Estimation of Leaf and Branch Area Indexes of Deciduous Trees Using Dual-Frequency Microwave Radiometric Data

Abstract

Remote sensing of forest canopies from airborne and spaceborne platforms using active and passive microwave systems is an advanced tool for ecosystem monitoring. Microwave radiometers could give additional information about dense forest biomass, where other remote sensing systems (optical radiometers, SAR) suffer the early saturation effect [1,2]. Ground-based zenith-looking radiometers have been applied for in situ monitoring of the seasonal evolution and temporal changes of deciduous tree groups [2–4]. Recent experimental investigations have shown that the X-band radiometric data are more sensitive to the changes in leaf volume than those of L-band [3,4]. A model, based on the radiative transfer theory, has been described and applied by Ferrazzoli [1] to simulate microwave forest emission. In recent works [5–7] an empirical model for estimation of crown emissivity of tree groups was proposed using single-frequency microwave radiometer data and a priori data about branch emissivity during defoliated period. These method and models give the possibility for an objective assessment of Leaf Area Index (LAI) and then — the total biomass of leaves of deciduous trees in temperate climatic zone.