Showing papers on "Tundra published in 1983"

Carbon-13 and carbon-14 abundances in alaskan aquatic organisms: delayed production from peat in arctic food webs.

Abstract: Inputs of terrestrial peat carbon to the nearshore Alaskan Beaufort Sea from erosion and fluvial transport are of the same magnitude as in situ primary production within 10 kilometers of shore. Nevertheless, carbon-13/carbon-12 ratios and carbon-14 abundances in marine organisms show that only small amounts of the terrestrial carbon are transferred beyond the microbial level. Freshwater organisms, however, are heavily dependent on peat, as shown by pronounced seasonal radiocarbon depressions in resident fish and ducks. Tundra ponds and lakes are areas where accumulated terrestrial peat carbon is apparently transferred to aquatic insect larvae and passed on to higher organisms. The lack of functionally analogous abundant marine prey organisms may explain why peat carbon is not efficiently transferred to apical food web species in the marine environment.

Increasing atmospheric carbon dioxide: possible effects on arctic tundra

Abstract: Cores of wet coastal tundra collected in frozen condition in winter were used as microcosms in a phytotron experiment that assessed the effects of doubling the present atmospheric CO2 concentration, increasing temperature, and depressed water table on net ecosystem CO2 exchange. Doubling atmospheric CO2 had less significance in regard to net carbon capture or loss in this ecosystem as compared to the significant effects of increased temperature and lowered water table level. Both of the latter are to be expected as atmospheric CO2 increases in the Arctic.

Trophic Exploitation and Arctic Phytomass Patterns

Abstract: Aboveground phytomasses of tundra communities and changes in moss phytomass after a lemming peak were reviewed to test the prediction of the hypothesis of exploitation ecosystems that herbivory limits the aboveground phytomasses of moderately unproductive plant communities. Aboveground phytomasses of arctic meadows on Truelove Lowland where brown lemmings do not occur are about five times as great as corresponding values from Barrow which is within the range of the brown lemming. The combination of Barrow data and data from tundra communities on Hardangervidda with primary production less than 600 gm-2 yr-1 shows no significant correlation between aboveground phytomass and primary productivity, whereas a weak positive trend is obtained from Truelove Lowland where the herbivore trophic level is impoverished. Data from Kilpisjarvi suggest an 8.4-fold increase in moss phytomasses during 7 yr of low lemming densities. Both the geographical patterns and the short-term dynamics at Kilpisjarvi are in full agreem...

Introduced and native leafhoppers common to the old and new worlds (rhynchota: homoptera: cicadellidae)

Abstract: Fourteen new records of introduced leafhoppers are added to the 157 leafhoppers previously recorded as occurring in both the Old and New worlds. Of these, 62 were erroneously recorded previously although 12 of the European species subsequently have been found in North America. Two North American species have been introduced into Europe, and one European species has been found in South America; North America has received 61 species from Europe, 3 from Asia, and 1 from Africa. One pan-tropical species is probably a recent introduction into the Caribbean from the Old World. There are 30 transboreal leafhoppers, 5 transarctic species inhabiting the tundra and alpine meadows, and 9 inhabiting temperate regions of both Eurasia and North America.The Aster leafhopper (Macrosteles quadrilineatus Forbes) is removed from synonymy with the transboreal sedge-feeding M. fascifrons (Stal) and 25 other confused species are distinguished in the genera Aphrodes, Euscelis, Evacanthus, Limotettix, Macrosteles, and Typhlocyba. These include 11 new species: Evacanthus bellaustralis, E. chlamidatus, E. grandipes, E. lacunar, E. nigramericanus, E. ustanucha, Macrosteles lagus, M. severini, M. tesselatus, M. vilbastei, and Typhlocyba frigida, all from North America, Balclutha punctata confluens Rey and Limotettix striola ferganensis Dubovsky are elevated to species status. One new generic synonymy, 23 new specific synonymies, and 3 new combinations are created.

