Soil properties in plantations of sessile oak ( Quercus petraea) and red oak ( Quercus rubra) in reclaimed lignite open-cast mines of the Rhineland

Abstract

We studied the soil properties of 18-year-old plantations beneath the crowns of the native sessile oak ( Quercus petraea) and of the introduced red oak ( Quercus rubra) growing on reclaimed lignite open-cast mines. The soil properties of both plantations, which are growing on either highly fertile (loess deposits, silty loam) or on low fertile (mixture of loess and sand deposits, clayed sand) soil, were measured and compared with values taken from 2-year-old Quercus robur plantations. In plantations of Q. petraeawe generally found higher values of total carbon (C org) and total nitrogen (N tot) in the upper soil, although the amount of organic matter in the O-horizon did not significantly differ. Soils of Q. petraea plantations also exhibited higher values for microbial and faunal life. For example, microbial activity, the respiratory quotient ( qCO 2) and C-mineralization were about twice as high as for the Q. rubra plantations. Collembola and mites (Oribatei), both belonging to the soil mesofauna, reached higher densities in the Q. petraea plantations. When growing on highly fertile soils, the amount of soil nutrients (K +, Ca 2+, Mg 2+, and PO 4 3−P) did not differ between the two plantations. However, when oak trees grew on the less-fertile soil, the amount of soil nutrients was significantly lower beneath red oak. The amount of soil nutrients beneath red oak was even lower than beneath 2-year-old Q. robur plantations; the soil properties of which are almost at the beginning stage of succession. The results suggest that nutrient depletion beneath red oak when compared to sessile oak is caused both by increased immobilization into woody biomass, and by increased recalcitrance of organic matter.