(1997). Voices in Stone: A Personal Journey into the Arctic past, The Game Drives of Rocky Mountain National Park, Freshwaters of Alaska: Ecological Syntheses. Arctic and Alpine Research: Vol. 29, No. 2, pp. 255-257.
Seasonal patterns of nitrogen (N) uptake were measured to assess the ability of the alpine herb Ranunculus adoneus to utilize the flush of N during snowmelt in an alpine tundra ecosystem. Development of mycorrhizal and dark septate fungi were also monitored within the roots of this snowbed plant in order to determine the role of these fungi in N acquisition. In addition, soil temperature, moisture, and inorganic N levels were measured to determine possible influences of edaphic factors on plant N uptake. In contrast to P uptake, which occurs late in the growing season and corresponds with arbuscular mycorrhizal (AM) development, N uptake occurred very early in the growing season before new roots and active AM fungal structures were formed. Soils at this time were cold and wet and NH4+ was the predominant form of inorganic nitrogen. Our data indicate that R. adoneus is able to take advantage of the early season flush of N by utilizing the previous year's root system which is heavily infected with a dark septate fungus. Given the high density of R. adoneus plants (135 plants per m(2)) in this snowbed system, they are a significant sink (ca. 0.5 g N per m(2)) for nitrogen released from within or beneath the alpine snowpack.
Part I The quarternary - the last glaciation and deglaciation: northern hemisphere (Laurentide) deglaciation - processes and responses of ice sheet/ocean interactions the last Scandinavian ice sheet and its down-wasting environment and climate of Sartan maximum and the late glacial in Siberia termination of the pleistocene and holocene changes in South America and other glaciated parts of the southern hemisphere. Part II The quarternary - macro-processes: sediment deformation beneath the Laurentide ice sheet megafloods and glaciation. Part III The permo-carboniferous - a paleographic reconstruction: Permian world topography and climate. Part IV The permo-carboniferous - the distribution and effect of the major glaciers of Gondwana glacial-postglacial transition in the late Paleozoic basins of southern South America a review of the permo-carboniferous glaciation in Africa transition from freezing to subtropical climates in the permo-carboniferous of Afro-Arabia and India Permian postglacial environments of the Australian Plate upper paleozoic glacial and postglacial deposits, central Transantarctic mountains, Antarctica some problems of the Permian (Asselian) glaciation and the subsequent climate in the Permian. Part V An older, precambrian glaciation - a comparative analysis: tectonic and glacio-eustatic controls on postglacial stratigraphy - proterozoic examples. Part IV quaternary and permo-carboniferous terrestrial weathering and organic deposits interpreting glacial climate from detrital minerals in sediments paleosols of the northern part of North America - their features and significance as indicators of past climates cold temperate peats and coals - their sedimentology and composition recent cold climate peats of central Canada and permo-carboniferous coals of Gondwana.
The lower Naknek River exposes thick (similar to 20 m) successions of glaciogenic sediment of pre-late Wisconsin age on the northern Alaska Peninsula. The stratigraphy of the deposits, and the physical and mineralogical properties of diamicton beds, together with recently reported geochronological evidence, prompt a reevaluation of the pre-late Wisconsin glacial history of the region. Three sites expose diamicton beds that can be separated from overlying units on the basis of geochronologic or sedimentologic criteria. These older diamicton beds predate formation of a last-interglacial marine-lag gravel at South Naknek bench. Data on younger diamicton units lack stratigraphic or geographic trends that indicate distinct tills related to separate ice advances. We therefore suggest that the regionally extensive surficial drift (from Pauls Creek, at the outer margin of the Mak Hill moraine, to the mouth of Naknek River) was deposited during a single glaciation. Lumping the drift into one unit is consistent with geochronological evidence indicating that ice from the Alaska Peninsula reached its maximum limit relatively recently, since the last interglaciation. We speculate that Johnston Hill, a prominent landform within the Limits of this drift sheet, was formed by ice thrusting of proglacial sediment during the late Pleistocene. Previously it was interpreted as a conventional moraine and ascribed to a separate, climatically significant and regionally correlative glaciation of pre-late Pleistocene age.
