Snow damage to tree species and its relationship with environmental variables in the Hyrcanian lowland Forests, Iran

Among environmental factors, snow is one that is not considered enough in the Hyrcanian forests. There was a heavy snowfall in central Hyrcanian forests in 2016 November which caused serious damages to the forest trees. To consider these damages, 70 sample plots of 40×40 meter were chosen with systematic random method in parcels 609, 629 and 632 in Liresara Forest district in Mazandaran province. In each plot, all damaged and undamaged trees and the form and the properties of damages were considered. According to the results, 9% of trees had been damaged by snow. Amongst the damages, stem breakage and uprooting were the most frequent, whereas bending of stump was the least frequent. The most damages occurred to Alnus subcordata (with 22 percent of whole individuals) and Carpinus betulus, and Acer velutinum and Diospyros lotus were slightly damaged. Furthermore, A. subcordata, C. betulus, Parrotia persica and Quercus castaneifolia were more severely broken, while Buxus hyrcana was more uprooted and Acer cappadocicum was more bent. The altitude class of lower than 200 meter had significantly the most damages; but slope classes did not show any significant differences. Concerning aspects, it was clarified that the most damages were on northern slopes. Altitude was significantly effective on extent of damage of A. subcordata and C. betulus, whereas Aspect was effective on C. betulus, A. cappadocicum and Tilia begonifolia. Young trees, grown after shelter cut of decades 1980 and 1990, whose diameter was 15-35 cm, were considerably vulnerable to snow.