Effets des contraintes (vents et embruns) sur la composition et la structure de la végétation des pentes drainées de l'île de la Possession (archipel Crozet, subantarctique)

1995 ◽  
Vol 73 (11) ◽  
pp. 1739-1749 ◽  
Author(s):  
Christopher Carcaillet
Keyword(s):  
Indian Ocean ◽  
Community Ecology ◽  
Key Words ◽  
Vegetation Dynamics ◽  
Salt Spray ◽  
Soil Surface ◽  
Vegetation Development ◽  
Vegetation Communities ◽  
Inhibition Model ◽  
Subantarctic Island

A study of the vegetation communities along two transects on the well drained slope of the Possession Island (subantarctic island, Indian Ocean) was carried out. The aim of this study was to investigate the structure of the vegetation under permanent pressure from gales and salt sprays and where there was no major perturbation. In the areas protected from gales, a Blechnum pennamarina community dominates. This fern hinders the vegetation dynamics in two ways : (i) by forming a very dense canopy that prevents sunlight from reaching shorter plants (passive competition) and (ii) by the accumulation of thick litter resulting from dead fronds. This community thus acts as the "inhibition" model of Connell and Slatyer. In areas exposed to gales and salt spray, B. pennamarina partly or completley disappears. The soil surface is consequently covered with several bryophytes and Azorella selago that form a mosaic on the soil surface. The vegetation dynamics end at this stage, despite the ability of B. pennamarina to colonize moss litter. The bryophyte community probably represent a stational climax stage acting as a "facilitation" model to B. pennamarina in an area protected from gales. It has therefore been concluded that the fernbrake community constitutes the optimal vegetation development on the well drained slopes of the Possession Island. Key words: climatic pressure, community ecology, bryophytes, Blechnum pennamarina, transect.

EFFECT OF CANOPY AND INCORPORATION ON METRIBUZIN PERSISTENCE IN SOILS

1989 ◽  
Vol 69 (3) ◽  
pp. 711-714 ◽  
Author(s):  
K. I. N. JENSEN ◽  
E. R. KIMBALL ◽  
J. A. IVANY
Keyword(s):  
Key Words ◽  
Half Life ◽  
Field Tests ◽  
Soil Surface ◽  
Bare Soil ◽  
Field Conditions ◽  
Row Width ◽  
Sampling Zone

The half-life of metribuzin applied to a bare soil surface was calculated to be 3–7 d over four field tests. An artificial cover erected after application or a shallow incorporation increased the half-life of metribuzin approximately 2.5- to 3-fold. Leaching out of the 0- to 5-cm-deep sampling zone could not account for loss of metribuzin. It was concluded that metribuzin persistence may be affected by volatility and/or photodecomposition losses under field conditions, especially shortly after application. Key words: Metribuzin half-life, volatility, photodecomposition, row width

scholarly journals Rituals and coutumes in the European slave trade on Madagascar in the 17th and 18th centuries

Afrika Focus ◽  
2016 ◽  
Vol 29 (2) ◽  
Author(s):  
Rafaël Thiébaut
Keyword(s):  
Indian Ocean ◽  
Key Words ◽  
Slave Trade ◽  
History Of ◽  
Indian Ocean World

In this text, we will retrace the commercial interactions linked to the slave trade between Europeans and Malagasy in the 17th and 18th centuries. As is often the case, this commerce was much more than a simple exchange of products, it can be termed a ritual, created by Malagasy sovereigns to which the Dutch and French merchants had to adhere. This ranged from presenting courtesy gifts up to the delivery of oral and written venerations, and represented an important cofirmation of power. The monarch often kept the upper hand over the Europeans who found themselves on hostile terrain, though the latter were not completely stripped of power as they effectively controlled the volume of this external commerce. Key words: slave trade, Indian Ocean World, local sovereignty, history of Madagascar, European companies 

Response of some vegetable crops to soil-applied halides

1992 ◽  
Vol 72 (4) ◽  
pp. 555-567 ◽  
Author(s):  
S. C. Sheppard ◽  
W. G. Evenden
Keyword(s):  
Key Words ◽  
Soil Surface ◽  
Competitive Interaction ◽  
The Other ◽  
Vegetable Crops ◽  
Tissue Concentrations ◽  
Industrial Pollutants ◽  
High Concentrations ◽  
Corn Kernels ◽  
Key Words Fluoride

