Hazel improves soil quality of sloping oak stands in a German low mountain range

Overview & Synopsis

We compared Quercus petraea monocultures with adjacent mixed oak-hazel (Corylus avellana) stands at gentle (14°) and steep (25°) slopes of the Ahr-Eifel. The influence of hazel on forest floor mass, soil nutrients, microbial properties and on the abundance of Lumbricidae was studied. Litter mass was greater in mixed stands than in oak monocultures, resulting in a thicker Ah-horizon. Additionally, the PO43-, Ca2+- and Mg2+-contents were higher and the Al3+-content lower in the upper soil of mixed stands. In contrast, the contents of organic carbon , total nitrogen and the C/N ratio did not differ between the two soils. Basal respiration, specific microbial activity (qCO2) and carbon mineralisation (Cmin) were higher in mixed stands than in oak monocultures. Lumbricidae showed low densities in three of the stands studied (15-21 ind./m2) and were almost absent at the oak monoculture on the steep terrain (2 ind./m2).