Tending of spruce stands of age class 2 by the method of final crop trees with respect to snow resistance

agentes nocivos agronomic characters arbre arbre brise-vent arbre forestier arbre pour bois de construction biological control biological development bosques breeding breeding aims conifere conifers crecimiento croissance crops cultivos economic plants environmental effects facteur nuisible fisiologia fonction physiologique forest plantations forest trees forests gimnospermas growth gymnosperme gymnosperms injurious factors lutte biologique neige nieve objetivo de mejoramiento pest control methods physiological functions physiologie physiology picea picea abies pinaceae plantas plantas protectoras plante plante de culture plante de protection plante pour construction plants precipitation protection des peuplements protective plants resistance to injurious factors silvicultura silvicultural systems silviculture sistemas silviculturales snow stand protection structural crops sylviculture timber trees trees vegetation windbreak trees