Inter and intra specific variation in nocturnal water transport in Eucalyptus. Tree Physiol

Summary To identify environmental and biological drivers of nocturnal vapour exchange, we quantified intra-annual, in-tra- and inter-specific variation in nocturnal water transport among ecologically diverse Eucalyptus species. We measured sap flux (Js) and leaf physiology (leaf surface conductance (gs), transpiration (E) and water potential (Ψl)) in three to five trees of eight species. Over 1 year, nocturnal Js (Js,n) contrib-uted 5–7 % of total Js in the eight species. The principal en-vironmental driver of Js,n was the product of atmospheric vapour pressure deficit (D) and wind speed (U). Selected ob-servations suggest that trees with higher proportions of young foliage may exhibit greater Js,n and nocturnal gs (gs,n). Com-pared with other tree taxa, nocturnal water use in Eucalyptus was relatively low and more variable within than between species, suggesting that (i) Eucalyptus as a group exerts strong nocturnal stomatal control over water loss and (ii) pre-diction of nocturnal flux in Eucalyptus may depend on simul-taneous knowledge of intra-specific tree traits and nocturnal atmospheric conditions