Showing papers on "Tundra published in 1977"

The Development and Movement of Tree Islands Near the Upper Limit of Yree Growth in the Southern Rocky Mountains

Abstract: Dwarfed and deformed plants of tree species occur as "tree islands" in a matrix of tundra vegetation near the upper limit of tree growth in the Southern Rocky Mountains. Many of these islands are asymmetrical, having a surface layer of dead branches to windward and some live branches to leeward. I made repeated observations of these islands in all seasons from 1956 to 1967 along a 1.75-km belt -20 m wide on Niwot Ridge in the Front Range west of Denver, Colorado. The location of islands was mapped on a transparent overlay on an aerial photograph, annual growth of stem tips was measured, and an abundance of notes and photographs was taken. Some tree islands of Engelmann spruce (Piteea engelmnannii) and subalpine fir (Abies lasiocarpa) are conspicuous because they grow in microsites in which no tree seedlings have been found, and which general observations suggest would be outside their environmental amplitude. These islands often have live branches connected to windward with dead branches, some of which have roots. These observations led to the hypothesis that some tree islands move along the ground climbing out of more moderate microsites in which a seed germinated and moving into microsites for which they are not well adapted. In this movement process, wind-exposed organs are killed, while leeward stems grow to leeward often taking root and forming an upright stem system in the process of "stem tip layering." Islands with interconnected live and dead stems to windward, illustrating movements of 5 m, are common; isolated dead stumps and wood fragments in a line extending to windward indicate that some islands may have moved at least 15 m. The origin of tree islands, support for the movement hypothesis, and other features of tree island ecology are discussed.

Root growth, respiration, and carbon dioxide evolution in an arctic tundra soil*

Abstract: Most of the living plant material of moist tundra in arctic Alaska is in the 0-to-10-cm layer of the cold soil, and above permafrost. This research measured root growth at low temperatures in plants of three dominant species of this tundra: a grass (Dupontia fischeri R.Br.) and two sedges (Carex aquatilis Wahlenb. and Eriophorum angustifolium Honck.). Respiration rates of roots and rhizomes were measured both in the field and under controlled conditions using an infrared gas analysis system. Two variations of measur

Modern pollen rain and vegetation of the St. Elias Mountains, Yukon Territory

Abstract: The vegetation of the area east of the Klutlan Glacier in the St. Elias Mountains is described with the methods of European phytosociology. Four major vegetation types are recognized: Picea glauca forests, Populus balsamifera forests, Betula glandulosa shrub–tundra, and Dryas integrifolia tundra.The modern pollen assemblages deposited in these vegetation types are determined by pollen analysis of surface moss polsters, lake muds, and moss samples from sedge swamps. Numerical analyses of the surface spectra indicate that spectra from the Dryas tundra and from the Populus forests are distinctive in their pollen composition. The variation in the percentage pollen content of samples from the Picea forests and the shrub–tundra is so great, even when spectra from a single sample type are considered, that no reliable distinctions can be made in modern pollen spectra from these two community types.

Response of microbial populations in Arctic tundra soils to crude oil

Abstract: Experimental crude oil spillages of 5 and 12 l/m2 were established on the four major topographically distinguished soils of Arctic coastal polygonized tundra The response of microbial populations to contaminating oil was found to depend on soil type and depth Increases in numbers of heterotrophs were initially restricted to the top 2 cm of the soils Increases in oil-degrading populations were found in oil-treated soils Increases in microbial populations in subsurface soils paralleled downward migration of the oil Some of the observed population increases probably resulted from input of plant residues and products from oil biodegradation

Overwinter Phenology of Plants in a Polar Semi-desert

Abstract: Arctic and temperate-latitude tundra plants must make efficient use of the growing season, because it is very short. A variety of leaf-development strategies permit growth in the cool summers. ... Winter phenology was observed under field conditions for 27 of 33 angiosperm species found on King Christian Island. ... The full significance of overwintering leaf condition and the variability of this pattern within the High Arctic needs further investigation.

