Effects of “classical” vs. “dynamic” silviculture of sessile oak-dominated stands in terms of height, diameter increments and natural mortality

Abstract: Traditional oak silviculture in Romania is associated with high labor costs and long rotation cycles which are imposed by current norms and regulations. A small-scale R&D project, consisting of a block with four plots of 200 m2, was established in 2001 in a 15-year old sessile oak-dominated stand. The stand was regenerated naturally through the application of group shelterwood cutting. In each plot, ”potential” final crop trees were selected based on vigor-quality-distribution criteria and marked with paint. Silvicultural interventions like cleaning-respacing and thinning of different intensities were performed in three plots (the fourth one was kept as control) in 2001, 2004 and 2009. The effect of stand density on diameter increment was more obvious when considering only the “potential” final crop trees than when all trees were considered. Their quadratic mean diameter (QMD) had reached values close to 20 cm at 35 (30-40) years in the plots with the lowest stand density (STT) and about 15-16 cm for other plots. STT stand with the lowest stand density shows low HDR values having slander trees. The mortality intensity between 2001 and 2019 was highest in the control plot and lowest in STT. Sessile oak showed the highest mortality, followed by Hungarian oak and Turkey oak. In all plots, trees had reached heights corresponding to the hg of ca. 15 m, which is normal for a sessile oak stand of high productivity. The obtained results indicate the ”dynamic”, crop tree silviculture with the active selection of the most valuable individuals as ”potential” final crop trees at the end of thicket stage as being a possible solution for managing sessile oak young and medium-aged stands. Nonetheless, these trees should be managed by subsequent crown thinning, in order to produce timber with as uniform as possible radial increments of 2-3 mm, as is requested by veneer and high-quality saw log buyers.