Summary

In spring of 1990, in both of the control sampling plots the earthworm
population significantly reduced (Table 3.2). In other sampling plots such sharp
population reduction was not observed. Obviously, it is related to changes of the soil
structure in the eutrophicated sampling plots and formation of humus horizon under
the O horizon. Such soils become habitable for earthworms not only in the upper
layer, but also in deeper layers, what enables them to migrate deeper in case of
unfavourable meteorological conditions. Therefore, earthworm density in
eutrophicated biocenosis is less subordinate to sezonal fluctuations, than in noneutrophicated-
the soils conformable to natural biotypes.
16
12
8
4
0
C
C
CB
Pumpuri Jaundubulti Vaivari Bulduri 1 Bulduri 2 Dzintari
Figure 3.1. All season mean density of earthworms per sample in Jūrmala
Sample plots. Columns having equal letters are not statistically different (ANOVA, Ftest;
α = 0,05)
3.4.3. Soil property change impact on earthworm communities
Greater diferences in soil acidity of upper horizons (O, OAh) in comparision
with other plots were observed in the eutrophicated sampling plots of Bulduri 2 and
Dzintari (Table 3.1). In the non-eutrophicated and partly eutrophicated sampling
plots the soils are assessed as very acid, but in both eutrophicated sampling plots pH
value corresponds to moderately acid soils. Taking into consideration the great
B
A
A
26