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Understanding trophic interaction within deep-sea marine communities is critically important as commercial exploitation increases in the Arctic. Undoubtedly, the Arctic marine environment will be subject to the same environmental and human stressors as its southern counterparts and, as a result, community stability is vulnerable. The objectives of this study were to test the predictive power of environmental variables on fish community composition using redundancy analysis and to determine if this information could be used to differentiate distinct trophic communities throughout the Davis Strait/Baffin Bay region. This analysis used data collected in benthic surveys from 2000 to 2004, and results indicate that water temperature, latitude, and depth strongly influence the distribution of fish species in this region. Latitude and water temperature were strongly negatively correlated, and the majority of species were distributed along the low latitude/high temperature to high latitude/low temperature gradient. Some fish species were more highly correlated with depth. Proportions of most by-catch species differed between northern and southern regions at each depth range. Since community structure changes gradually along environmental gradients, perhaps it is more appropriate to describe the communities as shifting their trophic status along environmental gradients rather than as distinct communities with distinct food webs in a specific region of the Arctic.
The study area spans the 15-km-wide ecotone between coastal tundra and open subarctic forest near Churchill, Manitoba, Canada. Study sites include Black Spruce Wetland, White Spruce Forest, Burned Forest, Forest-tundra Tree Island, and Tundra. These ecosystems are representative of ones that dominate the circumpolar north. Mid-winter snowpack characteristics were measured during 2002, 2003, and 2004, including depth, density, and snow water equivalent. These studies reveal differences induced by changing vegetation characteristics and associated microclimates. Despite the dramatic differences in canopy, the post-fire forest snowpack differed little from that of the unburned forests. Interannual variations were much less than intersite variations in most snowpack characteristics. These studies are intended to be repeated annually in order to establish a longitudinal study of snowpack variation across the Arctic treeline during a period of predicted dramatic change in climate.
The Churchill area has many examples of gravel-dominated, human-induced disturbances such as gravel pits and pads. These disturbances have occurred in a geographically small area with high biological diversity and detract from the aesthetics of this tourist destination. Eight treatments consisting of combinations of peat moss, seeding, fertilizer, snow fencing, and microrelief alteration were installed to improve the growth conditions on three gravel pits and two gravel pads ranging from predominantly tundra to predominantly boreal forest ecosystems. Plant-related assessments of the treatments (density, frequency, and cover) were made after the first and second growing seasons. Twenty-six species of plants were considered to be successful colonizers by at least one of the following criteria: >2% cover, >20% frequency, or >10 stems m−2. Androsace septentrionalis L., Carex L. spp., and Dryas integrifolia Vahl were the only taxa to meet all three criteria in both years. Differences related to the sites (i.e., seed bank, seed source, and substrate conditions) were greater than treatment differences. At three of the sites, seeded treatments had significantly more seedlings than the non-seeded treatments. These three sites were species-poor prior to revegetation testing and were dominated by the seeded species. The other two sites were dominated by species from the seed bank or from seed rain. Total seedling density on seeded plots increased by 17% compared to the controls while cover did not increase appreciably in the short term. Six native species were tested and three (Anemone multifida Poir., Hedysarum mackenzei Richards., and Linum lewisii Pursh) considered suitable for future use, adding to those tested by Firlotte (1998) in the Churchill region. It was determined that seed bank and potential for seed rain had a major influence on the success of seeding as opposed to substrate improvements alone.
Construction of ski runs has a very heavy impact on alpine ecosystems since it results in total destruction of the existing vegetation and profound alteration of the soil. Restoration work must thus set out to develop a protective plant cover immediately and promote re-establishment of a functional plant-soil system in the long term. The aims of the present study, conducted at the Monterosa ski resort (Val d'Ayas, Aosta, Italy) were to evaluate (1) how disturbance related to ski run construction at high altitude (2200–2600 m a.s.l.) has affected vegetation and soil properties compared to undisturbed sites, and (2) how vegetation and soil properties change in machine-graded ski runs with increasing time after hydroseeding. Herbaceous cover and specific composition, root density, physico-chemical soil properties, and aggregate stability were evaluated to determine the vegetation and soil dynamics of four runs constructed above timberline and hydroseeded 4, 6, 10, and 12 years ago, respectively, and of the adjacent undisturbed alpine pasture as control. The seeded species had quickly formed a cover that was still high even after 10 years. However, cover values were always extremely low for wild species, and this could be related to their strategies and to altered soil properties (higher pH, organic matter impoverishment, and loss of both fine particles and aggregates). The study indicated that more has to be done to conserve or restore physico-chemical soil properties as a decisive factor in establishing a self-sustaining native plant community.