Demographic patterns of seedling establishment and growth of native graminoids in an alaskan tundra disturbance

Abstract: SUMMARY (1) Presence or absence of buried seed was the major factor governing natural revegetation of a bulldozed disturbance in Alaskan tussock tundra. The viable buried seed pool contained 97% Eriophorum vaginatum and Carex bigelowii seed and was restricted to organic soil horizons. Consequently, disturbed organic soils reached a final seedling density of 250 seedlings m-2 (primarily Carex and Eriophorum) 4 years after disturbance, whereas mineral soils which were colonized by current seed deposition had only 30 seedlings m-2, including many grasses. (2) Fertilization enhanced the growth of grass and 2-4-year-old Carex seedlings fourto ten-fold but had no significant effect upon Eriophorum seedling growth. Growth was not significantly affected by presence of already established seedlings and did not differ between substrates, except for grasses which grew more rapidly on mineral than organic soils. (3) Seedling mortality during the first 2 years after germination was low (43% in Eriophorum, 27% in grass, and 13% in Carex) and did not differ between organic and mineral substrates. Mortality of 1- and 2-year-old seedlings was concentrated during the growing season, but mortality of larger seedlings was primarily a consequence of winter grazing. Mortality was increased by fertilization. (4) The greater vascular plant biomass and cover on organic than mineral soils was due primarily to recruitment from the buried seed pool. The increase in biomass and cover with fertilization was a consequence of a stimulation of growth by grass and Carex. (5) We recommend stockpiling and re-utilizing soil organic matter, supplemented under certain conditions by fertilization and sowing of seeds, as a mechanism of enhancing natural community restoration of arctic tussock tundra following man-made disturbances.

Stability and instability of natural and modified upper timberline landscapes in the colorado rocky mountains, usa

Abstract: The forest-alpine tundra ecotone of the Colorado Front Range is defined as the transition belt extending from the upper timberline (upper limit of closely-spaced, symmetrical trees) to the treeline (upper limit of tree species). Its dynamics and natural history are outlined. It is postulated that treeline and the upper part of the ecotone were established several thousand years ago under climatic conditions much more favourable to seedling establishment than those of today. Because the tree forms of the ecotone are able to maintain themselves over long periods by layering, the ecotone is extremely stable despite significant climatic fluctuation. This same characteristic renders it highly vulnerable to human impacts. In the last decade a change has begun from natural long-term stability to progressive short-term instability. The implications of this for wilderness area management are discussed.

Nutrient content and dynamics in north Swedish shrub tundra areas

Abstract: Forbs and leaves of deciduous shrubs had high concentrations of Ca, Mg, K, P, and N. Deciduous dwarf shrubs had intermediate concentrations but higher than evergreen dwarf shrubs. Monocots, cryptogams, woody and belowground tissues had low concentrations. Plant nutrient concentrations and nutrient content in soil organic matter increased from dry towards moist tundra areas. The residence time of nutrients was considerably less than ten years in surface litter, but several decades or centuries in total organic matter. The longest residence time was found in the moist part of the tundra. N, K, and P in Betula nana leaves were translocated to a great extent prior to leaf fall, whereas Mg and particularly Ca were only slightly translocated. As on other tundra areas shortage of nutrients probably limits plant growth. In that case short supply of N and F seems most probable due to retention in litter and soil organic matter.

Buried seed and standing vegetation in two adjacent tundra habitats, northern Alaska.

Abstract: A comparison is made of the species of the above ground vegetation and the buried seeds in a tussock tundra meadow, northern Alaska. Vegetation types are compared across a boundary between two habitats which have distinct differences in above ground vegetation. Sixteen species germinated from the soil cores. There were distinct differences between the species of buried seed and the species in the standing vegetation in the two tundra habitats. There was a positive correlation between the diversity of standing vegetation and the diversity of buried seeds. The significance of buried seeds and viable rhizomes in the soil cores is discussed with respect to seed reproduction in the arctic and revegetation.

Nutritional Ecology of Microtine Rodents: Food Habits of Lemmings near Barrow, Alaska

Abstract: Analyses of stomach contents and feces showed striking differences in the diets of the brown lemming ( Lemmus sibiricus ) and the collared lemming ( Dicrostonyx groenlandicus ) near Barrow, Alaska. Brown lemmings ate primarily grasses, sedges, and mosses, whereas collared lemmings ate primarily willow leaves and forbs. Brown lemming diets changed markedly with season and with habitat. Monocotyledons were always the most important food items; in winter and in drier habitats mosses became a more important component of the diet (up to 40%). Among the monocotyledons, brown lemmings consistently preferred tundra grass ( Dupontia fisheri ), consistently avoided a sedge ( Carex aquatilis ), and took a relatively constant amount of cottongrass sedge ( Eriophorum spp.) no matter what its availability. Differing food habits of lemmings in different habitats may have important consequences for their growth, reproductive performance, and population dynamics.