The halide elements are environmentally important and share some common attributes. The heaviest, I, and the lighest, F, are quite toxic and are important industrial pollutants. They are also effectively retained in soils. The others, Cl and Br, can be accumulated to high concentrations in plants, are used in agriculture and are highly mobile in soils. This study investigated the behaviour of the halides in plots, outdoor lysimeters, and laboratory sorption and excised-root experiments. Sorption on soil was ordered as F > I > Br > Cl. Concentrations in plants were generally ordered as CI ≥ Br > > F ≥ I, the inverse of the sorption ordering, as expected. Older tissues, which were also closest to the soil surface, had higher concentrations, and sequestered tissues, such as corn kernels and cabbage heads, had lower concentrations. There was evidence of competitive interaction among the halides and with soil anions such as phosphate and sulfate. This competition reduced the toxicity of I and modified tissue concentrations of the halides, P and S. Another interesting interaction was an increase in Cl and I sorption on soil solids when there were elevated levels or the other halides. Overall, the study of the halides in combination enhanced our understanding of their individual behaviours. Key words: Fluoride, chloride, bromide, iodide, vegetable

scholarly journals Seabird recovery and vegetation dynamics after Norway rat eradication at Tromelin Island, western Indian Ocean

2015 ◽  
Vol 185 ◽  
pp. 85-94 ◽  
Author(s):  
M. Le Corre ◽  
D.K. Danckwerts ◽  
D. Ringler ◽  
M. Bastien ◽  
S. Orlowski ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Vegetation Dynamics ◽  
Western Indian Ocean ◽  
Norway Rat

scholarly journals Statistical assessment of vegetation dynamics within protected areas using remote sensing data

2013 ◽  
Vol 43 (4) ◽  
pp. 5
Author(s):  
Maria Elena Menconi ◽  
David Grohmann
Keyword(s):  
Remote Sensing ◽  
Protected Areas ◽  
Vegetation Dynamics ◽  
Vegetation Index ◽  
Photosynthetic Activity ◽  
Remote Sensing Data ◽  
Ratio Method ◽  
Vegetation Development ◽  
Sensing Data ◽  
Landscape Factors

This study aimed to test the effectiveness of protected areas to preserve vegetation. The first step was to identify vegetation suitable areas, designed as areas with optimal morphological terrain features for a good photosynthetic activity. These areas were defined according to the following landscape factors: slope, altitude, aspect and land use. Enhanced vegetation index (EVI) was chosen as vegetation dynamics indicator. This method is based on a statistical approach using remote sensing data in a geographic information system (GIS) environment. The correlation between EVI and landscape factor was evaluated using the frequency ratio method. Classes of landscape factors that show good correlation with a high EVI were combined to obtain vegetation suitable areas. Once identified, these areas and their vegetation dynamics were analysed by comparing the results obtained whenever these areas are included or not included in protected areas. A second EVI dataset was used to verify the accuracy in identifying vegetation suitable areas and the influence of each landscape factor considered in their identification. This validation process showed that vegetation suitable areas are significant in identifying areas with good photosynthetic activity. The effects analysis showed a positive influence of all landscape factors in determining suitability. This methodology, applied to central regions of Italy, shows that the vegetation suitable areas located inside protected areas are <em>greener</em> than those outside protected areas. This suggests that the protective measures established by the institution of the parks have proved to be effective, at least as far as the status of vegetation development is concerned.

Grass response to shrub removal in two semi-arid vegetation communities.

2000 ◽  
Vol 22 (2) ◽  
pp. 220 ◽  
Author(s):  
M Page ◽  
RJS Beeton ◽  
JJ Mott
Keyword(s):  
Key Words ◽  
Grazing Pressure ◽  
Grass Cover ◽  
Ecosystem Impacts ◽  
Vegetation Communities ◽  
Specific Research ◽  
Stable Component ◽  
South West ◽  
Semi Arid ◽  
Arid Vegetation

The control of woody weeds in the mulga lands of south-west Queensland is commonly regarded as essential for restoration of degraded systems. However, these shrubs have become a dominant and stable component of many mulga land ecosystems, and their removal may have unknown ecosystem impacts. This paper reports an experiment to determine the effect of woody weeds and grazing pressure on grass recruitment, cover and diversity in two vegetation communities in Queensland's mulga lands. Both factors influence grass recruitment, cover and diversity, but the response differs between the two vegetation communities investigated. The overall grass cover is consistently greater in sites where woody weeds were removed, and where grazing pressure was lowest. However, in the Dunefields community the cover and frequency of grass plants responded more to the removal of woody weeds than in the Mulga Sandplain community. In contrast, in the Mulga Sandplain community the grasses responded more to reducing or removing grazing pressure. Results suggest that subtle differences between systems influence grass dynamics, highlighting the need for community-specific research and management. Key words: shrub removal, semi-arid vegetation, vegetation communities, woody weeds

