Delayed emergence of four conifer species on postfire seedbeds in eastern Canada

Abstract

This study compares the emergence of jack pine (Pinusbanksiana Lamb.), eastern white pine (Pinusstrobus L.), black spruce (Piceamariana (Mill.) B.S.P.) and balsam fir (Abiesbalsamea (L.). Mill.) for three seasons after sowing on two postfire seedbeds to test the hypothesis that conifer species differ in their ability to store viable seeds in the soil. Less than 20% of all viable seeds produced emergent seedlings in the first growing season. Emergence continued in the second growing season but not in the third. No viable seeds of any species were found at the end of the experiment. During the second growing season (July 1), the emergence of jack pine was greatest at the warmer and drier site but at the cooler and moister site, large numbers of black spruce emerged; by the end of the second season jack pine seedlings predominated at both sites. Although this delayed emergence accounted for <3% of the viable jack pine seeds sown, this percentage would be sufficient to produce a dense stand given normal postfire seedfall rates. It is suggested that delayed emergence from the soil along with partial seed retention in tree crowns are strategies of jack pine and black spruce which increase the probability of establishment even if the immediate postfire conditions are particularly inhospitable.