Life cycles and the distribution of psyllids (Homoptera) in arctic and subarctic Alaska

Abstract: Psyllids are small, phloem-feeding insects of perennial dicotyledonous plants. In Alaska, psyllids are most abundant and occur farther north on willows than on other host plants. Four of the five psyllid species of the arctic coastal plain are restricted in their nymphal development to the catkins of willows. For both willow-feeding species and species occurring on other host plants, the distribution of the host plant commonly extends farther north than does distribution of the characteristic psyllid species. Unlike tundra plants and soil invertebrates, psyllids and many other insect herbivores in the Arctic have annual life cycles. Rapid growth rate thus is essential to their success. A conceptual model based upon the effects of temperature upon growth rate of tundra plants and insects is offered as a hypothesis to explain the distribution of insect herbivores in arctic and subarctic Alaska.

Holocene vegetation history of the upper natla river area, northwest territories, canada

Abstract: A 2.3-m thick lenticular exposure of autochthonous peat provides a palynological and plant macrofossil record of vegetation development in the central Selwyn Mountains. This record spans at least the last 8640 yr. Interpretation of the fossil pollen profile is aided through numerical comparison with 15 pollen surface samples from the area. From 8640 to 7700 BP the region was dominated by a Betula tundra. This tundra became increasingly productive during the later stages of this episode. At approximately 7700 BP Picea expanded into the area. This relatively late rise of Picea was possibly a result of restricted migration up the mountain valleys. It appears that Picea was at its greatest dominance in the landscape from 7700 to shortly after 5000 BP and treeline was probably higher than present during this period.

Germinable seed banks of interior alaskan tundra

Abstract: Germinable seed numbers in the surface soil were estimated across three snowbank gradients in montane tundra of interior Alaska. Vegetation, productivity, and disturbance change with distance across these gradients. Seed densities are in the range 500 to 1800 seeds m-2 in the upper 5 cm of soil. An earlier study in Eriophorum tussock tundra nearby revealed over 2000 seeds m~2 in the upper 5 cm of soil. These results show that tundra seed banks (and presumably seed rain) are relatively larger than expected. Published reports do however suggest that seed bank size decreases with latitude in montane grassland, heath and tundra vegetations. Contrary to published theories, there was no significant relation between seed bank size and disturbance. Seed bank size increased with above ground vascular plant productivity. This is most simply explained by the conjecture that reproduction and seed rain increase with productivity. The relative abundance of graminoids in the seed bank is higher (and that of dicots, less) than what would be expected from their relative cover in the vegetation.

Productivity of Grassland and Tundra

Abstract: Grassland and tundra biomes are considered jointly in this chapter largely because they share a similar physiognomy and often are categorized as “grazing lands” because they support a relatively large trophic level of grazing herbivores We will use the term “tundra” to denote treeless regions north (and south) of latitudinal treelines or above natural altitudinal treelines (see Murray 1978) Similarly, “grassland” in this chapter refers to treeless (but not desert) systems in the warmer climates of lower latitudes and lower altitudes Savannas, systems characterized by scattered trees with open canopies, support a continuous grass understory and can be considered as a special element within grassland Grasslands and tundras are characterized by the dominance of graminoids (grass-like monocotyledons) and the general absence of trees, but they rarely occur contiguously They are often separated by forests from which they either can develop as a result of anthropogenic, biologic, or climatic effects

Evidence for Postglacial Paleoceanographic and Paleoclimatic Changes in Lake Melville, Labrador, Canada

