198
T.T. Veblen and P.B. Alaback
where they have had localized impacts on alpine vegetation. Pine marten
and various squirrel species were introduced to islands that did not have
them for historical biogeographical reasons. Squirrels may be affecting
availability of conifer seed or altering competitive relationships with birds.
One of the most significant examples of animal introductions affecting
forest processes in the perhumid rainforest region is the introduction of
Sitka black-tailed deer to the Queen Charlotte Islands in the early 1990s.
The Queen Charlotte Islands are an isolated group of islands 100 km off
of the coast of central British Columbia, well known as a partial glacial
refugium (Calder & Taylor, 1968). No natural predators of deer occurred
on the Queen Charlotte Islands. Deer are not native to the islands
although an isolated population of caribou occurred there historically.
The forest vegetation has been radically altered by the introduced deer
(Pojar & Banner, 1984). The affected forests retain only a small remnant
of the woody shrub stratum. Only bryophytes, ferns and unpalatable
herbs persist in the most heavily affected areas . Shrubs develop into
normal-sized plants only when rooted above the level at which deer
can browse, or when the shrub branches are above browsing height.
Chamaecyparis and Thuja regeneration is severely constrained by deer
because of its high nutritive value and palatability (Hennon, 1992), and
even Picea can be browsed. Because of the paucity of undergrowth (both
tree and shrub) these forests are park-like.
Elk were introduced about 10 years ago in southeast Alaska in one
small region (southern Etolin Island). The population is small and stable,
and local game managers do not believe there is a danger of a major
impact. If the population grows, however there will be major concern
because of the affinity of elk for riparian habitats, which are fragile
habitat for many native plant and animal species and are the most diverse
and productive habitats in most watersheds. Effects of elk on forage and
habitat selection for deer may be significant as well. Deer have also been
introduced north of their natural range in Prince William Sound and
Kodiak Island. Populations remain small and unstable in the Prince
William Sound area , but on Kodiak Island populations have expanded
steadily since their introduction in 1924 and are continuing to move
westward (Smith, 1979). The Kodiak Island populations differ from the
other Alaska populatons in their ability to tolerate winters in nonforested
habitats (natural shrublands) , beyond the western range of Picea and all
other conifers.
Anthropogenic Fire
Charcoal particles in sedimentary samples from northern Patagonia (c.
39°S) to Tierra del Fuego , document the occurrence of fire for at least
several thousand years (Heusser, 1987; Heusser et al., 1988). Although
more charcoal is found in association with pollen assemblages indicating
T.T. Veblen and P.B. Alaback
where they have had localized impacts on alpine vegetation. Pine marten
and various squirrel species were introduced to islands that did not have
them for historical biogeographical reasons. Squirrels may be affecting
availability of conifer seed or altering competitive relationships with birds.
One of the most significant examples of animal introductions affecting
forest processes in the perhumid rainforest region is the introduction of
Sitka black-tailed deer to the Queen Charlotte Islands in the early 1990s.
The Queen Charlotte Islands are an isolated group of islands 100 km off
of the coast of central British Columbia, well known as a partial glacial
refugium (Calder & Taylor, 1968). No natural predators of deer occurred
on the Queen Charlotte Islands. Deer are not native to the islands
although an isolated population of caribou occurred there historically.
The forest vegetation has been radically altered by the introduced deer
(Pojar & Banner, 1984). The affected forests retain only a small remnant
of the woody shrub stratum. Only bryophytes, ferns and unpalatable
herbs persist in the most heavily affected areas . Shrubs develop into
normal-sized plants only when rooted above the level at which deer
can browse, or when the shrub branches are above browsing height.
Chamaecyparis and Thuja regeneration is severely constrained by deer
because of its high nutritive value and palatability (Hennon, 1992), and
even Picea can be browsed. Because of the paucity of undergrowth (both
tree and shrub) these forests are park-like.
Elk were introduced about 10 years ago in southeast Alaska in one
small region (southern Etolin Island). The population is small and stable,
and local game managers do not believe there is a danger of a major
impact. If the population grows, however there will be major concern
because of the affinity of elk for riparian habitats, which are fragile
habitat for many native plant and animal species and are the most diverse
and productive habitats in most watersheds. Effects of elk on forage and
habitat selection for deer may be significant as well. Deer have also been
introduced north of their natural range in Prince William Sound and
Kodiak Island. Populations remain small and unstable in the Prince
William Sound area , but on Kodiak Island populations have expanded
steadily since their introduction in 1924 and are continuing to move
westward (Smith, 1979). The Kodiak Island populations differ from the
other Alaska populatons in their ability to tolerate winters in nonforested
habitats (natural shrublands) , beyond the western range of Picea and all
other conifers.
Anthropogenic Fire
Charcoal particles in sedimentary samples from northern Patagonia (c.
39°S) to Tierra del Fuego , document the occurrence of fire for at least
several thousand years (Heusser, 1987; Heusser et al., 1988). Although
more charcoal is found in association with pollen assemblages indicating