Canadian Forest Service Publications
Aboveground dry matter partitioning responses of black spruce to directional-specific indices of local competition. 2003. Newton, P.F.; Joliffe, P.A. Canadian Journal of Forest Research 33: 1832-1845.
Issued by: Great Lakes Forestry Centre
Catalog ID: 24382
Availability: PDF (request by e-mail)
This study assessed the effects of directional-specific indices of local competition on the partitioning of aboveground dry matter of individual black spruce (Picea mariana (Mill.) BSP) trees. Historical tree reconstruction sampling techniques were used to estimate stem, branch, and foliage ovendry masses by year of formation (cohort age-class) of 125 subject trees situated within 15 density-stressed stands. Component-specific modular mass proportion calculated on an individual and cumulative cohort age-class basis was employed as an index of dry matter partitioning. Analytically, local competitors were stratified into one of four competition classes based on their relative size differential with respect to the subject tree. Sequential competition analysis was used to assess directional-specific partitioning responses to competition accumulating upwards from below and downwards from above. Furthermore, within the sequential competition analysis framework, the effects of the individual competition strata on partitioning were assessed employing stepwise multivariate analysis of variance. The results supported the presence of an asymmetric relationship dominated by competition from above in which branch partitioning was the most affected. Specifically, competition from larger-sized competitors resulted in decreased branch mass proportions whereas competition from smaller-sized competitors had no appreciable effect. These results are in accord with the hypothesis that black spruce responds to competition via an adaptive phenotypic plastic response in which branch growth declines and (or) branch abscission rates increase with increasing competition from above.