scholarly journals The biology of the annual Salicornia europaea agg. at the limits of its range in Hudson Bay

1983 ◽  
Vol 61 (3) ◽  
pp. 762-773 ◽  
Author(s):  
R. L. Jefferies ◽  
A. Jensen ◽  
D. Bazely
Keyword(s):  
Seed Production ◽  
Surface Sediments ◽  
Hudson Bay ◽  
Salicornia Europaea ◽  
Marginal Populations ◽  
Marginal Population ◽  
Seed Mortality ◽  
The Difference ◽  
Intertidal Site ◽  
Adult Plants

The biology of a marginal population of the annual Salicornia europaea agg. has been examined at La Pérouse Bay, Manitoba, on the shores of Hudson Bay. Plants were confined to south-facing sites which became hypersaline in summer, but which were not covered by tides. The difference in temperature of surface sediments between south- and north-facing slopes was as much as 7 °C. Although most seedlings emerged in June, germination continued throughout the summer, but plants that appeared late in the season failed to set seed. Mortality of both seedlings and adult plants was low. Seeds or seedlings from a south-facing slope were transplanted during a 2-year period within the same site, into another south-facing site, to a north-facing site, and to an intertidal site. Germination either failed to occur or else was poor at the latter two sites. In addition, seed production of mature plants was low compared with that for individuals transplanted within south-facing sites. Additions of nitrogen to north-facing slopes increased overall seed output per plant, but the ratio of unripened to ripened seeds remained the same as that in plants from untreated plots. The results are discussed in relation to the ecology of marginal populations.

Morphological and isozyme variation in Salicornia europaea (s.l.) (Chenopodiaceae) in northeastern North America

1987 ◽  
Vol 65 (7) ◽  
pp. 1410-1419 ◽  
Author(s):  
S. L. Wolff ◽  
R. L. Jefferies
Keyword(s):  
North America ◽  
Atlantic Coast ◽  
Hudson Bay ◽  
Salicornia Europaea ◽  
Electrophoretic Variation ◽  
James Bay ◽  
Northeastern North America ◽  
Electrophoretic Patterns ◽  
Anther Length ◽  
Vegetative Characters

Morphological and electrophoretic variation has been documented within and among populations of Salicornia europaea L. (s.l.) in northeastern North America. Univariate and multivariate analyses (discriminant analyses) of measurements of floral and vegetative characters delimited three morphologically distinct groups of populations: Atlantic coast tetraploids (2n = 36), Hudson Bay diploids, and Atlantic coast and James Bay diploids (2n = 18). The two diploid groups were morphologically distinct from the midwestern diploid, S. rubra Nels., based on anther length, width of the scarious border of the fertile segment, and the overall width of the fertile segment. Electrophoretic evidence supported the delimitation of the three distinct morphological groups of populations of S. europaea with the exception of the population from James Bay, which had electrophoretic patterns identical with those of plants from Hudson Bay but resembled the Atlantic coast diploids morphologically. Most enzyme systems assayed were monomorphic. Only homozygous banding patterns were detected in diploid plants and electrophoretic variation was not observed within populations of S. europaea or S. rubra but was detected between groups of populations. Four multilocus phenotypes were evident; these corresponded to the major groups recognized on the basis of ploidy level and morphology. Reasons that may account for the paucity of isozymic variation are discussed.

The relationship between parasite load, crawling behaviour, and growth rate of Macoma balthica (L.) (Mollusca, Pelecypoda) from Hudson Bay, Canada

1991 ◽  
Vol 69 (8) ◽  
pp. 2202-2208 ◽  
Author(s):  
Shirley S. L. Lim ◽  
Roger H. Green
Keyword(s):  
Growth Rate ◽  
Macoma Balthica ◽  
High Tide ◽  
Somatic Growth ◽  
Parasite Load ◽  
Final Host ◽  
Hudson Bay ◽  
Tidal Level ◽  
Annual Growth Rings ◽  
The Difference

