Soil development under different tree species in relation to tree properties, a case study from post-mining sites in Eastern Germany

Abstract

Mining, and open cast mining in particular, causes severe environmental damage. Original soils are excavated and/or buried under layers of overburden. Afforestation of degraded post-mining land may support de novo soil formation in the post-mining overburden. In this study, we explore properties of soils developing on sandy post-mining overburden in former opencast coal mine Domsdorf in the eastern part of Germany, planted with seven tree species, pine (Pinus sylvestris), larch (Larix decidua), sessile oak (Quercus petraea), red oak (Quercus rubra), birch (Betula pendula), lime (Tilia cordata), and alder (Alnus glutinosa). In these tree species-specific plots, we studied soil C and N stocks in the organic horizon and mineral soil, determined pH and content of available nutrients, and explored the microbial community using phospholipid fatty acids and earthworm activity in thin soil sections. Soil parameters were related to tree parameters, diameter at breast height (DBH), pigments, nitrogen balance index (NBI), and C:N ratio of the foliage. Foliage C:N ratio decreased in the order of the trees listed above, while red oak showed the highest DBH and sessile oak the lowest DBH. The highest C content was observed under pine with the highest foliage C:N ratio and organic horizon accumulation, followed by birch with the highest earthworm activity. The organic horizon mass closely correlated with foliage C:N ratio. C and N accumulation in the mineral soil was the highest under birch and closely correlated with DBH. Availability of Ca2+ and other basic cations as well as pH is particularly high under red oak and larch. The presence of fungi positively correlated with foliage C::N ratio. Earthworm bioturbation positively correlated with pH and Ca2+ content. The overall results suggest that trees with various properties support various prevailing mechanisms of soil formation and accumulation of soil organic matter.