The Effects of Agroforestry Practices on Physical Propertiesin of Poplus Wood in Radial and Longitudinal Axes

The effects of intercropping with alfalfa as well as initial tree spacing on physical variations of Populus nigra betulifolia wood in radial and longitudinal axes are reported. Material was harvested from an agroforestry trial near Karaj city، Iran. Treatments included four initial-spacings between poplar trees intercropped with alfalfa as a nitrogen-fixing plant، as well as one control treatment (without alfalfa). Intercropping with alfalfa had a negative effect on wood density and shrinkage، but increasing initial spacing had a positive effect on them. Wood density، radial and tangential shrinkage decreased in longitudinal axis from bottom to top of tree trunk، whereas longitudinal shrinkage increased. Wood density and shrinkage in radial axis and at breast height level decreased from pith to bark; by 25% and 50% of tree this pattern was inverted for wood density. Statistical analysis showed the variation of shrinkage between treatments and in longitudinal axis was followed as density variation، but in radial axis density was not only effective factor on shrinkage.