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We studied Mount Washburn (Yellowstone National Park, Wyoming) to describe alpine ecosystem function and evolution at an important site in the North-Central Rockies. To describe the alpine environment we sampled major environmental nodes (north-faces, south-faces, snowbanks, ridges, talus, and ledges). Our analysis was bolstered by the measurement, over five years, of seasonal soil water and temperature. Clusters representing nodal plant communities explained 86% of scatterplot variability, after accounting for spatial location, in a strong (non-metric r2 = 0.98) NMDS ordination. Water inputs and nutrient storage (also significant predictors of community structure) increased while soil temperature fell from southern to northern nodes. Seasonal soil water availability was strongly influenced by transpiration. As a result soils dried earlier than expected under dense north-facing turf and later than expected under talus and ledges. We propose that abiotic and biotic processes have combined to increase resources for northern nodes at the expense of southern nodes since the last glaciation. This is because soils have continually blown with snow from south slopes to north-facing lee slopes, improving their water and nutrient status. Increases in vegetation have further increased water and nutrient capture and decreased water and nutrient losses in a biologically driven positive feedback loop.
Temperature is one of the major abiotic factors influencing distribution and productivity of alpine plant species. Although some edaphic parameters (e.g. soil acidity) have also been suggested as determinants in the spatial distribution of alpine vegetation, there is little background on the importance of soil chemical properties in altitudinal gradients, particularly in the high Andes. The present study determined whether soil chemical properties affect spatial distribution and abundance of alpine plants in an altitudinal gradient in the Andes of central Chile, emphasizing metal content. A direct gradient analysis took place at Yerba Loca Natural Sanctuary (YLNS), based on a geobotanical sampling conducted in 73 sites distributed from 1970 to 3330 m a.s.l. According to a Canonical Correspondence Analysis, the main soil chemical factors that explain the pattern of compositional variation of high Andean vegetation are, besides altitude, total soil copper (Cu) content, percentage of soil organic matter, and available phosphorus and nitrogen. An analysis of shoot Cu content conducted in 19 plant species found in sites with highest soil Cu contents (>250 mg kg−1) showed high levels of Cu in their shoots (>100 mg kg−1). These results demonstrate species or ecotypes with optimal distribution in soils with high Cu contents, such as Armeria maritima, Trisetum lasiolepis, and Montiopsis potentilloides, which may have tolerance to this metal.
Equilibrium-line altitudes (ELAs) were determined from reconstructions of 22 paleoglaciers at their extent during the local last glacial maximum (LGM) using the accumulation-area method. LGM ELAs thus derived ranged from 2980 to 3560 m and follow a statistically significant regional trend of rising ∼4.5 m km−1 to the east. Two approaches using a degree-day model were used to infer LGM climate by finding plausible combinations of temperature and precipitation change that (1) would be required to lower ELAs to their mean LGM values in both the Taylor Park/eastern Elk Mountains region and western Elk Mountains, and (2) provide steady-state mass balances to maintain individual glaciers. The results of these two approaches are convergent and suggest that in the absence of significant changes in precipitation, mean summer (or mean annual) temperatures within the study area during the LGM were on the order of about 7 °C cooler than at present. The model also suggests that even allowing for modest changes in LGM precipitation (±25%), the required mean summer temperature depressions are within ∼0.5 °C of these values. Furthermore, there appears to be no significant dependence on small potential changes in temperature seasonality (i.e., winter temperatures). The inferred magnitude of LGM temperature change in the study area is consistent with other estimates from the broader Southern and Central Rocky Mountain region.
