EFFECTS OF FIRE ON SEEDSHED FROM EUCALYPTUS REGNANS

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Abstract
Patterns of seedshed were studied in several burnt and unburnt stands of Eucalyptus regnans F. Muell. in central Tasmania by catching the seed in traps and examining the capsules on the trees. Timing of the seedshed is important because the bulk of the natural regeneration must normally come from the seed which is shed within one year after burning. In unburnt stands seed was shed throughout the year. During some years the pattern of seedshed was irregular, but after hot, dry summers one-half to three-quarters of the year's seedshed occurred in February-March-April. The capsules themselves were cast off in a less regular pattern; the fallen capsules still contained 16 per cent of the full seed loading. Fire may accelerate seedshed. If the leaves and twigs are scorched, the capsules also are killed and their seed is shed as soon as they dry out; this may take hours or weeks. If the tree is girdled the crown will wilt within days or months, depending on the depth of girdling and the subsequent weather. Seedshed occurs when the crown is wilting. Even if the crown remains green and apparently healthy seedshed may be affected. Sometimes all or nearly all the capsules of a heavy crop are abscissed in less than one month after the fire. More often only a proportion of the capsules is affected by the fire. It is considered that the pattern of seedshed after fire is generally such that the available seed is reasonably effective in producing regeneration.