SPATIAL AND TEMPORAL PATTERNS OF FINE-ROOT ABUNDANCE IN A MIXED OAK BEECH FOREST

Spatial distribution and seasonal fluctuation of fine root density (mass per unit soil volume) and abundance (mass or surface area per unit ground surface area) were investigated by the sequential coring technique in a 100-220 year old mixed Fagus sylvatica-Quercus petraea stand on acidic sandy soil in northwest Germany. The fine root systems of the two co-existing species overlapped completely with beech roots being twice as abundant as oak roots. Since Fagus and Quercus occupied equivalent parts of the canopy volume, oak appeared to be under-represented in the below-ground space. There was evidence for some degree of below-ground niche partitioning between the species in both the vertical and the horizontal direction. Oak fine roots were found to be more superficially distributed than beech roots in the organic layers, indicating a vertical stratification of the root systems of the two species. In the forest floor, fine roots were more abundant in the vicinity of oak stems where thicker organic layers occurred. However, this distribution pattern was not a consequence of a greater abundance of oak roots close to their parent stem, but was due to a higher frequency of beech roots here.