Abstract
The buds of Eucalyptus regnans are protected by an operculine involucre for 12 months and develop
as exposed umbels for a further 15-17 months. The flowering period is about 3 months but the
extreme range is from late February to early July at elevations of 600-750 m. Flowers remain open
for 1-2 weeks. Older trees tend to flower later than younger trees on the same site. Pollination is
probably effected chiefly by insects and birds. Flowering abundance follows a 2-year cycle with
a tendency for heavier production every fourth year, but this pattern may be interrupted by severe
insect attack on young shoots. Considerable losses occur at all stages of development owing to
abscission, and to damage by gall and other insects. Quantitative estimates of flowering from litter
trays indicate that the flower production of good years may be 25-65 times as great as in poor years.
The mature forest produced 2.15-15.5 times as many flowers as the pole stage trees, and 1.5-10
times as many as the spar stage forest. Estimates of the fruit set following the late autumn flowering
of 1954 indicate that that of the mature forest was 1.6 times as great as that in the spar stage forest
and 3.5 times as great as that in the pole stage forest. The corresponding relative flower abundance
in these forests was 1.5 and 3.8 respectively. However, the percentage of Rowers setting fruit from
the early autumn flowering of 1956 was very much lower. Most capsules abscind or dehisce or fall
attached to twigs within 3 years of their maturity. The quantitative estimate of flowering and fruit set
permits seed crops from heavy flowering to be forecast a few years ahead of seed fall.
Subject
Plant Science,Ecology, Evolution, Behavior and Systematics
Cited by
119 articles.
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