Dissolved organic matter (DOM) exported in glacier meltwater influences downstream biogeochemical processes, and climate warming may increase the meltwater DOM flux. In this study, we quantify and use fluorescence spectroscopy and parallel factor analysis (PARAFAC) to characterize DOM exported in glacier meltwater in Taylor and Wright Valleys, McMurdo Dry Valleys, Antarctica.

Andersen Creek, a proglacial stream draining Canada Glacier meltwater, exported ∼20 kg of DOM as dissolved organic carbon (DOC) to Lake Hoare during the melt season. Supraglacial snowpack DOM from all of the Dry Valley glaciers sampled exhibits “protein-like” fluorescence indicating that it contains potentially labile moieties that might be a favorable substrate supporting downstream microbial metabolism. However, this protein-like fluorescence does not persist in any of the meltwater streams surveyed, suggesting that it is quickly transformed by resident microbial populations and/or mixed with other DOM pools within stream channels or along its margins.

Given the seemingly ubiquitous protein-like fluorescent characteristic of glacier-derived DOM and the immediate change to the bulk DOM in glacier streams, a more thorough characterization of the bulk DOM pool from glacial sources and through downstream ecosystems would yield valuable information about the potential contribution of glacier melt to the global carbon cycle.

In recent decades, the use of some subalpine mountain grasslands in the Central Spanish Pyrenees has changed. Ski resorts have been developed and cattle herd management has shifted from the traditional “rotational-type” system in which grazing cattle are overseen by a herder to a “continuous-type” system that does not involve a herder. In 2005, the locations of 30 floristic inventories performed in 1972 were revisited and inventories were repeated in two adjacent similar areas, although one had been used for the development of ski runs and the other had not. The objective was to assess the effects of those changes on plant diversity and other characteristics of the grasslands. In both areas, plant diversity was significantly higher in 2005 than it was in 1972. Both areas had been grazed by cattle to a similar extent; thus, the results suggest that diversity was affected primarily by the change in the livestock grazing system. Livestock grazing within the skiing area appears to have counterbalanced any reduction in plant diversity that would have occurred because of the construction and use of ski runs. In the skiing area, legume cover and pastoral value decreased, the Ellenberg Nitrogen Index reflected lower soil nutrients available to plants, and the cover of plant species that regenerate by seeds increased between 1972 and 2005; such changes did not occur in the non-skiing area. The abundance of ruderal species increased more in the skiing area than in the non-skiing area. Between 1981 and 2000, the amount of bare ground increased only in the skiing area.

Snow particle size is an important parameter strongly affecting snow cover broadband albedo from seasonally snow covered areas and ice sheets. It is also important in remote sensing analyses because it influences the reflectance and scattering properties of the snow. We have developed a digital image processing method for the capture and analysis of data of snow particle size and shape. The method is suitable for quick and reliable data capture in the field. Traditional methods based on visual inspection of samples have been used but do not yield quantitative data. Our method provides an alternative to both simpler and more complex methods by providing a tool that limits the subjective effect of the visual analysis and provides a quantitative particle size distribution. The method involves image analysis software and field efficient instrumentation in order to develop a complete process-chain easily implemented under field conditions. The output from the analysis is a two-dimensional analysis of particle size, shape, and distributions for each sample. The results of the segmentation process were validated against manual delineation of snow particles. The developed method improves snow particle analysis because it is quantitative, reproducible, and applicable for different types of field sites.

A previous study of carbon isotopes in the sediments of a glacial lake in Costa Rica led to the hypothesis that changes in the migration of the intertropical convergence zone (ITCZ) over the course of the Holocene significantly affected the hydrology of the surrounding high-elevation páramo ecosystem. This hypothesis was based on millennial-scale changes in terrestrial n-alkane carbon isotope (δ¹³C) values in a sediment core from Lago de las Morrenas 1, a tarn on the Chirripó massif of the Cordillera de Talamanca. Here we present terrestrial n-alkane hydrogen isotope (δD) data, a more direct proxy of ecosystem drought stress, from the same core. These new data support the previous hypothesis and confirm that the effects of millennial-scale ITCZ dynamics in the circum-Caribbean region were not restricted to tropical lowlands. In southern Central America, these dynamics may have played a fundamental role in millennial-scale fire dynamics in high-elevation páramo ecosystems.

Wet snow avalanches breaking through to the base of the snowpack or overriding snowfree surfaces can entrain basal material and act as important agents of sediment transport in steep alpine catchments. Here we present results from 4 years of measurements at the Guggigraben catchment (Matter Valley, Canton Valais), quantifying the volume of sediment transported by avalanches each winter season. Sediment load was estimated by measuring the debris content within representative areas and then extrapolating the cumulative volume. Results reveal a total transported sediment volume of 70 m³ in 2009, 23 m³ in 2010, 15 m³ in 2011, and 35 m³ in 2012, which correspond to catchment-wide erosion rates of approximately 0.05, 0.02, 0.01, and 0.03 mm/a, respectively. Sediment appears to be sourced predominantly from within the main channel or one its tributaries, originating first from rockfall or landslides. Avalanches thus play an important role at the Guggigraben in transporting loose sediment from temporary storage sites to the fan and main river system. Within the bedrock gully and in the avalanche source region above, signs of abrasive wear were evident on exposed bedrock surfaces. These included rounded and scoured bedrock, fresh boulder impacts, and scratch marks on the gully walls.

