152
M.T.K. Arroyo et al.
with angiosperm trees (Veblen, 1982; Veblen, Delmastro , & Schlutter,
1976). The importance of competition from faster-growing angiosperms
suggested by Schmithiisen (1960) as an explanation for the distribution of
some South American gymnosperms was not supported by the presentday regeneration patterns of pure and mixed stands of Araucaria araucana
with Nothofagus species (Veblen , 1982). Rather A. araucana is seen
as a stress-tolerant strategist that has always favored harsh habitats,
independently of its relictual status.
Regal (1982) argued that anemophilous trees in general should be
restricted to marginal sites where pollen movement between conspecifics
would not be limited. This explanation seems unlik ely for the ecological
distribution of South American rainforest gymnosperms, which, as noted
above, can be often found in mixed stands with angiosperm trees.
Midgeley and Bond (1991) , recently showed that isolated individuals of
South African Podo carpus falcatus separated by 70 m from the nearest
reproductive male produced mature seeds, indicating that pollen can
move considerable distances without total dilution in mixed forests.
The three major rainforest zones (Table 8.4) shows progressive southward floristic impo verishment. We could only find records of 149 and 102
vascular plant species in the North Patagonian and Magellanic rainforest
zones, respectively. The Magellanic zone is quite well known (e.g. ,
Dollenz, 1982b; Pisano , 1977, 1980a, 1980b, 1989). However, modest
increases in species richness in the North Patagonian zone are expected
due to poor exploration . It is interesting that only 20 of all rainforest
species (mostly herbaceous species of low abundance, but including a few
ferns) have not been reported in the northern Valdivian rainforest zone.
On the other hand, some 255 (58%) species, on present knowledge, are
not found in rainforest south of this zone. Thi s implies th at practic ally all
species in the cool temperate rainforest can be found in the region bound
by its northern climatic limit and the southern extreme of Chiloe , and
that a very significant proportion of the species are only found here .
Consideration of non sea sonal rainforest (Table 8.2) (this provides the
best comparison for floristic data supplied by P. Alaback, this volume)
shows that there are some 249 species. The number of woody species , and
particularly the number of tree species, remains very high . Proportionately
there are more woody species here than in the total rainforest area
(44% ) , and only 7 tree species are absent from nonseasonal rainforest.
There are also still many shrubs.
Undoubtedly, it is the life-form spectru m that most sets South American
cool temperate rainforest apart from North American cool temperate
rainforest. Apart from trees, shru bs, hemiparasites, and ground herbs,
there are significant contributions of woody vines/climbing shrubs, herbaceous vines , and epiphytic angiosperms, virtually unknown in North
American rainforest (Al aback, this volume; Franklin, 1988). Th e cool
temperate rainforest of Tasmania also lacks vines . However, epiphytic
M.T.K. Arroyo et al.
with angiosperm trees (Veblen, 1982; Veblen, Delmastro , & Schlutter,
1976). The importance of competition from faster-growing angiosperms
suggested by Schmithiisen (1960) as an explanation for the distribution of
some South American gymnosperms was not supported by the presentday regeneration patterns of pure and mixed stands of Araucaria araucana
with Nothofagus species (Veblen , 1982). Rather A. araucana is seen
as a stress-tolerant strategist that has always favored harsh habitats,
independently of its relictual status.
Regal (1982) argued that anemophilous trees in general should be
restricted to marginal sites where pollen movement between conspecifics
would not be limited. This explanation seems unlik ely for the ecological
distribution of South American rainforest gymnosperms, which, as noted
above, can be often found in mixed stands with angiosperm trees.
Midgeley and Bond (1991) , recently showed that isolated individuals of
South African Podo carpus falcatus separated by 70 m from the nearest
reproductive male produced mature seeds, indicating that pollen can
move considerable distances without total dilution in mixed forests.
The three major rainforest zones (Table 8.4) shows progressive southward floristic impo verishment. We could only find records of 149 and 102
vascular plant species in the North Patagonian and Magellanic rainforest
zones, respectively. The Magellanic zone is quite well known (e.g. ,
Dollenz, 1982b; Pisano , 1977, 1980a, 1980b, 1989). However, modest
increases in species richness in the North Patagonian zone are expected
due to poor exploration . It is interesting that only 20 of all rainforest
species (mostly herbaceous species of low abundance, but including a few
ferns) have not been reported in the northern Valdivian rainforest zone.
On the other hand, some 255 (58%) species, on present knowledge, are
not found in rainforest south of this zone. Thi s implies th at practic ally all
species in the cool temperate rainforest can be found in the region bound
by its northern climatic limit and the southern extreme of Chiloe , and
that a very significant proportion of the species are only found here .
Consideration of non sea sonal rainforest (Table 8.2) (this provides the
best comparison for floristic data supplied by P. Alaback, this volume)
shows that there are some 249 species. The number of woody species , and
particularly the number of tree species, remains very high . Proportionately
there are more woody species here than in the total rainforest area
(44% ) , and only 7 tree species are absent from nonseasonal rainforest.
There are also still many shrubs.
Undoubtedly, it is the life-form spectru m that most sets South American
cool temperate rainforest apart from North American cool temperate
rainforest. Apart from trees, shru bs, hemiparasites, and ground herbs,
there are significant contributions of woody vines/climbing shrubs, herbaceous vines , and epiphytic angiosperms, virtually unknown in North
American rainforest (Al aback, this volume; Franklin, 1988). Th e cool
temperate rainforest of Tasmania also lacks vines . However, epiphytic