Previous research has shown that fires burn certain land cover types disproportionally to their abundance. We used quantile
regression to study land cover proneness to fire as a function of fire size, under the hypothesis that they are inversely
related, for all land cover types. Using five years of fire perimeters, we estimated conditional quantile functions for lower
(avoidance) and upper (preference) quantiles of fire selectivity for five land cover types - annual crops, evergreen oak
woodlands, eucalypt forests, pine forests and shrublands. The slope of significant regression quantiles describes the rate of
change in fire selectivity (avoidance or preference) as a function of fire size. We used Monte-Carlo methods to randomly
permutate fires in order to obtain a distribution of fire selectivity due to chance. This distribution was used to test the null
hypotheses that 1) mean fire selectivity does not differ from that obtained by randomly relocating observed fire perimeters;
2) that land cover proneness to fire does not vary with fire size. Our results show that land cover proneness to fire is higher
for shrublands and pine forests than for annual crops and evergreen oak woodlands. As fire size increases, selectivity
decreases for all land cover types tested. Moreover, the rate of change in selectivity with fire size is higher for preference
than for avoidance. Comparison between observed and randomized data led us to reject both null hypotheses tested
(a = 0.05) and to conclude it is very unlikely the observed values of fire selectivity and change in selectivity with fire size are
due to chance.Funding: This paper was supported by the Fundação para a Ciência e Tecnologia Ph.D. Grant SFRH/BD/40398/2007. JMCP participated in this research under the
framework of research projects ‘‘Forest fire under climate, social and economic changes in Europe, the Mediterranean and other fire-affected areas of the world
(FUME)’’, EC FP7 Grant Agreement No. 243888. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the
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