Variation in dry grassland communities along a heavy metals gradient.

Marcin W. Woch,Paweł Kapusta,Anna M. Stefanowicz

doi:10.1007/s10646-015-1569-7

Abstract

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.

Highlights

Heavy metals present in the soil at elevated concentrations can be the overriding factor of the plant species distribution
Since heavy metals are persistent contaminants, they affect the structure of plant communities on a short time scale, through the elimination of stress-sensitive species, and 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)
They occurred in three variants: (1) closed grassland dominated by Brachypodium pinnatum, (2) loose heavy metal grassland with Festuca ovina as the main component, and (3) grassland with woody and ruderal plants

Summary

Introduction

Heavy metals present in the soil at elevated concentrations can be the overriding factor of the plant species distribution. Since heavy metals are persistent contaminants, they affect the structure of plant communities on a short time scale, through the elimination of stress-sensitive species, and 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). 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)

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