海南岛橡胶林叶面积指数遥感估算模型比较研究

Comparison of Remote Sensing Estimation Models for Leaf Area Index of Rubber Plantation in Hainan Island

叶面积指数(LAI)是描述植被生长状况和冠层结构的一个重要参数,快速获取大面积植被与作物LAI对于生态系统科学研究、农林业生产指导具有十分重要的理论和实践意义。本研究选取海南岛典型热带作物——橡胶树为研究对象,构建基于卫星遥感植被指数的橡胶林LAI估算模型并分析其变化规律。结果表明,相较于归一化植被指数(NDVI)、绿色归一化植被指数(GNDVI)、比值植被指数(RVI)和宽动态范围植被指数(WDRVI)四个指数,增强植被指数(EVI)、土壤调节植被指数(SAVI)、差值植被指数(DVI)和改良土壤调节植被指数(MSAVI)四个指数同LAI之间的相关性较高。构建的基于不同植被指数的橡胶林LAI估算模型(一元线性、指数和对数模型)中,基于EVI指数的橡胶林LAI一元线性估算模型效果最佳,其决定系数R2为0.69。经验证,该模型估算的橡胶林LAI精度较高,观测和模拟的橡胶林LAI线性拟合R2为0.67,均方根误差RMSE为0.16,平均相对误差RE为-0.25%,但在橡胶林LAI中值区存在低估现象,同时在LAI高值区和低值区存在一定的高估现象。从空间分布来看,海南岛橡胶林LAI高值区(4.40~6.23)主要分布在海南岛西部儋州、白沙等市县,LAI中值区(3.80~4.40)主要分布在海南岛中部澄迈、屯昌、琼中等市县,LAI低值区(2.69~3.80)主要分布在海南岛东部和南部的定安、琼海、万宁、乐东、三亚等市县。总之,构建的基于EVI指数的橡胶林LAI一元线性估算模型精度较高,克服了NDVI、GNDVI、RVI等植被指数容易出现指数饱和问题,具有较好的科学性和良好的推广应用价值。

Leaf area index(LAI)is an important index to describe the growth status and canopy structure of vegetation,is of great theoretical and practical significance to quickly obtain LAI of large area vegetation and crops for ecosystem science re-search and agricultural&forestry production guidance.In this study,the typical tropical crop rubber tree in Hainan Island was selected as the research area,the LAI estimation model of rubber plantation based on satellite remote sensing vegetation indices was constructed,and its spatiotemporal variation was analyzed.The results showed that,compared with correlations between LAI and the indices of normalized difference vegetation index(NDVI),green NDVI(GNDVI),ratio vegetation index(RVI)and wide dynamic range vegetation index(WDRVI),correlations were higher between LAI and the indices of enhanced vegetation index(EVI),soil adjusted vegetation index(SAVI),difference vegetation index(DVI)and modified soil adjusted vegetation in-dex(MSAVI).Among the LAI estimation models based on different vegetation indices(linear,exponential and logarithmic models),the linear estimation model based on EVI index was the best,and its coefficient of determination(R 2)was 0.69.The ac-curacy of LAI estimation model was high.The linear fitting R 2 of observed and simulated LAI was 0.67,the root mean square error(RMSE)was 0.16,and the average relative error(RE)was-0.25%.However,there was underestimation in the middle val-ue and overestimation in the high and low value area of LAI.The high LAI values(4.40-6.23)were mainly distributed in Danzhou and Baisha in the west of Hainan Island,the middle LAI values(3.80-4.40)were mainly distributed in Chengmai,Tunchang and Qiongzhong in the middle of Hainan Island,and the low LAI values(2.69-3.80)were mainly distributed in Ding'an,Qionghai,Wanning,Ledong and Sanya in the east and south of Hainan Island.In summary,the linear estimation model for rubber plantation LAI based on EVI index obtained high accuracy,and has good values of popularization and appliance.