SOIL ORGANISMS - Soil Ecology - page 282

Even higher densities of 90,000 to 150,000 ind. were found in moist temperate
coniferous or deciduous forests, e.g., Douglas fir ( Pseudotsuga menziesii ) plantations in
Wales (O'Connor, 1967), beech ( Fagus sylvatica ) forest at Solling (Germany) (Schauer-
mann, 1977) and in Japanese subalpine forests (Kitazawa, 1977). However, low temper-
atures and moisture constraints strongly limit populations of Enchytraeidae. Much lower
densities have been recorded from forests in Scandinavia, USSR and Alaska: 27,500
to 90,000 ind. in a range of Finnish forests (Huhta et al., 1986), 10,000 to 25,000
ind. in Swedish pine forests (Lundkvist, 1981) and Hungarian deciduous forests
(Dozsa-Farkas, 1987) and only 3,800 to 6,800 ind. in coniferous and deciduous
woodlands in northern Sweden (Lohm et al., 1977). In temperate climate grasslands,
relatively low densities have been recorded: for example, 18,000-35,000 ind. at
Spiboke (Sweden) (Persson and Lohm, 1977), 10,000-25,000 ind. in a grassland on
limestone at Moor House (England) and 5,000-10,000 ind. in grass and lucerne leys at
Kjettslinge (Sweden) (Axelsson et al., 1984). In tropical soils, Enchytraeidae are either
absent or limited to a few hundred individuals per square metre in grasslands (Athias et
al., 1974) to a few thousand in forests (Chiba et al., 1975).
The abundance of Enchytraeidae is also related to the organic matter regime with
higher concentrations in mor than mull-type humus. These relationships, however, may
be minor in relation to the major temperature and moisture effects.
Most biomass estimates range from 1.3 to 13 g f wt (Petersen and Luxton, 1982).
The ratio of fresh to dry weight being 6.7 on average (Persson and Lohm, 1977). A max-
imum value of 53 g f wt was recorded from a Juncus moor at Moor House in England
(Cragg, 1961). The highest biomasses (>1 g dry wt, i.e., ca. 6.6 g f wt on average) have
generally been recorded in 'mild' tundra soils where individuals are generally larger than
in temperate and tropical soils. In temperate soils, biomass generally ranges between 1
and 10 g f wt (Petersen and Luxton, 1982) with exceptionally high values at Soiling,
in a German beech forest on a moder soil (Schauerman, 1977).
4.2.3.2 Community Structure
Species richness
Enchytraeid communities are generally not highly speciose. A maximum species richness
of 22 was recorded from meadows in the North of England (Standen, 1984), 21 in mull-
type soils in Norway (Abrahamsen, 1971) and 20 in hornbeam ( Carpinus sp.) forest in
Hungary (Dozsa-Farkas, 1987). However, 17 species were found in an apple orchard
in Bohemia (Chalupsky and Leps, 1985) and 10 in northern deciduous woodlands in
Sweden (Axelsson et al., 1984). Nonetheless, most communities include 3 to 7 species
(Persson and Lohm, 1977; Petersen and Luxton, 1982; Lagerlöf, 1987) and in some
Scandinavian coniferous forests, Cognettia sphagnetorum, an asexually reproducing
species may represent 90 to 100 % of the community (Lundkvist, 1981).
Spatial Distribution
Most Enchytraeid species have quite wide geographical distributions and some may
colonise a wide range of different habitats ( e.g., water courses, dry sandy soil or raw
humus) (Dash, 1990).