Development of structural root architecture and allometry of Quercus petraea

Root growth direction, radial distribution of roots, and biomass partitioning within the root system were examined on fifty-five 20 and 28-year-old sessile oak (Quercus petraea (Matt.) Liebl.) trees. The root systems were spatially subdivided into three concentric cylinders. Diameters and compass direction of roots were recorded at each point where they crossed one of the cylinders. Analysis of the distribution of root cross-sectional area (A(r)) at 30 cm radius from the stem showed clustering in a preferred direction only for 10 small trees (diameter at breast height (DBH) < 9 cm). A classification of four incline growth types was used to describe differences in root architecture associated with the different age stands. Approximately 75% of all roots kept their orientation throughout the root-soil plate on both plots. Equations were developed to describe allometric relationships between basal area, DBH, sum of A(r), and root biomass. With increasing stem diameter, the root biomass was allocated predominantly to and evenly distributed within the surface root system, effectively increasing tree stability. Results from this study support the idea that root system architecture is inherently determined and that DBH or proximal root diameter measurements are sufficient to predict root biomass of young sessile oak when sail properties are nonrestrictive.