Alpine plant communities are sensitive to global climate change, which has been predicted to cause increases in woody vegetation, possibly at the expense of herbs. We studied a community in western Maine, comparing the frequency and abundance of alpine plants in 2009 with frequency and abundance recorded in 1976. During the 33 years between surveys, the most common tree became more frequent, and as a result, the frequency of trees as a functional group increased. Shrubs did not become more frequent but did become more abundant, driven by the increasing abundance of two Vaccinium species. Several species provided evidence of strong affinities for the north or south slope of the mountain, but in most cases such evidence was apparent in a species' frequency or its abundance, not both, indicating that different forces regulate dispersal and vegetative growth of alpine plants, which could have implications for understanding responses to changing environmental conditions. Total species richness of the community increased, with the addition of several lower montane herbs. The changes are consistent with predictions and with observations made in tundra communities elsewhere.

A review of published literature and satellite imagery from the late 1960s onwards has revealed 90 surge-type glaciers in the Karakoram mountains, of which 50 have not previously been described in detail. These glaciers were identified by a number of surface features indicative of surge-type behavior such as looped moraines, rapid terminus advance, strandlines and rapid changes in surface crevassing. These observations indicate that surge-type behavior is more common and widespread than previously believed on Karakoram glaciers. There is strong spatial clustering of the surge-type glaciers, and a doubling in the number of new surges in the 14 years after 1990 (26 surges) than in the 14 years before 1990 (13 surges). This is coincident with a period of increased precipitation and positive glacier mass balance in this region, and supports previous studies which have found that mass balance has an important control on the frequency of glacier surging.

Wind-blown mineral dust derived from the crustal surface is an important atmospheric component affecting the Earth's radiation budget. Deposition of dust particles was measured in snow on Glacier No. 72, Mount Tuomuer, in the western Tian Shan, China. The mean concentration of dust particles (measured as the number of particles) with 0.57 < d < 26 µm in the snow pack is 706 × 10³ mL⁻¹, with a mean mass concentration of 3806 µg kg⁻¹. Dust number size distribution showed the dominant particles with d < 2 µm, while volume size distribution showed single-modal structures having volume median diameters from 3 to 25? µm. Results were compared with data from other sites in the Tian Shan and various Northern Hemisphere sites. A backward trajectory model was also employed to examine the transport process of dust particles in this region. Most of the air mass originated from southern China, e.g., the Taklimakan Deserts in springtime, during the Asian dust period. Transport of dust from southern Chinese deserts to adjacent mountains is in agreement with a growing body of evidence on the importance of dust inputs to alpine regions.

We document the post–Last Glacial Maximum (LGM) deglaciation history of a small catchment in Colorado's Front Range and model the glacial history responsible. We combine cosmogenic exposure dating of moraine boulders and glacial polish from 10 sites down the valley axis with a set of 1-D and 2-D numerical glacier models in which climate is represented by prescribed winter and summer mass balance profiles. Moraine ages of 24–18 ka constrain the LGM maximum glacial extent at 15 km downvalley from the range crest. Glacial polish sites decline in age along the center portion of the valley, dropping to roughly 12 ka by 5 km from the crest. This supports a monotonic but non-steady decline in glacier length. Modeling of the deglaciation history reveals that the equilibrium line altitude (ELA) rise from ∼18 ka to ∼14 ka was between 250 and 350 m, and that from ∼14 ka to ∼12 ka was between 100 and 150 m. Complete deglaciation requires at least another 250–300 m of ELA rise. A transient model run employing this ELA history can both reproduce the spatio-temporal pattern of glacial polish ages, and honor the constraints on maximum glacial extent. The full deglaciation between 18 ka and 10 ka can be modeled successfully with a 4.5–6 °C temperature rise and little to no change in precipitation.

