Effect of defoliation intensity and timing on the growth of Populus alba and Salix babylonica x Salix alba.

RUBIO, A.; LOETTI, V.; BELLOCQ, M.I.

BOSQUE (VALDIVIA)

UNIV AUSTRAL CHILE

Lugar: Valdivia; Año: 2013 vol. 34 p. 351 - 356

0304-8799

The effect of defoliation intensity on the height and diameter of two commercial Salicaceae was assessed at forestry plantations located in the Delta of the Paraná River, Argentina, over the spring and the summer. Experimental trees were randomly selected from two 1-year-old plantations of the most common clones planted in monoculture in forestry production, Populus alba ´Villafranca´ (¨I-58/57¨) and Salix babylonica x Salix alba (¨A-250/33¨). We used a completely randomized design with manual defoliation as the treatment and five levels, corresponding to different defoliation intensities: 100%, 75%, 50%, 25%, and 0% (control). Each defoliation level was performed on different trees at four times during the growing season: October, November, December and January. Tree height and diameter at breast height (DBH) were measured prior and after defoliation treatment. Results indicated that manual defoliation negatively affected growth of the studied clones (both height and diameter), depending on the timing and intensity of defoliation. Willows were only affected by defoliation conducted during the spring (October and November); complete defoliation caused the highest reduction in growth (46% reduction in height and 62% in DBH compared to the control). Manual defoliation of poplars had a significant effect on growth at any time during the spring-summer; trees subjected to 100% defoliation showed the highest growth reductions (up to 76% in height and 88% in DBH compared to control). Our study indicated that commercial poplars were less tolerant to defoliation than willows.