At ebb tide Macoma balthica makes crawling tracks on the intertidal sand flats near Churchill, Manitoba, on Hudson Bay. Clams from two tidal levels, mean low water and 1.0 m above mean low water, were sampled to compare the parasite load and growth rate of crawling versus buried Macoma. For each clam the number of trematode metacercariae present were counted and the growth rate was determined by the measurement of annual growth rings. Clams were infected by more metacercariae at the higher than at the lower tidal level, larger clams more than smaller ones and crawling clams more than buried ones. Increased exposure of the clams at the higher tidal level to shorebirds, the final host of the trematodes, is proposed as the reason for the difference in parasite load between the tide levels. High-tide clams (more parasitized) grew faster than low-tide ones (less parasitized), and crawlers (more parasitized) grew faster than the buried (less parasitized) clams. Enhanced somatic growth as a result of parasitic castration is proposed to be the most logical explanation to account for the faster growth of the parasitized clams.

Isotopic insights into smoothening of abandoned fan surfaces, Southern California

2006 ◽  
Vol 66 (1) ◽  
pp. 109-118 ◽  
Author(s):  
Ari Matmon ◽  
Kyle Nichols ◽  
Robert Finkel
Keyword(s):  
Surface Sediments ◽  
San Andreas Fault ◽  
Field Observations ◽  
Cosmogenic Nuclide ◽  
San Andreas ◽  
The Difference ◽  
Topographic Relief ◽  
Geomorphic Processes ◽  
Over Time

AbstractCosmogenic nuclide concentrations measured on abandoned fan surfaces along the Mojave section of the San Andreas Fault suggest that sediment is generated, transported, and removed from the fans on the order of 30–40 kyr. We measured in situ produced cosmogenic 10Be, and in some cases 26Al, in boulders (n = 15), surface sediment (n = 15), and one depth profile (n = 9). Nuclide concentrations in surface sediments and boulders underestimate fan ages, suggesting that 10Be accumulation is largely controlled by the geomorphic processes that operate on the surfaces of the fans and not by their ages.Field observations, grain-size distribution, and cosmogenic nuclide data suggest that over time, boulders weather into grus and the bar sediments diffuse into the adjacent swales. As fans grow older the relief between bars and swales decreases, the sediment transport rate from bars to swales decreases, and the surface processes that erode the fan become uniform over the entire fan surface. The nuclide data therefore suggest that, over time, the difference in 10Be concentration between bars and swales increases to a maximum until the topographic relief between bars and swales is minimized, resulting in a common surface lowering rate and common 10Be concentrations across the fan. During this phase, the entire fan is lowered homogeneously at a rate of 10–15 mm kyr−1.

Context-specific enhanced invasiveness of Raphanus crop–wild hybrids: A test for associations between greater fecundity and population growth

2014 ◽  
Vol 94 (8) ◽  
pp. 1315-1324 ◽  
Author(s):  
Lesley G. Campbell ◽  
Zachary Teitel ◽  
Maria N. Miriti ◽  
Allison A. Snow
Keyword(s):  
Population Growth ◽  
Seed Production ◽  
Plant Density ◽  
Genotypic Differences ◽  
Raphanus Raphanistrum ◽  
Invasive Potential ◽  
Population Growth Rates ◽  
Seed Mortality ◽  
Wild Hybrid ◽  
Context Specific

Campbell, L. G., Teitel, Z., Miriti, M. N. and Snow, A. A. 2014. Context-specific enhanced invasiveness of Raphanus crop–wild hybrids: A test for associations between greater fecundity and population growth. Can. J. Plant Sci. 94: 1315–1324. Evolution by crop–wild hybridization may create plant lineages with greater population growth rates, dispersal, and persistence than weedy progenitors, depending upon plant density. We asked: (1) how does hybridization affect demography and population growth rate (lambda, λ) and (2) how does density affect demography and λ? Over 1 yr, we followed wild radish, Raphanus raphanistrum and crop-wild hybrid, Raphanus sativus×R. raphanistrum, plants grown in 18 experimental sub-populations (originally derived from three wild and three hybrid populations) to assess contributions of germination, survival, and seed production to λ. We explored genotypic differences in demographic characteristics of low- and high-density populations (from populations grown at unmanipulated densities for three generations), using a LTRE. Hybrid populations had greater λs than weedy progenitors when grown in low (but not high) densities. Seed production was more influential on λ than germination or survival, and seed mortality was least influential. Our results indicate weedy Raphanus populations may be best controlled by limiting seed production, rather than killing plants outright or preventing seeds from germinating. Furthermore, relative invasiveness of genotypes is density-dependent, low-density conditions improving potential invasiveness of hybrid populations. We emphasize that assessing invasive potential of a plant will be more successful if one uses a comprehensive demographic approach accounting for a weed's entire life history.