Abstract: Foraminifera, dinoflagellates, and pollen in a radiocarbon-dated piston core from Lake Melville have been used to reconstruct a postglacial history of the fiord oceanography and regional climate. Present bottom water salinity in Lake Melville is about 5?/oo00 lower than on the inner Labrador Shelf because of a shallow sill in the Narrows at the fiord entrance. Foraminiferal assemblages suggest that about 5000 yr BP, the fiord salinity was about the same as the inner shelf. The postglacial change in fiord salinity is best explained by a shallowing of the sill, preventing the entry of saline inner shelf bottom water. A model of relative sea-level changes at the Narrows is proposed which shows that at 5000 yr BP, the sill was about 20 m deeper than present; at 7000 yr BP it was 50 m deeper, and it was 90 m deeper until the end of the marine maximum at 7500 yr BP. Pollen assemblages in the piston core indicate a succession of four major vegetation types in the Lake Melville drainage basin: from ca. 8000 to 7500 yr BP, low arctic tundra was replaced by shrub tundra; around 6000 yr BP, shrub tundra gave way to spruce woodland, which was followed by boreal forest around 5000 yr BP. A decline in absolute pollen concentrations during the past 4000 yr may indicate a recent climatic deterioration. Before forestation of the Lake Melville watershed, sedimentation in the fiord basin was three to four times higher than at present, but the maximum sedimentation rate of 0.26 cm yr-1 is much lower than in other large Canadian fiords, e.g., Knight Inlet.

A note on july senescence in tundra plants at eagle creek, alaska, u.s.a.

Abstract: Widespread senescence of leaves was observed on many tundra plant species as early as 15 July 1981 at three elevations near Eagle Creek, Alaska. This early senescence truncated an already-short growing season of between 44 and 87 d by 15 to 30 d. Correlative evidence assembled in this report indicated that cold overall temperatures may have been responsible. Heavy frost, drought, photoperiod, and low light levels-all factors which have previously been implicated as causing senescence of leaves-were discounted as possible explanations. The present data underscore the need for experiments under controlled conditions to determine the operative cues for onset of senescence in tundra plants.

The Radiation Balance of Typical Terrain Units in the Low Arctic

Abstract: This study was designed to achieve an understanding of the behavior of the summer radiation balance for a diversity of terrain types characteristic of the low Arctic near treeline in order to promote more accurate modeling of net radiation from measured or calculated solar radiation or all-wave radiation. Components of the radiation balance, including net radiation, incoming and reflected solar radiation, incoming and outgoing longwave radiation, and radiative surface temperatures, were measured or derived for four distinct terrain types near Churchill, Manitoba, from May through August, 1982. The terrain types were upland tundra, upland open spruce forest, lowland peat with moss vegetation, and lowland swamp covered with sedge grass. These represent an assemblage typical of the low Arctic in North America. Snowmelt from the tundra surfaces occurred at the end of April, a month earlier than normal. Snow in the forest persisted until mid-June, which is normal. On average for the summer, incoming solar radiation comprised 41 percent of the total incoming flux, the remainder consisting of longwave sky radiation. Surface albedos in the non-snow period were generally small, being largest and the same for the upland tundra and lowland peat at 0.15, less for the forest at 0.12, and least for the swamp, which ranged between 0.08 and 0.12. Albedos generally increased as the summer progressed. With snow in the forest, albedos above the forest canopy did not exceed 0.42. In common with observations in middle latitudes, the results indicate that under clear skies there was a strongly developed diurnal pattern of large albedos in morning and evening and smaller values at midday. This was not evident for cloudy days. The radiative surface temperatures at nonforested sites were always warmer than the overlying air on a daily basis, which was true also for the forest after final snowmelt. With snow, however, the forest floor was colder and the canopy warmer than the surrounding air. Differences in net radiation between surfaces were small for the full measurement period, and net radiation comprised between 59 to 65 percent of incoming solar radiation and 24 to 27 percent of incoming all-wave radiation.

Abiontic enzymes in arctic soils: changes in sulphatase activity following vehicle disturbance

Abstract: The effect of vehicle perturbation on sulphatase enzyme activity in arctic tundra soils was examined. Sulphatase activity was significantly less in disturbed (vehicle track) than that adjacent undisturbed tundra soils. Soil moisture and water movement appeared to be major controlling factors. The results of the study suggest that biochemical mineralization of organic sulphur in disturbed tundra soils is controlled by nutrient influx associated with water movement, altering sulphatase activity to a level consistent with the need for, as well as the supply of, the mineralized element.

