167 | Fascicule 4 ANNALS of Faculty Engineering Hunedoara – International Journal of Engineering Tome XIV [2016] – Fascicule 4 [November] ISSN: 1584-2665 [print; online] ISSN: 1584-2673 [CD-Rom; online] a free-accessmultidisciplinarypublication of theFaculty of Engineering Hunedoara 1. Elena C. MUŞAT, 2. Arcadie CIUBOTARU, 3. János SZÁVA A SHORT REVIEW REGARDING THE LOSSES RECORDED IN WINDFALL 1,2. Transylvania University of Brasov, Faculty of Silviculture and Forest Engineering, Department of Forest Management and Engineering, Brasov, ROMANIA 3. Transylvania University of Brasov, Faculty of Mechanical Engineering, Department of Mechanical Engineering, Brasov, ROMANIA ABSTRACT: Stability of trees is a current and very important issue in the context of increased of living standards that involving a pressure increasingly higher on the forest. The aim of this paper is to highlight the devastating impact of wind on trees stability and the factors that influence the behavior of trees under the action of wind. Windfalls have both negative economical and ecological effects, the latter having a particularly strong impact in the long term. In the paper are mentioned the windfalls produced in past on European level, with accent on wooden affected volumes, but are synthesized also information regarding the dynamics of windfalls at Romanian level. The rooting depth and the slenderness ratio are indicators that influence decisively the stability of trees. Keywords: windfalls, wind, resistance at wind 1. INTRODUCTION During their existence, the trees are constant subjected to the actions of some factors on which depends their mechanical and biological stability [15]. Due to the ecological and structural fragility at the action of environmental factors and of their ecological and eco productive importance, the forest ecosystems, especially those with spruce, have constituted the subject of many complex and interdisciplinary studies [3-5, 15, 26, 28, 33, 35 and 37]. However, the assessing of failure risk is very difficult [20] because must to be studied aspects related to tree biomechanics (architecture, structure, damage and defects, the roots characteristics, the peculiarities of wood) and also the stationary/localized/fixed to a place/ conditions (topography, geomorphology, soils and hydrology) and weather conditions (normal and catastrophic storms, wind, snow, ice and rain). Unlike other materials, trees, as living tissues, have the ability to increase and the consequence of this growth is exactly the changing of dimensions and mechanical proprieties [14]. The vertical growth of the trees is conditioned primarily by the bending movements resulted as response at wind and gravity actions [2]. Tare weight, air masses moving (with or without precipitations) require the trees especially at Figure 1. Forms of instability at spruce: a) bending and elastic buckling of the stem, in which case the stem will return to the original vertical position; b) bending and plastic buckling of the stem, in which case the stem remains deformed; c) breaking the stem; d) the overturning of the spruce by uprooting [15]