Assessment of Oak Dendrochronological Series in Protected Zone (Bulgaria) for Eustress Identification in Forest Stands

The paper presents results of Quercus cerris L. and Q. frainetto Ten. eustress investigations in SCI “Zapadna Stara Planina i Predbalkan” following a new holistic approach by applying an original software - SPPAM for the identification and assessment of eustress. The tree ring width sequences are approximated with polynomials with R2 > 0.45. It indexes as a ratio between measured and approximated values are computed. Years, where It is lower than a threshold value, are categorized as eustressed ones. Specified in the investigation climatic type of years are studied as adverse years according to the obtained eustress. A five grade scale for assessment of frequency, duration and negative deviation of It as eustress characteristics and their comparative analysis is proposed. The predominance of hot and dry adverse years on the growth is established. The eustress characteristics were scaled and compared. The potential risk for studied forest vegetation is estimated. The proposed holistic approach is convenient for the fast diagnosis of forest state. This approach allows also the expression of reactive functional types, which may support the vegetation modelling.