The Riviere George Caribou Herd (RGCH), in northern Quebec, erupted during a few decades to culminate at approximately 800,000 animals by 1990. The RGCH appeared regulated by competition for summer forage. Repeated browsing and trampling reduced summer range productivity to 50% compared to ungrazed areas, Lichens and dwarf birch having been mostly responsible for this reduction. A reconnaissance flight in 1991 and intensive field work the following two summers suggested that caribou use of dwarf birch leaves was light following the period of peak numbers. We hypothesized that birch stands would show signs of rapid and vigorous recovery in 1993-1994. We surveyed five heavily browsed birch stands, and two inaccessible, lightly browsed ones. Although utilization of birch leaves by caribou ranged between 0 and 6% during the 1994 growing season, heavily browsed stands exhibited no signs of rapid and strong recovery. Young plants did not abound in heavily browsed stands compared to lightly browsed ones, neither was wood accumulation faster in the former than in the latter. Stem density and height were similar in heavily browsed and lightly browsed stands. However, the leaf/wood ratio and the percent dry weight of leaves and wood were higher in lightly browsed than in heavily browsed stands, which resulted in approximately twice as high leaf biomass in lightly browsed than in heavily browsed stands. We hypothesized that previous intense caribou browsing caused a persistent suppression of dwarf birches, and that stems could not accumulate sufficient reserves during a growing season to deploy more leaves in the next spring in order to return the leaf/wood ratio to a normal value. We discuss the consequences of such a reaction of dwarf birch to herbivory on the demography of the RGCH.
A 5-yr ongoing demographic study of the extremely localized (ca. 0.5 ha), rare, high-alpine endemic Myosotis oreophila and the widespread M. pulvinaris, where their ranges overlap, has revealed widely fluctuating populations in both species. Three representative permanent study plots totaling 290 m(2) (6.4% of the total population area) were located near the center and on the margins of the M. oreophila population. High turnover rates have been confirmed by the loss of 1476 plants of M. oreophila and the recruitment of 1600 in the sample population over 5 yr. Three years of good recruitment and one of high mortality indicate that the total population of M. oreophila has varied by ca. 40%, from a maximum of ca. 21,800 to a minimum of ca. 13,000 plants over the 5-yr period. Thus it can be assumed that the whole population has essentially turned over in the 5-yr study period. The possible role of differential distribution of snowlie and/or snowmelt in this exposed high-alpine environment is being examined with experimental snow fences within and just beyond the limits of the M. oreophila population but monitoring of plant responses over the first 3 yr is inconclusive.The partially overlapping, but inversely related, distributions and density patterns of the leafy M. oreophila and cushion-forming M. pulvinaris have revealed similar demographic patterns and give no indication that either species is changing its status (i.e. advancing or reheating) along their respective margins. We tentatively endorse the rare status currently assigned to M. oreophila since the population, although extremely local, appears capable of maintaining itself despite a surprisingly rapid turnover of individual plants and the total population in a habitat where longevity of most of the high-alpine flora previously has been assumed.
Patterned wetlands occur extensively throughout the Canadian subarctic and boreal regions. These areas are important because of their hydrological and chemical interaction with other ecosystems, aquatic and terrestrial. However, there is a lack of knowledge on the hydrology of many wetland types in the boreal and subarctic regions, particularly patterned fens. This paper examines the relationship between the flux and storage of water both within a patterned wetland and between it and the adjacent ecosystems. It is hypothesized that patterned wetlands alternate between two hydrological phases. The first occurs when the water supply exceeds the depression storage capacity of the patterned wetland pools, and the wetland drains as a single source area, while receiving inputs from adjacent nonwetland portions of the basin. As a result, basin discharge during such periods is relatively high. The second phase occurs when the loss of water through seepage and evaporation leads to disconnection of the wetland pools into separate microcatchments within the pool-ridge complex. Under this condition, basin discharge is relatively low, maintained only by a limited source area immediately upstream of the outlet. Through an explanation of the hydrological processes and linkages among subsystems, an understanding of the processes governing runoff from a basin with a patterned wetland at its outlet is obtained. It is demonstrated that the discharge response of patterned wetlands is distinctive from that of other wetland types because the large storage capacity of the wetland pools delays runoff contributions from large portions of the wetland and surrounding basin.
Soils in the Antarctic Dry Valleys have been significantly influenced by soil formation factors such as parent material, climate, and topography. Factors common in more temperate zones, including chemical weathering and leaching of minerals, occur to a much lesser extent in these cold arid soils, leading to an accumulation of salts and bases, which will likely affect the distribution of soil biota. Since the intensity of these factors may vary with topography, this study examined the soil properties and soil invertebrate communities along an elevational gradient in Taylor Valley, Antarctica. We sampled from two spatial scales (1 X 1 m and 10 X 10 m) at three sites (83, 121, and 188 m a.s.l) on the south side of Lake Hoare in Taylor Valley, and examined soil moisture, nitrogen, carbon, pH, and electrical conductivity (which provides an estimation of soil salinity), as well as the distribution and community structure of soil invertebrates. We found significant differences in soil properties with elevation, along with associated differences in soil communities. Biodiversity was greatest at the lowest elevation, closest to the shore of Lake Hoare, where soil moisture, carbon, and nitrogen were highest, and salinity was lowest. Scottnema lindsayae dominated the nematode communities found at all sites. Electrical conductivity was higher and carbon and nitrogen contents were lower at the upper elevations. The distribution of both Eudorylaimus and Plectus appeared to be influenced by soil moisture; electrical conductivity affected the mortality of all three nematode genera found. Soil properties did differ with sampling scale, suggesting that changes in microhabitats not detected at sampling intervals of a meter or more may be more reliably detected by sampling at a smaller scale.
