Visual assessment of wilting as a measure of leaf water potential and seedling drought survival

Rainfall and soil moisture availability vary greatly both spatially and temporally. They are prime factors influencing species distribution patterns, diversity and habitat associations in a range of biomes, and limit primary productivity in many natural ecosystems, as well as in forestry and agricultural systems (Hawkins et al. 2003, Kozlowski & Pallardy 1997, Lieth 1975). Projections of drying trends, and increased frequency and intensity of drought events with climate and land-use changes (Hulme & Viner 1998, IPCC 2001) have fuelled an increased interest in the role of drought in determining the structure and function of natural and managed forest systems (Allen & Breshears 1998, Miles et al. 2004). Such projections accentuate the need to assess, understand and predict plant reactions to drought, as well as soil moisture variation at different scales.