Do heavy-metal grassland species survive under a Scots pine canopy during early stages of secondary succession?

Abstract

The highly specialized flora of localities affected by former metal ore mining and metallurgy is endangered by succession or intentional afforestation all over Europe. Its last remnants therefore deserve our attention. We examined whether Scots pine encroaching on a heavy-metal grassland (Olkusz Zn-Pb mining area, S Poland) is outcompeting specialized herbaceous species, as has been observed elsewhere. Plant species composition and richness sampled at 124 plots were analysed in relation to pine stand parameters (canopy cover, stand age, stand basal area), abiotic environmental factors (e.g. soil properties) and spatial variables (e.g. plot coordinates). Plots were divided into three shading categories and compared in terms of vegetation and habitat parameters. Scots pine outcompeted several light-demanding species, leading to a decrease of total species richness and cover. Characteristic species of this grassland (Biscutella laevigata, Silene vulgaris) and some metal-tolerant plants were clearly insensitive to shading. For these early successional species, more important was the availability of microsites with shallow skeletal soil or bare subsoil. Tree stand parameters differently affected grassland vegetation: canopy cover caused primarily a compositional shift in the community, while stand age was the principal agent of decline in species richness. Scots pine increased the soil concentrations of available Ca and Mg, and negatively affected soil development (organic matter and mineral particle accumulation), which might be beneficial to some shade-tolerant grassland species. Maintaining the studied grassland's present species richness and composition would require cutting woody plants less frequently than recommended for dry grasslands of non-metalliferous sites, and disturbing the soil surface.

Different strategies of Cd tolerance and accumulation in Arabidopsis halleri and Arabidopsis arenosa

“…Taking into account the high concentration of the phytoavailable forms of Cd (50-59 mg/kg) and Zn (409-460 mg/kg) compared to Pb (3.5-6.0 mg/kg), it is suggested that the main factors behind the adaptation of both of the investigated plant species to the toxicity of TMEs on the metalliferous site are Cd and Zn. This notion is supported by other authors, who also measured low concentrations of the bioavailable forms of Pb in metalliferous soils in Southern Poland and postulated that the effect of Pb on living organisms (soil mesofauna, microbes, arbuscular mycorrhizal fungi and plants) is negligible or substantially lower than that ofCd and Zn (Gucwa-Przepióra, Błaszkowski, Kurtyka, Małkowski, & Małkowski, 2013;Kapusta et al, 2011;Kapusta, Szarek-Łukaszewska, Jędrzejczyk-Koryci nska, and Zagórna (2015). Moreover, it has been demonstrated that the Pb distribution in the A. halleri plants was different compared to Cd and…”

Secondary Serpentine Forests of Poland as a Refuge for Vascular Flora

“…As shown in this study, thermophilic Scots pine artificial stands on serpentinites are a specific type of community that ensures the development of many light-demanding species. Equally rich in rare species are secondary Scots pine forests of loose structure, developing on polymetallic outcrops in central Poland [57], or spontaneous mixed forests with Pinus sylvestris on limestone screes in abandoned quarries [28]. The orchid Goodyera repens, rare in Poland, has also shown expansion in the latter type of community in recent years [58].…”