Development phases and structural characteristics of the Penteleu-Viforta virgin forest in the Curvature Carpathians

Abstract

The stand structure of a virgin forest situated at an average altitude of 1130 m a.s.l. in the Milea Viforâta Nature Reserve (Southern Carpathians, Romania) was investigated to determine the specific development phases of the forest and understand how they influence the stand structure, with the aim of providing optimal solutions and structural models for sustainable forest management. All trees with breast height diameter (dbh) ≥ 8 cm were inventoried in the study plot (1 ha), and the main dendrometrical variables were measured. Radial increment cores were taken from all the trees and were subsequently processed. A total of 317 trees from three species - European beech (Fagus sylvatica), silver fir (Abies alba) and Norway spruce (Picea abies) - were sampled at different development phases (optimum, ageing, breakdown and dieback, rejuvenation). Testing stand structural diversity with the Gini index, a minimal stability was found in the rejuvenation development phase and a maximum stability in the ageing phase. No significant match was found between standard theoretical functions (Normal, Weibull, Gamma and Exponential) and the observed distribution of tree diameter. Also, it was confirmed that dominance of beech in all development phases is a consequence of its high competitive ability and its capacity to endure difficult environmental and biologically stressful conditions. The results revealed a series of structural models specific to these forest ecosystems, which can help managing forests under the selection system.