Reconstructed holocene bioclimates

Abstract: Paleopodzols and frost wedge polygons in and near the forest/ tundra ecotone indicate that Holocene fluctuation of the forest border has varied from 280 km (170 mi) north to a minimum of 50 km (30 mi) south of the modern forest border in southwest Keewatin. The 320 km (200 mi) wide range for Keewatin appears to decrease systematically northwestward across Mackenzie and northeastward across Labrador. Significant forest/tundra border displacements occurred at least six times during the postglacial period in response to relatively conservative changes in the incidence of Arctic and Pacific derived air masses.

Distribution pa'i"i'erns of belowground standing crop in arctic tundra at barrow, alaska*

Abstract: Measurements of belowground standing crops of arctic tundra vegetation near Barrow, Alaska, were made by depth increment and plant category to determine patterns of spatial and seasonal variation. In 1965 in a vegetationally heterogeneous area, total subsurface standing crops (live plus dead) varied horizontally from 1520 to 2185 g m-2. The estimated living portion varied from 735 to 1435 g m-2. Between 69 and 91% of the living material was concentrated in the top 10 cm of soil. Both horizontal and vertical distribution of the subsurface standing crop appeared to be related to variation in soil moisture, postulated soil aeration, and depth of thaw.

Validation of A Model of the Effect of Tundra Vegetation on Soil Temperatures

Abstract: A model of physical processes of heat transfer through vegetation canopies and soil was developed for the tundra and tested with data from the wet coastal tundra near Point Barrow, Alaska. The total leaf area index of the canopy was varied by clipping and adding dead material to different plots. Air and soil temperatures were monitored continuously in the growing season to validate the model. Calculated air and soil temperatures were within 1?C of the measured temperatures through the profiles. Calculated and observed depths of thaw were usually within 0.01 m through the season. Deviations were greatest during a period of snow. Sensitivity analyses indicated that the important variables and processes, many difficult to measure, are those relating to evaporation from the wet moss surface under the canopy.

Effect of vegetation on limestone solution in a small High Arctic basin

Abstract: To evaluate the effect of tundra vegetation on limestone solution processes, the present study was carried out in a small basin in southwestern Ellesmere Island, N.W.T. A test reach was selected along the stream, and water samples were collected at regular intervals from a seepage point entering the reach, a soil water pit at the bottom of a vegetated slope along the test reach, and from the stream at the outlet of the reach. Hydrochemical characteristics of the samples were described by several measured and calculated variables including water temperature, pH, calcium and total hardness, bicarbonate concentration, equilibrium partial pressure of carbon dioxide, and indices of saturation with respect to calcite and dolomite. Throughout the growing season of 1975, all samples indicated higher concentrations in water hardness and in bicarbonate than those reported in nonvegetated areas of the Arctic. A rising trend was apparent in these data, with the concentrations reaching a seasonal maximum in late summe...

The Water Balance of a Small Pond in the High Arctic

Abstract: Tundra ponds are ubiquitous features in the High Arctic. The water balance of one such pond situated on Ellesmere Island was found to be dependent upon the groundwater supplies from the internally-drained basin in which it was located. For the basin as a whole, evaporation constituted an important component of the water balance, accounting for over 90 per cent of the rainfall over a summer period of less than six weeks. Changes occurring in the quantity of water in the pond in response to rainfall were found to depend upon the degree of saturation of the active layer of the underlying permafrost.

Nitrogen Fixing Lichen Roles from Desert to Alpine in the Sangre de Cristo Mountains, New Mexico

