Agriculture Reference
In-Depth Information
Results
The morphological traces of earthworm activity in soil can be explained tentatively by the physi-
cochemical data, particularly by ionic equilibria in the soil solution. Earthworm activity in the soil
was evidently species specific, but it depended on soil type. Calcophilous species can induce well-
developed vermic characters in rendzina, which represents their natural habitat, but when placed
in acid soils, especially in acid brown soil, they do not. The size of the structural elements in soil
(casts and burrows) depends on the size of the earthworms, but their stability and degradation are
conditioned by differences between soil types, especially by the chemical and physicochemical
properties of plasma, and texture. Thus, in a rendzina, because of the existing chemical equilibria
and physical properties, the vermic structure is more stable than in acid brown soil, in which the
casts rapidly break down. The nature of the cement of soil aggregates depends on the soil chemical
composition, but differences detected in the cement composition of the casts of the two
Octodrilus
species showed a specific or selective influence of the earthworms on soil structure. The CaCO
3
treatment of soil leads to a marked improvement in soil structure (i.e., in the conservation and
stabilization degree of both discrete earthworm casts and burrow layers). Special neoformations
with calcium, iron, and aluminum were observed in different parts of the soil profile. These included
ferric and humic earthworm burrow linings in variants with acid soils, which could be regarded as
protecting the earthworms against adverse environmental conditions, and semicolloidal and semi-
crystalline gels, the function of which is unknown.
The alterations induced in soil by earthworms are sometimes so great that they affect not only the
mobile ionic structure of the soil, but also the clay minerals (i.e., its most stable constituents). If the
bioaccumulation of potassium and the changes in clay mineral ratio detected in our experiments actually
represent an illitization (alteration of the structure of clay minerals), then this could be evidence that
earthworms can produce much more rapid and profound changes in soils than hitherto believed. It is
generally accepted that profound alterations in soils are very slow, taking hundreds or thousands of
years. Our experiment lasted only 16 months, so this issue needs further investigation.
CONSERVATION OF THE ENDEMIC
OCTODRILUS
SPECIES IN
THE CARPATHIANS
The endemic
Octodrilus
species, which have proved to be interesting for science and important to the
stability of unique natural ecosystems in the Carpathians, are endangered by two common human
activities: creation of air-soil pollution and sylvicultural cutting, especially clear-felling of the forests.
E
FFECTS
OF
A
IR
P
OLLUTION
ON
E
ARTHWORMS
The largest part of the Romanian Carpathians is currently protected from or is not affected by
destructive air pollution. Nevertheless, over a limited area, air pollution does affect earthworms,
as well as whole ecosystems. The earthworm fauna from one of the most polluted areas in Romania
(namely, the Ampoiu valley) in the Apuseni Mountains was investigated (Pop 1987). Here, sulfur
dioxide and dusts containing heavy metals are discharged into the air from a metal-chemical works
in Zlatna. The effects of these on the earthworm populations were directly related to the distance
from Zlatna. In an old beech forest with well-developed tall trees in the immediate neighborhood
of the pollution source, I found no earthworms. The vegetation and soil type, as well as a study of
several unpolluted control forests, indicated that conditions would normally be suitable for an
earthworm community such as
O. frivaldszkyi, Allolobophora dugesi, A. rose
a
, D. byblica
, and
D.
clujensis
, with an approximate density of 15 to 20 earthworms per square meter and a biomass of
35 to 50 g per square meter.
Earthworms in the most polluted area, which includes the beech forest near the chemical works,
were presumably killed either by the direct action of pollutants or by starvation induced by