Sensitivity of Plant Communities and Soil Flora to Seawater Spills, Prudhoe Bay, Alaska,

Abstract: : Secondary recovery of oil at Prudhoe Bay, Alaska, will involve transporting large quantities of seawater in elevated pipelines across tundra for injection into oil-bearing rock strata. The possibility of a pipeline rupture raises questions concerning the effects of seawater on tundra vegetation and soils. To evaluate the relative sensitivities of different plant communities to seawater, eight sites representing the range of vegetation types along the pipeline route were treated with single, saturating applications of seawater during the summer of 1980. Within a month of the treatment 30 of 37 taxa of shrubs and forbs in the experimental plots developed clear symptoms of stress, while none of the 14 graminoid taxa showed apparent adverse affects. Live vascular plant cover was thus reduced by 89 and 91% in the two dry sites and by 54, 74 and 83% in the three moist sites, respectively. Live(green) bryophyte cover was markedly reduced in the moist experimental sites in 1981. Bryophytes in all but one of the wet-site experimental plots were apparently unaffected by the seawater treatment. Two species of foliose lichens treated with seawater showed marked deterioration in 1981. All other lichen taxa were apparently unaffected by the seawater treatment. The absorption and retention of salts by the soil is inversely related to the soil moisture regime. In the wet sites, conductivities approached prespill levels within about 30 days. In such sites, spills at the experimental volumes are quickly diluted and the salts flushed from the soil. In the dry sites, on the other hand, salts are retained in the soil, apparently concentrating at or near the seasonal thaw line.

Bird use of arctic tundra habitats at Canning River Delta, Alaska

Abstract: Seasonal patterns of abundance of shorebirds and Lapland Longspur were studied at the Canning River delta. Study plots with differing habitat characteristics were examined: upland, mesic, and lowland tun­ dra, and coastal saline flats. Nesting density was greatest in the mesic plot, but the lowland received intense use by late summer tran­ sients; use of the saline habitat was consistently high. Cold weather in July, 1980 probably reduced prey availability. Aquatic habitats, especially polygon troughs, produced a high proportion of the adult in sect biomass. Comparison of energetic requirements of birds with the energetic value of their prey supply suggests that food could have limited reproductive success. Availability of both aquatic and ter­ restrial insects may contribute to high breeding bird density in struc turally diverse habitats. Heavy use of wet/flooded tundra by late summer migrants probably reflects abundance of midge (Diptera: chironomidae) larvae in pond sediments.

Relations entre spectres polliniques contemporains et topographie dans la vallée de la Coppermine, Territoires du Nord-Ouest

Abstract: Thirty six moss polster samples from forest tundra and shrub tundra collected along the Coppermine River Valley, N.W.T., result in six pollen assemblages associated with type landforms. Forest sites on moderately steep slopes of approximately 12° yield spectra dominated by spruce. Spectra dominated by Salix (>50%) exist only at isolated sites where the shrub is the principal species found. Flat, well-drained surfaces on gentle slopes exposed to wind produce spectra dominated by more than 50% Betula. The assemblage Betula–Ericales corresponds to gentle slopes actively modified by cryogenic processes. The assemblages Betula–Salix and Salix–Betula are found on gentle, poorly drained slopes or in zones of shrub tundra where Salix is a pioneer species on surfaces newly exposed to weathering. The assemblage Betula–Picea is not a specific indicator since it is found on various topographic sites. The paper proposes one example of the utilization of these relationships between pollen spectra and landforms, for the...

Features of cryogenic environment in soils of continental tundra and arid steppe on the southern Khangai slope under electron microscope

Abstract: Morphoscopic studies were conducted with the aid of SEM and TEM microscopes, on quartz grains and fractions not exceeding 2 μm, on soil samples from the continental tundra, alpine meadow and arid steppe. The aim of these studies was to define the features and properties of the quartz grains and fractions, produced by the environment of the cryoarid continental climate of Central Asia. It has been established that in cold and humid climates processes of cryogenic and hydrothermic splitting occur on the surface of quartz grains and in cold and dry climates processes of cryothermic scalling. The increase in the surface area of disintegrated minerals under continental climate conditions is accompanied by cryochemical coating by mineral-organic compounds.