Changes in mixed forest plantations after snow damage in the Northwest Rhodopes

Abstract

The changes in diameter structure of Pinus sylvestris ( L. ) in addition to similar previous study on Pinus nigra ( Arn.) in mixed Austrian black pine – Scots pine plantations after damages from abundant wet heavy snow in the region of Velingrad – Northwest Rhodopes were studied. А period without significant abiotic influences (1997-2007) and following one (2007-2017) were compared, in which small-scale natural disaster caused by snowfalls was observed (2015). The analysis was made with variation distribution curves of the stems according to natural degrees of thickness. It is confirmed that the reason for deviations from the normality of the trees distribution is their right asymmetry as consequence of trees with smaller diameters loss as a sum result of the natural loss and the heavy snow. This is proved by analysis of the curves of mean variation rows for percent stem distribution according to natural degrees of thickness  and Skewness and Kurtosis coefficients. The dynamics in the trees number distribution of both species forming the composition by Gini index was investigated as well as the diameter, height, basal area, volume and assortment structure.