Zhiwei Wu , Hong S. He , Jian Yang , Zhihua Liu, Yu Liang
Science of the Total Environment
Fire occurrence Climate Human Relative importance Boreal forest
Fire signiﬁcantly affects species composition, structure, and ecosystem processes in boreal forests. Our study objective was to identify the relative effects of climate, vegetation, topography, and human activity on ﬁre occur- rence in Chinese boreal forest landscapes. We used historical ﬁre ignition for 1966–2005 and the statistical meth- od of Kernel Density Estimation to derive ﬁre-occurrence density (number of ﬁres/km2). The Random Forest models were used to quantify the relative effects of climate, vegetation, topography, and human activity on ﬁre-occurrence density. Our results showed that ﬁre-occurrence density tended to be spatially clustered. Human-caused ﬁre occurrence was highly clustered at the southern part of the region, where human population density is high (comprising about 75% of the area's population). In the north-central areas where elevations are the highest in the region and less densely populated, lightning-caused ﬁres were clustered. Climate factors (e.g., ﬁne fuel and duff moisture content) were important at both regional and landscape scales. Human activity factors (e.g., distance to nearest settlement and road) were secondary to climate as the primary ﬁre occurrence factors. Predictions of ﬁre regimes often assume a strong linkage between climate and ﬁre but usually with less emphasis placed on the effects of local factors such as human activity. We therefore suggest that accurate forecasting of ﬁre regime should include human inﬂuences such as those measured by forest proximity to roads and human settlements.