The Vegetation Resilience After Fire (VRAF) index: Development, implementation and an illustration from central Italy

A suitable index is proposed to evaluate the natural short–medium-term recovery capability of vegetation in burnt areas. The study area covers 2450 km2 in western Tuscany (Province of Pisa, Italy). This region is characterized by a typical Mediterranean climate and is subject to fire damage during the dry summer season. Damage is mitigated where a natural rapid regrowth of vegetation prevents soil erosion, supporting the return to a natural pre-fire state.
The Vegetation Resilience After Fire (VRAF) index is based on the vegetation association, soil type and geology, and on morphological features such as slope and aspect. The results are proposed as georeferenced maps defining areas with different vegetation resilience for both high and medium burn severity. The VRAF maps estimate the natural ability of vegetation to recover after fire, and suggest where human intervention is required to improve this capability. The VRAF index was checked by monitoring vegetation regrowth after fire in three burnt areas over a five-year period using spectral signatures, the feature space and the NDVI derived from remote sensing data. This analysis indicates that the high values of the VRAF index correspond to a recovery period of almost three years. Field surveys were performed to further test the results. On the whole, the VRAF index is a good parameter for assessing the capability of vegetation to recover in northern Mediterranean areas.