Persistence ofPseudotsuga menziesii (Douglas-fir) in temperate coniferous forests of the Pacific Northwest Coast, USA

Abstract

Old-growthPseudotsuga-Tsuga forests of the Pacific Northwest Coast of North America are characterized by the presence of large, old trees ofPseudotsuga menziesii var.menziesii (Douglas-fir). Colonizing soon after a stand-replacing disturbance,P. menziesii persists in these forests, coexisting for centuries with the late-successional species.P. menziesii survives by maintaining emergent status in the uppermost part of the forest canopy, above the crowns of competing late-successional species. After reaching maximum tree height and crown size,P. menziesii maintains shoots and foliage of the established crown by epicormic shoot production. In this review, we propose that attaining emergent status in the upper canopy combined with the process of crown maintenance contributes to the persistence ofP. menziesii into later stages of succession, making this species a long-lived pioneer that between infrequent disturbances can coexist with late-successional species for centuries.