One of the major remaining obstacles to understanding how ecosystems process carbon (C) and nitrogen (N) within soil organic matter (SOM) is landscape heterogeneity. While many studies have investigated landscape heterogeneity in total SOM C and N, less information exists on landscape patterns for differently aged constituents within SOM. These differently aged constituents can show distinct landscape-level patterns and levels of heterogeneity that contribute to our understanding of the production and decomposition processes that create SOM. Using field measurements from an alpine-subalpine ecosystem and geostatistical analyses, I show here that C and N in the older more recalcitrant SOM of mineral soil have more defined spatial patterns and are less heterogeneous than C and N in the newer more labile SOM of mineral soil at the forest-alpine tundra ecotone (SOM C: CV = 45% in older, 59% in newer; partial sill [sill minus nugget, i.e., percent of variation explained by spatial autocorrelation] = 38% in older, 11% in newer; SOM N: CV = 50% in older, 48% in newer; partial sill = 6% in older, 44% in newer). I also demonstrate that C∶N ratios show better spatial patterns and reduced landscape heterogeneity when compared with their constituent C and N concentrations (CV of total SOM C = 41%, total SOM N = 31%, total SOM C∶N = 20%; partial sill of total SOM C = 15%, total SOM N = 18%, total SOM C∶N = 64%). The reduced heterogeneity and strong relationships between C and N in older SOM suggest that landscape variation in the chemical composition of the SOM in mineral soils converges over time, possibly as a result of greater chemical variation in plant inputs relative to the products of decomposition reactions.
The Cariboo Mountains form the northern extension of the Columbia Mountains, spanning a distance of about 300 km in central British Columbia (BC), Canada. Cool air temperatures, abundant snowfall, and strong winds (especially above treeline and along exposed ridges) would suggest frequent and intense blowing snow events. The occurrence of intense blowing snow episodes is confirmed by automated wind and snow depth measurements at several sites in the area. Simulations conducted with a numerical model forced by meteorological observations recorded from 2006 to 2009 reveal a high frequency of blowing snow episodes at three high-elevation sites in the Cariboo Mountains. This process is especially prominent on the exposed ridge of Browntop Mountain (elevation of 2031 m a.s.l.) where snow transport by wind is calculated to occur as much as two-thirds of the time during some winter months. Simulated blowing snow fluxes remain high at this site with monthly transport and sublimation rates reaching 5301 Mg m−1 and 31 mm snow water equivalent (SWE), respectively. Blowing snow is also shown to be a dominant process in snow accumulation at the upper Castle Creek Glacier site (elevation of 2105 m a.s.l.), with strong winds generating sharp declines in snow depth and the erosion of more than 200 cm of snow depth during two successive winters. The results presented in this study suggest that blowing snow contributes significantly to snow accumulation and the mass balance of glaciers in BC's Cariboo Mountains.
Changes in Arapaho Glacier, Front Range, Colorado, are determined using historical maps, aerial photography, and field surveys using ground penetrating radar (GPR) and Global Positioning System data. Arapaho Glacier lost 52% of its area during the 20th century, decreasing from 0.34 to 0.16 km2. Between 1900 and 1999 glacial area loss rates increased from an average of 1500 m2 yr−1 to 2400 m2 yr−1. Average glacial thinning between 1900 and 1960 was 0.76 m yr−1, but slowed to 0.10 m yr−1 between 1960 and 2005. Its maximum thickness is approximately 15 m. If recent trends in area loss continue, Arapaho Glacier may disappear in as few as 65 years. However, the decline in thinning rate suggests that the glacier is retreating into a corner of its upper cirque in which increased inputs of snow from direct precipitation and avalanching, and decreased insolation will greatly slow its rate of retreat. This may be generally true for many temperate-latitude cirque glaciers.
