Arboriculture & Urban Forestry 39(3): May 2013 RECOMMENDATIONS FOR HEALTHY AND DROUGHT-RESILIENT TREES The following are key water management strategies that are essential to achieving sustainable landscapes with trees: • • satisfy water requirements for healthy trees, not just for tree survival optimize soil environment to achieve resilient, healthy, and extensive root systems • ensure site rainfall is fully utilized • water deep (if required) to achieve wetting of soil profile at depths greater than 200 mm • water proactively rather than wait for signs or evidence of stress • • • • adopt “water banking” approach in soil, prior to high water-demand period recycled water quality should be checked for potential short- and long-term (accumulation) risks, such as toxic- ity or degraded soil health regularly check what is happening in the soil, sample it or use soil moisture sensors evaluate water delivery system hydraulically and in-soil water distribution performance CONCLUSION Experiences in the maintenance of urban forests during dry years have shown that a thorough understanding of the tree requirements and site conditions is essential to achieving a sustainable urban forest. The starting point is selecting the right species by taking into account the site’s microclimate, special constraints, and the tree’s desired functional performance. Soil moisture sensors have proven to be very powerful tools in providing information about plant water use, soil water behav- ior, root system activity, and effectiveness of rainfall and irriga- tion. Measurement of net rainfall reaching the ground, follow- ing interception by the tree canopy, has also assisted in building the knowledge base necessary to successfully maintain trees. A range of techniques have been developed and employed at RBG Melbourne to assist in the scheduling of irrigation and complex landscape plantings. These include site-specific and seasonally adjusted landscape crop coefficients, stress indicators to identify refill points, and soil water banking. Acknowledgments. The authors wish to express their appreciation for the instrumentation expertise and data collection of Mr. Steven Liu, Curator Assistant, Environmental Horticulture, Royal Botanic Gardens Melbourne. LITERATURE CITED Allen, G.R., L.S. Pereira, D. Raes, and M. Smith. 1998. FAO irrigation and drainage paper 56: Crop evapotranspiration, guidelines for com- puting crop water requirements. Food and Agriculture Organization of the United Nations: Rome, Italy. Anonymous. 2011. Calibration Manual For Sentek Soil Moisture Sen- sors Version 2.0, Sentek Pty, Ltd. Accessed 02/20/2013. Boland, D.J., M.I.H. Brooker, G.M. Chippendale, N. Hall, B.P.M. Hyland, R.D. Johnston, D.A. Kleinig, M.W. McDonald, and J.D. Turner. 2006. Forest Trees of Australia, 5th edition. CSIRO Publishing. 768 pp. 123 Bramwell, D. 2007. The response of botanic gardens to climate change. BG Journal 4(2):3–8. Charlesworth, P. 2000. Irrigation Insights No. 1, Soil Water Monitoring. CSIRO Land and Water. Land and Water Australia: Canberra. 96 pp. Climate Change in Australia. 2009. Science Update 2009 issue one. Accessed 11/10/2011. Connellan, G.J. 2013. Water Use Efficiency for Irrigated Turf and Land- scape. CSIRO Publishing, Collingwood, Victoria, Australia. 416 pp. Connellan, G., and P. Symes. 2006. The development and evaluation of landscape coefficients to determine plant water requirements in the urban environment. In: Proc. of Irrigation Association of Australia Conference, May 2006, Sydney, Australia. Costello, L.R., and K.S. Jones. 2000. A Guide to Estimating Irrigation Water Needs of Landscape Plantings in California. Sacramento, University of California Cooperative Extension, California Depart- ment of Water Resources. Accessed 10/02/2011. Coutts, A.M., J. Beringer, and N.J. Tapper. 2007. Impact of increasing urban density on Local climate: Spatial and temporal variations in the surface energy balance in Melbourne, Australia. Journal of Applied Meteorology and Climatology 46:477–493. CSIRO. 2008. Climate Change in Victoria. Department of Sustainability and Environment, The State of Victoria, Melbourne, June 2008. Ac- cessed 11/15/2011. CSIRO. 2010. Climate variability and change in south-eastern Australia: A synthesis of findings from Phase 1 of the South Eastern Australian Climate Initiative (SEACI). Accessed 11/15/2011. Dallman, P.R. 1998. Plant life in the world’s Mediterranean climates: California Native Plant Society, University of California Press: Berkeley and Los Angeles, California. 257 pp. David, T.S., M.O. Henriques, C. Kurz-Besson, J. Nunes, F. Valente, M. Vaz, J.S. Pereira, R. Siegwolf, et al. 2007. Water-use strategies in two co-occurring Mediterranean evergreen oaks surviving the summer drought. Tree Physiology 27:793–803. Dunkerley, D. 2011. Interception processes and rates on vegetation in a major urban area: Metropolitan Melbourne, Australia. Geophysical Research Abstracts Vol. 13 EGU 2011: 4016, 2011. Harris, R. 1998. Irrigation of Newly Planted Street Trees. In: Proceed- ings of Conference on The Landscape Below Ground II, Second International Workshop on Tree Root Development in Urban Soils March 5–6, 1998. San Francisco, California. International Society of Arboriculture: Champaign, Illinois, U.S. Hawkins, B., S. Sharrock, and K. Havens. 2008. Plants and climate change: Which future? Botanic Gardens Conservation International, Richmond, UK. Howard, J.L. 1992. Quercus lobata. In: Fire Effects Information System, USA Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Accessed July 2009. . Howe C., R.N. Jones, S. Maheepala, and B. Rhodes. 2005. Implica- tions of Potential Climate Change for Melbourne’s Water Resources: CSIRO Urban Water and CSIRO Atmospheric Research and Mel- bourne Water, Melbourne, Victoria, Australia. 26 pp. Kendal, D. 2011. Potential effects of climate change on Melbourne’s street trees and some implications for human and non-human ani- mals. In: Proceedings of 2011 State of Australian Cities Conference, Melbourne, Australia. ©2013 International Society of Arboriculture
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