Assessment of Vegetation Parameters in Olive Trees in the Region of Alentejo: a Comparison of Direct and Indirect Methods

Vegetation parameters, such as leaf area index (LAI) and ground cover (GC) are commonly related to biosphere processes, being used in models to estimate yield and crop water requirements. Several direct and indirect methods have been developed to determine LAI. However, a simple approach to assess this parameter is still missing. In this study different methods were tested to calculate LAI of olive trees in an intensive irrigated and a traditional rainfed olive grove. The average LAI on a projected area basis was estimated to be 5.88 and 2.75 m(2) m(-2) at the irrigated and rainfed site, respectively corresponding to 1.01 and 1.05 m(2) m(-2) on a total area basis. The average GC for a single tree was 5.7 m(2) under irrigated and 18.0 m(2) under non-irrigated conditions corresponding to 17.5% and 37.3% of each total area (32.4 m(2) and 48 m(2) respectively). Moreover, a tool is proposed to simplify the decision making between the use of LAI and GC, as the GC is much easier to obtain. A comparison between the methods is given and the future prospective of the decision making tool is discussed.