Agriculture Reference
In-Depth Information
TABLE 7.5
Proportion of Total Density (D%) and Biomass (B%) of Lumbricid Species in Three Soil
Types with Vermic Characters from the Carpathians
Cambic Rendzina, Padis,
August 16, 1979
Brown Earth, Buces Vulcan,
June 6, 1972
Podzolic Brown, Abrud,
June 12, 1992
Species
D%
B%
D%
B%
D%
B%
Allolobophora dacica
26.5
2.2
13.9
1.7
Dendrobaena alpina
12.l
0.8
Dendrobaena byblica
22.7
1.2
4.4
0.4
25.0
1.5
Dendrobaena clujensis
2.2
6.0
22.2
6.6
Lumbricus polyphemus
1.5
0.3
Octolasium lacteum
2.9
0.6
5.6
0.4
Octodrilus aporus
48.5
92.5
Octodrilus bihariensis
15.2
7.0
Octodrilus compromissus
11.8
1.7
Octodrilus exacystis
4.4
2.3
Octodrilus frivaldszkyi
28.8
85.0
Octodrilus permagnus
33.3
89.8
Total community (g/m
2
)
66.0
257
34.0
200
18.0
98.0
of 256 g/m
2
was recorded in the cambic rendzina, followed by that in the eubasic brown earth (200
g) and a much lower biomass of 98 g/m
2
in the podzolic brown soil.
M
ORPHOLOGY
AND
M
ICROMORPHOLOGY
OF
S
OIL
P
ROFILES
All three soil types are rather shallow, with a depth of 50 to 60 cm in rendzina and podzolic brown
soils and 70 to 80 cm in eubasic brown earth. Coarse rocky fragments occur sparsely in the A
horizon, up to 10 to 20% in the AB, and more than 40 to 50% in the B horizons (
Figure 7.14
)
(Pop
and Vasu 1995).
The most distinctive feature of these soils is the presence of a 4- to 6-cm thick surface layer
of discrete, stable, and large (2 to 4 cm in diameter) earthworm casts. The earthworm cast layers,
described as Am′ (mollic) or Aou (ochric-umbric) horizons, consist of old, hardened, and rather
rounded earthworm casts, not linked or united together, as well as fresh casts, mostly in conical
heaps. Such a cast heap can weigh as much as 200 to 300 g (oven dried).
All the species of cohabiting earthworms must interact to influence soil formation, but the more
evident and quite unusual traces or characters are those produced by the giant species. The size of
the structural elements in the soil (burrows and casts) depends on the size of the earthworms and
is species specific. Experimental studies suggested that the stability or degradation of the surface
earthworm casts is conditioned by the physicochemical properties of the plasma and the texture of
the soil, in which calcium plays an important role; in rendzina, the vermic structure, produced by
the same species, is more stable than in acid soils (Pop et al. 1992).
In the deeper horizons, the diameter of the earthworm casts diminishes, and the horizons appear
more compact. The A horizon has a crumb structure; the AB and B horizons have an angular blocky
structure. Earthworm burrows with a diameter up to 1.5 cm occur through the entire soil profile.
Micromorphological studies showed that the earthworm cast structure does not totally disappear
even in the deeper horizons. Reliable evidence of the strongly vermic character of these soils is
shown in a series of structure photograms of the rendzina profile to the depth of 40 cm; the presence
of hard rocks hindered us from sampling deeper
(
Figure 7.15
)
.
