A total of 24 hybrid poplar clones grown in Windsor and St-Ours in southern Quebec, Canada, were characterized for chemical properties (pH, acid buffer capacity, and base buffer capacity). This test group of 10-year-old poplar clones (spring of 1993 to winter of 2002) was comprised of 12 clones grown in Windsor and 12 clones grown in St-Ours. At both locations, there were four hybrids: P. deltoides (D); P. deltoides x P. nigra (D x N); P. trichocarpa x P. deltoides (T x D); and P. maximowiczii x P. balsamifera (M x B). Thus, each hybrid included three clones. In addition, 3 replicates of two clones derived from D and D x N hybrids grown in Windsor were tested to examine the block (sub-location) influence of clone type on wood chemical characteristics.
Results showed that both hybrid and geographic location affected wood chemical characteristics, based on the average values of the same hybrid. In general, the fast-growing poplar clones (as determined by tree diameter) in St-Ours showed higher pH and acid buffer capacity, but lower base buffer capacity than those grown in Windsor. For clones within the same hybrid, observations showed that clone type had more influence on acid and base buffer capacities than on pH value, and the extent of the influence depended on each individual hybrid. In terms of variations in wood chemical properties within the same clone, replicate measurements of two clones (one from D hybrid and one from D x N hybrid) showed greater variations in base buffer capacity than in pH and acid buffer capacity. This study implies that differences in the wood chemical properties examined depend not only on wood genotype, but likely also on site quality, which correlates well to wood physical properties such as tree diameter, basic wood density and fiber length.