Managing and Monitoring Tree Health and Soil Water Status
During Extreme Drought in Melbourne, Victoria
Peter B. May, Stephen J. Livesley, and Ian Shears
Abstract: Drought can lead to mortality in urban tree populations. The City of Melbourne, Victoria, Australia, manages a large population of trees that provide important ecosystem services and cultural heritage values. Between 1997 and 2009 Melbourne was affected by a serious drought resulting in significant tree health decline. Elms and planes in particular, were badly affected. This paper presents data from a survey of tree health status, and of studies of retrofitted buried drip line irrigation. A study of soil wetting in autumn of 2009 found that the use of drip irrigation had, in most cases, little or no effect on soil moisture levels and a modeled study of tree water use showed that water delivered by drip irrigation provided only a fraction of the water required by a mature tree. By contrast, drip irrigation in late winter was able to recharge soil moisture levels. Mechanisms responsible for the decline in tree health seen during the drought are discussed. While the drought has temporarily been alleviated, climate change scenarios for southern Australia suggest that increased rainfall variability and drought events will be more common. The experiences gained during the recent drought event provide useful information for urban tree managers planning for the future.
Keywords: Australia; Climate Change Strategy; Drip Irrigation; Drought; Melbourne; Platanus × acerifolia; Retrofitted Irrigation; Soil Moisture;
Tree Health, Tree Water Use; Ulmus procera.