Changing patterns of forest fires-climate relationships during 1961–1997 in Greece: Is it the effect of climate change?

Using documented fire records and monthly weather data spanning 37 years (1961-1997), we aim to explore long-term trends in the spatiotemporal variability of the relationship between fire occurrence and the Bagnouls-Gaussen aridity or xerothermic index (BGI). By examining this relationship, we test the theoretical framework of the intermediate fire-productivity hypothesis in an eastern Mediterranean country, Greece, to unveil the driving factors shaping fire activity. We particularly investigate whether the influence of drought conditions is more accentuated in the northern part of the country due to the presence of biomass-rich, rarely-dry ecosystems compared to the southern part. Two patterns in the relationships between fires and climate have been observed in Greece along a north-south gradient, which can be explained by the intermediate fire-productivity hypothesis. According to this hypothesis, fire activity presents two extremes (minima) at the ends of the fuel moisture-fuel amount gradient. The first occurs in northern Greece, in biomass-rich areas where fuels are abundant and the dominant limiting factor for fires is climate (in terms of aridity). The second occurs in southern Greece in biomass-poor ecosystems, where fires are constrained by fuel availability rather than climate. A changing pattern of forest fire-climate relationships during 1961-1997 in northern Greece is evident, probably as a result of climate change. In summary, northern Greece appears to be experiencing a climate-driven shift away from a climate-limited (moisture-limited) fire regime, while southern Greece maintains a stable, fuel-limited regime. This divergence underscores the varying impacts of climate and ecosystem characteristics on fire dynamics across Greece.