Productivity of a managed grazing system is dependent upon both the grazing strategy of ungulates and decisions made by humans. Herds of domestic reindeer (Rangifer tarandus tarandus) graze on discrete ranges of the Seward Peninsula, Alaska with variable production rates. We show that the ¹⁵N natural abundance of reindeer forages vary significantly and the δ¹⁵N value of collagen deposited in antler bone from spring until ossification was significantly correlated with the δ¹⁵N signature of the diet. Calf weight in June was related to isotopic signatures in antler and soft tissue of adult females, and was inversely correlated with the absolute differential between summer and winter serum δ¹⁵N values. This observation suggests that female reindeer with smaller calves had catabolized more body protein during winter than females in adjacent herds. Moreover, in herds with smaller calves, female reindeer consumed proportionately more shrubs in early spring resulting in a strong relationship between δ¹⁵N signatures of antler collagen deposited in May and calf weight. These data suggest female reindeer catabolizing relatively more body protein during winter may attempt to compensate by increasing consumption of high-protein catkins and leaf buds of shrubs during May. Herders with relatively smaller calves in their herds may be able to improve protein balance of reproductive females and thus increase calf productivity by increasing access to shrub habitats during spring.

Vegetation in primary succession is influenced by multiple stochastic and environmental factors at different spatial and temporal scales. In this study we analyze the effect of meso-topographic heterogeneity on vegetation development following the retreat of Glaciar Seco in the southern Patagonian Andes. Composition and cover of algae, lichens, mosses, and vascular plants were recorded in 580 plots located in different topographic positions within a chronosequence of eight consecutive moraines. Sample plots were characterized by topographical and surface features. Spatiotemporal patterns in vegetation composition and their relationships to environmental factors were assessed by classification and ordination. We recognized eight communities that correspond to four major successional stages. The successional sequence is characterized by a physiognomic development from pioneer saxicolous lichens (first stage) to secondary colonizer lichens (second stage), followed by shrub colonization (third stage) and the development of Nothofagus spp. forests (fourth stage). Alternative successional trajectories on different topographic positions vary in the sequence of these four major successional stages, with the trajectories on the moraine ridge-top and base not going through some of the stages. A variance partition procedure shows that time since deglaciation and topographic position on the moraines account for comparable amounts of vegetation variance, emphasizing the importance of spatiotemporal analysis of vegetation development on heterogeneous landscapes. Broad trends in vegetation development follow environmental gradients. However, emergence and persistence of vegetation patterns can also be attributed to dynamic geomorphic processes such as moraine slope degradation affecting boulder distribution along the moraine foreslope. At the landscape scale, successional trajectories converge to a Nothofagus-dominated state, but significant variability remains in the understory due to the differential distribution of cryptogams along the moraine topographic gradient. Convergence is mostly related to the expansion of communities from more favorable sites towards the harsher moraine crest, but it is not a process of gradual deterministic changes along the different successional pathways.

Fens and wet meadows are important mountain wetland types, but influences on assemblage structure of associated invertebrates are poorly understood compared with other aspects of the ecology of these habitats. We sought to determine the relative contributions of terrestrial and aquatic invertebrates to diversity and abundance in these wetlands, the extent to which terrestrial and aquatic invertebrate assemblages differ with wetland type, and to what degree the aquatic assemblages vary as a function of slow sheet flow. We compared assemblages in fens and wet meadows, with and without flow, at 80 backcountry sites dispersed across the 6200 km² landscape of Yosemite, Sequoia, and Kings Canyon National Parks in the Sierra Nevada mountains of California, U.S.A., using standard aquatic and terrestrial sweep netting. Cicadellid leafhoppers, aphids, and thomisid crab spiders were the most abundant terrestrial taxa. Cicadellids, Lepidoptera, anthomyiid, muscid, chloropid, and ephydrid flies, and thomisids were more abundant in fens than in wet meadows. Only mirid leaf bugs were significantly more abundant in wet meadows than fens. Sphaeriid clams and chironomid midges dominated aquatic assemblages both with and without flow. Chloroperlid stoneflies, mites, clams, and flatworms were all more abundant in flow, and Hemiptera and mosquitos were significantly more abundant in quiescent water. Mosquitos were more abundant in wet meadows, but there were few other population differences as a function of wetland type. Terrestrial diversity was 1.1 to 2.0 times that of aquatic diversity, depending on metric and habitat. Fens had greater terrestrial abundance, richness, evenness, and diversity than wet meadows; there were fewer differences as a function of wetland type for aquatic fauna. Presence or absence of slow sheet flow had more effect on these aquatic assemblages than did wetland type. Cluster analyses, ordination, and multi-response permutation procedures were generally consistent with the univariate results. Vegetation-based wetland classifications should be extrapolated to faunal assemblages with caution, particularly for aquatic invertebrates.

