Drought deaths in Eucalyptus globulus (Labill.) plantations in relation to soils, geomorphology and climate

R.J. Harper, Keith Smettem, J.O. Carter, John Mcgrath

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28 Citations (Scopus)

Abstract

The occurrence of tree deaths in young, 3to 6 year old Eucalyptus globulus plantations establishedon farmland in south-western Australia wasfound to be strongly related to factors indicative ofpoor soil water storage capacity. Seven years afterplanting tree survival was significantly less on soils2 m deep (22% vs 70%).This is due to the limited ability of some soils to storea sufficient proportion of the annual rainfall within theroot-zone to meet the plant water demand in a regionwith a recurrent annual summer drought. There arepractical difficulties in routinely surveying soils todepths in excess of 2 m over broad areas, to predictthe likelihood of tree death. On the granitic basementrocks of south-west Western Australia, the occurrence of ferricrete gravels provides a useful surrogateindicator for the presence of deeper soils. In thisregion the distribution of soil depth and soil fertilityhas a geomorphic basis, being related to previouspatterns of deep weathering and regolith stripping.Soils have developed on various horizons of deeplyweathered profiles, formed from granites andgneisses. These materials have been stripped to avariable extent by erosion, leading to a range of soildepths. The original weathered profiles, which correspondto the soils with ferricrete gravels, comprise thedeepest soil/regolith materials (~30-50 m deep);whereas along drainage lines the regolith has beencompletely stripped, the soils are shallow and plantationsare most susceptible to drought. Knowledge ofthe relationship between soil depth and plantationperformance allows regional indications of droughtrisk to be developed from regional soil mapping andthe production of more efficient sampling designs forsite assessment.
Original languageEnglish
Pages (from-to)199-207
JournalPlant and Soil
Volume324
Issue number1/2
DOIs
Publication statusPublished - 2009

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