Seedling biomass and element content of Pinus sylvestris and Pinus nigra grown in sandy substrates with lignite

Reclaimed mine soils in the Lusatian mining district (Eastern Germany) are often comprised of sandy materials containing high amounts of lignite. Lignite can absorb nutrients and water, but its high pyrite and Al content may restrict access of roots to these pools. We assessed the influence of lignite on growth, seedling shoot and root element content and root lengths of Pinus sylvestris L. and Pinus nigra Arn. in lignite-containing and lignite-free substrates. Rhizotrons were filled with mining substrate in which lignite was finely dispersed (L-substrate), a model substrate with alternating layers of quartz sand and lignite (SL-substrate), and a sandy substrate from a natural forest without lignite (S-substrate). After 11 months, shoot dry mass of P. sylvestris significantly decreased in the following order: S-substrate > SL-substrate > L-substrate, whereas root dry mass was similar in all substrates. P. sylvestris in S-substrate was characterized by high shoot and root contents of N and P, whereas plants grown on L-substrate had high shoot and root contents of Ca and a high root content of Al. In L-substrate, shoot dry mass of P. nigra was significantly greater than that of P. sylvestris and the Ca content in the roots of P. nigra was twice as high than in P. sylvestris roots (P ≤ 0.1). The high Ca content in the roots may explain the better growth of P. nigra in these mining substrates which are often characterized by high Al content.