Survey on adaptation and wood yield of Populus nigra clones in comparative populetum of Sanandaj (final stage)

In this trial, 14 clones ofPopulus nigra were studied during 2001-2008 in Sanandaj, Kurdistan province. Planting of cuttings were accomplished in early March of 2000 and transplanting and planting of saplings were conducted in early April of 2001 with space of 3m × 3m based on the Randomized Complete Block Design (RCBD) with 3 replications. Each plot contains 25 saplings that were planted as 5×5 (9 saplings as main and 16 as buffer) and some morphological and qualitative characteristics were evaluated every year. Results showed that the first and second years after planting (2000 and 2001) were "establishing phase" of saplings, which showed a very low portion of diameter at breast height (DBH), tree height (H) and wood volume (V) increment. Total means of DBH, H and V in the sixth year of experiment (2007) as final year of the study were 15.2 cm, 9.82 m and 107.55 m³/ha, respectively. Analysis of variance showed significant differences at p≤0.01 among poplar clones for all studied traits. This provides a suitable background for selection of superior clones. The combined analysis of variance revealed significant differences of clone × year interaction variance, indicating that clones responses to years conditions were different. According to the comparisons of means with Duncan’s test (p≤0.01), clones of P.n. 56/52, P.n. 56/75, P.n.62/140, and P.n. 63/135 were superior clones among the studied clones with DBH of 17.9, 18.3, 15.7 and 16.0 cm, tree height of 10.61, 9.94, 10.53 and 10.01 m, wood volume (V) at the end of the experiment 153.68, 148.79, 119.87 and 118.19 m³/ha, mean annual volume growth of 25.61, 24.80, 19.98 and 19.70 m³/ha/y and mortality percentage due to drought stress in 2007 about 25.93%, 29.63%, 40.74% and 48.15%, respectively. Superior clones showed moderate to good vitality, mainly safe from a contamination by pests point (in the normal conditions of 2000-2007) and straight stems. The wood yield of superior clones was about 1.1-1.4 times more than clones average and 1.3-1.6 times more than 2 standard clones (P.n.Saghez and P.n.Grizah) averages. Order of superior clones in the third to the seventh years of trial was almost similar. Therefore, decreasing of study time from 10 to 5 years could be possible in elimination trails. The occurred drought stress in 2007 resulted in (i) decreasing of growth of all clones and changing of order of superior clones, (ii) attacking of Melanophylla picta to field due to poor growth as secondary stress and (iii) early fall in the all clones. Because of various environmental stresses in Iran, we recommend that the stress effects (mainly drought stress) and clone tolerance as important parameters in clone selection and breeding programs should be evaluated in the future studies of clone adaptation.