Estimating tree density in oak savanna-like lsquo;dehesa’ of southern Spain from SPOT data

Abstract

The main objective of this study was to establish a method of estimating tree density in savanna-like vegetation systems using the highest spatial resolution available from satellite data (SPOT-1 panchromatic = 10  m resolution) based on the assumption that for sparse trees on a contrasting herbaceous background, spatial filters may provide a direct mapping of tree cover. The study was performed in the ‘dehesas’ oak-woodland of southern Spain. This particular landscape is characterized by the presence of scattered evergreen oak trees (Quercus ilex and Q. suber) whose density ranges from 0 to 80 even-aged mature trees per hectare which gives the appearance of a savanna-like vegetation. Tree density can be accurately estimated by SPOT-1 panchromatic data after numerical filtering. This method allows the mapping of tree density of the dehesas, a key parameter reflecting the functional vegetation-soil-climate equilibrium which exists for both woody and herbaceous strata.