Drivers of lightning- and human-caused fire regimes in the Great Xing'an Mountains

Fire is a major disturbance in forest ecosystems. An understanding of the trends of forest fires and of the main factors driving ignition is important both for establishing effective fire prevention policies and for predicting future changes. By analyzing climate, fuel, and social influences, we identified the major factors controlling changes in lightning- and human-caused fire regimes over the period 1967-2006 in the Great Xing'an Mountains, which is the most fire-prone area of China. We found that both fire frequency and burned area of lightning-caused fires increased during this period, but human-caused fires showed the opposite trend. The first lightning-caused fire in the spring fire season occurred earlier each year, but the first human-ignited fire was generally delayed. These changes imply that the occurrences of lightning- and human-caused fires were driven by different mechanisms. Climatic factors are the dominant drivers of lightning-caused fires, but not of human-caused fires. However, the driving factors behind the first fire occurrence time in the spring fire season for the two ignition mechanisms were similar, i.e., different types of accumulated energy. To avoid bias in projecting fire events, management policy should be considered in areas in which human-caused fires dominate, e.g., the Great Xing'an Mountains.