Where and How European Beech Deadwood Influences Soil.

Deadwood, namely coarse woody debris (CWD), can influence forest soil properties as reported from several studies in boreal, temperate and tropical forests. Yet to what extent and in what manner is not universally the same. Different effects can be attributed to the variety of metabolites released during decomposition, which in turn depend on species and decay processes. Such metabolites are especially sensitive to geologic and climatic conditions as well as disturbances, especially man-made ones, meaning how deadwood impacts soil could depend on such factors. In this study, where and how European beech (Fagus sylvatica L.) deadwood influenced soil properties was tested through paired points near deadwood and 2-3 m away at eight predominantly beech stands in SW Germany. These sites included mull and moder forest floor types, calcareous and silicate bedrock, protected and harvested stands (including time since last harvested), and deadwood in various decay stages.

Preliminary tests indicate that deadwood influenced soil organic matter, chemical and physical properties not equally under various climatic, management and decay conditions. Water extractable organic C (OC), aromaticity and free particulate OC near deadwood increased the most at moder-silicate sites, long-time protected stands and very decayed stems. Aggregate-occluded particulate OC increased only for very decayed stems, while mineral-bound C did not change under any conditions. In contrast, total organic N decreased at mull-calcareous sites, harvested stands and moderately decayed stems. Changes to porosity and pore-diameter distributions were mostly limited to mull/moder-calcareous/silicate conditions; only meso-pores (10-0.2 μm) decreased in percent volume also at medium-term harvested stands and moderately decayed stems. Results for CuO-oxidized lignin, exchangeable cations and organic layer properties will also be presented.

We hope to elucidate forest management-relevant interactions between deadwood, site conditions, decomposition and harvesting.