The ecosystems of alpine snowbed habitats are reviewed with emphasis on ecosystem functioning and capability to adapt to current and predicted global change. Snowbeds form in topographic depressions that accumulate large amounts of snow during the winter months, and the final snowmelt does not occur until late in the growing season. Many species preferentially grow in snowbed habitats and some of these are even restricted to these habitats. In this review we identify several ecosystem services which snowbeds provide to the alpine landscape. For instance, snowbeds provide a steady water and nutrient supply to adjacent plant communities and offer newly emerged high-quality food for herbivores late in the growing season. We also propose that alpine snowbeds are much more productive than earlier thought, especially when the very short growing season and often high grazing pressure are taken fully into account. Furthermore, we propose that bryophytes and graminoids (grasses, sedges, and rushes) probably will be most negatively impacted by global change, and the snowbed plant communities will be invaded by species from adjacent plant communities, especially by shrubs and boreal species. As snowbed plants have special growth conditions, their sensitivity and ability to respond rapidly to changes in annual snowfall patterns make snowbed communities particularly vulnerable in a warmer climate, and thereby sensitive indicators of global change.
In 2003 a partial bison skull was recovered by Ashley National Forest archaeologists from an elevation of 3840 m (12,600 ft) above mean sea level on Gilbert Peak in the Uinta Mountains of Utah. The skull consists of a portion of the frontal, occipital region, and horn cores including horn sheaths. Through the analysis of the individual cones of the horn sheath, a record of the animal's dietary and migration patterns were obtained. While high-altitude bison remains have been discussed in the scientific literature periodically, they have not gone beyond the descriptive. In addition to descriptive and metric analysis of the skull, radiometric assay and stable isotope analyses were applied. The radiocarbon age of the specimen is 150 ± 40 yr BP (cal. a.d. 1725–1778). Metric analysis of the skull indicates it was an older adult male, which compares well with Bison bison athabascae (wood bison) in size and is larger than either Bison bison bison (plains bison) specimens or other high-altitude bison. However, it is probable this individual represents a member of the species Bison bison bison, but phenotypic characteristics (e.g., large horn size) may be the result of gene flow. More definitive taxonomic placement of the Gilbert Peak bison may not be resolved without genetic analysis.
Shrubs may act as nurse plants by facilitating the establishment and/or survival of under-story herbaceous plants under stressful conditions. Such interactions may promote the movement of montane species into alpine plant communities. We studied potential nurse effects of alpine willow shrubs (Salix spp.) on fireweed (Chamerion angustifolium) at three life history stages: seed, established seedling, and adult. Mechanisms for nurse effects were assessed at each stage by placing transplants into modified microsites containing shade and wind protection, as well as into unmanipulated microsites in open meadow and willow under-story habitats. Seedling establishment occurred only under the willow canopy and even there was extremely rare. Willows and experimental microcosms that simultaneously increased shade and reduced wind velocity strongly promoted over-winter survival of established seedlings and adults. All adult transplants surviving over the winter persisted over the subsequent growing season. For seedling transplants, extremely high mortality in exposed plots over the winter limited our power to experimentally detect nurse effects during the next growing season. Results suggest that by promoting persistent snow cover over the winter, willows enhance survival of fireweed at its upper range limit, potentially favoring its spread into alpine habitats.
The optimum pH of two species of snow algae from Upstate New York were assessed by studying three axenic strains of Chloromonas tughillensis in a pH range of 3.0–7.0 and three non-axenic strains of Cr. chenangoensis in a pH range of 3.0–8.0. Growth was examined at 0.5 pH intervals. Cell counts at the termination of the experiments differed among strains and among pH intervals in individual strains for both species, and strains of Cr. tughillensis responded differently to changes in pH (p < 0.001) while strains of Cr. chenangoensis did not (p = 0.193). Cell counts and absorbance data for Cr. tughillensis indicated an optimum pH of 4.9–6.1 using regression analysis. Strains of Cr. chenangoensis exhibited higher but insignificantly different counts between pH 7.0 and 8.0 with maxima at pH 7.5, but pH optima were not determined. When the range was expanded to include pH 8.5–9.0, an optimal pH of 7.0–8.0 was determined for strain CU 722B, and this is the first snow alga reported to have an optimum alkaline pH. The highest absorbance values, however, occurred between pH 3.0–4.5 and pH 7.0–8.0. The pH values recorded in the field were 5.0–5.3 for Cr. tughillensis and 6.7–7.6 for Cr. chenangoensis.
