Aspects saisonniers de la fixation de l’épifaune benthique de l’étage infralittoral de l’estuaire du Saint-Laurent

1973 ◽  
Vol 30 (7) ◽  
pp. 867-880 ◽  
Author(s):  
E. Bourget ◽  
G. Lacroix
Keyword(s):  
Interspecific Competition ◽  
Salinity Gradient ◽  
Settlement Period ◽  
Competition For Space ◽  
Polydora Ciliata ◽  
June July ◽  
Autumn And Winter ◽  
Balanus Balanoides ◽  
Hydrodynamic Factors ◽  
Hard Substrata

This work conducted during two seasons (May–October 1969, 1970) was designed to study the dynamic aspects of the settlement of benthic epifauna on hard substrata. The stations were distributed on a 200-km distance, the salinity gradient ranging from 15 to 27‰. Although over 60 species were identified on the plates, the analysis shows that only three of these are abundant: Polydora ciliata, Balanus balanoides, and Balanus crenatus. In general, the settlement period of the species is very short and most of the settling processes are concentrated in June, July, and August. The populations reached a peak of abundance during settlement and decreased regularly afterwards. This decrease is due mainly to intraspecific and interspecific competition for space, accumulation of sediment, and hydrodynamic factors in autumn. The marked physical seasonality of this subarctic environment, more than true biotic succession, is reflected in the development of the community: during the summer, the community is biologically accommodated, whereas in autumn and winter it is physically controlled.

Cellular Automaton Models of Interspecific Competition for Space--The Effect of Pattern on Process

1992 ◽  
Vol 80 (3) ◽  
pp. 527 ◽  
Author(s):  
Jonathan Silvertown ◽  
Senino Holtier ◽  
Jeff Johnson ◽  
Pam Dale
Keyword(s):  
Cellular Automaton ◽  
Interspecific Competition ◽  
Competition For Space

Competition and the response of three plant species to a salinity gradient

1991 ◽  
Vol 69 (11) ◽  
pp. 2497-2502 ◽  
Author(s):  
N. C. Kenkel ◽  
A. L. McIlraith ◽  
C. A. Burchill ◽  
G. Jones
Keyword(s):  
Salt Tolerance ◽  
Interspecific Competition ◽  
Poa Pratensis ◽  
Salinity Gradient ◽  
Belowground Biomass ◽  
Peak Performance ◽  
Total Biomass ◽  
Salinity Response ◽  
Hordeum Jubatum ◽  
Puccinellia Nuttalliana

Three grasses (Poa pratensis, Hordeum jubatum, and Puccinellia nuttalliana) were grown in monoculture and three-species mixture at each of eight salinity levels in a controlled environment chamber. In monoculture, all species grew best when no salts were added to the nutrient medium. When salts were added the species showed differing degrees of salt tolerance. Percent decreases in total biomass with increasing salinity and shifts in aboveground to belowground biomass ratios suggested increased salt tolerance in the order P. pratensis < H. jubatum < P. nuttalliana. In mixture, all species showed a significant change in salinity response when compared with their responses in monoculture. Interspecific competition resulted in P. pratensis being suppressed at all but the lowest salinities. Hordeum jubatum showed the least suppression at intermediate salinities, while P. nuttalliana was least suppressed at the highest salinities. These results indicate that interspecific competition results in a shift in the peak performance of more salt-tolerant species toward the high end of the salinity gradient. The species distributions in our experimental mixtures reflected those observed in the field, suggesting that competition plays an important role in structuring inland saline plant communities. Key words: halophyte, glycophyte, community, Hordeum jubatum, Puccinellia nuttalliana, Poa pratensis.

Seasonal variations in the component fatty acid distributions of the lipids of Balanus balanoides

1972 ◽  
Vol 52 (4) ◽  
pp. 839-845 ◽  
Author(s):  
Doris Gardner ◽  
J. P. Riley
Keyword(s):  
Fatty Acid ◽  
Seasonal Variations ◽  
Marked Decrease ◽  
Early Spring ◽  
Component Fatty Acid ◽  
Lipid Fractions ◽  
Phospholipid Ratio ◽  
June July ◽  
Food Reserves ◽  
Balanus Balanoides

