Variation in dry grassland communities along a heavy metals gradient
Variation in dry grassland communities along a heavy metals gradient
Marcin W. Woch 0 1 2 3 4
Paweł Kapusta 0 1 2 3 4
Anna M. Stefanowicz 0 1 2 3 4
0 Anna M. Stefanowicz
1 Paweł Kapusta
2 & Marcin W. Woch
3 W. Szafer Institute of Botany, Polish Academy of Sciences , Lubicz 46, 31-512 Krako ́w , Poland
4 Institute of Biology, Pedagogical University of Krako ́w , Podchora ̨ z_ych 2, 31-054 Krako ́w , Poland
The aim of this study was to investigate the variation in plant communities growing on metal-enriched sites created by historical Zn-Pb mining. The study sites were 65 small heaps of waste rock covered by grassland vegetation and scattered mostly over agricultural land of southern Poland. The sites were described in terms of plant coverage, species richness and composition, and the composition of plant traits. They were classified using phytosociological methods and detrended correspondence analysis. Identified plant communities were compared for vegetation parameters and habitat properties (soil characteristics, distance from the forest) by analysis of variance. The variation in plant community parameters was explained by multiple regression, in which the predictors were properties of the habitat selected on the basis of factor analysis. Grasslands that developed at low and high concentrations of heavy metals in soil were similar to some extent: they were composed on average of 17-20 species (per 4 m2), and their total coverage exceeded 90 %. The species composition changed substantially with increasing contamination with heavy metals; metal-sensitive species withdrew, while the metal-tolerant became more abundant. Other important predictors of community structure were: proximity to the forest (responsible for the encroachment of competitive forest species and ruderals), and the thickness of the surface soil (shallow soil favored the formation of the heavy metal grassland). The heavy metal grassland was closely related to the dry calcareous grasslands. The former was an earlier succession stage of the latter at low contamination with heavy metals.
Historical mining; Heavy metal; Dry grassland; Species richness; Species composition
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Heavy metals present in the soil at elevated concentrations
can be the overriding factor of the plant species
distribution. Numerous studies on the vegetation of metalliferous
sites showed that plant species richness and composition
changed dramatically under the influence of soil
contamination with arsenic, cadmium, chromium, copper, lead,
mercury, nickel or zinc (e.g. Simon 1978; Clark and Clark
1981; Lejeune et al. 1996; Brown 2001; Proctor 2003;
Strandberg et al. 2006; Becker and Bra¨ndel 2007; Va´lega
et al. 2008; Myking et al. 2009; Lucassen et al. 2010;
Mapaure et al. 2011; Pandey et al. 2015). Since heavy
metals are persistent contaminants, they affect the structure
of plant communities not only on a short time scale,
through the elimination of stress-sensitive species, but also
in the long term, by exerting a strong selective pressure on
local populations leading to the emergence of new
metaltolerant ecotypes/varieties (Prasad and Hagemeyer 1999;
Ernst 2006; Baker et al. 2010).
The most conspicuous effect of microevolution induced
by heavy metals is endemic metallophytes. They are
obligate metallophytes, i.e. they have developed various
adaptations to cope with metal toxicity and are restricted
to metal-enriched habitats (Kruckeberg and Kruckeberg
1989; Prasad and Hagemeyer 1999). Currently, a high rate
of population decline of these species is recorded, which
provokes actions towards their conservation (Whiting et al.
2004; Baker et al. 2010; Baumbach 2012). Other
metallophytes are more cosmopolitan (facultative
metallophytes). They are derived from common species and,
owing to their great genetic and phenotypic plasticity, can
colonize both metalliferous and non-metalliferous soils
(Ernst 2006).
The residual nature, extreme fragmentation and
dispersion, and a great geochemical diversity of metal-enriched
habitats as well as floristic peculiarity of some (the
occurrence of very rare endemics) make it difficult to
perform large-scale studies that could improve our
understanding of the European heavy metal grassland. Studies
concerning the relationship between the concentration of
heavy metals in soil and plant species distribution are
usually based on a fairly dense sampling of single and
relatively small areas (Simon 1978; Brown 1994;
Strandberg et al. 2006; Becker and Bra¨ndel 2007; Grodzin´ska and
Szarek-Łukaszewska 2009). The effect of heavy metals on
vegetation can be difficult to assess in these types of works,
because it is often partly related to other soil
characteristics, such as pH, Ca concentration, or thickness of organic
layer (Simon 1978; Brown 1994; Becker and Bra¨ndel
2007). Moreover, strong connections (short distances)
between the surveyed vegetation patches may significantly
bias data by spatial autocorrelation—the structure of a
plant co (...truncated)