Flowering phenology is a key life history trait that strongly influences reproductive success. We investigated the relationship between flowering phenology and functional traits of 48 alpine herb species using the Leaf-Height-Seed (LHS) scheme developed by Westoby (1998) to quantify the ecological strategy of the plant species. Phenological data were obtained by weekly observation of fifty 0.5 × 0.5 m² quadrates. Specific leaf area (SLA), height, and seed size of 48 alpine herbs were measured. Comparative generalized estimating equations and generalized linear models suggested that flowering peak date was positively correlated with size of maternal plant (biomass and height) and negatively correlated with seed size. Species with a longer flowering period were smaller and produced bigger seeds than those with a short flowering season. Flowering peak date and duration were negatively correlated, although this correlation was mainly present in annuals, which are relatively rare in the alpine meadow. Relationships between flowering phenology and specific leaf area (SLA) were weak. There were only weak effects of phylogeny on the relationships between flowering phenology and functional traits. Wind-pollinated species flowered earlier than insect-pollinated species. Annuals flowered longer than perennials. Relationships between flowering phenology and functional traits indicate that there is a tradeoff between maternal and reproductive growth, and flowering time may underlie the correlation between plant height and seed size.

Trees in the southern Siberian Mountains forest-tundra ecotone have considerably increased their radial and apical growth increments during the last few decades. This leads to the widespread vertical transformation of mat and prostrate krummholz forms of larch (Larix sibirica Ledeb) and Siberian pine (Pinus sibirica Du Tour). An analysis of the radial growth increments showed that these transformations began in the mid-1980s. Larch showed a greater resistance to the harsh alpine environment and attained a vertical growth form in areas where Siberian pine is still krummholz. Upper larch treeline is ≥10 m higher than Siberian pine treeline. Observed apical and radial growth increment increases were correlated with CO₂ concentration (r  =  0.83–0.87), summer temperatures (r  =  0.55–0.64), and “cold period” (i.e. September–May) air temperatures (r  =  0.36–0.37). Positive correlation between growth increments and winter precipitation was attributed to snow cover protection for trees during wintertime.

In this study, we analyzed the effect of topography, particularly slope, on the expansion rates and population dynamics of Echinospartum horridum at small spatial and temporal scales in the grassland communities of Ordesa–Monte Perdido National Park (OMPNP) (NE Spain). E. horridum is a thorny cushion dwarf, endemic of Spain and south of France, forming dense mono-specific large patches difficult to be penetrated by other plants and large herbivores once it is established. Between 2005 and 2007, we collected demographic parameters from 300 marked plants of E. horridum that were distributed in the center and the edge of four patches. At the patch edge, two of the four patches had a high slope (≥10°) and two had a low slope (<10°), whereas at the patch centers the slope was high (18°–30°). To calculate invasion speed, we use aerial photographs from 1981 and 2003. Plants in the center of patches had lower growth rates, fewer flowers, and higher crown death rates than did the plants at edge of patches. Slope influenced significantly invasion rates: the speed of expansion was lowest on gentle slopes, probably because of competition with grass. The speed of diffusion from 1981 to 2003 varied from 2.09 m yr⁻¹ on the steep slopes to 1.93 m yr⁻¹ on the shallow slope. Plant dynamics at patch edges suggest that colonization by E. horridum will continue in the grasslands of the OMPNP.

In a warming climate, sexual reproduction may play an important role in plant community composition in arctic tundra. As temperatures increase and currently immobilized soil nutrients become available, flowering, fruiting, and germination conditions will likely improve. We examined how experimentally adding soil nutrients for 13 and 20 years affected species composition, flower and fruit production, seed dispersal, composition of the seed bank, and seedling establishment in a dry heath plant community in northern Alaska. Fertilizer addition significantly shifted adult community composition by decreasing lichens and evergreen shrubs and increasing abundance of a bunchgrass, Hierochloe alpina, and dwarf birch, Betula nana. More seeds were dispersed adjacent to nutrient amended plots, particularly of B. nana, and soil seed banks differed significantly between control and fertilized soils reflecting the adult communities in the field. Few seedlings were observed in any field plots. However, seeds of H. alpina likely played a role in the community shift because this species has few, small individuals in control plots, yet is densely packed in fertilized plots. B. nana, on the other hand, appears to be increasing in relative abundance via vegetative growth of existing individuals. Therefore, although sexual reproduction leading to seedling establishment is rare currently, as nutrients become more available in a warming climate, individuals may recruit from seed more often as long as space is available.

