PATTERNS OF LIGHTNING-CAUSED, AND PEOPLE-CAUSED FIRES IN PENINSULAR SPAIN

A comparative study of lightning-, and people-caused fires is presente d for peninsular Spain, for the period 1974-1994. Based on records of fire reports, yearly trends for fires started by the two causes were c ompared. Fire reports assign each fire to one 10x10 km grid-cell withi n the country. This information, together with data on the cause and d ate of fire, elevation, size of fire, type of vegetation burned, and m eteorological conditions at the time of fire initiation, was incorpora ted to a raster-based geographic information system for further analys is and mapping. Additional information incorporated to the GIS for eac h grid-cell was the phytogeographic sector to which it belonged and th e main land-use types. The study shows that the number of fires has in creased recently and, particularly, that of lightning fires. Annual fi re occurrence of the two causes was significantly correlated. People-c aused fires were widespread throughout most of the country, whereas li ghtning-caused fires, although also widely dispersed throughout Spain, were more clustered together in certain areas, mainly in the eastern part of the country and along certain mountain ranges. The difference between the geographic distribution of the fires started by the two ca uses was statistically significant. Additionally, lightning-caused fir es occurred at upper elevations and were more clustered towards the su mmer than people-caused fires. Furthermore, in those grid-cells where fires of both causes occurred, lightning fires tended to occur at uppe r elevations, affected more woodlands, produced smaller maximum fire-s izes, and were started under different meteorological conditions than people-caused fi-es. Fire frequencies were small, and fire rotation pe riods high, in most phytogeographic sectors of the country for fires c aused by lightning, not so for fires caused by people. In general, fir e temporal-, and geographic-patterns, and fire characteristics of ligh tning-caused fires were different from those of people-caused fires.