Development of a Keetch and Byram-Based drought index sensitive to forest management in Mediterranean conditions

The present work aims to take a closer look at the behavior of two releases of the Keetch-Byram drought index (KBDI) under different forest management strategies in Mediterranean conditions. Since these versions of the index were demonstrated to be insensitive to the changes in water balance caused by different thinning treatments, a new KBDI-based index sensitive to silviculture operations was developed. This new approach enabled us to simulate the benefits achieved from a thinning operation in terms of forest fire risk reduction. Abatements of 22.5% and 26.4% in KBDI were obtained for the 2009 and 2010 high-risk forest fire periods, respectively, due to thinning. The reductions observed in the short-term did not disappear in a long term. A plot thinned 10 years ago showed KBDI reductions of 12.5% and 6.7% with respect to a non-managed plot (control treatment) in the same period. Finally, in order to make possible application of the new index to other stands, coefficients of the index were based on well-known and easy to get tree-related and physiological variables.