Fuel age, weather and burn probability in Portugal

• Author(s): Fernandes, Paulo ; Loureiro, Carlos ; Magalhães, Marco ; Ferreira, Pedro ; Fernandes, Manuel
• Date: 2012
• Persistent ID: http://hdl.handle.net/10348/1394
• Origin: Repositório da UTAD
• Subject(s): fire frequency; fire regime
• Document Type: Article
• Language: English

Description

The relative influence of the factors acting upon burn probability, namely fuel and weather, is not well understood, especially in Europe. We use a digital fire atlas (1975-2008) and apply survival analysis to individual fires (1998-2008) to describe how burn probability changes with fuel age in Portugal. The typical FRI (fire return interval) and median fire-free interval vary regionally from 23 to 52 and 18 to 47 years, respectively. Increase of the hazard of burning with time is generally near linear, denoting moderate fuel-age dependency as in some other shrub-dominated Mediterranean environments. Analysis of complete fire intervals resulted in shorter FRI and higher fuel-age dependency of burn probability than findings that included censored observations. Increasingly severe weather conditions either expressed through fire size or by extreme fire danger, concurrently decreased fuel-age dependency and selected for older fuels. The results are discussed from the viewpoints of fire suppression and fuel treatments.