Environmental Engineering Reference
In-Depth Information
F i g . 4
a
-
c
Approximation of the relationship between
fractions of non-mycorrhizal (
a
), facultative mycorrhizal
(
b
), and mycorrhizal (
c
) plant species and duration of suc-
cession in different parts of the dump (I, II, and III - plots)
by logistic curves.
Asterisk
- position of the
bottom
(
a
,
b
)
and
top
(
c
) of critical points marking the end of a period of
rapid change of indicators
which absolute (in years) duration of existence is
known have allowed to characterize quantita-
tively the rate of change in the ratio of plants of
different groups of mycotrophy. We believe pre-
cise dating of events occurring during the forma-
tion of communities to be a signifi cant advantage
for the observation of successions on artifi cial
anthropogenic substrates. According to our
data, the ratio of the number of species of dif-
ferent groups of mycotrophy stabilizes fairly
quickly. Within the fi rst 5 years of overgrowth,
the share of mycorrhizal species reaches about
60-70 % on all plots and doesn't subsequently
change.
The observed changes are explained with the
help of two hypotheses. The fi rst assumption is
that there is lower competitiveness of non-
mycorrhizal species as compared with mycorrhi-
zal ones. Greater competitiveness of mycorrhizal
species was demonstrated experimentally
(Heijden et al.
1998
,
2003
), and this explanation
is accepted in part of studies, describing succes-
sions in natural communities (Pezzani et al.
2006
; Püschel et al.
2007a
). The second assump-
tion is that the ratio of different types of mycot-
rophy in the course of succession may depend
only on their rate of settlement, i.e., ruderal, or
on the level of reactivity of different species. The
positive relationship between ruderal of Grime
et al.'s (
1988
) environmental strategy and the
avoidance of mycorrhizal fungi has been dis-
cussed previously (Grime et al.
1988
; Francis
and Read
1995
; Cornelissen et al.
2001
). There
is a known pattern of increased occurrence of
non-mycorrhizal species among species with
ruderal strategy as compared with competitive
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