Abstract:

Objective: This study aims to understand the spatial and temporal distribution of lightning fires in the Daxing’anling Mountains and the dynamic changes over the past 42 years by analyzing the occurrence history of lightning fires in the region from 1980 to 2021, so as to provide a scientific basis for the prevention and control of lightning fires. Method: Based on the statistical data of lightning fires in the Daxing’anling Mountains from 1980 to 2021, the administrative division of the study area and the DEM digital elevation model, the elevation, aspect and slope distribution maps and corresponding areas of the study area were obtained by processing the DEM data and calculating the corresponding areas. Combined with the study zoning map, the spatial-temporal distribution characteristics and dynamic change trend of lightning fires were analyzed. Result: 1) From 1980 to 2021, a total of 1 651 lightning fires occurred in the Daxing’anling Mountains, with a total area of 473 088.8 hm². Approximately 89.4% of lightning fires burned within 100 hm². The number of lightning fires from 2000 to 2021 was about 3.5 times that of from 1980 to 1999. Around 95.9% of the lightning fires occurred from May to August, and 52% of the lightning fires occurred from 13:00 to 17:00. The number of lightning fires increased rapidly in the days following the end of the spring fire prevention period on June 15. In terms of longitude, lightning fires were mainly concentrated near the two centers of 121.2°E and 122.5°E. In terms of latitude, 80% of lightning fires were concentrated between 51°N and 53.5°N. There were significant differences in the lightning fire density and lightning fire area ratio among different administrative divisions, with Heilongjiang being overall higher than Inner Mongolia. The lightning fires were concentrated on slopes of 4°–12°, accounting for 48.9% of the total. When the slope was greater than 4°, the number of lightning fires decreased with the increase of the slope. The most lightning fires occurred within 600–800 m altitude, accounting for 33.2% of the total, while only 1.3% of lightning fires occurred in areas above 1 200 m. The southwest slope had the largest number of lightning fires, with 219 (13.9%). The northwest slope had the fewest lightning fires, with 177 (11.2%). 2) The result of Pearson correlation analysis between impact factors and lightning fires showed that there was a highly significant negative correlation between the number of lightning fires and longitude (R=–0.155, P≤0.001), slope (R=–0.523, P≤0.001), the corresponding elevation area (R=0.336, P≤0.001), forest bureau area (R=0.559, P≤0.001), the corresponding slope area (R=0.734, P≤0.05). There was no significant correlation between the number of lightning fires with latitude, altitude and the corresponding aspect area. From 1980 to 1985, the number of active days of lightning fires was the least and the most stable (35±16.1) days. 3) From 1986 to 1997, the number of active days of lightning fires began to rise to (77.3±58.5) days. 3) From 1998 to 2011, the number of active days of lightning fires reached the peak of (112.1±47.9) days, and from 2012 to 2021, the number of active days of lightning fires decreased to (68.1±33.2) days. The period 1980?2021 was divided into 8 periods with a 5-year interval. From the third period to the seventh period, the first peak day of lightning fires gradually moved forward. Conclusion: The number of lightning fires has significantly increased since 2000, with the most lightning fires in June and the least in August of the year, and with the most at 13:00?16:00 and least at 23:00?5:00. The spatial distribution of lightning fires has a tendency to gather, and except slope, all other spatial types basically conform to the law that the larger the area, the more the number of lightning fires. There is obvious difference in the distribution of lightning fires in different aspect, mainly manifested as more in the south than in the north, and more in the east than in the west. The active days of lightning fires from 1980 to 2021 can be roughly divided into four periods, namely 1980?1985, 1986?1997, 1998?2011, and 2012?2021, reflecting the dynamic change of “flat, rising, peak and fall”. On the annual scale, there is no obvious regularity on the day of the first peak of lightning fire, but on the scale of 5-years, from the beginning of the third period to the end of the seventh period, the date of the first peak of lightning fires accumulatively advances by 24 days.

Key words: Daxing’anling Mountains, lightning fires, spatiotemporal distribution, dynamic characteristics