The structure of a mature stand and the following sapling stage in the process of planned regeneration on a site of a monodominant sessile oak forest (Quercetum petraeae Čer. et Jov. 1953., subass. tilietosum) in the NP ,,Đerdap”

Abstract

The paper shows the structure of a mature stand, as well as the structure of the sapling stage that followed after the planned regeneration on the experimental plot in a monodominant sessile oak site (Quercetum petraeae Čer. et Jov. 1953., subass. tilietosum), in the area of NP „Đerdap“. The research is based on the dendrometric measurements in a mature stand in 1992, and in the following sapling stage in 2017 on a permanent sample plot. The mature stand in 1992 was around 150 years old with only sessile oak represented in the tree layer on the permanent experimental plot. The canopy closure was estimated at 0.7-0.8 and 275 trees per hectare were determined, with 90.9% of the trees in the first biological position (BP-1, including Kraft’s dominant and codominant trees), 57.5% of the trees with good stem quality (SQ-1) and with 91.6% of healthy trees (A0). The basal area was 35.9 m2•ha-1, the total volume 470.5 m3•ha-1, the current volume increment 5.6 m3•ha-1, and the mean stand diameter was 40.8 cm with a mean stand height of 24.2 m. Based on the shown structural elements, it was a good quality, well preserved and highly productive stand. In the sapling stage that followed after the planned regeneration, in 2017, seven tree species were determined including silver lime. The canopy closure was estimated at 1.0 with 3425 trees per hectare, with 38.9% of the trees in the first biological position (BP-1), 10.6% in the second biological position (BP-2, including Kraft’s intermediate trees) and 50.5% in the third biological position (BP-3, Kraft’s suppressed trees). The basal area is 22.7 m2•ha-1, the total volume 178.3 m3•ha- 1, the mean stand diameter 9.2 cm and the mean stand height 11.7 m. Silver lime is represented by 80.9% of the total number of trees and by 91.1% in the total basal area with a mean diameter of 9.8 cm. Sessile oak is represented by 10.9% of the total number of trees and by 1.7% in the total basal area with a mean diameter of 3.6 cm. Other hardwood species (hornbeam, wild service tree, field maple, Norway maple, beech) were represented by 8.2% of the total number of trees and by 7.2% in the total basal area with a mean diameter of 8.6 cm. In the total number of trees in the first and the second biological position, silver lime is represented by 94.1%, sessile oak by 0.4%, and the trees of other hardwood species by 5.5% The structure of the sapling stage shows that during its formation, the continuity of the sessile oak stand with the previous rotation was not obtained. In the structure of a sapling stage, there is no biological potential of sessile oak trees that could represent the basis for the further development in the stand in the current rotation so the management plans should instruct the silvicultural measures towards silver lime and a small number of hardwood species.