16. A Comparison of the Ecology and Conservation Management
327
92% of the ferns are shared with Australia , 69% with new Zealand, and
only 8% (4 species) are shared with South America (Jarman et al., 1986).
About two thirds of the lichen flora have an austral cool temperate
distribution (Galloway, 1988; Kantvilas, 1990). Only 5% of the rainforest
lichens and about 4% of the bryophytes are endemic, in contrast to the
spermatophytes where , approximately 75% are endemic.
Ecology
Ecological Succession
The distribution and proportions of rainforests, eucalypt forest, and nonforest communities in the lowland high rainfall areas of Tasmania are
determined largely by fire (Gilbert, 1959; Jackson, 1968; Ashton, 1981a,b;
Brown & Podger, 1982a; Ellis, 1985; Podger, Bird, & Brown , 1988), with
large areas of pure rainforest being found only where average fire frequencies are greater than 400 to 600 years.
Once a closed canopy is established in a rainforest, it preserves a humid
interior with rapid decomposition of fine fuels , especially on high-base
status soils. It is thus generally resistant to fire. However in older forests ,
when individual Nothofagus stems die , they remain as dead snags for
some time and support a column of lichens and bryophytes. In severe
drying weather and strong winds , these " ladder fuels " act as traps for
spot fires and provide ignition and entry points for rainforest fires (A.B.
Mount, personal communication). Such fires can burn fiercely and rapidly
traverse long distances. For example the 1982 Savage River fire burned
through a strip of rainforest 25 km by 5 km wide in one night (Barker,
1991).
A single wildfire in a rainforest is followed by a succession of mosses
and liverworts, such as Funaria and Marchantia (Cremer & Mount, 1965;
Duncan & Dalton, 1982) , and a flush of seral vascular species such as
Senecio spp., Pteridium escu!entum, Gahnia grandis , and Leptospermum
spp (Hill, 1982; Hill & Read, 1984; Barker, 1991), together with the
slowly establishing seedling and vegetative regeneration of the original
rainforest elements. The fire-sere species generally have attributes conducive to further fire; they are flammable, have high essential oil contents,
and produce rapid fine-fuel accumulation because of their generally short
life spans or early twig death. In addition, their litter may have high levels
of phenols, which inhibit rapid decomposition. The seral species recover
readily from fire either by vegetative growth or from soil-stored or widely
disseminated seed. Thus repeated fires further promote these species and
kill any remaining rainforest elements. The complete conversion of areas
of implicate rainforest to moorland and scrub by repeated firing over a 60
year period has been documented by Podger et al. (1988).
If there are no further fires beyond the initial one, rainforest eventually
will reestablish on the site . Thus there are many " pole" stands of even-
327
92% of the ferns are shared with Australia , 69% with new Zealand, and
only 8% (4 species) are shared with South America (Jarman et al., 1986).
About two thirds of the lichen flora have an austral cool temperate
distribution (Galloway, 1988; Kantvilas, 1990). Only 5% of the rainforest
lichens and about 4% of the bryophytes are endemic, in contrast to the
spermatophytes where , approximately 75% are endemic.
Ecology
Ecological Succession
The distribution and proportions of rainforests, eucalypt forest, and nonforest communities in the lowland high rainfall areas of Tasmania are
determined largely by fire (Gilbert, 1959; Jackson, 1968; Ashton, 1981a,b;
Brown & Podger, 1982a; Ellis, 1985; Podger, Bird, & Brown , 1988), with
large areas of pure rainforest being found only where average fire frequencies are greater than 400 to 600 years.
Once a closed canopy is established in a rainforest, it preserves a humid
interior with rapid decomposition of fine fuels , especially on high-base
status soils. It is thus generally resistant to fire. However in older forests ,
when individual Nothofagus stems die , they remain as dead snags for
some time and support a column of lichens and bryophytes. In severe
drying weather and strong winds , these " ladder fuels " act as traps for
spot fires and provide ignition and entry points for rainforest fires (A.B.
Mount, personal communication). Such fires can burn fiercely and rapidly
traverse long distances. For example the 1982 Savage River fire burned
through a strip of rainforest 25 km by 5 km wide in one night (Barker,
1991).
A single wildfire in a rainforest is followed by a succession of mosses
and liverworts, such as Funaria and Marchantia (Cremer & Mount, 1965;
Duncan & Dalton, 1982) , and a flush of seral vascular species such as
Senecio spp., Pteridium escu!entum, Gahnia grandis , and Leptospermum
spp (Hill, 1982; Hill & Read, 1984; Barker, 1991), together with the
slowly establishing seedling and vegetative regeneration of the original
rainforest elements. The fire-sere species generally have attributes conducive to further fire; they are flammable, have high essential oil contents,
and produce rapid fine-fuel accumulation because of their generally short
life spans or early twig death. In addition, their litter may have high levels
of phenols, which inhibit rapid decomposition. The seral species recover
readily from fire either by vegetative growth or from soil-stored or widely
disseminated seed. Thus repeated fires further promote these species and
kill any remaining rainforest elements. The complete conversion of areas
of implicate rainforest to moorland and scrub by repeated firing over a 60
year period has been documented by Podger et al. (1988).
If there are no further fires beyond the initial one, rainforest eventually
will reestablish on the site . Thus there are many " pole" stands of even-