Abstract: Lichens containing blue-green algae were measured by transects and reconnaissance in six major temperate vegetation types to estimate possible significance in annual nitrogen budgets and patch dynamics within ecosystems, and to estimate how a functional ecosystem attribute, i.e. nitrogen fixation, correlates with vegetation structure. Lichen cover was negligible in sagebrush desert, pinyon-juniper woodland, ponderosa pine forest and alpine tundra, but averaged 72 m2ha-1 in Douglas fir forest and 33 m2ha-1 in sprucefir forest. North slopes of Douglas fir forest had the highest average cover, 130 m2ha-'. All macrolichens were terrestrial species of Peltigera with P. canina the overwhelming dominant. Based on published laboratory nitrogen fixation rates, lichens probably provide a significant input to the total annual nitrogen budget in the Douglas fir north slope forests and possibly in the spruce-fir forests. A feedback loop relating the role of nitrogen fixing lichens to patchiness within ecosystems is hypothesized. Nitrogen fixing lichens correlate poorly with vegetation structure. Excluding the cold alpine tundra, moisture is considered the primary determinant of nitrogen fixing lichen abundance. Nitrogen fixation by lichens containing blue-green algae is believed widespread in many terrestrial ecosystems (Rogers et al., 1966; Fogg & Stewart, 1968; Denison, 1973; Henriksson & Simu, 1971; Hitch & Stewart, 1973; Alexander & Schell, 1973; Crittenden, 1975; Forman, 1975). The importance of the fixed nitrogen and its roles in the ecosystem are at present largely uncertain due to the paucity of quantitative studies on the distribution of nitrogen-fixing lichens. Nitrogen from lichens may play a significant role in the annual nitrogen budget of an ecosystem by affecting primary productivity and nutrient recycling rates, compartment sizes and outputs. Denison (1973) and Pike et al. (1972) measured the biomass of epiphytic lichens in a tall, wet Douglas fir [Pseudotsuga menziesii (Mirb.) Franco] forest in Oregon and, using two methods, estimated a nitrogen input of 1.8 or 10 kg N ha-1 yr-1. 1 We greatly appreciate Eustaquio Castro-Mendoza for transportation and sampling aid in the field, and James R. Gosz for comments on the manuscript. We also are grateful to William F. Mahler and Ronald K. Wetherington for countless courtesies and stimulation while the research was in progress at the Ft. Burgwin Research Center, Southern Methodist University, Taos, New Mexico 87557. 2 Department of Botany, Rutgers University, New Brunswick, New Jersey 08903. 3 Department of Biology, Southern Methodist University, Dallas, Texas 75275. This content downloaded from 157.55.39.102 on Mon, 03 Oct 2016 05:17:12 UTC All use subject to http://about.jstor.org/terms 562 THE BRYOLOGIST [Volume 80 Forman (1975) measured lichen cover and biomass in a tropical montane rainforest in Colombia and using published laboratory nitrogen fixation rates crudely estimated an input of 1.5-8 kg N ha-1 yr-1. Becker et al. (1977) found nitrogen fixing lichen biomass in a 2.7 ha North Carolina oak forest to average 0.02 kg ha-1, with a maximum 0.18 kg ha-1 for a moist section, and concluded that lichens cannot be significant contributors of nitrogen to the forest as a whole. Other studies have measured or estimated nitrogen fixation of lichen patches or microsites within an ecosystem. For example, some samples within an ecosystem were reported to have high nitrogen fixation rates in a moist mild tundra in Iceland (Crittenden, 1975), a tundra at Point Barrow, Alaska (Alexander & Schell, 1973), Antarctic tundras (Fogg & Stewart, 1968; Horne, 1971), several temperate sites in Great Britain (Hitch & Stewart, 1973), a New Mexican desert (Shields et al., 1957), an Arizona desert (Cameron & Fuller, 1960) and an Australian arid zone (Rogers et al., 1966). A second role of nitrogen produced by lichens, unlike atmospheric nitrogen input, may be in producing environmental heterogeneity within the ecosystem and the consequent patchiness in distribution of organisms. In the American tropics the abundance of nitrogen fixing lichens appears to drop off sharply with decreasing moisture (Forman, 1975). Hitch and Stewart (1973) documented experimentally the overriding importance of moisture deficits in limiting nitrogen fixation by lichens. To better understand which ecosystems may depend on biological nitrogen input, the abundance of lichens in a broad spectrum of ecosystems needs study, especially with respect to moisture gradients. In the broader context of relating ecosystem structure and function, such a study might permit comparison of this functional attribute (nitrogen fixation) with a range of different ecosystem or vegetation structure. Gosz (1975) studied the nutrient and hydrologic dynamics in a spectrum of ecosystem types in the Sangre de Cristo Mountains of New Mexico and found atmospheric nitrogen input varied with elevation as a result of large quantities of precipitation at high elevations and of dust at low elevations. Nitrogen output in stream water varied elevationally as a result of a complex of six factors. Nutrient loss was generally minimal in the intermediate elevation, highly productive Douglas fir forest. The objective of this study was 1) to determine the amount of nitrogen fixing lichens in major vegetation types of the Sangre de Cristo Mountains of New Mexico and 2) to estimate whether or not lichens may be significant in the nitrogen budget or patchiness of terrestrial ecosystems of southwestern North America, and whether or not this functional ecosystem attribute, nitrogen fixation, is related to vegetation structure or climate.

