Study On Burn Severity And Its Spatial Pattern In Southern Jiangxi

Forest fire is the first of the forest three natural disasters(fire,disease,insect pests),is one of the main factors driving the change of forest landscape structure and function.Burn severity is a key index to reflect the severity of forest fire.The composition and allocation of patches with different burn severity will affect the reconstruction pattern of plant community after forest fire.Accurate assessment of burn severity and analysis of its landscape pattern are of great importance for understanding the ecological processes and changes in landscape pattern caused by forest fire,and also for implementing effective forest fire management strategies.In this paper,forest fires in Ganzhou City,Jiangxi Province during 2018-2022 were studied based on Landsat8 OLI remote sensing images,topography,vegetation,and meteorology and field survey data.1)Different models were constructed to screen the optimal spectral index of burn severity evaluation,and confusion matrix(overall accuracy and Kappa coefficient)was used to verify the evaluation accuracy;2)The spatial pattern and influencing factors of burn severity were analyzed by means of random forest model;3)Finally,the landscape pattern of patches with different severity was quantified by landscape pattern index,and the influencing factors of landscape pattern with burn severity were analyzed by geographic detector model.The main research results are as follows:1)The five modeling results of burn severity evaluation showed that the quadratic and cubic polynomial models had the best fitting results.d NBR,Rd NBR and RBR have good accuracy in 12 spectral indices of burn severity evaluation.Among them,d NBR index has the best evaluation effect,and the overall classification accuracy reaches 58%;2)The burn severity in southern Jiangxi was mainly low and moderate severity,accounting for more than 65% of the total burned area.Pre-fire vegetation coverage and human activities are the main factors affecting the spatial pattern of burn severity in southern Jiangxi.High severity burning patches were mainly distributed in areas with high vegetation coverage before the fire,more than 2 km away from the nearest road,sunny slope,uphill slope and steep slope;3)The landscape pattern of patches with different burn severity was significantly different.High burn severity patches have low fragmentation degree,small patch severity and regular shape.The patches with moderate and low severity of fire had high degree of fragmentation,high severity and complex shape.The burning patch area is larger in the high altitude area.The degree of fragmentation in the gentle slope area is greater;4)Topographic factor is the most important factor affecting the landscape pattern of high severity patches,followed by climatic conditions.Climate factors mainly affect patch edge density,patch connectivity and patch shape.