Relating leaf area index of natural eucalypt vegetation to climate variables in southern Australia

We address a need for a rapid technique to estimate the leaf area index (LAI) of pre-existing natural vegetation. This is required to determine the effects of agroforestry plantings on deep drainage from agricultural land. Previous work shows: (1) a relationship between the hydrologic ‘footprint’ of tree belts and their lineal leaf area (leaf area per metre of belt, LLA, m2 m−1), relative to the LAI of natural vegetation and (2) that the LAI of natural vegetation is related to plant-available soil moisture and climate. We evaluated relationships between LAI measured at 37 sites across southern Australia and (1) annual average rainfall, P; (2) annual average pan evaporation, E0; (3) ‘available rainfall’—annual average rainfall, P, minus annual average pan evaporation, E0; (4) a climate wetness index P/E0; (5) Spechtʹs soil evaporative index, k = 0.0045 + 71.57/E0. P was the best indicator for the data set used, i.e. LAI = 0.003P + 0.41 (r2 = 0.80).