Accumulation and properties of soil organic carbon at reclaimed sites in the Lusatian lignite mining district afforested with Pinus sp.

The accumulation of organic carbon mainly derived from litter fall and necromass (Corg recent) has been investigated within the forest floor horizons and the mineral topsoil (0-4 cm and 4-10 cm) at reclaimed forest stands of the Lusatian lignite mining district as well as on an undisturbed forest stand in the general region, planted with Pinus sylvestris (L.) or Pinus nigra (Arnold). Recently formed organic carbon (Corg recent) was differentiated from organic carbon derived from lignite and lignite derivatives (Corg geogenic), which are inherent in the dumped substrate at post-mining sites, by 14C measurements. Total organic carbon (TOC) was characterized by 13C CPMAS NMR spectroscopy. The storage of TOC, Corg recent, Corg geogenic, and of organic carbon structures was examined. We found that the accumulation of Corg recent increased with stand age at all investigated stands. The results indicate that at the reclaimed stands accumulation of Corg recent takes place in the same order of magnitude when compared to the undisturbed stand. Storage of TOC in the mineral topsoil (0-10 cm) amounted from 2.6 kg m−2 to 7.0 kg m−2 at the reclaimed stands and to 2.6 kg m−2 at the undisturbed stand. At reclaimed stands TOC in the mineral topsoil can be attributed mainly to Corg geogenic. The calculated pools of Corg geogenic effect physico-chemical soil properties. Our results indicate that Corg geogenic in the substrate may compensate in part the lack of soil organic matter derived from soil development as storage for nutrients and water.