Article Figures & Data
Tables
- Table 1.
Adaptations of Australian tree species to aridity (Ashton 1975; Moore 1981; Pate and McComb 1981; New 1984; Moore 1990; Knox et al. 1994; King 1997; Atwell et al. 1999; Ladiges et al. 2005).
Adaptation Mechanism Examples Sclerophylly Maintains cellular volume Many Australian genera, such as Acacia, and members of the Proteaceae and Myrtaceae families Altered leaf anatomy Reduces leaf surface area Hakea and Acacia species with rolled needle like leaves Phyllodes/cladodes Reduces surface area; reduces evapotranspiration Most Australian Acacia species Vertically hanging leaves Reduces absorption of radiation Many eucalypt species Leaf/pinnule movement Reduces exposed leaf surface area Bi-pinnate Acacia species; Lophostemon confertus Cuticular adornment Reduces evapotranspiration Many genera, such as Eucalyptus, Acacia, and Casuarina, with hairy, spiny, or glaucous leaves Stomatal crypts Reduces evapotranspiration Banksia species, Hakea species Cuticular ledges Reduces evapotranspiration Eucalyptus preissiana, E. obliqua Stomatal closure in response to atmospheric vapor deficit Reduces transpirational water loss Eremophila macgillivrayi, Myoporum floribundum, Myoporum platycarpum, Pittosporum phylliraeoides, Geijera parviflora Facultative deciduousness Reduces growth but allows survival over tropical dry period Some Blakella eucalypts, such as E. clavigera, E. grandiflora, and E. brachyandra Lignotubers/basal burls Rapid regrowth after foliage loss Most eucalypts; Acmena smithii Epicormic buds Rapid regrowth after foliage loss Most eucalypts Deep tap root Allows access to deeper soil water profile E. camaldulensis High root:shoot ratio Increases soil volume accessed for water supply E. camaldulensis Strategy Mechanism(s) Growth Examples Drought avoidance Grow where and when water is available Unaffected until water is limiting Eucalyptus regnans, E. camaldulensis, E. marginata Drought tolerance by improved water status Increased rooting volume Improved Acacia mearnsii, E. camaldulensis, E. clelandii, E. trivalvis Increased root density Improved E. camaldulensis, Acacia mearnsii Good stomatal control Usually reduced Casuarina littoralis, E. calophylla, Eremophila macgillivrayi, Pittosporum phylliraeoides, Myoporum floribundum Capacity for osmotic adjustment Usually reduced Atriplex nummularia, E. viminalis Reduced leaf surface area Usually reduced Acacia melanoxylon, Acacia mearnsii, E. clavigera, E. grandiflora, E. brachyandra Larger root:shoot ratio Usually reduced E. camaldulensis, E. marginata, Acacia mearnsii Drought tolerance by maintaining cell volume More elastic cell walls Usually reduced Acacia aneura Dehydration tolerance Cells and physiology unaffected by reduced water content Usually reduced or restricted E. rossii, E. viminalis, Acacia aneura Note: Columns 1–3 of this table are extended and modified from Atwell et al. 1999. Column 4 is based on the author’s experience with these Australian species.
- Table 3.
Australian Tree species with full or facultative deciduousness, usually in response to a dry period (Australian Plant Study Group 1980; Francis 1981; Boland et al. 1984; Snape 2002).
Species Common name Brachychiton rupestris bottle tree Brachychiton discolor lacebark tree Brachychiton bidwillii rusty kurrajong Brachychiton australis large leaf bottle tree Ehretia acuminata koda Erythrina vespertilio bat wing tree Ficus superba deciduous fig Ficus virens white fig Ficus fraseri sandpaper fig Gmelina leichhardtii white beech Lysiphyllum cunninghamii native bauhinia Lysiphyllum carroni native bauhinia Lysiphyllum hookeri white bauhinia Nauclea orientalis leichhardt tree Peltophorum pterocarpum yellow poinciana Sterculia quadrifida peanut tree Terminalia catappa sea almond Toona australis red cedar - Table 4.
Characteristics of a eucalypt displacement series from wetter to drier environments (Pate and McComb 1981).
Characteristic altered as environment dries Greater root:shoot ratio
Increasing root:shoot ratio in response to water stress
Slower stomatal response to decreasing xylem water potential
Slower decline in leaf turgidity with increased water stress
Lower rate of transpiration in wetter soils
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