中南半岛野火变化特征及其与土壤水分的相互作用

Variation of Wildfires and Its Interaction with Soil Moisture on Indo-China Peninsula

[目的]分析野火变化特征并探讨火点数与不同深度土壤水分的关联性,为评价生态文明建设和人类生产生活提供科学依据。[方法]基于SNPP/ⅦRS卫星火点监测、火烧迹地和SMAP土壤水分等数据,使用统计方法多角度对2016—2021年中南半岛野火变化特征进行分析,探讨不同干湿条件下火点数与0—5cm和0—100cm2个不同深度土壤水分的相互作用。[结果]①中南半岛火点数和火烧迹地年内主要出现在2—4月,二者在时空分布上具有较高的一致性,多集中在缅甸西部与印度接壤区域、缅甸中部以东和老挝北部。②2—4月火点主要出现在林地、灌木地和耕地,而易发生在归一化植被指数(NDVI)为如下3个等级的区域:0.2<NDVI≤0.4,0.4<NDVI≤0.6,0.6<NDVI≤0.8,但其所占比例随地表覆盖类型和月份的不同存在一定差异。③特旱和重旱条件下火点区明显较无火点区广,火点数集中程度更高;土壤水分随火点数的增加整体呈减少趋势,但极端干湿条件下,土壤水分随火点数变化存在由减转增的“拐点”,且“拐点”值随时间延后而减小。④滞后1~2个月的火点数与土壤水分相关程度最高;日时间尺度上土壤水分对火点数变化同期响应快,且土壤水分和NDVI高的区域关联性更强。[结论]土壤水分亏缺是中南半岛火点高发的重要驱动力。火点数与土壤水分之间相互作用,二者之间存在显著负向关联性。

[Objective]The variation characteristics of wildfires and determine the correlation between the number of wildfires and soil moisture at different depths were analyzed in order to provide a scientific basis for evaluating the construction of ecological civilization and human production and life.[Methods]We used SNPP/ⅦRS satellite fire monitoring,fire site,and SMAP soil moisture data with statistical methods to analyze the change characteristics of wildfires on the Indo-China Peninsula from 2016 to 2021,and to explore the correlation between number of wildfires and soil moisture at 0-5 cm and 0-100 cm under different dry and wet conditions.[Results]①Wildfires and burned areas on the Indo-China Peninsula mainly occurred from February to April in a year.The number of wildfires and burned areas had a high consistency in spatial and temporal distribution,mostly being concentrated in the border area between Western Myanmar and India,the area east of Central Myanmar,and Northern Laos.②From February to April,fires mainly occurred in forest land,shrub land,and cultivated land,and were prone to occur in regions where the normalized difference vegetation indices(NDVI)were as below:0.2<NDVI≤0.4,0.4<NDVI≤0.6,and 0.6<NDVI≤0.8.However,the proportion of primary and secondary fire points was different with different land cover types and months.③Under extreme drought and severe drought conditions,the fire point area was significantly wider than the no fire point area,and the degree of fire point concentration was higher.Soil moisture showed an overall decreasing trend with increasing number of fire points.However,under extreme dry and wet conditions,soil moisture changed with number of fire points.There was an“inflection point”that changed from decrease to increase,and the“inflection point”value decreased with time delay.④The correlation between soil moisture and the number of fire points with a lag of one to two months was the highest.On a daily time scale,soil moisture responded quickly to the change of fire points in the same period,and the correlation between soil moisture and NDVI was stronger in the areas with high NDVI.[Conclusion]Soil water deficit was an important driving force for the high occurrence of fire points on the Indo China Peninsula.There was a significant negative correlation between the number of fire points and soil water.