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Vol. 20, No. 3, 1988

The Influence of Ice Layers on the Travel Time of Meltwater Flow through a Snowpack  
David Jon Furbish
The flow of water in the vicinity of ice layers within an isothermal snowpack is examined using Darcian laws. Treated as semipermeable boundaries, ice layers may reduce the residence time of water within the pack by delivering saturated flow to the downslope ice-layer edges, whence flow is transmitted downward faster than the speed of an unsaturated wave of meltwater that would exist in the absence of ice layers. This could produce a more rapid runoff than might be expected from a homogeneous snowpack. The effectiveness of this flow-timing mechanism depends on changing rates of meltwater influx. If a stratified snowpack is treated as an anisotropic medium, the anisotropy must be modeled as time-dependent over individual diurnal cycles.
Full Text: | JSTOR | pp. 265-272
Morphometric Analysis of Pleistocene Glacial Deposits in the Kigluaik Mountains, Northwestern Alaska, U.S.A.  
Darrell S. Kaufman, Parker E. Calkin
Since the earliest studies of alpine glacial geology, descriptive evaluation of moraine morphology has remained an important relative-age criterion. However, the development of moraine morphology as a quantitative relative-dating tool has lagged considerably behind other techniques. Morphometric and other relative-age data were collected on early- to late-Pleistocene end moraines located in the Kigluaik Mountains of Seward Peninsula, Alaska. Slope-frequency, Fourier, and linear regression analyses of topographic profiles measured along and normal to moraine axial-crests were used to generate nine indices of surface irregularity. Discriminant analysis indicates that average slope, calculated from the slope-frequency distribution, is the best single distinguishing criterion, and that even a few simple field measurements of morphometry provide a viable basis for subdividing and correlating moraines. Morphometric and other relative-age data constrain the timing of glaciations in the Kigluaik Mountains, and suggest that successively older advances are separated by intervals of increasing duration. In addition, morphometric study of moraines can offer insights into processes controlling landscape degradation.
Full Text: | JSTOR | pp. 273-284
Techniques in Lichenometry: Identifying the Yellow Rhizocarpons  
James B. Benedict
Species of Rhizocarpon subgenus Rhizocarpon are distinguished from each other based on differences in external thallus morphology, internal anatomy of fruiting bodies, and chemistry of intracellular and extracellular lichen substances. Differences in geographical distribution and ecology aid in identifying certain species. Using the procedures described in this paper, and keys such as that of J. Poelt (1988, this volume), it should be possible for a lichenometrist with no previous taxonomic experience to identify rhizocarpons to the section level with little difficulty, and to the species and subspecies levels under many circumstances. In regions where the subgenus has been inadequately studied (e.g., the Rocky Mountains of western North America), specimens having intermediate characteristics may prove difficult to identify using existing keys.
Full Text: | JSTOR | pp. 285-291
Rhizocarpon Ram. em. Th. Fr. Subgen. Rhizocarpon in Europe  
J. Poelt, Z. C̆ernohorský, Judith Schaefer
Failure to accurately identify the lichen species used in lichenometry is a serious potential source of dating error. This paper provides a dichotomous key to the thirty-seven species of Rhizocarpon subgenus Rhizocarpon currently recognized in Europe; eighteen of these species have also been reported from North America. The key is presented in the hope that it will encourage greater taxonomic precision among lichenometrists (Translator).
Full Text: | JSTOR | pp. 292-298
A Peat-Producing Empetrum Heath in Coastal North Norway  
H. Edvardsen, A. Elvebakk, D. O. Øvstedal,L. Prøsch-Danielsen,J. T. Schwenke, T. Sveistrup
A conspicuous type of heath dominated by Empetrum hermaphroditum has been investigated in the western coastal region of Troms, northern Norway (70°N, 20°E). The soil of the Empetrum heath lacks mineral soil horizons and podsol development. Instead, a peat profile up to 1 m has accumulated, which resembles the pedology of ombrotrophic bogs rather than the other Empetrum-dominated communities in northern Norway. The high peat accumulation rate in this heath is probably a response to the cold and wet climate, the retarded metabolism of the carbon supply in the soil, and, possibly, allelopatic properties of Empetrum. The heath type is classified as Pleurozio-Empetretum hermaphroditi Øvst. nov. ass. within the alliance Phyllodoco-Vaccinion myrtilli Nordh. 43. Several species with a coastal distribution pattern are associated with this community. Palynological investigation indicates that one stand of this association has been stable, lacking Betula, for about 1400 yr. For this reason we believe that exposure to strong winds and sea spray, rather than grazing, is the primary factor preventing the establishment of Betula. This hypothesis is supported by the relatively high content of magnesium in the soil. The Empetrum heath is regarded as the climax community of convex siliceous habitats near the sea in the investigation area.
