| Ecological public forests are an important foundation for building national ecological security and an important guarantee for realizing the "Two Mountains" concept.After two decades of protection and development,the ecological public forest system in Hunan Province has been constructed with a stable structure and complete functions.Currently,due to the lack of a comprehensive evaluation of the ecological public forests in Hunan Province and little understanding of the spatial pattern and driving factors of biomass in the public forests,this study focuses on different vegetation types(coniferous forest,broad-leaved forest,coniferous and broad-leaved mixed forest,bamboo forest,and shrub)of ecological public forests in Hunan Province.The study selects the modeling variables of Landsat 8 OLI by stepwise regression and Boruta algorithm,constructs biomass inversion models for different vegetation types of public forests,and explores the spatial pattern of biomass in different vegetation types of public forests.Additionally,this study clarifies the driving factors of biomass in different vegetation types of public forests in combination with topographic and socio-economic factors.The main research results are as follows:(1)The comparison of the biomass inversion models shows that the random forest model has the highest estimation accuracy,followed by the support vector machine and decision tree models,while the multiple linear regression model has the lowest estimation accuracy.Vegetation type classification inversion can effectively improve the estimation accuracy of forest biomass.The R2 values of the biomass estimation of coniferous forest,broad-leaved forest,coniferous and broad-leaved mixed forest,bamboo forest,and shrub estimated by the RF model are 0.74,0.73,0.76,0.79,and 0.74,respectively,and the RMSE values are 31.76,21.57,15.76,25.60,and 2.11 t·hm-2,respectively.(2)The biomass of ecological public forests in Hunan Province presents a strip distribution pattern that gradually increases from the central to the southwest and northeast.The total biomass of ecological public forests in Hunan Province is 338 million tons,with an average biomass of 68.31 t·hm-2,and the biomass range is from 0.85 to 177.63 t·hm-2.The average biomass of each vegetation type is:coniferous forest(100.33 t·hm-2)>bamboo forest(71.33 t·hm-2)>coniferous and broad-leaved mixed forest(62.44 t·hm-2)>broad-leaved forest(59.27 t·hm-2)>shrub(4.65 t·hm-2).Among them,the biomass of coniferous forest is as high as 215 million tons,broad-leaved forest biomass reaches 48 million tons,coniferous and broad-leaved mixed forest biomass is 37 million tons,bamboo forest biomass is 33 million tons,and the biomass of shrub is only 4 million tons.(3)Topographic and socio-economic factors have a significant impact on the spatial pattern of biomass in ecological public forests.Overall,Altitude,Slope,and Aspect have a significant positive impact on the distribution of biomass,while Gross Domestic Product,(GDP)and Population(POP)have a significant negative impact on the distribution of biomass.The spatial pattern of biomass in different types of ecological public forests has significant differences in response to the feedback effects of each driving factor.Slope has the greatest impact on coniferous forest,coniferous and broad-leaved mixed forest,and shrub,while POP has the greatest impact on broad-leaved forest and bamboo forest.This study constructed forest biomass inversion models based on different vegetation types using remote sensing monitoring data and field measurement data.By exploring the spatial pattern and driving factors of forest biomass in different vegetation types of public forests in Hunan Province,the research fills the gap in the monitoring of forest biomass in public forests in Hunan Province.It provides a new method to improve the accuracy of forest biomass estimation and data support for the sustainable management of public forests in the future. |
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