Litter fall, canopy leaf area and environmental conditions were monitored in a regrowth stand of Eucalyptus maculata Hook. in Kioloa State Forest on the south coast of New South Wales, from spring 1977 to winter 1992. Litter fall during the first half of the study period was strongly influenced by two of the most serious droughts that had occurred in 100 years. Canopy renewal and, hence, leaf fall and changes of leaf area index (LAI), were also influenced by the flowering phenology of E. maculata. Total annual litter fall (including bark shed from lower boles) averaged 5.7 t ha-1 and ranged from 3.1 up to 7.5 t ha-1. The respective means (plus absolute ranges) of annual leaf, twig and bark fall were 2.8 (1.5–4.2), 0.9 (0.3–1.4) and 1.6 (0.5–3.1) t ha-1. Forest LAI varied between 0.7 and 5 m2 m-2. Leaves comprised 50% of the average annual litter fall; bark shed from lower boles of E. maculata contributed 0.63 t ha-1 to average annual bark fall. Flower buds were produced by a proportion of overstorey trees of E. maculata about every second year. Synchronous production and flowering of buds on all trees was observed only once in 15 years. Less than 15% of flower buds (overall) produced fruit.

The canopy dynamics of a regenerated 16-year-old stand of pole and sapling E. maculata were studied for 2½ years by repetitive non-destructive measurements in tree crowns accessed from a 20 m high scaffold tower. Average canopy leaf area density over a sample plot of 36 m2 was 0.23 m2 m-3 at a leaf area index of 4.3. Some 75% of leaf area was held in the canopies of overstorey eucalypts above 10 m in height. Average size of leaves increased gradually from top to bottom of tree canopies. Foliage production was usually concentrated in the upper crowns of trees where there was a higher proportion of active shoots, more frequent growth flushes and more rapid turnover of leaves than in lower canopy layers. Leaf area in the upper canopy fluctuated widely but increased in the long term, in mid canopy was more or less maintained and in lowest canopy declined. Crops of developing flower buds present on uppermost branches delayed and/or reduced shoot growth. Foliage production occurred in all months of the year. There was a unimodal annual rhythm of growth rate reaching a maximum in summer and a minimum in winter. Variable water supply, however, influenced production to peak in spring, summer or autumn. No shoot growth occurs in E. maculata at Kioloa when daily mean temperature (averaged for weekly intervals) falls below c. 10½C in winter. An upper temperature limit for growth could not be defined. The species apparently lacks dormancy mechanisms. Shoot growth is 'opportunistic' and occurs whenever environmental conditions are favourable. Patterns of leaf production and leaf fall were variable but peaks showed a general synchrony. Leaf fall, however, tended to lag behind leaf production. Leaves of all ages were shed but main losses were from older cohorts. Some 49% (s.d.±18%) of new leaves were lost while still small or immature, mainly during periods of vigorous shoot growth or low water supply. Browse of immature foliage was light. Normal senescence and leaf fall accounted for almost the entire loss of mature foliage.

The severe 7-month drought in coastal and adjacent tablelands regions of New South Wales in the latter half of 1980 caused heavy leaf-shedding, wilting of persistent foliage and bark-splitting in forest eucalypts. Defoliation of individual sample trees of E. maculata ranged from 50 to 97% of pre-drought leaf area. Leaf area index of a stand of E. maculata was reduced from c. 4.3 to 0.8. E. maculata was less susceptible to drought than E. globoidea and E. pilularis but more susceptible than E. Paniculata in mixed forest on the same site. Rapid recovery of the canopy occurred in autumn after the break of the drought and leaf areas of all sample trees attained pre-drought values or above by summer 1981-82. Leaf-shedding in response to severe water deficit appears to have been of adaptive significance in enhancing tree survival in a drought of this duration.

A study was made of the variation in moisture content of fine dead fuel (FFM) in relation to 1) differences of fuel type (needles, leaves, twigs, bark), 2) different fuel locations (dead canopy and surface litter), 3) contrasting management of plantations (unthinned-unpruned vs thinned-pruned) and 4) environmental factors (air temperature (T) and relative humidity (H); moisture content of duff (D) and topsoil (S)). The variation of live (green needle) fine fuel moisture content (LFMC) in relation to needle age, canopy location (shaded vs unshaded) and season was also studied in Pinus radiata D. Don plantations over 2 years. Mean differences of moisture content between the several types of fuel exposed to the same atmospheric conditions were generally significant and ranged from 0.6% (pine twigs vs eucalypt twigs) up to 2.8% oven dry weight (ODW) (eucalypt bark vs recently cast pine needles). T and H were highly correlated between study sites in pine plantations and an official meteorological station at Canberra airport, 15 km away. In the pine plantations, mid afternoon moisture contents of pine needle litter (litter FFMs) were mostly higher than moisture contents of dead needles in canopies (aerial FFMs); the mean differences between litter FFMs and aerial FFMs were statistically significant. FFMs in the unthinned-unpruned plantation were also generally higher than those in the thinned-pruned plantations. Regression analyses of relationships between FFM and environmental variables showed that T and H in combination explained a large proportion of the variation in aerial FFM but much less of the variation in litter FFM. However, the inclusion of either D or S in multiple regression models accounted for significant amounts of the variation in litter FFM. LFMC decreased with needle age and, for full-grown needles, was up to 25% (ODW) higher in shaded compared to unshaded canopy locations. Seasonal patterns of change in LFMC of full-grown needles were not well defined. Variation in the parameters and the precision of FFM regression relationships between fuel locations and stands with contrasting management demonstrate the site specificity and limitations of empirical FFM models. The results suggest that for prediction of aerial FFM, models based on a combination of T and H are most appropriate; while, models that include a soil moisture variable may predict FFM of litter fuels more accurately. However, the intrinsic variation in FFM revealed in this study indicates that such models, although providing a useful guide, may not predict FFM with the accuracy required for fire behaviour models during high fire danger weather - when fuel moistures are low.

During the first half of 1965 an unprecedented drought caused widespread wilting of native trees from southern Queensland to the New South Wales-Victorian border. The reaction of some of the native vegetation in parts of the Australian Capital Territory and Monaro Region has been studied. Rainfall from January 1 to June 30 was less than one-quarter of the normal, and by the end of March signs of water stress were apparent over a wide area. The communities most severely affected were dry sclerophyll forests, especially on shallow, stony soils on northerly and westerly aspects. The ability of Eucalyptus spp. to withstand sustained severe dehydration is shown by the fact that the relative moisture content of living leaves could be reduced to 40-45 %, and maintained at these levels for long periods. The prolonged period of dehydration caused general drying out of the trees, rather than leaf and twig desiccation only. In the most severe cases, shrinkage and fissuring of the bark of E. rossii, with ultimate separation at the cambium, was observed. It is suggested that so-called ineffective summer rain in south-eastern Australia is both effective and essential for the native communities on soils of low water-holding capacity. The role of drought in the distribution of native communities is discussed.