基于遥感的平潭木麻黄生物量快速估算

Rapid estimation of Casuarina equisetifolia biomass based on remote sensing

福建省平潭综合试验区是海峡两岸交流合作的试验区,木麻黄(Casuarina equisetifolia)作为平潭主要的沿海防护乔木,在平潭主岛广泛分布。采用归一化比值植被指数(Normalized difference vegetation index,NDVI)对木麻黄生物量快速估算,可为区域尺度的单一乔木生物量快速、无破坏估算提供参考,同时为评价主岛生态系统生产潜力和经营管理提供数据支撑。采用RS和GIS技术,对平潭主岛2017年4月的Landsat 8 OLI影像进行处理,以实地调查数据为基础,利用专家分类知识库(Knowledge base system,KBS)提取木麻黄信息,以NDVI为自变量,引用木麻黄公式获取的木麻黄生物量为因变量,建立NDVI与生物量的反演模型,对主岛木麻黄生物量进行估算,采用K-均值聚类法对各乡镇木麻黄进行分区统计。结果表明:(1)基于专家分类知识库的木麻黄提取,总体精度达81.3%。(2)建立的5种常用模型,通过显著性检验,R值均在0.67以上,NDVI与木麻黄生物量之间存在相关性,采用NDVI估算区域生物量可行,多项式的拟合效果最佳(R=0.72,MRE=23.00%,RMSE=21.62 t·hm^-2,r RMSE=24.94%)。(3)根据二项式模型估算出平潭主岛木麻黄生物量为738235.98 t,单位面积生物量为161.34 t·hm^-2,以较高水平生物量分布占主导地位。(4)主岛木麻黄总体分布趋势表现为:西北多、东南少,分布主要集中于农田和沿海尤其是五大风口,其中以平原镇、芦洋乡和中楼乡所处的长江澳风口分布最密集,防护面积最大;流水镇、北厝镇和苏澳镇木麻黄生物量水平最高;芦洋乡、中楼乡、岚城乡、平原镇和敖东镇较高;白青乡、澳前镇位于中等水平;潭城镇最低。

The Pingtan Comprehensive Experimental Community in Fujian Province is an experimental community for cross-strait exchanges and cooperation.As the main coastal protection species in Pingtan,Casuarina equisetifolia is widely distributed in the main Pingtan Island.In this study,normalized difference vegetation index(NDVI)was used to quickly estimate the biomass of C.equisetifolia,which could provide a reference for rapid and non-destructive estimation of single species biomass at the regional scale.Meanwhile,it could provide a basis for evaluating the production potential and management of the main Pingtan Ialand ecosystem.Using RS and GIS technology,the OLI image of the main Pingtan Island in April 2017 was processed.Based on field survey data,the C.equisetifolia information was extracted by knowledge base system(KBS).NDVI was used as the independent variable and C.equisetifolia biomass obtained from the C.equisetifolia formula was used as the dependent variable.Inversion models between NDVI and biomass were established to estimate the C.equisetifolia biomass in the main Pingtan Island.Cluster analysis was used to analyze the C.equisetifolia of each town in the main Pingtan Island.The results revealed that:(1)The overall accuracy of the C.equisetifolia extraction based on KBS was 81.3%.(2)The five common models established passed the significance test.The R values of the five models were all above 0.67,which indicated that there was a correlation between NDVI and the C.equisetifolia biomass.It was feasible to use NDVI for estimating regional biomass.The polynomial fitting effect was the best(R=0.72,MRE=23.00%,RMSE=21.62 t·hm^-2,r RMSE=24.94%).(3)According to the binomial model,the C.equisetifolia biomass amounted to 738235.98 t,161.34 t·hm^-2 on average in the main Pingtan Island.The main Pingtan Island was dominated by higher level biomass.(4)According to the distribution trend of the C.equisetifolia in the main Pingtan Island,there was more in the northwest and less in the southeast,mainly concentrated in farmland and coastal areas,especially in the five major tuyeres.Among them,Changjiang’ao Tuyere had the most densely distribution and the largest protection area,including the Pingyuan,Luyang and Zhonglou towns.The levels of the C.equisetifolia biomass of Liushui,Beicuo and Su’ao towns were the highest,followed by Luyang,Zhonglou,Lancheng,Pingyuan and Aodong towns,and which in Baiqing and Aoqian towns were at the medium levels,while it in Tancheng town was at the lowest level.