Single tree effects of sessile oak (Quercus petraea (Matt.) Liebl.) within pure stands (Pinus sylvestris L.) on topsoil properties

The purpose of the present study was the characterisation of single tree effects of sessile oak within pure pine stands on humus quality and quantity. At five distances of two single oaks (fig. 1) the following parameters were investigated: humus layer thickness, humus form, C/N-ratio in Oh-horizon and acidity in L-, Of-, Oh- and A-horizon. Humus form (table 2 and 3), C/N-ratio and acidity (fig. 4 and 5) depend on the distance of single oaks. At least for one study area an oak-specific effect could be proved for humus layer thickness between the plots close to sessile oak and the plots predominantly influenced by Scots pine (fig. 3). The study points out causes of changing parameters depending on single tree distances and discusses the need for further research with respect to spatial heterogeneity of single tree effects.