Full Text: | JSTOR | pp. 299-309
Pollen Spectra from Lake Surface Sediments in the Swiss Alps  
Rolf W. Mathewes
Alpine pollen spectra in the Swiss Alps were found to be highly similar to one another, but different from forested sample sites at lower elevations. Principal components analysis confirms this subjectively assessed pattern. Nonarboreal pollen (NAP) values (including Alnus viridis) are greater than 70% in treeless sites, characterized by high grasses, sedges, and composites, as well as many rare alpine indicators. Pollen concentrations are consistently highest in alpine sediments, suggesting low rates of sediment accumulation. The smallest water-body, termed a "microbasin," ( ≤ 100 m2) best represented local tundra vegetation. Regional differences in alpine lake samples are apparent, with higher pollen frequencies of local grasses and composites in the Oberalppass sites, and higher regional pollen types such as Castanea in the San Bernardino Pass.
Full Text: | JSTOR | pp. 310-324
Community Level Phenology of Grassland above Treeline in Central Himalaya, India  
Jeet Ram, S. P. Singh, J. S. Singh
The developmental stages of 142 alpine plant species were observed during 1984/85 in the grassland site of Rudranath bughiyal (30°28′N, 79°20′E; 3250 to 4200 m) in the Central Himalayan region. The growth initiation synchronized with the beginning of the spring temperature rise and the resultant snowmelt, and peaked after 30 to 40 d. In this alpine grassland, the peaks of the various phenophases succeeded one after another over about 4 mo, from early June to early October. This study supports the notion that in the unfavorable environment of the high elevations the primary plant strategy is to complete the growth cycle rapidly in order to assure the survival of the species.
Full Text: | JSTOR | pp. 325-332
Microenvironment and the Distribution of Two Species of Draba (Brassicaceae) in a Venezuelan Paramo  
William A. Pfitsch
The microenvironments of the habitats of two species of Draba in Venezuelan paramo were characterized. The rosette species D. chionophila occurs in extensive areas of frost-heaved soil with very low plant cover and species richness; D. arbuscula and other shrub species occur preferentially on rock outcrops, areas with higher plant cover and species richness. The thermal mass of the rock outcrops results in air temperatures near the soil surface and soil temperatures that are 2 to 4°C higher than in the frost-heaved soil habitat throughout the day and night. Minimum soil temperatures in the habitat of D. chionophila frequently are low enough after dawn to inhibit the uptake of water (0 to 3°C); the rock soils are not. The thin soils on rock outcrops became quite dry during extended periods without precipitation, while the frost-heaved soils of D. chionophila habitat did not. Consequently, the microenvironmental limitations imposed in the habitat of D. chionophila are primarily due to the pronounced diurnal temperature fluctuations and low soil temperatures. The warmer soils of the rock outcrop habitat of D. arbuscula reduce the potential for a dirunal temperature limitation, but are subject to seasonal drought. The occurrence of rock outcrops contributes to the diversity of microenvironments on the paramo landscape, through both diurnal and seasonal effects, and this heterogeneity is reflected in the distribution of plant species on the landscape.
Full Text: | JSTOR | pp. 333-341
The Effects of Topography and Nutrient Status on the Biomass, Vegetative Characteristics, and Gas Exchange of Two Deciduous Shrubs on an Arctic Tundra Slope  
U. Matthes-Sears, W. C. Matthes-Sears, S. J. Hastings, W. C. Oechel
The effect of topography and water drainage patterns on the nutrient status, aboveground biomass, vegetative characteristics, and leaf gas exchange of Betula nana and Salix pulchra were studied on an Alaska tussock tundra slope. To help evaluate whether any differences found were due to variation in nutrient availability or other factors that varied along the gradient, fertilizer-treated plots were used as a comparison. The highest nitrogen and phosphorus concentrations occurred in plants from water-drainage areas, indicating improved nutrient availability. Downslope movement and accumulation of these nutrients, on the other hand, appeared limited and localized. While aboveground biomass of the two shrubs was also consistently higher in drainage areas, it was not closely correlated with tissue nutrient levels, indicating that other factors besides nutrients are involved in controlling the biomass of these species along the gradient. The variation in vegetative characteristics suggests that S. pulchra may be more strongly limited by nutrient availability on the slope than B. nana. Net photosynthesis and leaf conductance were unaffected by nutrients both on the slope and in fertilized plots, but were depressed at the drier end of the moisture gradient on the slope during a midseason period of drought.
