Effects of Pruning to Promote Trunk Extensionon Annual Growth Rhythm of Paulownia

This paper aims to confirm the optimal pruning intensity to promote paulownia growth. Annual dynamic of 8 growth indicators for pruning of three-year-old Paulownia to promote tnmk extension were simulated under 7 treatments. The results showed that annual growth process could be modeled reliably by Richards' function. Eight growth parameters were developed including fast-growing point (t0), initialp oint of fast-growing period (tl), final point of fast-growing period (t2), fast-growing period (t), growth period (Dg), maximum day increment (AGRmax), maximum annual increment (A). Effects of pruning to promote trunk extension on growth parameters were analyzed. Paulownia remaining 3-6 lower branches after pruning had relatively longer fast-growing period (t), growth period (Dg), higher average day increment (Am), maximum day increment (AGRmax) and maximum annual increment (A). Therefore, lower diameter growth of original trunk did not decrease significantly, and upper diameter growth increased to some extent, Height and diameter growth of grafting trunk, and form ratio of grafting trunk were relatively higher. Total stock volume increment was improved significantly under the condition that stock volume increment of original trunk did not decrease.

This paper aims to confirm the optimal pruning intensity to promote paulownia growth. Annualdynamic of 8 growth indicators for pruning of three-year-old Paulownia to promote trunk extension weresimulated under 7 treatments. The results showed that annual growth process could be modeled reliably byRichards function. Eight growth parameters were developed including fast-growing point (t0), initialpoint of fast-growing period (t1), final point of fast-growing period (t2), fast-growing period (t), growthperiod (Dg), maximum day increment (AGRmax), maximum annual increment (A). Effects of pruning topromote trunk extension on growth parameters were analyzed. Paulownia remaining 3~6 lower branchesafter pruning had relatively longer fast-growing period (t), growth period (Dg), higher average day increment(Am), maximum day increment (AGRmax) and maximum annual increment (A). Therefore, lower diametergrowth of original trunk did not decrease significantly, and upper diameter growth increased to someextent. Height and diameter growth of grafting trunk, and form ratio of grafting trunk were relatively higher.Total stock volume increment was improved significantly under the condition that stock volume incrementof original trunk did not decrease.