ions in saline soils inhibits growth of manyplants. Salinisationof soilsandgroundwaterisa seriousland-degradationproblemin aridand semi-aridareas, andis increasing steadily in many parts of the world, causing major problems for crop productivity. On a world scale,there is an area of around 380 million hectares that is potentially usable for agriculture, but where production isseverelyrestrictedbysalinity.Theseareasoccurpredominantlyin regionswhereevaporationexceedsprecipitation(Flowerset al., 1977).The problemof saline soils is ever-increasing,due to poorirrigationand drainage practices,expansion of irrigated agriculture into arid zones with high evapotranspirationrates, or land-clearing, which leadsto rising saline water tables (“drylandsalinity”). World-wide, 100 million ha, or 5% of the arable land is adverselyaffected by high salt concentration,which reducescrop growthand yield.Dryland salinity is a major environmental problem in southern Australia. The impacts of agricultural clearingthrough salinisation extend across the continent, but they are particularly severe and extensive in the wheatbeltof southwest Western Australia, where over 1.8 million hectares is currently salt-affected, with up to 8.8 millionhectares (33%) at risk by 2050 (Hatton, 2003). The replacement of native vegetation by agricultural crops andpastures has disturbed the water balance that existed prior to European settlement, and has markedly elevated theamount of water leaking beyond the root zone of introduced species, and contributing to groundwater systems.Estimates of annual leakage beneath the root zone ofannual crops range from 0 to 63 mm per annum (Eberbach,2003). Physical, chemical and biological constraints in soil horizons impose an additional stress on plants insouthernAustralia,restrictingplantgrowthanddevelopment.Hardsetting,crusting,compaction,acidity,alkalinity,nutrient deficiencies and toxicities due to boron, carbonates and aluminium are major factors that cause theseconstraints(Rengasamyet al., 2003).These large-scale environmental problems in southern Australia which affect agricultural and natural parts ofthelandscapeaswellasthetownsinthisarea,providedtheimpetusfortheestablishmentofacooperativeresearchcentre dealing with plant-based solutions for dryland salinity. The center is based in Perth, in Western Australia,withseveralnodesinotherstatesinsouthernAustralia(NewSouthWales,SouthAustralia,Victoria).Theperceivedsolution for the problem is to use plants to work towards restoring the water balance. This raises questions, firstly,on the original water balance and how the native vegetation dealt with it. Secondly, there are questions on whatplants should be used, and how the system should be managed, to restore the water balance. These issues wereaddressed duringa workshopin Perth, Australia. This special issue is the result of that workshop.Natural woodlandecosystemsin southwesternAustralia have beenexaminedin termsof their spatial structure.Complexpatternsatdifferentscalesconferresiliencetothewoodlandsystem.Mostofthiscomplexityhasbeenlostin the current agricultural system, and many current degradation problems may well be related to this. The chal-lengeforthefutureis, therefore,todevelopcomplexityandresilienceinagriculturalsystems,whilemaintaininganacceptable level of production (Hobbs & Cramer, 2003). Woodlands in southwestern Australia are evergreen andtranspire throughout the year, despite the long, hot and dry summers of the Mediterranean climate. Results froma case study in a species-rich woodland have been used to discuss the ecological and physiologicalproperties thatappear to be essential features of this and similar communities. Some of these features will have to be mimickedto ensure a sustainable land-use system. The question is: which features must be mimicked, and which ones arebest avoided if the aim is high productivity? Deep-rootedness allows the dominant species to access soil moisture