Bamboo Forest Mapping In China Based On Landsat-8/Sentinel-2 Time Series Images And Its Zonal Characteristics Analysis

Bamboo forest is an important forest resource,and bamboo plants have important and obvious ecological,economic,and cultural values.Due to the combined influence of water and heat conditions,bamboo forests are mainly distributed in tropical and subtropical regions worldwide,and there are also fewer bamboo forests in temperate regions.China is the richest country in the world in terms of bamboo resources and is known as the"Kingdom of Bamboo".A comprehensive and accurate understanding of the spatial distribution of bamboo forest resources can help scientific planning,management,and development of bamboo forest resources,as well as provide important data support for the analysis and evaluation of the ecological service.However,the traditional manual survey method of bamboo forest resources requires a lot of human,material,and financial resources,and it is difficult to monitor the dynamic changes of bamboo forests.Therefore,it is of great scientific and practical significance to mapping bamboo forests in China based on images.In this study,Landsat-8 and Sentinel-2 time-series images were employed to carry out the mapping of bamboo forests in China with 30m and 10m spatial resolutions.The differences between the two results were compared and analyzed.And the vertical zonality and horizontal zonality characteristics of bamboo forest spatial distribution in China were further analyzed.The results show that:(1)The overall classification accuracy of bamboo forest mapping in China based on Landsat-8 and Sentinel-2 images was 93.71%and 94.30%,respectively;the kappa coefficients were 0.7824 and 0.8663,respectively;the producer accuracy was 79.21%and 92.47%,respectively;the user accuracy was 89.78%and 90.21%,respectively;which indicate that the classification results are reliable.(2)The total area of bamboo forests in China extracted based on Landsat-8images was 849.68×10~4 ha,with the five provinces of Fujian,Hunan,Jiangxi,Zhejiang and Sichuan having the most abundant bamboo forest resources,and the total area of the five provinces accounted for about 70%of the national bamboo forest area.(3)The total area of bamboo forest in China extracted based on Sentinel-2images is 796.28×10~4 ha.Among them,the bamboo forest area of Hunan,Jiangxi,Fujian,and Zhejiang provinces are all over 1 million ha,and the area of bamboo forest in Sichuan Province is also close to 1 million ha,and the total area of bamboo forest in the five provinces accounts for 66.57%of the national bamboo forest area.(4)In terms of the contribution of classification features,it was found that the use of multiple vegetation indices and statistical values to characterize vegetation phenological changes can effectively improve the accuracy of bamboo forest classification.And the classification performance of the same index in different phenological periods also has large differences.Specifically,BI(Bamboo index)and MVI(Multi vegetation index),with the ability to distinguish different vegetation types,contributed more to the improvement of bamboo forest classification accuracy.In addition,using the NDMI(Normalized difference moisture index)to characterize vegetation canopy water content and GCVI(Green Chlorophyll Vegetation Index)to characterize vegetation canopy chlorophyll variation also contributed to improving the classification accuracy.This is mainly due to the differences in canopy water content and chlorophyll content between bamboo plants and other vegetation types during a specific phenological period.(5)The results of the zonal analysis of the spatial distribution of bamboo forests showed that bamboo forests in China were mainly distributed in the eastern region south of 32°N.And the area of bamboo forests showed a decreasing trend from east to west.The bamboo forests are mainly distributed in the mountainous hills between 200and 1200 meters above sea level,which is mainly influenced by human activities and the distribution of water and heat.Bamboo forests are mainly located in areas with a land surface temperature of 19℃～25℃and precipitation of 1200 mm～2000 mm,which is related to the ecological characteristics of bamboo plants that prefer temperature and humidity.In addition,bamboo forests form a"bimodal"distribution of precipitation,consisting of bamboo forests in southeastern China and around the Sichuan basin.Mapping bamboo forests in China and analyzing the spatial distribution patterns of water and heat will help to provide an important reference for global bamboo forest mapping,as well as a theoretical and data basis for bamboo-related industrial planning and ecological assessment of bamboo forests.