9. A Comparative Review of Forest Dynamics and
Disturbance in the Temperate Rainforests of North
and South America
Thomas T. Veblen and Paul B. Alaback
ln this chapter, we review and compare North and South American
temperate rainforests in terms of patterns of forest dynamics and natural
disturbance, stand responses to disturbances, human modifications of
disturbance regimes, and the effects of recent climate variation on forest
dynamics. Contemporary ecologists view vegetation change as the outcome
of interacting populations constrained by fluctuating environmental conditions (Glenn-Lewin, Peet, & Veblen, 1992; Pickett, Collins, & Armesto,
1987). Disturbance accounts for much of the environmental heterogeneity
in time and space. Substantial research is now devoted to characterizing,
qualitatively as well as quantitatively, the spatial and temporal characteristics of disturbances, or "disturbance regimes," that are relevant to a
particular population or community (Pickett & White, 1985).
Temperate rainforests are distinguished from other temperate forest
types by the prevalence of evergreen trees in climates characterized by
cool summer temperatures, relatively mild winters, and abundant moisture
throughout the year (Alaback, 1991; Brown & Read, this volume; Veblen,
Schlegel, & Oltremari, 1983). The climates of temperate rainforests are
generally characterized by annual precipitation greater than 1400 mm, of
which 10% or more occurs during the summer months, and by a mean
temperature of less than 16°C during the warmest month (Alaback, 1991).
The temperate rainforests of North and South America may be divided
into three subtypes on both continents: subpolar, perhumid, and seasonal.
173
Disturbance in the Temperate Rainforests of North
and South America
Thomas T. Veblen and Paul B. Alaback
ln this chapter, we review and compare North and South American
temperate rainforests in terms of patterns of forest dynamics and natural
disturbance, stand responses to disturbances, human modifications of
disturbance regimes, and the effects of recent climate variation on forest
dynamics. Contemporary ecologists view vegetation change as the outcome
of interacting populations constrained by fluctuating environmental conditions (Glenn-Lewin, Peet, & Veblen, 1992; Pickett, Collins, & Armesto,
1987). Disturbance accounts for much of the environmental heterogeneity
in time and space. Substantial research is now devoted to characterizing,
qualitatively as well as quantitatively, the spatial and temporal characteristics of disturbances, or "disturbance regimes," that are relevant to a
particular population or community (Pickett & White, 1985).
Temperate rainforests are distinguished from other temperate forest
types by the prevalence of evergreen trees in climates characterized by
cool summer temperatures, relatively mild winters, and abundant moisture
throughout the year (Alaback, 1991; Brown & Read, this volume; Veblen,
Schlegel, & Oltremari, 1983). The climates of temperate rainforests are
generally characterized by annual precipitation greater than 1400 mm, of
which 10% or more occurs during the summer months, and by a mean
temperature of less than 16°C during the warmest month (Alaback, 1991).
The temperate rainforests of North and South America may be divided
into three subtypes on both continents: subpolar, perhumid, and seasonal.
173