Early height growth of mixed eucalypt species regeneration established by clearfall, burn and sow treatments at four locations taking in a range of different forest sites in eastern and north-eastern Tasmania has been compared with that of natural regeneration on adjoining areas which were clearfelled at the same time but not burnt. The natural regeneration was of various origins but was generally still quite small at the time of the burn and sow treatments, which it pre-dated by up to 12 years. Height has been measured several times at each site during the period 2-10 years post-burn.On two relatively wet sites (approximately 1250 mm and 1000 mm mean annual rainfall) the burn and sow treatments produced significantly faster early height growth than the unburnt treatments, but on the two drier sites (approximately 850 mm and 800 mm mean annual rainfall) growth rates did not differ significantly between treatments. On the drier sites the unburnt treatment allowed vigorous coppice shoots to establish an initial height advantage which has so far been maintained.These early results suggest that, on productivity grounds, the case for slash burning is not so strong in Tasmania's drier, more open, lower quality forests as in the wetter, higher quality forests. Nevertheless, in the drier forests slash burns are still used more often than not, mainly to facilitate future fire protection.
Even-aged, mixed species eucalypt regeneration with a wide range of initial stockings was established on a Tasmanian moist sclerophyll site by using a range of sowing rates. Stocking, growth and development were monitored on permanent measurement plots from the time of regeneration to age 16. Initial stocking data were combined with volume data from the age 13 and 16 measurements and used in conjunction with local expert knowledge on stand development to produce a preliminary model which predicts how initial stocking will affect the standing volume at any given age. This paper presents the model and outlines some other aspects of stand development for which the study, with its detailed information including the spatial location, species and size at repeated measurements of every tree on the plots, will provide a valuable data base.
Height data to 20 years are presented for a study previously reported by Lockett and Candy ( 1984) on the effects of slashburning on growth rates of eucalypt regeneration established following clear-falling. The study covers a range of forest types on five sites throughout Tasmania with rainfalls ranging from 800mm to 1800mm.On the two driest sites, the initial conclusion that slash burning had no significant impact on height growth has been confirmed by subsequent measurements. On the three wetter sites, there was a consistent trend which suggests that slash-burning caused growth rates to be more than doubled in the third year post-bum. This effect progressively declined and finally disappeared between years ten and fifteen. The net result of burning would be a shortening of the rotation by a maximum of five years, or less where natural regeneration is already established, or can be established earlier in the absence of a slash-bum. Operationally, the decision whether to bum or not will involve balancing these growth effects against the stocking, size and potential vigour of new natural regeneration or older advance growth and the desirability of preserving it. This may require consideration of how difficult it is to establish regeneration on the site and how much the risk of wildfire will be increased if slash is left unbumt.
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