Directly measured growth rates of two lichens (Pseudephebe minuscula and Rhizocarpon sections Rhizocarpon and Superficiale) from Svalbard made over a two-decade interval (1984–2007) are presented. Growth rates were determined by measuring the change in area of the lichen thalli from digital images and converting area to diameter. Pseudephebe diameter growth rates ranged from 0.2 to 1.5 mm yr⁻¹ and Rhizocarpon grew 0.05 to 0.30 mm yr⁻¹. Growth rates of both are a function of thalli size—growth rates increase with increasing thallus size up to 70 mm diameter for Pseudephebe and 30 mm diameter for Rhizocarpon. While these directly measured growth rate results are consistent with other recent directly measured lichen growth studies, they are not consistent with indirectly determined age-size curves that show a negative correlation between size and growth rate (i.e., rapid “great growth” followed by slower “linear growth”). We explore several reasons to explain the apparent discrepancy between directly measured and indirectly determined growth rates, including climate change, increased nutrient fluxes, and population sampling differences between the two methods. We argue that indirectly determined growth curves, which integrate the effects of changing growing conditions over time, remain the best basis for lichenometric dating.

About 5.6% of the drainage area of the Tanana River, Alaska, is covered by mountainous glacierized regions, and most of the other area by forests (51%) and wetlands (9%) with discontinuous permafrost. The water discharge and sediment load from glacierized and non-glacierized regions within the drainage area were represented by observed data of the proglacial Phelan Creek and the non-glacial Chena River, respectively, which are both the tributaries of the Tanana River and ultimately drain to the Yukon river basin. In the glacier-melt periods of 2007 and 2008, the runoff rate and suspended sediment concentration in Phelan Creek was 15 times and 36 times as high as those in the non-glacial Chena River, respectively. As a result, the mean sediment yield in the glacier-melt periods of 2007 and 2008 for Phelan Creek (24.8 t km⁻² day⁻¹) was estimated to be 640 times as high as that in the Chena River (0.039 t km⁻² day⁻¹). Hence, the glacierized regions were considered to be a major source of the fluvial sediment. In order to quantify the contribution of water discharge and sediment load from the glacierized regions to those of the Tanana River, the time series of water discharge, Q, and sediment load, L, in the glacier-melt periods were simulated by a tank model coupled with the L-Q equations (Nash-Sutcliffe efficiency coefficients, 0.41 to 0.82). The model indicates that the glacier-melt discharge accounted for 26–57% of the Tanana discharge, while the sediment load from the glacierized regions solely accounted for 76–94% of the Tanana sediment load. The remaining contribution (6–24%) of the sediment load was probably due to the fluvial resuspension of glacial sediment deposited previously in the river channels.

Past debris-flow and snow avalanche activity was assessed for the Reiselehnrinne (Tyrol, Austria) using growth disturbances in growth-ring series of 372 Norway spruce (Picea abies (L.) Karst.) trees. Determination of events was performed by analyzing (a) the number and (b) intensity of growth disturbances within tree-ring series and (c) the spatial distribution of affected trees. Differentiation of debris flow from snow avalanche events was based on the intra-annual position of scars, callus tissues or tangential rows of traumatic resin ducts, and on the spatial distribution of trees with simultaneous reactions in the tree-ring series. We introduce a weighting factor to substantiate the dating of past process activity in a comprehensive way and to compare individual events as to their intensity and total number of tree-ring responses. The accuracy of the dendrogeomorphic assessment was then evaluated by comparing the reconstructed event frequency with chronologies available for the Reiselehnrinne. Comparison of tree-ring with historical data demonstrated clearly that the reconstructed event frequency contains the majority of past debris flow and snow avalanche events in the Reiselehnrinne, but that dating of events is not always possible, especially if they are clustered in time or have a limited spread on the cone.