Amelioration of wood ash toxicity and jack pine establishment

Fresh wood ash inhibits the germination and early survival of some conifers but this ameliorates with leaching. It was unknown, however, how much precipitation and time it takes for wood ash to become a favourable seedbed. Laboratory and field studies showed that the rate of leaching of conifer and aspen ash was dependant on the amount of water, but a break between watering periods allowed the ionic content of ash to recover and rise. Field trials on a wildfire site and experimental plots in the Northwest Territories and Alberta indicated that 600-700 mm of water could leach 2-3 cm of ash sufficiently to allow some establishment of jack pine (Pinus banksiana Lamb.), equivalent to that on undisturbed and vegetated duff. Precipitation in excess of 1000 mm appeared necessary for substantial jack pine establishment. With normal precipitation levels these levels of establishment would take 1-2 years (600-700 mm) and 2-3 years (1000 mm). After 1 year, jack pine seedfall from serotinous cones is complete and the opportunity for seedling establishment on ash has been lost. Wildfire sites with deep wood ash tend to be dominated by Betula and Salix species