In the Colorado Front Range, rock glacier distribution has been noted on U.S. Geological Survey maps and in several publications; however, a comprehensive account of distribution is not available. When analyzed in a Geographic Information System (GIS), Digital Elevation Model variables (elevation, slope, or aspect) could reveal unique topographic characteristics of rock glaciers. The objectives of this study are to provide an accurate, complete account of rock glacier locations in a digital format, to compare topographic variables of rock glacier form and activity classes, and to evaluate glacier and rock glacier topographic information. Rock glacier locations were obtained from previous studies and were re-digitized on high-resolution digital orthophotos. Glacier distribution was determined through classification of a satellite image. Topographic information for rock glacier form and activity classes as well as for glaciers was obtained through zonal overlay in a GIS. Results indicate that tongue-shaped rock glaciers occur at higher elevations, have more northerly aspects, and have gentler slopes compared to lobate rock glaciers. Active, inactive, and fossil forms showed typical elevation and aspect gradients. Active rock glaciers are found at the highest elevations and most northern aspects. Inactive rock glaciers are found at lower elevations on all aspects with a tendency to face northeast, and fossil rock glaciers occur at the lowest elevations on all aspects. Topographic variables for all rock glaciers were statistically different compared to glacier locations; however, active tongue-shaped rock glaciers had similar topographic variables compared to glaciers, but lobate forms showed a significant difference. In the Front Range, active tongue-shaped rock glaciers are developed by glacial processes and active lobate forms are the product of periglacial processes.
Climate change may bring about geochemical changes in arctic regions as a result of increasing thaw depth. In order to better understand current watershed geochemistry and mineral weathering and provide a basis for predicting the geochemical effects of active-layer thickness increase, we examined elemental chemistry and 87Sr/86Sr of streams and sequential and total digests of soils, permafrost, and soil parent materials from seven glacial deposit surfaces of varying geomorphic ages in arctic Alaska in the vicinity of the Philip Smith Mountains quadrangle (69°N, 150°W). We found overall greater exchangeable K concentrations, exchangeable and acid digestible P and Ca concentrations, acid digestible and total Ca/Na and Ca/Sr, and lower acid digestible 87Sr/86Sr in permafrost than in active-layer mineral soil. Of the surfaces with similar parent material, stream and soil data suggest that weathering has progressively depleted calcium carbonate in the active layer with increasing surface age. Our results suggest that increasing thaw depth will lead to increasing carbonate and Ca supply to soils and streams, as well as spatially variable increases in P and K supply. Geochemical differences between active-layer soil and permafrost suggest the possibility of using stream geochemistry to detect changes in active-layer thickness in watersheds.
Surface microrelief, permafrost table configuration, ground-ice, and soil organic-matter contents are described for three sites near Inuvik, N.W.T., that are characterized by collapsed, poorly developed, and well-developed earth hummocks, respectively. The diameters of collapsed earth hummocks were significantly greater than those of well-developed vegetated hummocks. Hummock relief and interhummock distance increased along the continuum of forms, with the widest spacing and greatest relief measured at the site with well-developed vegetated hummocks. A bowl-shaped permafrost table mirrored the surface relief of most hummocks, but the collapsed hummocks were underlain by a planar or domed permafrost table. Segregated ice lenses parallel to the permafrost table, and small bodies of intrusive ice, were observed beneath the developing and well-developed hummocks. The configuration of the permafrost table and hummock relief, long-term observations of active-layer and hummock change, and hummock response to surface manipulation indicate that formation of a bowl-shaped permafrost table in association with organic accumulation and development of near-surface ground ice thrusts soils inward and upward causing hummock growth, whereas thaw subsidence may cause outward spreading and hummock collapse. Reaction-wood rings in black spruce trees growing on hummocky terrain indicate that tree tilting was associated with active-layer thinning and hummock growth. Cessation of reaction wood coincided with a period of active-layer deepening, degradation of ground ice, and outward spreading of the hummocks. In subarctic forests, hummock dynamics may be driven by ecological change associated with the fire cycle or climate change.
