Assessment of vegetation parameters in olive trees in the region of Alentejo. A comparison of direct and indirect methods

Mestrado em Engenharia Agronómica - Instituto Superior de AgronomiaVegetation parameters, as the leaf area index (LAI) and the 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 in the past decades to determine the LAI. However, a simple approach to assess this parameter is still missing. In this study we tested the operability and precision of different methods to calculate the LAI of 6 and 20 year old olive trees (Arbequina and Cobrançosa), under irrigated and non-irrigated conditions in the region of Alentejo. The average LAI on a projected area basis was estimated to be 5.88 and 2.75 m2 m-2 at the irrigated and non-irrigated sites, respectively, corresponding to 1.01 and 1.05 m2 m-2 on a total area basis. Furthermore, a tool was introduced to simplify the decision making between the use of the LAI and the GC. The determination of the GC is much easier than the LAI in practical uses. The average GC was 5.7 m2 under irrigated and 18.0 m2 under non-irrigated conditions. A detailed comparison between direct and indirect methods is given and the future prospective of the decision making tool is discussed