Growth and yield of mixed polyclonal stands of populus in short-rotation coppice

Eight clones of poplar were used to compare the growth and productivity of monoclonal and polyclonal mixed plantations in short-rotation coppice. At t he end of the eighth growing season, the diameter at breast height (DBH) an d height of trees were measured and dry weight and yield were estimated. Po lyclonal mixtures did not affect mortality. Few differences in growth were observed between clones in monoclonal plots. Polyclonal mixture slightly af fected the growth and tree size of the clones compared with monoclonal plot s. No increase in stand heterogeneity in relation to clone deployment was o bserved. A neighbourhood index was calculated for each tree and was signifi cantly affected by polyclonal mixture. However, the relationship between th e neighbourhood index and the DBH indicated that this effect did not cause a great change in DBH. Consequently, dry weight and yield productivity were not affected by clone deployment.