Vegetational development and the effect of geese on vegetation at La Pérouse Bay, Manitoba

1979 ◽  
Vol 57 (13) ◽  
pp. 1439-1450 ◽  
Author(s):  
R. L. Jefferies ◽  
A. Jensen ◽  
K. F. Abraham
Keyword(s):  
Salt Marshes ◽  
The Arctic ◽  
Hudson Bay ◽  
Salicornia Europaea ◽  
Carex Aquatilis ◽  
Eriophorum Angustifolium ◽  
Lesser Snow Geese ◽  
Puccinellia Phryganodes ◽  
Water Saturated

The salt marshes at La Pérouse Bay, Manitoba, are described. Unconsolidated, water-saturated sediment is colonized by Hippuris tetraphylla, Puccinellia phryganodes, and Carex subspathacea. These sediments undergo frost heave, and on elevated mounds, Elymus arenarius var. mollis and Salix brachycarpa become established. This last species is the dominant one of the low willow tundra, which is the characteristic vegetation of the coastal strip. Where drainage is impeded in the upper marsh, relatively high salinities occur and species such as Salicornia europaea agg. and Triglochin maritima are present.A population of 10 000 to 20 000 lesser snow geese (Anser caerulescens) feed, in summer, on Puccinellia phryganodes, Carex subspathacea, Potentilla egedii, and Elymus arenarius var. mollis. The birds strip the shallow turf of Puccinellia in low lying areas between clumps of willow. This terracing of the surface creates depressions which become filled with water and ice. The role of geese in producing these ponds in the upper levels of salt marshes in the Arctic does not appear to have been reported previously. The ponds are subsequently colonized by Carex aquatilis and Triglochin maritima. The salt marsh gives way to an extensive fresh water marsh dominated by species of Salix, Eriophorum angustifolium, Calamagrostis neglecta, and Dupontia fisheri. The results are compared with data from other salt marshes in Hudson Bay and in the Arctic.

scholarly journals Growth of the white clover plant in relation to seed production

1980 ◽  
Vol 1 ◽  
pp. 56-63
Author(s):  
R.G. Thomas
Keyword(s):  
Key Words ◽  
Seed Production ◽  
White Clover ◽  
High Latitude ◽  
Trifolium Repens ◽  
Growth And Development ◽  
The Difference ◽  
White Clover Plant ◽  
Clover Plant

The growth and development at the stolen apex of white clover is described, particularly in relation to inflorescence initiation, and the factors controlling such initiation are reviewed for the range of cultivars which has been studied. The difference between the responses to environment in plants of Mediterranean and high latitude origin are emphasized. Key words: Trifolium repens, growth, flowering, photoperiod, temperature, seed production.

scholarly journals Magnitude and seasonality of wetland methane emissions from the Hudson Bay Lowlands (Canada)

2011 ◽  
Vol 11 (8) ◽  
pp. 3773-3779 ◽  
Author(s):  
C. A. Pickett-Heaps ◽  
D. J. Jacob ◽  
K. J. Wecht ◽  
E. A. Kort ◽  
S. C. Wofsy ◽  
...  
Keyword(s):  
Transport Model ◽  
Model Simulation ◽  
Methane Emissions ◽  
Hudson Bay ◽  
Atmospheric Methane ◽  
Chemical Transport Model ◽  
Hudson Bay Lowlands ◽  
The Difference ◽  
Boreal Wetland ◽  
Aircraft Data