Reindeer Pastures in the Subarctic Territories of the U.S.S.R.

Abstract: The Subarctic includes the whole tundra zone and the forest-tundra zone, which is the area transitional between tundra and taiga zones. The subzone of northern taiga is also added here by some authors. In such a wide interpretation Subarctic coincides roughly with the term “Far North”, broadly used in literature, especially in the economic one. In the north the Subarctic borders on the Arctic desert zone of Arctic region, in the south) on the taiga zone of Boreal region.

Urbanization and Pollutant Effects on the Thermal Structure in Four Climatic Regimes

Abstract: A numerical model based on the Eulerian conservation equation simulated the urban heat island in tropical, desert, mid-latitude and tundra climatic regimes in a two-dimensional mode. Data are based on typical climatological descriptions. Experiments to identify the effects of individual urbanization characteristics showed anthropogenic heating to be important in the mid-latitudes and tundra, and that radiative effects of pollutant aerosols are minimal except in the tundra. Four types of urban heat islands, over a day's duration, both negative and positive, are possible in various climatic regimes and seasons. Simulations showed that a positive heat island forms in the urban arm in the absence of sun, and negative heat islands are formed as the daylight lengthens. The largest urban thermal effects occurred in the tundra regions and relatively small effects occurred in the tropics and deserts.

Distribution, Abundance, and Biomass of Colorado Alpine Tundra Arthropods

Abstract: Population densities, distributions, and biomass of predominant soil and surface active arthropods were determined for major alpine tundra plant communities on Niwot Ridge, Colorado. Sampling (soil...

Soil fauna of the Polar desert at Cape Cheluskin, Taimyr Peninsula, USSR

Abstract: Cape Cheluskin on the North of the Taimyr Peninsula represents the northernmost mainland of the Earth. It belongs to the Polar desert zone, which also occupies the islands of the Arctic Ocean. The first studies on the soil fauna communities were carried out there in the summer of 1974. Polar desert habitats with different types of moss-lichen cover were compared. Small mesophilous forms were found to be characteristic of the soil animal population, Enchytraeidae, Collembola, Chironomidae larvae and Nematoda predominating. Absence of some groups of invertebrates, which are widely distributed in tundra (earthworms, Tipulids, Oribatid mites, beetles) was recorded. Population density of invertebrates in moss-lichen communities was relatively high and their biomass averaged 6-8 g m-2 and in some plots up to 20 g m-2. Invertebrates hardly occurred in the bare ground, where lichens and algae only were found. The biomass in such habitats reached over 1 g m-2. Trophic relations of soil organisms and patterns of the formation of animal communities in soils of the Polar desert are discussed.

Reproduction and growth of the tundra hare (Lepus othus).

Abstract: Data are presented on the growth and reproduction of the tundra hare ( Lepus othus Merriam) from the Clarence Rhode National Wildlife Refuge, western Alaska. The estimated average growth rate for juvenile hares is 37.2 grams per day over a 102 day growth period from a birth weight of 100 grams to a minimum adult weight of 3900 grams. The single annual litter averages 6.3 (N = 10). A conception period from 13 to 29 April and a parturition period from 29 May to 4 June are deduced from estimated embryo ages.

