基于点模式法的湖南省林火时空分布特征

Spatiotemporal distribution characteristics of forest fires in Hunan based on point pattern methods

【目的】林火是影响森林生态系统的一个既特殊又重要的生态因子,发现林火在时间、空间上的动态与趋势有助于掌握林火发生规律,部署森林防火重点区域,为防灾减灾提供应急决策方案。【方法】以湖南省24年间(1999—2022年)林火档案资料为数据源,采用Ripley K函数、中心点和标准差椭圆法、核密度分析法进行了林火的空间聚集性、林火密度和扩展趋势等空间统计分析。【结果】湖南省1999—2022年林火发生总密度为0.008 7次/(km^(2)·a),空间上存在3个林火聚集点。1999—2003年的年均单位面积林火密度为0.016 7次、2004—2008年为0.034 8次、2009—2013年为0.021次、2014—2018年为0.005次、2019—2022年为0.006次,1999—2013年内的3个时序区间湖南省林火分布都具有多个聚集区域,自2014年之后林火聚集区不明显;【结论】湖南省1999—2022年间的林火空间分布存在显著的空间聚集性与地理相关性,存在明显的森林火灾高密度区域,林火密度整体呈波动下降趋势,林火密度最高的区域为娄底市、株洲市、郴州市和邵阳市东部;并且2013—2018年以及2019—2022年区间的林火密度明显下降;1999—2022年的总体林火平均中心位于邵阳市,同时也是林火高密度区域,林火高密度区域还包括株洲市、郴州市,湖南省林火总体扩散趋势是向湖南省东南方向的永州市、郴州市扩展;湖南省各区划1999—2022年间的GDP发展分布呈现高度聚集性,聚集区域主要是长株潭区域以及衡阳市、益阳市范围,GDP分布的空间变异极小,与林火空间分布方向重叠区域面积占71.29%,重叠面积较高。

【Objective】Forests are the most widely distributed,complex,and resources-abundant ecosystems on dry land.Wildfire is a special and important factor affecting forest ecosystem.Discovering the dynamics and trends of forest fires in time and space helps to grasp the rules of forest fire occurrence,which is a fundamental work for deploying fire prevention priorities.【Method】Using forest fire archive data from Hunan province over the past 24 years (1999-2022) as the data source,spatial statistical methods such as Ripley K function,center point and standard deviation ellipse method,and kernel density analysis were used to analyze the spatial clustering,forest fire density changes,and expansion trends of forest fires in Hunan province.【Result】The total density of forest fires in Hunan province from 1999 to 2022 was 0.008 7 times /(km^(2)·a),and there were three forest fire aggregation points in space.The annual forest fire density of unit area from 1999 to 2003 was 0.016 7 times,from 2004 to 2008 it was 0.034 8 times,from 2009 to 2013 it was 0.021 times,from 2014 to 2018 it was 0.005 times,and from 2019 to 2022 it was 0.006 times.The forest fire distribution in Hunan province during the 3 periods from 1999 to 2013 had multiple aggregation areas,and since 2014,the forest fire aggregation areas have not been obvious.【Conclusion】There is a significant spatial clustering and geographical correlation in the spatial and temporal distribution of forest fires in Hunan province from 1999 to 2022 and the overall forest fire density shows a fluctuating downward trend.There are obvious high-density areas of forest fires,including Loudi city,Zhuzhou city,Chenzhou city,and the eastern part of Shaoyang city,the overall average center of forest fires from 1999 to 2022 is located in Shaoyang city,the spread trend of forest fires in Hunan province is to expand towards Yongzhou and Chenzhou cities in the southeast;And the forest fire density significantly decreased between 2013 to 2018,as well as 2019 to 2022.The GDP development distribution of various districts in Hunan province from 1999 to 2022 shows a high degree of aggregation,mainly in the Changsha-Zhuzhou-Xiangtan region,as well as Hengyang and Yiyang cities.There is a tiny spatial variation of GDP distribution,and the overlapping area of GDP distribution and the spatial distribution of forest fires accounts for 71.29%,which is relatively high.