Why Engelmann spruce does not have a persistent seed bank

Abstract
Piceaengelmannii Parry ex Engelm. becomes established after fire by dispersing seeds into a burn, not through the maintenance of a persistent soil seed bank. The objective here was to determine causes of spruce seed loss from the bank to understand its lack of a persistent seed bank. One hundred seeds placed in soil cores were enumerated for 2.5 years and divided into three treatments: (i) varying the amount of protection from predators, (ii) keeping litter intact or removing it, and (iii) placing seeds on top of litter or between litter and mineral soil. For all treatments, fewer than 5% of seeds remained at the end of the study. Predation caused the greatest loss to the seed bank, much greater than germination in all treatments. Removal of litter increased germination, but predation occurred at the same rate; therefore, the total rate of loss to the seed bank increased. Seeds placed between litter and mineral soil experienced greater germination and less predation than seeds placed above the litter layer. However, increased germination balanced the reduced predation so there was little difference in the total rate of loss to the seed bank from seeds placed in either location. Further, seeds appeared to lose viability within two seasons. Thus, there is no persistent seed bank because of high predation and a rapid loss of viability.

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