A study has been made of the seasonal variations in the component acids of the lipid fractions of Balanus balanoides. The relative proportions of the polyenoic acids in the triglycerides drop sharply during the winter. They reach a minimum in the early spring and then gradually rise to a maximum in the late autumn. These changes are largely balanced by increases in the saturated acids, principally 16:0 and 18 :o.1 During the winter there is a marked decrease in the triglyceride to phospholipid ratio as the depot fats are mobilised as food reserves. The proportions of the polyethenoid acids in the phospholipids decline slowly during the winter and spring and attain their minimum in June-July. This fall is mainly counterbalanced by increases in the amounts of saturated acids, principally 14:0 and 16:0. It seems likely that the observed decreases in the polyenoic acids are brought about by selective utilization of these compounds as reserves during the winter when food is scarce and depot lipid has been depleted.

The Spread of Elminius Modestus Darwin In North-West Europe

1958 ◽  
Vol 37 (2) ◽  
pp. 483-520 ◽  
Author(s):  
D. J. Crisp
Keyword(s):  
East Coast ◽  
Irish Sea ◽  
North Coast ◽  
Long Distance ◽  
North West ◽  
The North ◽  
Competition For Space ◽  
South East England ◽  
The Irish Sea ◽  
Balanus Balanoides

Material collected prior to 1940 indicates that Elminius modestus was not present on British coasts at that time.Elminius increased in abundance in south-east England from 1946 to 1950 and extended its range as far as the Humber, where it halted.Its advance westwards along the south coast was similarly halted at Portland, but by 1948 independent colonies had been established in several of the river systems of Devon and Cornwall, in Milford Haven, and in the Bristol Channel.The first populations in the Irish Sea were in Morecambe Bay. From there Elminius spread rapidly south and west along the north coast of Wales, and more slowly north and west towards Galloway, eventually bridging the sea to the Isle of Man.Detailed observations showed that Elminius advanced along the uniformly favourable north coast of Wales as a definite front moving at a rate of approximately 20–30 km per year. Around Anglesey where tidal currents were stronger it appeared simultaneously in many scattered centres.A distinction is drawn between marginal dispersal taking place under the influence of normal agencies at the boundary of an existing population, and remote dispersal due to an artificial or freak transport over a long distance. In the case of Elminius the maximum distance that is likely to be bridged by marginal dispersal in the absence of strong residual drifts is about 30 miles.Elminius probably first appeared near Southampton, and was introduced into the Thames estuary area probably by remote dispersal. Thence it spread along the east coast and was transported to Holland. Its extension into south Devon, the Bristol Channel, the Irish Sea, and to the French coast must also be attributed to remote dispersal.The main ecological effects of Elminius result from competition for space with Balanus balanoides. Since Elminius breeds in summer, its dominance has a profound effect on the composition of the summer plankton, greatly increasing the number of barnacle nauplii, presumably at the expense of other larvae.

A field study of settlement behaviour in Balanus balanoides and Elminius modestus (Cirripedia: Crustacea) in relation to competition between them

1979 ◽  
Vol 59 (3) ◽  
pp. 575-580 ◽  
Author(s):  
B. E. Barnett ◽  
S. C. Edwards ◽  
D. J. Crisp
Keyword(s):  
Field Study ◽  
Growth Rates ◽  
Intraspecific Competition ◽  
Intertidal Zone ◽  
South West ◽  
Competition For Space ◽  
Balanus Balanoides ◽  
Settlement Behaviour

There can be little doubt that competition for space, both inter- and intraspecific is a major factor in barnacle ecology. Southward & Crisp (1956) first pointed out the role of competition between Balanus balanoides (L.) and Chthamalus stellatus (Poli) in south-west Britain which Connell (1959, 1961) later demonstrated experimentally. Crisp (1958) discussed competition between the indigenous B. balanoides and the immigrant Elminius modestus Darwin in the intertidal zone, and measurements of growth rates, using manipulated populations of these two species, indicated that inter- and intraspecific competition for space after settlement is intense (Crisp, 1964).

