Response of eucalypt species to drought

Abstract

The response of three eucalypt species (Eucalyptus pulchella. Eucalyptus coccifera and Eucalyptus delegatensisj to a severe drought in the summer of 1982/83 was examined at Snug Plains, south-eastern Tasmania. Few large differences in leaf water potential (\j/i) or stomatal conductance (gs) were apparent even at the height of the drought when both ii/i and soil water potentials (y/s) reachedca. -4.5 MPa. However. E. pulchella maintained a higher relative water content (RWC) in its leaves than E. coccifera and E. delegatensis, and showed less severe crown damage. After the first light rains substantial interspecific differences in i^/ and gs occurred. Eucalyptus pulchella restored normal \j/i, gs and RIVC more rapidly than the other two species and. even for severely droughted trees, crown growth commenced via epicormic buds near the ends of its branches while for E. delegatensis and E. coccifera crown regeneration was via epicormic buds arising from stems and larger branches. This resulted in a change in dominance in certain stands and showed that E. pulchella was more drought-resistant than E. coccifera. which was in turn more resistant than E. delegatensis. This conclusion was confirmed during competition experiments using potted seedlings. However, potted seedlings differed from mature field trees by maintaining moderate gs at high vapour pressure deficits and closing stomata at fl below ca. -2.0 MPa. Substantial variation in the severity of drought symptoms was observed over short distances. This variation appeared to be determined by the moisture-holding capacity of the .soil and the biomass of the stand. Although differences in the rooting patterns of seedlings were evident, field measurements of i/// and ij/s suggested that all three species were exploiting the same water resource.In contrast to previous studies, the results suggest that large interspecific differences in tissue hydration and crown damage may be present, even though differences in i///, gs and characteristics of the root system may appear small.

Selection of species and provenances for low-rainfall areas: physiological responses of Eucalyptus cloeziana and Eucalyptus argophloia to seasonal conditions in subtropical Queensland

“…2). A similar lowering of leaf water potential reported for Eucalyptus wandoo (Colquhoun et al, 1984) and for Eucalyptus pulchella (Davidson and Reid, 1989) was associated with the ability to extract more water from the soil-a characteristic reported for eucalypts growing on drought prone sites (Doley, 1967;Ladiges, 1975;Clayton-Greene, 1983). The tendency to maintain relatively high gas exchange indicates little regulation of water loss as has been reported for E. marginata (Doley, 1967;Colquhoun et al, 1984), E. calophylla (Colquhoun et al, 1984), E. microcarpa (Attiwill and Clayton-Greene, 1984) and E. leucoxylon (Sinclair, 1980).…”

“…Availability of water, nutrients and suitable temperatures are among the most important factors that limit plant productivity and yield across sites (Turner and Kramer, 1980;Kramer, 1983;Beadle and Turnbull, 1992;Landsberg, 1997). Studies of water relations of various eucalypts growing in their natural environments during times of severe drought have reported either avoidance or tolerance, or both mechanisms of adaptation, to water stress (Doley, 1967;Sinclair, 1980;Attiwill and Clayton-Greene, 1984;Davidson and Reid, 1989;Prior et al, 1997b;Prior and Eamus, 1999). Species that are profligate in their water use are reported to avoid tissue water deficit by maintaining access to a water source through deep root systems (Doley, 1967;Sinclair, 1980;White et al, 2000) enabling them to maintain high pre-dawn water potentials, relatively high stomatal conductance and presumably continued transpiration even under moderate water stress (Davidson and Reid, 1989;Abrams, 1990).…”

Effect of increasing salt concentration on emergence, growth and survival of seedlings of Salvadora oleoides (Salvadoraceae)

“…High relative water content of leaf is considered an adaptation to xeric conditions. Davidson & Reid (1989) studied the response of three Eucalyptus species to severe drought in the summer of 1982/83 at Snug Plains, south-eastern Tasmania, Australia and reported that E. pulchella maintained higher relative water content of leaf and is a relatively drought-resistant species. Pandey et al (1994) found that Prosopis chilensis contains high relative water content in leaf and grows successfully in dry regions of Western India.…”

Adaptation of Leaf Water Relations to Climatic and Habitat Water Availability

“…Similarly, leaves with highly elastic tissues reduce steep declines in cell turgor because their cells contain more water at full turgor and can sustain larger declines in volume [1]. Pressure-volume relationships are routinely used to estimate these key parameters of leaf physiology [7] and are often interpreted as indicators of species drought tolerance i.e., the ability to maintain physiological function at low water status [8,9].…”