Volume 32, Issue 2 pp. 241-252
RESEARCH ARTICLE

Changes in evapotranspiration components following replacement of Eucalyptus regnans with Acacia species

Sandra N.D. Hawthorne

Corresponding Author

Sandra N.D. Hawthorne

School of Ecosystem and Forest Sciences, University of Melbourne, Baldwin Spencer Building, Parkville, Victoria, 3010 Australia

Correspondence

Sandra N. D. Hawthorne, School of Ecosystem and Forest Sciences, University of Melbourne, Baldwin Spencer Building, Parkville, Victoria 3010, Australia.

Email: [email protected]

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Richard G. Benyon

Richard G. Benyon

School of Ecosystem and Forest Sciences, University of Melbourne, Baldwin Spencer Building, Parkville, Victoria, 3010 Australia

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Patrick N.J. Lane

Patrick N.J. Lane

School of Ecosystem and Forest Sciences, University of Melbourne, Baldwin Spencer Building, Parkville, Victoria, 3010 Australia

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First published: 04 December 2017
Citations: 4

Abstract

Forest species composition may change following a disturbance. This change can affect long term water yield from forested catchments when the replaced and replacement species have different evapotranspiration rates. Following strip-thinning experiments that removed 50% of the overstorey basal area in several Eucalyptus regnans water supply catchments in south eastern Australia, Acacia spp. (Acacia dealbata and Acacia melanoxylon) became the dominant overstorey species in most of the cut strips. More recently, low regeneration of E. regnans following wildfires in 2009 may result in mixed Acacia and E. regnans stands in some catchments. We compared transpiration of E. regnans and Acacia stands in the uncut and cut strips of a catchment that was strip-thinned in early 1980s (Crotty Creek). We also compared transpiration and throughfall in a mixed E. regnansA. dealbata regrowth stand 20 years after clear-fell logging (Road 8). Sap flow was measured for 13 and 6 months at Crotty Creek and Road 8, respectively. In both studies, mean daily sap flow density of Acacia spp. was lower than of E. regnans. Estimated Leaf Area Index of E. regnans stands was slightly greater than that of Acacia spp. Stomatal conductance (gc), estimated by inverting the Penman–Monteith equation, differed between the species suggesting species-level physiological differences with Acacia being more sensitive to vapour pressure deficit than E. regnans. Throughfall measurements at Road 8 indicated interception was slightly higher in A. dealbata but only enough to offset about 13% of the difference in transpiration. Replacement of E. regnans by Acacia dominated stands may, therefore, decrease catchment evapotranspiration and increase streamflow.

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