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Vegetation measures

Mount Usu / Sarobetsu post-mined peatland
From left: Crater basin in 1986 and 2006. Cottongrass / Daylily


[ abudnance | dominance ]


The total number of individuals or amount of resources present in a specific area. Typically, used qualitative, relative, or subjective manner rather than an absolute number or amount.


For convenient use

The species is

  • A: abundant
  • C: common
  • F: frequent
  • O: occasional
  • R: rare

in the given area (or ecosystem)

Cover or coverage (被度)

The area of ground covered by plants. Usually we use the marginal projection of the aboveground parts of plants, shown below.

cover estimation frame

A: An example of frame for establishing quadrat (方形区) for the measurement of cover. ← field equipment (野外調査道具)
B: Cover is not for the absolute cover. We estiamte the projection of the plants, as indicated by interrupted lines.
Cover-abundance scale, or dominance scale

Table 2.1. A comparison of cover scales used to recording vegetation plots including the traditional Braun-Blanquet scale (1928), the original Domin scale (1928), a variant of the Domin scale by Krajina (1933), and the scales of the Carolina (Peet et al. 1998) and New Zealand vegetation surveys (Allen 1992). The brown letters indicate how the newer indices nest into the Braun-Blanquet scheme. (Modified after van der Maarel & Franklin 2013)

Range of coverBraun-BlanquetDominKrajinaCarolinaNew Zealand
Single individualr, solitary with small cover++11
Sporadic or few+, Few, with small cover (pronounced 'cross')1111
0-1%1, numerous, but less than 1/20 cover, or scattered, with cover up to 1/202121
5-10%2, any number, with 1/20-1/4 cover (5-25%)4453
25-33%3, any number, with 1/4-1/2 cover (25-50%)6674
50-75%4, any number, with 1/2-3/4 cover (50-75%)8885
75-90%5, any number, with cover more than 3/4 of the reference area (> 75%)9996
Daubenmire's cover classes

Class (%): 1 (0-5), 2 (5-25), 3 (25-50), 4 (50-75), and 5 (75-100)
(Daubenmire 1959)

Biomass (バイオマス)

The mass of living organisms in a given area (or ecosystem) at a given time. We often use dry mass for plant ecology. See also biome and productivity.
Biomass profile diagram
biomass profile
Phytomass (ファイトマス)
= plant biomass (biomass of the plants only)
Necromass (ネクロマス)
(s.s.) organic material consisting of or derived from dead organisms
(s.l.) the total mass of dead organisms (of a given type, in a given area, etc.)

population (個体群)

Density (密度)

The number of plants per unit area. Usually we use this parameter for trees and plants of which individuality is clearly recognized.

Frequency (頻度)

Number of plots that the target species occurs.

[ dominance | dominant species | type | references ]

Dominance (優占度)

  1. The (relative) degree to which one or a few species predominate in a community in terms of numbers, crown closure, importance, and/or biomass
  2. In genetics, the ability of one allele to suppress the phenotypic expression of another allele in the heterozygote. The suppressed allele is then recessive to the dominant allele.

In my lectures, the definition #1 is used.

Dominant species (優占種)
Species that is (are) dominant in the given area. The dominant species often characterize the community structure and function.


Relative density (相対密度, %)
= (number of individuals of a species)/(total # of individuals) × 100
Relative dominance (相対優占度) (%)
= (dominance of a species)/(dominance of all species) × 100
Relative frequency (相対頻度) (%)
= (frequency of a species)/(sum frequency of all species) × 100
Importance value (重要度) (IV)
= Relative density + relative dominance + relative frequency

(Max = 300), or

= (Relative density + relative dominance + relative frequency)/3

(Max = 100)