Low nitrogen (N) supply is a limiting factor for plant growth in most terrestrial ecosystems. N-fixing legumes therefore have the potential to facilitate surrounding vegetation by increasing soil N levels. This effect should be especially pronounced in low-productivity habitats where ambient soil N levels are low, such as in alpine areas. We examined whether plant species composition, community diversity measures, and soil N levels differed with and without the presence of two alpine legumes, Oxytropis lapponica (Wahlenb.) Gay and Astragalus alpinus L., in a Dryas octopetala heath at Finse, Norway. Species composition and richness differed between plots with and without Oxytropis in one of two study sites, as other plant species were positively associated with the legume. None of the measured community properties differed between plots with and without the presence of Astragalus. The contrasting influence of the two legume species corresponds to our findings of higher soil N levels below Oxytropis, but not Astragalus. Differences in microhabitat N levels may explain why only Oxytropis acts as a facilitator. By affecting local species composition Oxytropis increases spatial heterogeneity, which may increase total species richness of the ecosystem.

Subsistence in northern regions with cold climate and long winters relies to a large extent on fuelwood access and logistics. The preferred sources of fuelwood in pre-industrial times in northern Scandinavia were dead standing Scots pine trees. To assess historical impacts of Sami settlement sites on surrounding forests, and effects of burning wood on living conditions inside their huts, we burned pine wood in a Sami tent hut during winter, as realistically as possible, then analyzed fuelwood consumption, temperatures, and CO levels inside it. Hourly wood consumption rates ranged from 5.0 to 7.4 kg, corresponding to an estimated average annual consumption of ca. 22,000 kg or 42 m³ per hut. The smoke created by the fire and the low indoor temperature at the periphery of the hut limited the comfortable living space to approximately a third of the total space. We estimate that areas up to 300 m from settlements were used for fuelwood collection, but deliberate, recurring tree girdling to produce snags suitable for fuelwood might have reduced this area. Overall, the landscape impact of settlements was low, affecting less than 2.2% of the utilized lands. We conclude that experimental simulations of historical resource uses can provide valuable quantitative data for verifying or challenging qualitative interpretations and thoroughly modeling human effects on ecosystems over time.

On forested paths, dendrogeomorphology has been demonstrated to represent a powerful tool to reconstruct past activity of avalanches, an indispensable step in avalanche hazard assessment. Several quantitative and qualitative approaches have been shown to yield reasonable event chronologies but the question of the completeness of tree-ring records remains debatable. Here, we present an alternative semi-quantitative approach for the determination of past snow avalanche events. The approach relies on the assessment of the number and position of disturbed trees within avalanche paths as well as on the intensity of reactions in trees. In order to demonstrate that no bias was induced by the dendrogeomorphic expert, we carry out a statistical evaluation (Classification and Regression Trees, or CART) of the approach. Results point to the consistency and replicability of the procedure and to the fact that the approach is not restricted to the identification of high-magnitude avalanches. Evaluation of the semi-quantitative approach is illustrated on a well-documented path in Chamonix, French Alps. For the period 1905–2010, comparison between the avalanche years recorded in a substantial database (Enquête Permanente sur les Avalanches, or EPA) and those defined with dendrogeomorphic techniques shows that the avalanche record reconstructed from tree-ring series contains 38% of the observed events.

Caching decisions have been studied for many species, but large-scale variation of selective preferences due to environmental heterogeneity has rarely been examined. We investigated large-scale patterns of selective caching behavior in the American pika (Ochotona princeps), a non-hibernating generalist herbivore that caches vegetation in haypiles to serve as winter food. At 13 sites throughout the southern Rocky Mountains, we identified the three most common available and cached plant species and analyzed them for dietary quality. Selectivity at each site was measured as the difference between average quality of the most common cached and available vegetation. Pikas consistently cached materials of higher quality than the most common available vegetation. Selectivity for high nitrogen corresponded to quality of available plants and site summer temperature, whereas selectivity for high water content was negatively correlated with elevation. Our results indicate that pikas cache a variety of plant materials while using different selectivity cues, illustrating the complexity of pika caching behavior across a range of environmental conditions and forage values. Future studies on caching behavior should take into account differential selectivity due to environmental heterogeneity.

Expected shifts in the upper forest limit of many mountain ranges due to anthropogenic climate change will likely be constrained by current and historical land-use practices. We used historical maps and Landsat satellite imagery to analyze timberline change for the entire Carpathian range in Eastern Europe. Our objectives were (1) to compare 19th and 20th century timberline elevations across regions differing in sociopolitical history and land-use trends; and (2) to quantify how land-use patterns and environmental influences were associated with changes in timberline position. Timberline changes across geopolitical regions were consistent with regional variations in re-settlement rates and population shifts following World War II. Important predictors for timberline rise were the mainly biophysical factors of slope steepness, timberline elevation, shrub cover, topographic curvature, aspect, and proximity to roads. For horizontal migration, important predictors were proximity to shepherd's huts, elevation, population density, forest composition, and shrub cover. Overall, cultural influences were critical for understanding the response of Carpathian timberlines to global change, yet biophysical influences proved important where reforestation was already occurring. In mountain ranges with prevalent agricultural abandonment, forest migration associated with climate warming may lead to increased contrast in the forest-alpine ecotone between areas with and without intensive land-use.

The soil seed bank and seed germination capacity of Poa annua in the vicinity of the Polish Antarctic Station (South Shetlands, Antarctica) were investigated. It was documented that annual bluegrass can reproduce sexually and produce a functional seed bank of close to 5000 seeds/m² under maritime Antarctic conditions. Comparison of germination between Poa annua and two native plant species revealed that Poa annua seeds can germinate as fast or even faster than native species, and are more vigorous. Our studies show that in the Antarctic Poa annua can successfully reproduce sexually and produce fully developed, viable caryopses that are able to survive the maritime Antarctic winter, not only in a soil bank, but also directly in the previous year's inflorescences.