Environmental Engineering Reference
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and mixed environmental strategies (Grime et al.
1988
; Betekhtina and Veselkin
2011
). Our data
do not allow arguments to accept or reject any of
the two hypotheses, but the second hypothesis
has a number of circumstantial evidence.
Extremeness of conditions of the investigated
dump is caused by several factors (Kuprijanov
and Manakov
2008
): fi rstly, high density of clay
substrates prevents seed reproduction on many
species; secondly, moderate and severe saliniza-
tion and low content of elements of mineral nutri-
tion; and thirdly, lack of water availability on
plots II and III. In conformity with the polymod-
elling concept of phytocenoses organization
(Mirkin and Naumova
1998
) studied communi-
ties best meet the abiotic S-model describing
communities of plants-patients (stress tolerants
by Grime et al.
1988
) in extreme abiotic condi-
tions. In such circumstances, competition is
weakened, and the structure and dynamics of
vegetation communities is determined in fi rst
place by regularities of populational dynamics
of individual species. To describe the succes-
sions in these communities, the most suitable is
the model of neutrality (Mirkin and Naumova
1998
). The applicability of this model to the
studied communities is confi rmed, in particular,
by observations of
Glycyrrhiza uralensis
,
Medicago falcata
,
Silene suffrutescens
,
Stipa
lessingiana
, and some other plants typical of
zonal communities. On plot III, these species
have settled in the fi rst favorable settlement for
the period before start of observations, i.e., in
the interval between 1971 and 1978. However,
over further 30 years, their seed reproduction was
not registered, probably due to increasing unfa-
vorable abiotic conditions. Therefore, these spe-
cies felt out of communities. Also, the pessimal
conditions (mostly salinization) are probably a
reason that to the dump such conventional weed-
steppe species with traits of competitive strategy
as
Centaurea cyanus
L. and
Echinochloa crus-
galli
(L.) Beauv. and typical steppe plants such as
Festuca valesiaca
were not found (Kuprijanov
and Manakov
2008
).
In compliance with the model of a neutral fl ow
of successions it can suggest the following expla-
nation of the observable facts. From the local pool
of species most of them (probably 70-85 %) are
mycorrhizal (Selivanov et al.
1964
; Eleusenova
and Selivanov
1973
); many species consistently
colonize dump. But the penetration rate in the
new location of non-mycorrhizal pioneer ruderals
(e.g., species Brassicaceae and Chenopodiaceae),
ruderals with features of stress tolerants (halo-
philic Chenopodiaceae) are higher than the rate
of penetration of mycorrhizal perennials from
Asteraceae, Fabaceae, and Poaceae families. This
explains the predominance of non-mycorrhizal
and facultative mycorrhizal plant species in the
fi rst period of colonization. Subsequent growth of
the mycorrhizal species is explained by the occu-
pancy of new mycorrhizal species. Disappearance
of non-mycorrhizal species from species counts
is expressed not clearly (see Table
3
). Over time,
the composition of species that can exist in harsh
abiotic conditions of the dump stabilized, and the
prevalence in it of mycorrhizal plants refl ects their
dominance in the local fl ora as a whole. It seems
that competitive advantages of mycorrhizal plants
may be more important in determining the abun-
dance of species at plots, i. e., of their participation
in the creation of a common covering or biomass of
communities.
In conclusion, we consider it necessary to draw
attention to the important fact for correct extrapo-
lation of described conformity to natural laws on
other situations. The subject of analysis in this
report is mycorrhizal status of plant species. This
characteristic, which is separated from the con-
crete conditions, describes only the probability of
the introduction of the individual or individuals of
cenopopulation in interaction with mycorrhizal
fungi. There are cases where mycorrhizas were
found sporadically in plants considered universally
non-mycorrhizal everywhere and conversely were
not found at the usual mycorrhizal plants. The last
is probably especially true for abiotic adverse
habitats (Nozadze
1989
) including technogenic
(Chibrik et al.
1980
) or disturbed pioneer habitats
(Miller
1979
). Thus, our data cannot be directly
interpreted as an indication of changing in the
course of succession tightness of interaction of
plants with arbuscular fungi in the investigated
dump. They only show that during spontaneous
development of vegetation, the ratio of plants that
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