Abstract. The Hudson Bay Lowlands (HBL) is the second largest boreal wetland ecosystem in the world and an important natural source of global atmospheric methane. We quantify the HBL methane emissions by using the GEOS-Chem chemical transport model to simulate aircraft measurements over the HBL from the ARCTAS and pre-HIPPO campaigns in May–July 2008, together with continuous 2004–2008 surface observations at Fraserdale (southern edge of HBL) and Alert (Arctic background). The difference in methane concentrations between Fraserdale and Alert is shown to be a good indicator of HBL emissions, and implies a sharp seasonal onset of emissions in late May (consistent with the aircraft data), a peak in July–August, and a seasonal shut-off in September. The model, in which seasonal variation of emission is mainly driven by surface temperature, reproduces well the observations in summer but its seasonal shoulders are too broad. We suggest that this reflects the suppression of emissions by snow cover and greatly improve the model simulation by accounting for this effect. Our resulting best estimate for HBL methane emissions is 2.3 Tg a−1, several-fold higher than previous estimates (Roulet et al., 1994; Worthy et al., 2000).

scholarly journals Radiocarbon Reservoir Ages from Freshwater Lakes, South Georgia, Sub-Antarctic: Modern Analogues from Particulate Organic Matter and Surface Sediments

Radiocarbon ◽  
2004 ◽  
Vol 46 (2) ◽  
pp. 621-626 ◽  
Author(s):  
Steven G Moreton ◽  
Gunhild C Rosqvist ◽  
Sarah J Davies ◽  
Michael J Bentley
Keyword(s):  
Organic Matter ◽  
Particulate Organic Matter ◽  
Surface Sediment ◽  
Surface Sediments ◽  
Freshwater Lakes ◽  
South Georgia ◽  
Proxy Records ◽  
Paired Samples ◽  
Important Region ◽  
The Difference

Lake sediments have the potential to preserve proxy records of past climate change. Organic material suitable for radiocarbon dating often provides age control of such proxy records. Six shallow freshwater lakes on the sub-Antarctic island of South Georgia were investigated for carbon reservoir effects that may influence age-depth profiles from lake sediment records in this important region. Paired samples of particulate organic matter (POM) from the water column and surface sediment (bulk organic carbon) were analyzed by accelerator mass spectrometry 14C. POM in 4 lakes was found to be in equilibrium with the atmosphere (~107% modern), whereas 2 lakes showed significant depletion of 14C. In each lake, the surface sediment ages were older than the paired POM age. Surface sediment ages showed a much greater range of ages compared to the equivalent POM ages, even for lakes located in close proximity. We conclude that sediment disturbance during coring, bioturbation, and periodic resuspension of sediments are likely factors causing the difference in the apparent age of surface sediments.

Mosaics of vegetation and soil salinity: a consequence of goose foraging in an arctic salt marsh

1995 ◽  
Vol 73 (1) ◽  
pp. 75-83 ◽  
Author(s):  
Diane S. Srivastava ◽  
R. L. Jefferies
Keyword(s):  
Salt Marsh ◽  
Water Content ◽  
Soil Water ◽  
Surface Sediments ◽  
Plant Biomass ◽  
Hudson Bay ◽  
Upward Movement ◽  
High Biomass ◽  
Lesser Snow Geese ◽  
Evaporative Loss

Grubbing of roots and rhizomes of salt-marsh graminoids by lesser snow geese at La Pérouse Bay, Manitoba, on the Hudson Bay coast, has resulted in a vegetational mosaic. Bare sites, devoid of vegetation, occur adjacent to intact swards (high biomass sites). At some sites destruction of swards is incomplete (low biomass sites). In 1991 and 1992, highest soil salinities occurred in midsummer; surface sediments were flushed of salts by meltwater in spring and by tides in autumn. By late July, in both years, the soil was hypersaline in low biomass and bare sites, unlike that in the high biomass sites. The highest soil salinities were recorded in bare sites, especially in large bare patches. Aboveground plant biomass (g∙m−2) was a much better predictor of the salinity of soil water than the water content or redox potential of soil. Evaporative loss of water from tubes buried in sediments was higher in bare sites compared with that in vegetated sites. Differences in evaporation between sites led to large differences in the salinity of soil water but only small differences in soil water content. The upward movement of salts from buried Tyrell Sea sediments appears responsible for the development of hypersaline conditions. Key words: grubbing, goose grazing, plant biomass, sodium, soil water, hypersalinity.

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