Temporal variation of surface roughness over a tundra surface

Abstract: The roughness of a tundra surface, characterized by Z0, shows a systematic variation throughout the spring and summer seasons. The change of 2 orders of magnitude, from 0.01 before melt to 2.8 cm in the summer, is not gradual but rather proceeds in a stepwise manner. Relatively rapid increases in Z0 are shown to result from (1) rapid snowmelt, which exposes tundra tussocks, and (2) subsequent growth of the vegetation canopy. The corresponding increase in turbulent mixing, characterized by the drag coefficient CD, significantly affects heat fluxes over the tundra surface. Thus for heat flux modeling studies, accurate estimates of surface roughness and surface drag are essential. The time series of Z0 and CD presented here should be of considerable use to modelers working in the Arctic.

Geobotanical and ecological observations at two locations in the west-central siberian arctic

Abstract: Preliminary results of a field excursion to the Siberian Arctic in July 1976 are reported. The excursion was part of a bilateral exchange of American scientists to the Institute for Extreme North Agricultural Research at Norilsk. Two field sites were visited: Lake Ayan (ca. 69?N, 94030'E) in the mountainous Putorana Plateau 200 km east of Norilsk; and Pura River (ca. 72?30'N, 86?E) in the rolling, moderately drained tundra of the western part of the Taimyr Peninsula. The ecosystems at each site are described, emphasizing associations between landforms, plant communities, and fauna. Generalized profiles illustrate the landform/plant community relations. The main plant species of each community are tabulated. Both study sites are important wildlife habitats. Lake Ayan is surrounded by Larix dahurica forest, Snow-sheep (Ovis nivicola) live above the for

Energy balance and ground thermal regime studies broughton Island, Northwest Territories, Canada

Abstract: This paper examines the relationship between energy balance and ground thermal regime over a variety of tundra surfaces in a low arctic environment. The Bowen ratio and energy balance data emphasized the dominance of latent heat fluxes over the freely evaporating terrain. The sensible heat flux was negative, owing to persistent surface inversions, and supplied energy for evaporation. The ground heat flux was minimal until July 6 and the major increase on that date resulted in a sharp rise in the rate of ground thawing. The deepest measured penetration (80 cm) was achieved in moist sandy soil, compared with 50 cm depth in adjacent clay loam, despite the similarity between Bowen ratios at both sites. Energy balance data do not account for active layer variations and independent soil factors appear to exert the major control on ground ice melt. The paper concludes with a discussion of Bowen ratios and energy balance at the study area vis-a-vis other snowfree tundra environments.

Polar Deserts of the Taimyr Peninsula (Poliarnye Pustyni Poluostrova Taimyr)

Abstract: : This article characterizes the natural conditions, the floral and faunal composition, and the vertical and horizontal structure of the communities in the Northernmost point of Eurasia-Chelyuskin Cape. In comparison with the tundra zone, there is a sharp impoverishment of flora and fauna in all groups, especially flowers, birds and mammals, and also a change of dominance in growth cover and in animal population. The basic features of the communities are a very rarified cover, the fractionation and isolation of plants growing in the turf, slowness of the decomposition process, absence of peat accumulation, concentration of life in the narrow band near the surface of the ground, a tendency towards reduction in size of the species of animals and plants, the replacement of large forms by smaller forms, the formation of cushioned forms in plants, especially in mosses and lichens. A characteristics feature is also the absence of intrazonal grouping, especially mixed grass and grassy meadows. On the basis of the data obtained, the Chelyuskin region belongs to the polar desert zone, the southern boundary of which apparently runs through Taimyr at 77 deg N latitude.

The boundary of the arctic and principles of delimitation

Abstract: After a historial review of various attempts to define the limits of the Arctic on the basis of individual climatic parameters, the author recommends the southern limit of the tundra zone. It is argued that purely meteorological characteristics are unsatisfactory for Arctic regionalization because of the widely spaced network of observation stations and the smooth changes in parameters from place to place. An ecological limit such as the southern tundra boundary, on the other hand, represents an integration of a whole set of parameters and incorporates more climatic information than the isopleth of any meteorological element taken by itself. Although there is a real need for applying similar regionalization principles in land and oceanic areas, the relationship between climate‐forming factors and marine environments has not been adequately studied. For the purpose of the present paper, the boundaries of the Arctic in oceans are defined by the extent of intrusion of Arctic waters into the North At...