Site conditions and species identity have a combined effect on fine root growth of trees in pure and mixed stands.
However, mechanisms that may contribute to this effect are rarely studied, even though they are essential to
assess the potential of species to cope with climate change. This study examined fine root overlap and the linkage
between fine root and stem growth of European beech (Fagus sylvatica) growing in pure and mixed stands with
Douglas fir (Pseudotsuga menziesii) or Norway spruce (Picea abies) at two different study sites in northwestern
Germany. The study sites represented substantially different soil and climate conditions. At each site, three stands, and at each stand, three pairs of trees were studied. In the pure beech stand, the pairs consisted of two beech trees, while in the mixed stands each pair was composed of a beech tree and a conifer. Between each pair, three evenly spaced soil cores were taken monthly throughout the growing season. In the pure beech stands, microsatellite markers were used to assign the fine roots to individual trees. Changes in stem diameter of beech were quantified and then upscaled to aboveground wood productivity with automatic high-resolution circumference dendrometers. Keywords: Fine root growth, Stem growth, Trade-off, Cost-benefit ratio, Belowground territoriality, Conspecific neighbors, Heterospecific neighbors
