Tales from the Blackgum, a Consummate Subordinate Tree

摘要

No species in the eastern United States better exemplifies a ubiquitous yet subordinate tree than does blackgum (Nyssa sylvatica). What enables blackgum to grow nearly everywhere, but almost always at very low densities? It is the longest-lived hardwood species in the eastern United States, with a maximum age that can exceed 650 years. It is inherently slow growing, which most likely explains its great longevity and high shade tolerance; it is also one of the few tree species that are fire resistant as well as shade tolerant. Blackgum can grow in bottomlands or at xeric sites, being tolerant of both flooding and drought. Despite these ecologically beneficial attributes—and the fact that early loggers systematically avoided blackgum because of its tendency to rot—this slow-growing tree is rarely dominant. Blackgum has so far simply persisted as a marginal species. The future of blackgum is uncertain, however, because of the opposing forces of global warming and increased competition from other tree species. This article synthesizes a broad range of ecological studies that relate to the unique behavior of blackgum as a consummate subordinate, something that is poorly understood for this and other similar species in the ecology literature.