LOW ROOT TEMPERATURES AND GROWTH OF EUCALYPTS 
73 
tection of an overwood. Since 1967, 4800 ha of 
forest have been logged by clear felling on Errin- 
undra Plateau. Because of limited seed pro¬ 
duction, it has not been possible to regenerate 
these stands with pure E. nitens. Various mix¬ 
tures of E. nitens, E. delegatemis and E. fasti gala 
have been used, with extensive areas regener¬ 
ated by a seed mixture containing equal pro¬ 
portions of all three. To date regeneration of all 
three species has occurred without a particular 
problem due to frost. 
Because fire intensity is exponentially related 
to slope (McArthur 1967) fires burn less in¬ 
tensely on plateaus, and possibly less frequently. 
The multi-aged stands observed in Tasmania 
(Webb et al. 1983) are favoured on plateaus 
because fires create favourable seed bed con¬ 
ditions but have less tendency to destroy the 
overwood, particularly where this consists of 
mature trees. Forests with these structures have 
been observed over a long period in E. reg/tans 
and E. delegatensis forests in Victoria and Tas¬ 
mania (Lindenmayer et al. 1990). Similar struc¬ 
tures have been recorded in mixed stands of E. 
nitens and E. delegatensis in the headwaters of 
the Rodger River (Chesterfield et al. 1983), and 
inE. on Errinundra Plateau. Fires in 1939 
burnt the margins of Errinundra Plateau and, at 
one point where the regrowth occurred amongst 
a scattered stand of E. nitens , the multi-aged 
structure is clearly evident (Chesterfield et al. 
1988). More recently, during burning of logging 
debris on Errinundra Plateau, approximately 
one hectare of mature forest recovered after 
complete defoliation by heat scorch. Thus, pro¬ 
vided adequate gaps occur, the formation of 
multi-aged stands is not an improbable event. 
The modification of the fire regime by plateau 
topography that favours the formation of multi¬ 
aged eucalypt stands also protects and encour¬ 
ages the development of rainforest in areas 
where soils and rainfall are adequate. In Vic¬ 
toria, Atherosperma moschatum, Nothofagus 
cunninghamii and Elaeocarpus holopetalus are 
important constituents of the E. nitens environ¬ 
ment and, in the absence of fire, produce heavily 
shaded soils at maturity. Forests with similar 
composition and structure occupy similar en¬ 
vironments in Tasmania. Here somewhat un¬ 
even aged stands of£. delegatensis first declined 
in the early 1960s, following a period of approxi¬ 
mately 140 years without fire. Die-back was 
associated with the development of dense, 
closed forest understories. Trees of all age classes 
and canopy positions were affected and the on¬ 
set of die-back was influenced by elevation. 
Below 750 m, stands with a similar understorey 
were unaffected. After studying soil chemical 
factors, Ellis & Graley (1987) concluded that the 
small differences were more likely to be the re¬ 
sult rather than the cause of successional 
changes. Ellis (1971) initially proposed that tem¬ 
perature changes in the root environment were a 
possible explanation. Over a two year period he 
recorded mean annual soil temperatures at a 
depth of450 mm which were 2-3°C higher under 
grass in comparison with the rainforest under¬ 
storey. After considering the environmental 
lapse rate he calculated that the rainforest in¬ 
vasion was equivalent to an altitudinal increase 
of 335-520 m, placing stands at 915 m, well 
above their altitudinal limit. Although the cause 
of die-back has not been ascertained with any 
certainty, the results for height growth in this 
study support the hypothesis that low soil tem¬ 
peratures may be a factor contributing to the 
decline in E. delegatensis. The natural post fire 
succession in this forest type is toward under¬ 
stories that are open at maturity and dominated 
by grasses, forbs, and ferns over the greater part 
of their range. Heavily shaded soils associated 
with a closed forest understorey are rarely pres¬ 
ent. 
The similarities between the vegetation, fire 
regime and successional changes that have 
occurred on the elevated montane plateaus of 
Victoria and Tasmania are striking, with the 
exception that in Victoria, in areas where the 
rainforest understorey is dense, die-back of the 
E. nitens overstorey has not been observed. It is 
recognised that E . nitens can tolerate the incur¬ 
sion of rainforest species for longer periods than 
either E. delegatensis or E. regnans (United 
Nations Food and Agriculture Organisation 
1979). 
In the montane forests of southeastern Aus¬ 
tralia, fires over a wide elevation zone extending 
above and below the snow line have been suf¬ 
ficiently frequent to favour eucalypt species cap¬ 
able of producing regular and reliable seed 
crops. Although E. nitens has proven to be of 
equal or superior vigour to most of its competi¬ 
tors in growth trials, it is an unreliable and poor 
seed producer (United Nations Food and Agri¬ 
culture Organisation 1979, Turnbull & Pryor 
1978, Boland et al. 1980), particularly when 
compared to E. regnans, E. delegatensis and E. 
fastigata. Therefore, as the frequency of fire in¬ 
creases, the proportion of E. nitens in mixed 
stands is likely to decline, as noted in the Rodger 
River (Chesterfield et al. 1983). 
The role of fire in the natural distribution of E. 
