that the water equivalence of the Bolivian rock glacier store has been quantified and is a first step toward assessing the contribution and importance of alternative high altitude water sources.

The potential long-term effects of thaw slump disturbances on tundra ecosystems include a significant reorganization of tundra plant communities. In this study, vegetation sucession of stabilized retrogressive thaw slumps was investigated using four age classes: 10, 20, and 250 years old, and undisturbed areas. While still active, slumps are characterized by bare soil, pools of water and liquefied mud, and the initial colonization of graminoids and forbs. Between 0 and 20 years after stabilization, the slump vegetation is characterized by low diversity, grass-dominated vegetation communities with a high percent cover of dry bare ground. This is followed after a few hundred years by a forb, dwarf shrub, and bryophyte-dominated community with a high percent cover of litter. With future warming expected, the presence and areal extent of thaw disturbances are predicted to increase. These findings suggest that the result would be an altered tundra species composition, which remains distinct for at least several centuries.

The Emerald Lake Basin provides a long-term site for research on hydrology, ecology, and biogeochemistry, as well as baseline data for a representative subalpine watershed in the Sierra Nevada of California. Field studies provided quantitative data on the biomass, net primary production, and nutrient allocation of major subalpine shrub and meadow communities. Measurements carried out over two growing seasons found aboveground biomass per unit canopy area was 3857 g m^-2 in Chrysolepis sempervirens, 3360 g m^-2 in Salix orestera, and 1614 g m^-2 in Phyllodoce breweri. The biomass for Chrysolepis and Salix canopies were high compared to other published data for subalpine and alpine shrublands, but the Phyllodoce biomass was comparable to values for ericaceous heath in the Rocky Mountains and European Alps. Wet and dry meadows had 377 and 98 g m^-2, respectively, in aboveground living tissues, comparable to values from the Rocky Mountains and European Alps. Belowground biomass for shrub communities was the highest for Phyllodoce (3670 g m^-2), followed by Chrysolepis (2400 g m^-2) and Salix (2070 g m^-2). The wet meadow community had a surprisingly high belowground biomass of 2897 g m^-2, reflecting the dominance of large perennial herb species. This resulted from a root:shoot ratio of 8.21 compared to 5.72 in the dry meadow community. Canopies of Chrysolepis and Salix had root:shoot ratios of 0.62 and 0.61, respectively, and Phyllodoce a ratio of 2.27.

Alpine grassland and permafrost occupy about two thirds and one half of the total area of the Qinghai-Tibetan Plateau (QTP), respectively. Soil water, which can be affected by permafrost thawing and precipitation, is important for vegetation growth in this region. It is therefore vital to consider the effects of both thawing and precipitation when studying the effect of climate warming on alpine grassland on the QTP. In this study, we examined two adjacent basins, one semiarid and the other semihumid, in the northeastern section of the QTP. We used remote sensing data to compare fractional vegetation cover (FVC) and the relationships between FVC and land surface temperature (LST) in different types of frozen ground; the samples were analogous to a chronosequence of climate warming and permafrost thawing. Our analysis produced three significant results: (1) the FVCs of the semihumid basin were significantly greater than those of the semiarid basin for most types of frozen ground (p < 0.05); (2) the changes in FVC along the climate warming and permafrost thawing chronosequence were different in the two basins, with the maximum FVC occurring on the transition permafrost zone in the semiarid basin and on the seasonal frost zone in the semihumid basin; and (3) at the peak of the growing season, only the three warmest types of frozen ground in the semiarid basin had a negative relationship between FVC and LST, suggesting that vegetation growth was limited by water. Therefore, we concluded that the responses of alpine grassland to climate warming in the permafrost regions are complicated by precipitation and permafrost thawing; specifically, grasslands will not necessarily simply degrade as the climate warms, as suggested by previous plot-scale studies.

At the landscape scale, the response of alpine treelines to increasing temperatures often varies due to second-order factors such as terrain properties, vegetation structure, and land use. In this study, we examined the influence of topographic and vegetation-structure variables on spatial patterns of treeline ecotone shifts in the Sudetes Mountains (Czech Republic). The changing positions of the alpine timberline and alpine treeline were determined from orthogonal aerial images allowing comparisons between 1936 and 2005. Our results showed that the alpine timberline advanced upward at an overall rate between 0.30 m yr^-1 in the Hrubý Jeseník Mountains (eastern part of the Sudetes) and 0.43 m yr^-1 in the Giant Mountains (western part of the Sudetes). Forest infilling was substantially greater than advances above original alpine treeline positions. Forest upward shifts occurred mostly on sites with already established, well-dispersed trees and low levels of prostrate dwarf pine cover. Topographic variables such as altitude and heat load affected forest advance if initial tree cover was low. The occurrence of competitive prostrate shrubs and the presence of climatically extreme convex parts of slopes appear to be important second-order factors affecting treeline ecotone shifts, particularly at wind-affected treelines.

A combination of Landsat and ASTER satellite scenes are used to quantify changes in the areal extent of glaciers in 130 basins across the Southern Patagonian Icefield (SPI). There was extensive net overall loss, with a reduction in ice area of 542 km² (∼4% of the SPI) between the late 1970s and 2008/2010. For glaciers measured within individual periods, average losses occurred at a rate of 3.24% decade^-1 between 1976/1979 and 1984/1986, 2.04% decade^-1 between 1984/1986 and 2000/2002, and 2.24% decade^-1 between 2000/2002 and 2008/2010. This indicates sustained losses, but no evidence for a recent acceleration. Since the 1980s, glaciers located in the northwest part of the SPI experienced the highest mean annual loss rates at 2.9% decade^-1. Mean glacier elevation provides the only significant topographic control on glacier changes for all measurement periods, and glacier losses are consistent with recent warming and changes in precipitation observed for this region.

The function of Alpine marmot subspecies burrows and factors influencing their distribution were investigated at 17 sites in the Tatra Mountains in Slovakia, Europe. Topographic variables and habitat types expected to influence the location of the Tatra marmot burrows were observed and examined. In the various locations of the studied home ranges (summer, winter and grazing areas, marmot trails) and outside the family territories, we recorded 36 vegetation samples including several reliefs. The collected data were analyzed using multivariate analysis.

The summer areas of the marmot home ranges in the Tatra Mountains are often located within the alpine zone in communities of the Braun-Blanquet alliance Juncion trifidi (siliceous short stem grasslands) and in chionophilous communities on stable scree slopes of the alliance Festucion picturatae (tall stem grasslands). Marmots usually avoid habitats that have the lowest trophic benefits and the most extreme sites with low-stems or mat-grass communities in the alliance Nardion strictae, dense stands of dwarf pine in the alliance Pinion mugo (krummholz), and dwarf-shrub and lichen communities in the alliance Loiseleurio-Vaccinion. Marmot habitats in summer have suitable grazing areas. The most preferred habitats for foraging are grasslands and tall herb plant communities dominated by Calamagrostis villosa, Trisetum fuscum, and similar tall grass species.

The most important factor influencing the locations of different parts of home ranges is the gradient of the relief structure. According to their functional differentiation, the location of a marmot burrow is most significantly influenced by the presence of convex geomorphic features and reinforced rock forms.