PREPLANTING PHYSIOLOGICAL STRESS ASSESSMENT TO FORECAST FIELD GROWTH-PERFORMANCE OF JACK PINE AND BLACK SPRUCE

This study examined the possibility that pre-planting physiological as sessment, after heat stressing, could be used to forecast stem Volume increment after 4 years. Several stocktypes of black spruce (Picea mar iana (Mill.) B.S.P.) and jack pine (Pinus banksiana Lamb.) were expose d to 45-50 degrees C of heat stress for 15-20 min in the dark, and pla nted on sites with or without competing vegetation controlled. Pre-pla nt testing involved post-stress assessment of chlorophyll fluorescence , net photosynthetic rate, and root growth potential. Pre-plant physio logy appeared to be useful in forecasting and distinguishing the compe titive potential of the different stocktypes. Chlorophyll fluorescence parameters such as the ratio of variable to maximal fluorescence (Fv/ Fmax) ill black spruce and the difference between the maximum M and th e intermediate steady-state S (FM-S) in jack pine, measured 1 day afte r the stress exposure, were more closely correlated (Pearson product-m oment and Spearman-rank correlation greater than or equal to 0.95) tha n photosynthetic rate or root growth potential to stem volume incremen t.