Some Measures of Uniformity in Vegetation Analysis

Dahl, Eilif

doi:10.2307/1931822

Cited by 58 publications

(33 citation statements)

References 3 publications

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“…The similarity between vegetation units is expressed in % as the ratio between two times the number of species shared by two units, and the sum of the total number of species in the two units, multiplied by 100 (Sorensen 1948;Dahl 1957). An index of uniformity is calculated for each vegetation unit from the number of samples and the ratio between the total number of species sampled and the mean number of species per sample (Dahl 1960).…”

Section: Numerical and Statistical Methodsmentioning

confidence: 99%

Phytosociology and ecology of old hay meadows in Hordaland, western Norway in relation to management

Losvik¹

1988

Vegetatio

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Well-drained mown hay meadows in Hordaland, western Norway, were investigated. The hay meadows are either managed in a traditional or in a semi-traditional way. Traditional management in the area involves little or no use of manure or fertilizer, mowing once or twice a year with a first cut later than June 23, clearing in spring and intensive grazing for short periods in spring and autumn. Semi-traditional management involves use of small to medium quantities of commercial fertilizer, often in addition to manure. Grazing may be irregular, light or lacking.Eight units of hay meadow vegetation are described, all assigned to the class Molinio-Arrhenatheretea, orderArrhenatheretalia; four units to the Atlantic alliance Cardaminion pratensis, association CardaminopratensisConopodietum majoris (with three subassociations); one unit to the alliance Arrhenatherion elatioris, three units are provisionally grouped as Galium uliginosum-Knautia arvensis meadows.Continuous management of these meadows has resulted in characteristic species compositions, which vary along a west-east climatic gradient, and are related to the amount of commercial fertilizer used and the natural mineral-content of the soil.These hay meadows seem to be best maintained by continuing the traditional management regime. Grazing in spring and in autumn reduces fast growing dominants and creates openings for new seedlings of annuals and biennials. A late first cut allows for ripening of the seeds and creates openings for light for the species of the lower field layer. A list of species characteristic of traditionally managed permanent hay meadows is presented, and possible effects of present changes in management on the species composition of the meadows are discussed.The amount of organic matter in the topsoil is small in most stands. The pH values are between 4.0 and 5.6. The highest values were recorded in soil where little or no commercial fertilizer is used, and where the subsoil is naturally rich in minerals. A tendency to Mg impoverishment in the best fertilized stands is demonstrated. Species-rich stands on Ca-rich soils are poor in P.The expected changes in vegetation, future use, and conservation of permanent hay meadows in Hordaland are discussed.

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Section: Numerical and Statistical Methodsmentioning

confidence: 99%

Phytosociology and ecology of old hay meadows in Hordaland, western Norway in relation to management

Losvik¹

1988

Vegetatio

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“…A number of expressions of homotoneity is available (e.g. Dahl, 1960;Westhoff & van der Maarel, 1973;Whittaker, 1972) but there is difficulty in interpreting values since they lack standardization. However, by all measures we used, our lateritic upland vegetation appears very heterotoneous.…”

Section: Species Richness Homotoneity Fidelitymentioning

confidence: 99%

“…for the two quotients. We calculate Curtis ' (1959) index of homogeneity as 62% and Dahl's (1960) index of uniformity as 0.85. Beta diversity, calculated simply as (total species/mean richness)-I is 3.5.…”

Section: Species Richness Homotoneity Fidelitymentioning

confidence: 99%

Regional variation in mediterranean-type shrublands near Eneabba, south-western Australia

Griffin¹,

Hopkins

Hnatiuk³

1983

Vegetatio

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Kwongan vegetation (sclerophyllous shrublands) growing on a single soil type was surveyed over a 5 000 km 2 area centered about Eneabba, Western Australia. All samples were on laterite, a deeply weathered, infertile soil developed since the Tertiary over much of the ancient, subdued landscape of south-western Australia. The vegetation was rich in angiosperm plant species and, although quite uniform in structure, highly variable floristically, suggesting the existence of a complex mosaic of species distributions. Of the four floristic groups defined using both ordination and classification techniques, the group including the Mt Lesueur area was the most distinctive. Site groupings were predominantly regional although the influence of climatic factors, particularly potential evaporation, was significant. Biogeographic patterns of each of the major plant families were not coincident. The geographic arrangement of the floristic groups does not correspond with existing vegetation maps compiled primarily on the basis of physiognomy.

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“…2 Boyd calls this process the OODA Loop and likens it to a turning fighter engagement. The idea is that if one can turn inside their adversary they can defeat them.…”

Section: The Decision Making Processmentioning

confidence: 99%