We studied the differences between areas undisturbed and disturbed by Ctenomys in the structure, diversity, and composition of a Puna desert plant community. We also studied differences in nutrient distribution in the soil produced by the activity of tuco-tucos. Within the plant community, plant and soil samples were taken from different sites, and at each site, both disturbed and undisturbed areas were sampled. We hypothesized that the activity of this rodent affected plant community structure, specific composition, diversity, and nutrient distribution (N, K, and P). Results at the plant population and community level and for soil nutrient concentration suggest that Ctenomys mendocinus could be a keystone species, capable of orienting the dynamics of the plant community studied in this ecosystem. Nevertheless, further manipulative experiments are necessary to confirm that the differences found between disturbed and undisturbed areas are indeed caused by the activity of Ctenomys.
Fluvial processes play a crucial role in landscape development in periglacial regions. Geomorphological studies have yielded contrasting inferences about the importance of various environmental factors to drainage density. In this paper, 12 explanatory variables, based on relief, vegetation, soil, and rock type, were used to explain the controlling factors of drainage density in an area of 2880 km2 in subarctic Finland. Analyses were performed at multiple spatial scales (1, 4, 16, and 64 km2) based on two novel statistical methods, namely generalized linear modeling (GLM) and hierarchical partitioning (HP). The results of the GLM and HP analyses were broadly concordant. Most of the variation in drainage density can be explained by soil and vegetation variables. Drainage density increased with proportion of rock and gravel soils and alpine vegetation, and decreased with peat cover. Variables based on topography and rock type explained only a small amount of the variation in drainage density. The results also confirm the profound influence of the spatial scale on the geomorphologic systems: factors influencing drainage density yield different results depending on the spatial scale at which drainage density is analyzed. The large data sets and the use of rigorous statistical techniques at four different scales add the confidence and generality for the present results.
We measured thalli diameters of the lichen Rhizocarpon subgenus Rhizocarpon on 48 individual lobes of 18 rock glaciers and rock glacier complexes in the Elk Mountains and Sawatch Range of central Colorado. Cumulative probability distribution and K-means clustering analyses were used to separate lichen thalli measurements into statistically distinct groups, each interpreted as representing a discrete episode of rock glacier activity driven by an interval of cooler climate. Lichen ages for these episodes were assigned using a growth curve developed for Rhizocarpon geographicum in the nearby Front Range. An early Neoglacial episode, ca. 3080 yr BP, is correlative to other glacial and periglacial activity in the southern Rocky Mountains and surrounding areas and broadly corresponds to an interval of climatic deterioration evident in several other proxies of Holocene climate. The younger two episodes, ca. 2070 and 1150 yr BP, are also coeval with regional (Audubon) glacial and periglacial activity but are thus far not widely recognized in other climate proxies.
Some of the world's highest-altitude butterflies belong to the tribe Pierini of the family Pieridae. Two nominal species of Baltia occur in arid-semiarid oreal environments in Central Asia, the Himalaya, and Pamir to over 5500 m. At least 13 species currently placed in four genera (Phulia, Infraphulia, Pierphulia, Piercolias) occur in similar environments at similar altitudes in the high Andes. These genera all share numerous morphospecializations whose functional relation to the oreal environment is not understood. Their evolutionary and biogeographic relationships have been debated for over a century. We performed a phylogenetic analysis based on sequencing portions of the mitochondrial cytochrome oxidase subunit I and subunit II regions (COI and COII), incorporating all the genera but Piercolias and a variety of suspected relatives. The results from analyses of COI and COII were compared to relationships inferred from morphological and ecological characters. We conclude that Baltia is not the sister-group of the Andean genera, which are clearly nested within a Neotropical clade. The “Camelid scenario” deriving all the genera from a common ancestor no longer appears viable.