Sexual maturity and related phenomena in the domestic fowl

1955 ◽  
Vol 46 (1) ◽  
pp. 9-18 ◽  
Author(s):  
E. S. E. Hafez ◽  
G. A. R. Kamar
Keyword(s):  
Growth Rate ◽  
Body Weight ◽  
Domestic Fowl ◽  
Sexual Maturity ◽  
Growth Curves ◽  
Effect Of Temperature ◽  
Relative Growth ◽  
Heavy Body ◽  
June July ◽  
Autumn And Winter

Three hundred and eighty-two Fayomi pullets were available from different hatches throughout the year. The age and body weight, as well as the weight of first eggs at sexual maturity in relation to growth curves, were recorded. The fertilizability and hatchability of the first eggs laid at sexual maturity were also examined from one hundred pullets hatched during the months of November and August.1. (a) The winter hatches (December, January and February) reached sexual maturity at 183 days and at a body weight of 1093 g. The weight of the first ten eggs was 31·8 g., while the period from first to the tenth egg was 26 days. Summer hatches (June, July and August) reached sexual maturity at 165 days and at a body weight of 1124 g., while the weight of the first ten eggs was 32·4 g. and the period from first to tenth egg was 31 days. Autumn hatches (September, October and November) reached sexual maturity at 159 days and at a body weight of 1023 g., while the weight of the first ten eggs was 31·4 g. and the period from first to tenth egg was 23 days.(b) Summer and winter hatches attained sexual maturity at an older age and heavier body weight, and laid heavier first ten eggs in a longer period than autumn hatches.2. The growth curves were higher for the summer hatches than for the spring (March, April and May) ones. Winter and autumn hatches were intermediate. Summer hatches attained sexual maturity at a higher relative growth rate than autumn and winter hatches. In Egypt (30° N.), the effect of temperature seems to override that of daylength in respect to growth and sexual maturity.3. Yearly differences in the attainment of sexual maturity were significant, mainly in December hatches. Individual differences were minimized during summer hatches.4. (a) The first egg laid can be fertilizable and even hatchable. When sexual maturity was attained at an old age or a heavy body weight, the first eggs laid had a greater chance of being fertilizable and hatchable. This is due to the weight of first eggs laid and to the season at which sexual maturity is attained.(b) The attainment of sexual maturity as measured by the fertilizability and hatchability of first eggs, seems to be a gradual phenomenon.

Interspecific Competition for Space Between Wetland Plants with Clonal Growth

Wetlands ◽  
2014 ◽  
Vol 34 (5) ◽  
pp. 1003-1012 ◽  
Author(s):  
Étienne Paradis ◽  
Marie-Ève Bellavance ◽  
Bastien Fontaine ◽  
Jacques Brisson
Keyword(s):  
Interspecific Competition ◽  
Clonal Growth ◽  
Wetland Plants ◽  
Competition For Space

The distribution and phenology of arbuscular mycorrhizae along an inland salinity gradient

1995 ◽  
Vol 73 (9) ◽  
pp. 1318-1327 ◽  
Author(s):  
Perry C. Johnson-Green ◽  
Norm C. Kenkel ◽  
Thomas Booth
Keyword(s):  
Arbuscular Mycorrhizal Fungi ◽  
Soil Salinity ◽  
Mycorrhizal Fungi ◽  
Arbuscular Mycorrhizae ◽  
Salinity Gradient ◽  
Arbuscular Mycorrhizal ◽  
Early Spring ◽  
Vegetation Zones ◽  
Salt Pan ◽  
June July

The distribution and seasonal patterns of arbuscular mycorrhizal fungi activity were studied in an inland boreal salt pan site in north-central Manitoba. Semipermanent study regions were set up in each of five vegetation zones along a continuous salinity gradient. Roots of Hordeum jubatum, Distichlis stricta, Agropyron trachycaulum, Sonchus arvensis, Spartina gracilis, and other species were collected from the study regions over six time periods: April, June, July, August, and October of 1991, and May of 1992. These roots were used to quantify mycorrhizal colonization, as well as arbuscule and vesicle formation. Arbuscular mycorrhizal fungi were prevalent in the three vegetation zones with lowest soil salinity, with > 40% of the observed root pieces colonized. Colonization was < 2% in the other two zones, where soil salinity was consistently greater throughout the growing season. The only common pattern in the phenology of mycorrhizal activity was a low level of activity in the early spring. Mycorrhizal activity in most plant species occurred at high levels throughout the summer and fall. Differences in patterns of activity appeared to be linked to differences in phenology of root growth, and not to edaphic differences among vegetation zones. Key words: Manitoba, arbuscules, fungi, gradient, mycorrhiza, phenology, salinity, vesicles.

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