Polycyclic growth and branching in the upper crown in provenances of lodgepole pine

Journal Article

Development

The percentage of shoots that originated from polycyclic growth in first-order branches and branch numbers in upper annual segments of leader growth were determined from trees of seven provenances of Pinus contorta Dougl. ssp. latifolia Engelm. from British Columbia and the Yukon, growing in a provenance trial at Prince George, B.C. The number of first-order branches varied among provenances and year of growth and was related to the frequency of extra cycles. The percentage of polycyclic shoots was greatest in the 2nd and 4th years of branch growth, although this varied with year and provenance. Total branch numbers were influenced mostly by variation in first- and second-order branch numbers. Second-order branch numbers were greatest in the second and third segments of leader growth (from the top down), but this was influenced by year of growth and provenance. The high levels of second-order branching corresponded to the greater frequency of polycyclic branches in these positions. The fast-growing southern provenance had the most branches, while the slow-growing Yukon source had the least. The slower-growing provenances had the most first-order branches per unit height.