Breeding penguins are the major source of nutrients for terrestrial ecosystems in the Maritime Antarctic. The impact of penguin rookeries on vegetation patterns and diversity was examined by descriptive and quantitative methods along a transect from penguin rookeries to areas distant from penguin impact. Several vegetation zones related to varying degrees of rookery impact have been recognized: (1) areas under the immediate influence of fresh penguin guano and trampling support little or no vegetation; (2) the adjacent zone is covered with nitrophilous green algae, locally also cyanobacteria; (3) the next zone is dominated by the Antarctic hair-grass; (4) further on, a zone dominated by mosses is formed; (5) finally, the zone least affected by penguin impact is dominated by lichens. With increasing distance from penguin rookeries, vegetation zones become less distinct and more complex; along consecutive zones vegetation richness and diversity increase and dominance decreases. Change in species composition is gradual with a broad overlap of species distributions, and the distinct zones are the result of differences in life-forms and growth-forms of the dominant species. This ecological gradient, comprising a few species and being relatively simple, offers unique opportunities to study hypotheses concerning ecological processes and patterns.
Surface conditions in the non-mountainous areas of the central Tibetan Plateau were measured in a field survey in February 2004, and water balance parameters such as precipitation, sublimation, and water equivalent of snow cover were examined through the 2003/2004 winter by in situ automated measurements. Snow cover was shallow and coexisted with snow-free areas, producing large surface temperature heterogeneity under strong insolation. Clear diurnal variation was found in the meteorological observation. The precipitation and total sublimation from November 2003 to January 2004 were estimated as 15 mm and 17 mm, respectively, and the remaining equivalent snow water quantity in the beginning of February 2004 was 8 mm. Imbalance of the water budget was mainly due to the uncertainty of snow cover proportion within the mesoscale area. Importance of a redistribution process of the snow was proposed to explain the consistency of surface heating and remaining snow cover.
Species distributions may be limited by substrate boundaries due to constraints at either the germination or seedling establishment life history stages. In a community of alpine tundra plants from the Sierra Nevada, some species are widespread, occurring across all four substrates studied: diorite, granite, hornfels, and marble. Other species are restricted to fewer soil types. We collected seeds from 12 species and performed a reciprocal transplant experiment in growth chambers using native soils. Eleven species germinated and established equally well across all soil types, indicating substrate chemistry did not alone determine species field distributions. However, two patterns emerged that may contribute to our understanding of species composition and dominance across substrates. First, species more dominant on the drier substrates reached at least half their total germination within two weeks of planting. Species more dominant on the wetter substrates required a longer period in wet soil to germinate. Second, there is a strong correlation between species relative abundance and percent germination, indicating that high percent germination may contribute to some species' dominance. To determine the influence of soil type on plant size, a subset of species were grown for more time. All species were larger on hornfels and marble than on granite and diorite, indicating that species have the highest growth on the most nutrient-rich soils, rather than on their native soils. Taken together, these data suggest that water may be the limiting factor for species germination, and the differential nutrient availability across soil types has a strong influence on early seedling growth.
The vegetation composition of four contiguous permanent plots was analyzed during 37 of 42 years between 1959 and 2001 to evaluate successional processes following the cessation of human trampling in alpine tundra. The plots were established adjacent to the Rock Cut parking lot at ~3658 m elevation along Trail Ridge Road in Rocky Mountain National Park, Colorado. Due to limitations in the original study design, the lack of true replication required that the plots be treated individually when subject to indirect ordination analysis to follow trends in overall plant composition and cover. The three most abundant species in the study plots were Artemisia scopulorum, Acomastylis rossii, and Kobresia myosuroides. At the beginning of the study in 1959, total cover ranged from 20 to 55% in the four plots. By 1961, three of the four plots achieved total canopy cover values of at least 100%. Vascular plant species richness (number of taxa per plot) averaged 20 in 1959, but by 1967 had nearly doubled to 37. During the first several years, rates of seedling emergence were high among most taxa with the notable exceptions of K. myosuroides and A. rossii. However, likely due to desiccation and needle ice, seedling mortality was high. K. myosuroides spread exclusively from remnant tufts, as did three species of cushion plants which survived the trampling. The overall decline in plant cover during the last two decades of this study, particularly for K. myosuroides, indicates that long-term unassisted regeneration of severely degraded alpine tundra sites will take more than a century. While there have been periods of plant colonization and spread, climate factors such as a series of heavy snow years, and unchecked soil erosion from trails, can limit plant establishment and stop the recovery process, or push the recovery back by several decades. The negative influence of soil erosion, and quite possibly additional trampling, over a significant portion of the study plot points to the critical importance of using extreme care when establishing long-term monitoring plots, particularly in high-use areas.