The Czech Republic's Giant Mountains are a unique locality for studying snow algae because representatives of both significant genera, Chlamydomonas and Chloromonas (Chlorophyta), are regularly found there and are capable of completing their life cycle in several weeks. Physical and chemical environmental characteristics of two sites were measured in June 2008 and the photochemical processes of the snow algae were studied using variable chlorophyll fluorescence techniques. Correlations between the environmental conditions and the rapid light curve parameters were evaluated. The environment was characterized by stable snow temperature (Tsnow; −0.6 to −0.3 °C) but variable air temperature (Tair; 4.3 to 15.3 °C), photosynthetically active radiation (PAR; maximum of approximately 2000 µmol m−2 s−1), and ultraviolet radiation (UVR; 0.135 to 2.27 mW cm−2). The snow chemical composition at both experimental sites was similar, regardless of whether snow algae were present or not, and the nutrient concentrations resembled mesotrophic to eutrophic water. Only concentration of P-PO43− was significantly higher in the presence of algae. Vegetative and mating cells of Chloromonas cf. nivalis were observed on the snow surface down to a depth of 6 cm. The maximum quantum yield in a range from 0.479 to 0.624 indicated only minor or no stress conditions. While the relative electron transfer rate (142 to 241) and the initial slope (0.287 to 0.505 µmol−1 m2 s1) were negatively related to Tair, PAR, and UVR, the saturation irradiance values were very stable (350 to 489 µmol m−2 s−1). Various strategies of acclimation to high PAR and/or UVR at different stages of the life cycle are proposed.
Gentiana leucomelaena (Gentianaceae), an alpine herbaceous species of the Qinghai-Tibetan Plateau, has two colors of flowers (blue and white) that bloom in early spring. In order to determine the effect of petal color on flower interior temperature and behavior in the gentian, we investigated the differences in timing of flower opening and closure and the interior temperature of blooming flowers between the two colors, while recording the ambient temperature, light intensity, and relative humidity over the flowering season from March to May of 2009. When the flowers were open, the anther temperature was higher in the white flowers than in the blue flowers in various weather patterns; in particular it was about 2 °C higher on sunny days. Relative to the ambient temperature, the anther temperature was 1.27 °C higher in the white flowers, but was 0.41 °C lower in the blue flowers. Compared to blue flowers, white flowers opened later but closed earlier in the day at a higher ambient temperature. The two-factor two-level experiment (10 °C vs. 20 °C and 10,000 lux vs. darkness) indicates that temperature is the factor eventually determining the timing of flower opening and opening rates, but light may accelerate flower opening at the same temperature. The dye experiment, in which blue flowers were painted with red and purple food coloring, showed that the purple flowers had higher anther temperature, opened later but closed earlier, relative to the red ones. These results suggest that flower interior temperature is affected by both flower color and behavior in the species. In addition, we surveyed the percentages of the two flower colors in the field during the flowering season and also experimentally placed individuals with flower buds into growth chambers with contrasting day/night temperatures (12 °C/2 °C, 15 °C/2 °C, and 20 °C/2 °C), so as to examine the temperature effect on flower color frequency. A greater proportion of white flowers emerged in the early stage of the flowering season and in the low-temperature chambers, but blue ones dominated the late season and in the high-temperature chambers. This suggests that the color differentiation in the species is associated with temperature. The different strategies of adaptation to temperature might have allowed for flower color polymorphism.
Poa alpina grass plays a predominant role across the entire range of primary succession on alpine glacier forelands. One demographic factor that reacts clearly to changing environmental conditions is reproduction. Using permanent plot data, the complete life cycle of Poa alpina was studied along a successional gradient of the Rotmoos glacier foreland (2300–2400 m a.s.l., Central Alps, Austria) over a period of three years. We used matrix modeling to study the importance of the generation of plantlets and seedlings along the successional gradient and their ability to form adult individuals, and we hypothesized that plantlets develop faster to adults than seedlings because they start already with 3–4 developed leaves.
The study showed that plantlet and seedling fecundities of Poa alpina changed differently in the course of succession: seedling establishment was observed over the entire range of the successional stages, whereas plantlet establishment almost vanished with ongoing succession. In the pioneer stage, plantlets were more important than reproduction by seedlings. But we found neither a higher survival rate nor a significant advantage in development to adults for plantlets compared to seedlings. Opportunistic reproduction—plantlets under harsh abiotic conditions, seeds under increasing density—may therefore explain the fact that the species is ubiquitous along the whole glacier foreland.