Full Text: | JSTOR | pp. 342-351
Topographic Position Effects on Growth Depression of California Sierra Nevada Pines during the 1982-83 El Niño  
J. K. Armstrong, K. Williams, L. F. Huenneke, H. A. Mooney
The El Niño-Southern Oscillation event of 1982-83 was associated with severe winter weather in California, including increased snow accumulations in the Sierra Nevada relative to 1984. We examined the ratio of 1983 needle length to 1984 needle length in two speces of pines growing near timberline in the Sierra Nevada for evidence of growth depression during the El Niño year. Trees of both Pinus albicaulis (whitebark pine) and P. contorta var. murrayana (lodgepole pine) were sampled from four topographic positions at the study site: a meadow on the valley floor, north- and south-facing slopes, and at high elevation near treeline. In all cases, average needle length in 1983 was less than that in 1984. The degree of growth depression varied among topographic positions and between species. Whitebark pines displayed the greatest variation in sensitivity to climatic change. Differences in sensitivity between species were associated with habitat restrictions; e.g., whitebark pines at high elevations were least affected by the El Niño year, while lodgepole pines were most affected when growing at high elevations. It is hypothesized that observed variation in growth depression among topographic positions is due to both differences in the length of the 1983 growth season associated with timing of snowmelt and decreased temperatures during the 1983 growing season.
Full Text: | JSTOR | pp. 352-357
Dependence of Great Basin Bristlecone Pine on Clark's Nutcracker for Regeneration at High Elevations  
Ronald M. Lanner
Great Basin bristlecone pine, Pinus longaeva D. K. Bailey, has small, winged seeds typical of wind-dispersed conifers. It is characteristically found on rigorous sites at high elevations. On such sites it regenerates far more frequently from seed caches of Clark's nutcracker, Nucifraga columbiana Wilson, than from wind-dispersed seeds. On mild low-elevation sites where it rarely occurs, however, bristlecone pine establishes predominantly from wind-dispersed seed. Thus, most populations of bristlecone pine are maintained by nutcrackers on sites to which the species is only partially adapted, but which it can tolerate.
Full Text: | JSTOR | pp. 358-362
Note on Skeletal Injuries in an Adult Arctic Wolf  
Maria Pasitschniak-Arts, Mark E. Taylor, L. David Mech
The desiccated corpse of an arctic wolf (Canis lupus) was recovered from central Ellesmere Island in summer 1986 near the skeleton of a musk-ox (Ovibus moschatus). External examination showed no evidence of the cause of death. Two old injuries, however, became apparent after the skeleton was cleaned. The right zygomatic arch and mandible had been fractured, as well as the right upper carnassial. Four left ribs (T9-12) had also been broken. The pattern and spacing of the skull and rib fractures suggest the impact of a hoof of a large ungulate such as a musk-ox was the cause. The wolf was old, and the bony fracture calluses were smoothed over, indicating old injuries.
Full Text: | JSTOR | pp. 363-365
Discussion of "Glaciers and the Morphology and Structure of the Milne Ice Shelf, Ellesmere Island, N.W.T., Canada" by Martin O. Jeffries   correspondence
Donald S. Lemmen, David J. A. Evans, John England, Martin O. Jeffries
Full Text: | JSTOR | pp. 366-371
Colorado Flora: Western Slope. By William A. Weber   reviewed work
John R. Spence
Full Text: | JSTOR | pp. 373-374
Geomorphic Systems of North America. By W. L. Graf   reviewed work
J. Brian Bird
Full Text: | JSTOR | pp. 374-375
Fjords: Processes and Products. By James P. M. Syvitski, David C. Burrell, Jens M. Skei   reviewed work
John T. Andrews
Full Text: | JSTOR | pp. 375-
Modelling Snowmelt-Induced Processes. By E. M. Morris   reviewed work
G. J. Young
Full Text: | JSTOR | pp. 375-376
Very Slow Flows of Solids: Basics of Modeling in Geodynamics and Geophysics. By Louis A. Lliboutry   reviewed work
W. Tad Pfeffer
Full Text: | JSTOR | pp. 376-377
The Greenland Caribou: Zoogeography, Taxonomy, and Population Dynamics. By Morten Meldgaard   reviewed work
John P. Kelsall
Full Text: | JSTOR | pp. 377-378
On the Track of Ice Age Mammals. By Anthony J. Sutcliffe   reviewed work
John T. Hollin
Full Text: | JSTOR | pp. 378-
Rock Glaciers. By John R. Giardino, John F. Shroder, Jr., John D. Vitek   reviewed work
Ole Humlum
Full Text: | JSTOR | pp. 378-379