The Question of Eastern White Pine (Pinus strobus L.) on Extreme Sites: History and Ecology in the Northeast Uplands of Connecticut
Eastern white pine (Pinus strobus L.) is one of the most familiar, charismatic, and economically important softwood tree species of eastern North America, but it is also one of the most ecologically puzzling. White pine occurs on a variety of soils and topographies and will establish itself through multiple modes of succession, such that it has acquired a reputation as an ecological generalist of few limitations (Abrams, 2001). However, we should not make the mistake of assuming this has always been the case. While its distribution is broad, white pine does not compete well with hardwoods on most mesic sites (Hibbs, 1982), and its regeneration is often problematic (L. F. Smith, 1940). Indeed, rather than consider white pine a generalist, it may be more useful to describe it as a fugitive species (sensu Hutchinson, 1951), although one that is exceptionally long-lived, that moves by windblown seed among scattered patches distributed across the landscape as disturbance permits (Sauer, 1988). This habit has allowed it to proliferate widely in the wake of land-use change. The ecological breadth of white pine as seen in the forests of southern New England today is largely an artifact, the unintentional creation of [Euro-American] human hands. This regional expansion and proliferation of white pine may be considered part of a global phenomenon of “pine invasions” (Richardson and Bond, 1991). As noted by D. M. Smith (1950: 1), few species of North American trees are more highly prized than white pine, but even fewer have been so dramatically affected by human activity, “or are less capable of flourishing without [human] assistance.” Indeed, through large portions of its range, white pine\\\‘s presence in natural stands is so ecologically precarious that \\\“almost any unfavorable factor may result in widespread retreat\\\” of the species (Shirley, 1945: 538)
What lies behind this obscuring cloud of anthropogenic noise? If we subtract the contribution of three centuries of land-use history to the autecology of white pine, what is left over? It is difficult to quantify what the niche of white pine may have been in the forests of southern New England prior to European settlement in the early 1600s, and the historical limits of the species’ distribution have long remained controversial (Bromley, 1935; Cronon, 1983; Abrams, 2001). The major argument of this study is that the key to these questions lies in white pine’s unusual tolerance of extreme sites.