BIOMASS PRODUCTION AND ENERGY POTENTIAL OF SOME EASTERN COTTONWOOD (Populus deltoides Bartr. ex Marsh.) CLONES IN RELATION TO PLANTING SPACING

The possibility of biomass production was studied in an experimental trial stand with four clones of Eastern cottonwood Populus deltoides Bartr. ex Marsh. cl.457, cl.450, cl.618 and cl. 55/65 and three stand densities a) 1.2 x 1.0 m (8330 plants-ha(-1), b) 1.2 x 0.75 m (11110 plants-ha(-1) and c) 1.2 x 0.5 m (16600 plants-ha(-1). Field trials were conducted on sandy-loamy form of fluvisol. Total determined volume of trunk, bark, and branches in the first two-year cycle for the used Eastern cottonwood ranged from 27.391 m(3).ha(-1) in clone 450 at planting distance of 1.2 x 1.0 m, subtreatment (a) to 42.006 m(3).ha(-1) in clone 618, subtreatment (c) at planting distance of 1.2 x 0.5 m. After renovation of stand using the regeneration force of shoots from the tree stumps the produced wood mass in the second two-year cycle ranged from 54.664 m(3).ha(-1) in clone 55/65, subtreatment (a) to 79.235 m(3)-ha(-1) in clone 450, subtreatment (b). In additon to clone selection a significant influence on biomass yeald was also exerted by stand density (number of plants-ha(-1)). The largest amount of heat energy would be obtained in subtreatment (c) at density of 1.20 x 0.5 m by combustion of biomass of above ground part of clone 55/65: 364.02 GJ.ha(-1) in the first cycle, and 659.83 GJ.ha(-1) in the second, or a total of 1023.85 GJ.ha(-1).