# How Environmental Factors Affect Forest Fire Occurrence in Yunnan Forest Region
## 5 Conclusions  
In Yunnan, the occurrence of forest fires has been controlled by local environmental factors and is driven by meteorological characteristics, among which \(\mathrm{RH_{min}}\) is the dominant factor. Based on the LR model established by data of fire points in Yunnan from 2005 to 2019, the key threshold of \(\mathrm{RH_{min}}\) was 28.07\(\%\)\(\pm\) 11.85\(\%\) at the 50\(\%\) level of forest fire probability. \(\mathrm{RH_{min}}\) was the most important environmental factor affecting the occurrence of forest fires in Yunnan over the years studied. The importance of \(\mathrm{T_{max}}\) for forest fire events ranks second. The key threshold of \(\mathrm{T_{max}}\) over the period studied was 21.23 \(\pm\) 11.15 \({}^{\circ}\)C, and the peak forest fire period in Yunnan was in spring and summer, when Yunnan has its dry season. Thus, the combustible substance was relatively dry, so \(\mathrm{T_{max}}\) easily became a natural source of forest fire. \(\mathrm{RH_{min}}\) and \(\mathrm{T_{max}}\) are spatially complementary, and the path of monsoons from the Western Pacific Ocean and the Indian Ocean corresponds to areas with the highest \(\mathrm{T_{max}}\) threshold. The results of this study allow us to use the key thresholds to determine the local early warning signs of forest fire and provide suggestions for preventing forest fires.  
Based on this analysis of the results of this study, we propose several fire protection measures for Yunnan. First, in the LR model of data from Yunnan during 2005-2019, the most important environmental factor is \(\mathrm{RH_{min}}\). Therefore, forest fire monitoring and risk assessment should focus more on changes in the \(\mathrm{RH_{min}}\) threshold and daily relative humidity, especially in the Eastern and Western regions of Yunnan, where monsoons have the greatest influence. Fire-prevention services should also design the distance between regional roads and the forest zone to improve forest fire prevention measures. Controlling the sources of fire in the forest zone is also a vital step to curb fire outbreaks. According to recent statistical data, human-caused forest fires have become more frequent [21], even exceeding the number of forest fires caused by climate change [67], and the use of fires for farming and culture in spring and summer, especially in the agricultural and forest lands, should be a major concern for the authorities. To better understand the combustibility of combustible substances in different regions, combustibility experiments should be implemented on different plant species to understand how they adapt to different degrees of forest fire, and also to raise public awareness of forest fire prevention through related scientific activities. Additionally, the management strategy should be tailored to the characteristics of each region (e.g., the strong monsoons of the Western and Southeastern parts of Yunnan), and meteorological data reports should be fully exploited. For the central plateau of Yunnan and the area where the three rivers merge, forestry engineering should be adopted to reduce the combustible substance load by appropriately adjusting the forest stand structure. For a tropical forest zone and alpine grassland areas, more reasonable management measures of the forest zone and livestock should be implemented to reduce forest fires.  
Conceptualization, Z.Z. and F.Z.; funding acquisition, F.Z.; writing--reviewing and editing, Z.Z., X.D. and F.Z.; field investigation, experiment, and data analysis, Z.Z., S.L., L.W. and F.Z.; All authors have read and agreed to the published version of the manuscript.  
This study was financially supported by the National Natural Science Foundation of China (Grant No. 32160374) and Yunnan Fundamental Research Projects, China (Grant No. 20210 AT070045).  
Not applicable.  
The authors declare no conflict of interest.