Effect of seed predation, shade and soil organic matter on the early establishment of eastern white pine and balsam fir seedlings

Abstract

Eastern white pine (Pinus strobus L.) does not regenerate well in the absence of fire, or without mechanical exposure of mineral soil, while balsam fir (Abies balsamea L. Mill.) is a common understory species on sites occupied by white pine. We conducted two experiments to explain the difference in regenerative success of these two species. First, the effect of shade and soil organic matter on the emergence of white pine and balsam fir were compared using soil monoliths from a regenerating white pine stand. Balsam fir germination was significantly lower than white pine germination at different shade levels and at different levels of soil organic matter. Second, seed predation was compared between balsam fir and white pine in a non-regenerating white pine stand. Predation of white pine seeds was 10 times greater than balsam fir predation even when seeds of white pine and balsam fir were left as a mixture on the forest floor. We speculate that seed predation is a critical factor in white pine succession and that seed predators favour balsam fir succession by selecting white pine seeds. Key words: seed predation, fire ecology, Pinus strobus, Abies balsamea, Peromyscus maniculatus, succession