EFFECT OF TYPE, RATE AND INCORPORATION OF LIME AND OF NITROGEN FERTILIZER AND GYPSUM ON MOVEMENT OF LIME IN SOIL COLUMNS

1986 ◽  
Vol 66 (4) ◽  
pp. 757-762
Author(s):  
P. B. HOYT ◽  
B. G. DROUGHT ◽  
G. H. NEILSEN ◽  
E. HOGUE
Keyword(s):  
Key Words ◽  
Soil Ph ◽  
Nitrogen Fertilizer ◽  
Soil Surface ◽  
Deionized Water ◽  
N Fertilizer ◽  
Soil Columns ◽  
Downward Movement ◽  
Type Rate

Soil columns were used to study downward movement of calcite and dolomite applied at two rates on the soil surface or incorporated 0–5 cm deep in combinations with gypsum and surface-applied N fertilizer. The columns were irrigated with 800 mm of deionized water applied over 3 wk. Incorporation of the liming materials greatly accelerated their downward movement in soil. Calcite and dolomite were equally effective in raising soil pH at the lower depths. Neither gypsum nor fertilizer nor doubling the liming rate had much effect on lime movement. Key words: Lime movement, calcite, dolomite, gypsum

Vegetation development on skid trails and burned sites in southeastern British Columbia

1993 ◽  
Vol 69 (1) ◽  
pp. 75-80 ◽  
Author(s):  
E. T. Oswald ◽  
B. N. Brown
Keyword(s):  
British Columbia ◽  
Key Words ◽  
Tree Growth ◽  
Burned Area ◽  
Tree Seedlings ◽  
Vegetation Development ◽  
Engelmann Spruce ◽  
Forest Region ◽  
Invading Species ◽  
Study Sites

Vegetation development, including both planted and natural tree seedlings, was examined over a 5-year period on an area in the ESSFmw subzone of the Nelson Forest Region which was clearcut, skid logged, burned, and planted with 2 + 0, 313, Engelmann spruce. Study sites included the cutbank, mid-trail, and sidecast portions of the skid trails and the intervening prescribed burned area. Fireweed was the most prominent invading species, and affected tree growth, particularly on the sidecast, by shading and crowding the trees. Black huckleberry, regenerating from root stalks, was common on the burned sites, but had marginal influence on Engelmann spruce development over 5 years. The best tree growth occurred on the burned sites, followed by the sidecast, mid-trail, and cutbank sites. Consideration should be given to omitting the cutbank planting site and moving the mid-trail planting site inward on slopes of 30% or more. Key words: Engelmann spruce, ESSFmw biogeoclimatic subzone, slash burn, vegetation succession, fireweed

RELATIONSHIPS BETWEEN LEAF AND SOIL BORON AND BORON TOXICITY OF PEACHES IN BRITISH COLUMBIA

1985 ◽  
Vol 65 (1) ◽  
pp. 213-217 ◽  
Author(s):  
G. H. NEILSEN ◽  
P. B. HOYT ◽  
J. YORSTON ◽  
W. VAN LIEROP
Keyword(s):  
British Columbia ◽  
Key Words ◽  
Soil Profile ◽  
Soil Surface ◽  
Boron Toxicity ◽  
Leaf Boron

Soil and leaf boron were determined in British Columbia peach orchards exhibiting a range of B concentration, including suspected toxicity. B toxicity always occurred when leaf concentration in May exceeded 130 mg/kg, and frequently occurred when leaf B concentration in July was between 50 and 83 mg/kg. Revised leaf standards were suggested to indicate a desirable range of 26–50 mg/kg leaf B in July. Leaf and soil B for peaches were generally correlated. Exceptions occurred when soil B was concentrated near the soil surface or deep in the soil profile. Leaf B in July was from 26 to 50 mg/kg when soil B to a 90-cm depth ranged from 0.2 to 0.4 mg/L of soil. Key words: Boron toxicity, leaf and soil B, peaches

WIND EFFECT ON DISCER INCORPORATION OF HERBICIDE GRANULES INTO SOIL

1985 ◽  
Vol 65 (2) ◽  
pp. 239-247
Author(s):  
R. L. KUSHWAHA ◽  
W. B. REED
Keyword(s):  
Key Words ◽  
Soil Surface ◽  
Distribution Patterns ◽  
Wind Effect ◽  
Surface Distribution ◽  
Combined Operation ◽  
Wind Velocities

Soil surface distribution patterns of herbicide granules from a Gandy dribble type applicator were determined under different wind velocities in the laboratory and verified in the field. Results indicted that a combined operation of application and incorporation during seeding with a discer would not provide satisfactory placement of granules assuming wind velocities that occur normally in Saskatchewan during the seeding period. Key words: Wind, discer, herbicide granules, incorporation

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