The rates of many processes that control rock breakdown into transportable particles are dependent upon rock temperature. In particular, frost-cracking depends largely upon the time spent within a range of subzero temperatures I call the frost cracking window. I present simple analytic solutions, detailed time series of thermal data from a field site, and a numerical model of subsurface temperatures that constrain the expected depth dependence of frost cracking. Analytic solutions using sinusoidal surface temperature histories result in predicted vertical profiles of frost-cracking intensity that depend upon the location of the frost-cracking window within the range of surface temperatures. In some cases, the expected frost cracking intensity decreases monotonically with depth, while in others it displays a distinct maximum at depth. I use hourly temperatures measured over the I-yr interval April 1995 through March 1996, at 8 depths up to 42 cm into a granitic bedrock surface in the Laramie Range, Wyoming, to constrain an in situ thermal diffusivity of 1.7 mm(2) s(-1). These temperature histories suggest that frost cracking at this site should decrease monotonically with depth into the rock. I also use this time series of temperatures to calibrate a numerical thermal model in which the top boundary condition is set by a surface radiation balance. The data require both a low albedo of the rock surface (0.1), and a high atmospheric transmissivity (0.9). I then explore the expected near-surface temperatures at other sites by running the model with different annual mean temperatures, latitudes, and slopes. The resulting simulations suggest that at lower mean annual temperatures, as are found in higher latitude and altitude sites, the frost cracking maximum should both amplify and deepen into the subsurface.
The distribution pattern of individual plant species, as well as of plant communities, at the transition between the alpine and the nival environment (= alpine-nival ecotone) is likely to he drastically affected by climate change. Currently, the best way to explore the vegetation structure and to detect possible changes is the application of spatial modeling to predict vegetation patterns over larger areas combined with dynamic modeling techniques. Schrankogel in Tyrol, Austria, was selected as a typical high alpine mountain to establish and test such models. As a first step, the predictive model for the spatial pattern of species and plant communities is presented here. Direct and indirect gradient analyses (CA, CCA) were combined with GIS-techniques based on a fine-grained Digital Elevation Model (DEM; pixel size: 1 m(2)). Approximately 1000 field samples (vascular plant species and cover within 1 m(2) squares) distributed over the alpine-nival ecotone of the mountain were taken as the vegetation data input. Topographic descriptors were derived from the DEM as habitat characters of those samples. Using the correlations between vegetation samples and habitat characters, single plant species as well as community distribution could be predicted for the pixels of the whole model area (the studied ecotone area contained a total of 650,000 pixels) for which habitat characters were known from the DEM. Distinct distribution patterns at different spatial resolutions appeared for individual species, species groups, and communities in relation to the relief. Descriptors of relief curvature and roughness explained more of the variability than "classical" terrain attributes, such as elevation or exposure. Nevertheless, the altitudinal gradient was clearly reflected by the CCA ordination. As species richness of vascular plants was recorded in each sample plot, biodiversity distribution patterns could be modeled. These patterns showed the general trend of decline of biodiversity with altitude, but with a maximum of species richness at the ecotone itself. Since the relief modifies the high mountain climate remarkably, this differentiated relief dependency of vegetation supports the view that this type of environments will be affected significantly by climate change.
Climate-induced environmental changes are likely to have pronounced impacts on CO2 flux patterns in arctic ecosystems. We initiated a long-term experiment in 1994 in moist tussock and dry heath tundra in arctic Alaska in which we increased summer air temperature (ca. 2°C) and increased winter snow accumulation (shortening the growing season approximately 4 wk). During the 1996 snow-free season, we measured ecosystem CO2 flux weekly in order to quantify net carbon gain or loss from these systems. Over the duration of the snow-free season, both dry heath and moist tussock tundra exhibited a net loss of carbon to the atmosphere, ranging from 12 to 81 g C m–2 depending upon experimental treatment. Elevated summer temperatures accelerated net CO2 loss rates over ambient temperatures in both deep and ambient snow treatments, and increased the total amount of carbon emitted during the snow-free season by 26 to 38% in ambient snow plots and by 112 to 326% in deep snow plots. Increased snow accumulation had less impact on CO2 flux than did warming, and snow effects on total carbon loss were not consistent between the two temperature regimes. Ecosystem respiration exceeded assimilation on most sampling dates throughout the season. These data, coupled with winter carbon losses recently demonstrated in the same ecosystems, indicate that the moist and dry arctic ecosystems we examined are currently net sources of atmospheric carbon on an annual basis, and that anticipated global warming may increase carbon losses from these systems.
