Containerized Pinus banksiana and Pinus resinosa seedlings were grown in a mine drift at the 1400 m (4600’) level at INCO Ltd’s Creighton Mine to age 14 weeks prior to hardening-off and out-planting on disturbed and stressed lands. Planting sites were: a) land denuded because of base-metal smelting activity, and b) an aggregate borrow pit. Both sites had been reclaimed recently by application of lime and fertilizer, and
seeding to grasses and legumes.
Two crops were examined; a fall out-planted crop and a spring out-planted crop. Five hardening-off treatments were used: I) constant 13° C, II) fluctuating 13° C night, 23°C day, III) constant.8°C, IV) fluctuating 8° C night, 23° C day, and V) constant 23° C. Daytime photoperiod was 12 h for fall out-planted seedlings and 20 h for spring out-planted seedlings. Plants were assessed for degree of survival, amount of flushing and overall growth.
Best survival (spring, 90%; fall, 70%) was obtained on the site denuded by smelter activity, irrespective of season. The most effective hardening-off treatment in spring was a continuous 23° C regime whereas the most effective fall treatment was a 8° C night:23° C day regime. This same regime provided the best growth response for fall-planted seedlings of both species. Overall, seedlings at the Coniston site showed the best
performance. This success is attributed to a better microenvironment.