Evaluation of the forest wheel tractor LKT 81 Turbo at timber skidding and a functional model of the multioperational thinning machine from the viewpoint of efficient utilization of their power supplies

abattage d'arbres arbre pour bois de construction consumo de energia conversion primaire des bois corta energy consumption energy losses equipment characteristics equipo forestal evaluation felling forestry equipment hauling labour productivity maquinaria de tala mathematical models mejoramiento del rodal methode methods productividad del trabajo saca de la madera stand improvement timber trees tracteur tractores tractors tree felling equipment