Eighteen percussion piston cores were recovered from Wonder Lake and three nearby kettle ponds in Denali National Park and Preserve, Alaska. Three prominent tephra deposits, two felsic and one mafic, have been recognized in the upper 1 to 3 m of the cores. Because of the relatively low magnetic susceptibility (MS) of the lacustrine sediment, tephras appear as prominent MS peaks allowing confident correlation of core stratigraphies. These MS-based correlations are supported by microprobe geochemical analyses of 11 tephra samples from six of the cores. Five accelerator mass spectrometer (AMS) radiocarbon ages, determined from terrestrial plant remains, closely constrain the timing of these ashfall events. Microprobe results indicate that the youngest tephra is correlative with the Jarvis Ash, which has an accepted age of 3660 ? 125 '4C yr BP The next older felsic tephra is correlative with the middle Holocene Oshetna tephra. New 14C ages reported in this study suggest that this regionally extensive tephra was deposited about 6000 '4C yr BP Neither of these tephras has previously been identified this far west, indicating that both are significantly more extensive than previously thought. A fine-grained basaltic ashfall deposit, identified in several of the Wonder Lake cores and dated to ca. 10,000 14C yr BP, is a newly discovered tephra that provides an important stratigraphic marker horizon at the Pleistocene-Holocene boundary in central Alaska.
Four closely related species of Pedicularis (Scrophularirtceae), an abundant plant genus in the Arctic, with different breeding systems were analyzed for amount and distribution of genetic variation at three sites at Qeqertarsuaq, West Greenland. Isozyme variation was found in two enzyme systems (phosphogluconate dehydrogenase and phosphoglucomutase) in only one of the of the species (P. lanata). Average genetic diversity (H-e) was 0.028, including monomorphic loci. Compared to the other three species investigated, P. lanata possesses the breeding system with the highest capacity for outcrossing in the study area and also shows the greatest morphological variation within is geographic distribution. There seems thus to be accordance between the morphological variation, breeding system and the population genetic results.
The influence of the dominant tussock grass Festuca varia Haenke on the species growing in its vicinity was investigated. Festuca varia forms round tussocks on gentle slopes and rows on steep slopes. The two forms differed in their effect on community structure and species composition. When tussocks were arranged in rows, different environmental conditions above and below the row were observed. Dense litter and shoot cover below the row change considerably the environment for the plants, so that species number above the row was higher than below the row. The distance between neighboring rows and row width determined also the species number in spaces between the rows. Round tussocks influenced other species mostly through litter production; distance to the neighboring round tussock was another determinant of species number. The number of species recorded within tussocks was lower than between them. However, 25% of the studied tussocks were inhabited and not less than 14 species was found within them. Festuca varia mostly limited species number and cover on a small scale, but did not influence the overall species composition in the grasslands. The pool of diaspores of accompanying species from the patches within the community may support the populations in the vicinity of F. varia tussocks.
Three species of small mammals, Mastncomys fuscus and Rattus fuscipes (both rodents), and Antechinus swainsonii (a small dasyrurid marsupial) live in the subalpine heathlands of southeastern Australia. This study records the climate and microclimate of these heathlands. Temperature was recorded at three sites at Smiggin Holes in Kosciusko National Park-just above the shrub layer, in a runway, and 30 cm below ground. Long-term meteorological data for ambient temperature, rainfall, and thickness and duration of snowpack are also presented. In summer, these small mammals experience temperatures of +5 to +10 degrees C while active and foraging at night, and temperatures of about +10 degrees C in burrows during the day. In winter, the snowpack provides good insulation resulting in a constant temperature of 0 to -1 degrees C in both runways and burrows regardless of the ambient air temperature above the snow. The climate and microclimate in the Australian Alps has many influences on the biology of small mammals; these include a short reproductive season, delay in the time to maturity and initiation of reproduction, reduced activity or torpor in winter, and relatively stable interannual population numbers.
Living and dead foraminifera have been investigated along three transects away from tidewater glaciers of northern Novaya Zemlya. There are three glacier-proximal dominant foraminiferal taxa: Allog...
