Root Depth, Leaf Area and Daytime Water Relations of Jarrah (Eucalyptus marginata) Forest Overstorey and Understorey During Summer Drought

Abstract

Foliage projective cover of trees on high and low rainfall jarrah forest sites was 1.6 and 1.2 times that of their understorey respectively. Corresponding leaf area index ratios were 7.2 and 3.4 times. Tree and understorey species developed substantial water deficits on both sites during the summer drought, although water deficits developed more rapidly and became more severe on the site receiving less rainfall. Stornatal conductances and midday water potentials of deeply rooted trees (root depth > 10m) remained higher than those of less deeply rooted understorey plants for 1-2 months in the absence of rain. Daily cycling of water potential and stomatal conductance was detected in most plants throughout the summer. This is interpreted as indicating that the plants did not become dormant during summer drought.