The effects of agroforestry practices on fiber attributes in <Emphasis Type="Italic">Populus nigra</Emphasis> var. <Emphasis Type="Italic">betulifolia</Emphasis>

The effects of intercropping with alfalfa and initial tree spacing on fiber properties in Populus nigra var. betulifolia are reported on the basis of a study of 15 trees. The trees were harvested from an agroforestry trial near Karaj city, Iran. Treatments included four initial spacings of 3 m × 4 m, 3 m × 6.7 m, 3 m × 8 m, and 3 m × 10 m intercropped with alfalfa as nitrogen-fixing plant, as well as one 3 m × 4 m treatment without alfalfa. Results showed that initial spacing and intercropping with alfalfa increased the growth rate. Also, alfalfa-intercropping had increasing effects on all fiber dimensions, especially on diameter and wall thickness. The effect of initial spacing on fiber attributes based on ring numbers was not statistically significant; however, whole-disk fiber length, weighted by ring area, was increased with stem diameter. The reason for this increase may be traced to the fact that much of the basal area of fast-growing trees is concentrated in farther rings from the pith that have longer fibers. Clear correlation was not found between fiber length and growth rate and therefore, no firm conclusion can be made in this regard.