植被叶面积指数(Leaf Area Index,LAI)是重要的生态学参数,被广泛用于指示植被密度、生物量、碳、氮物质循环以及气候变化对生态系统的影响,也作为生态过程模型的重要输入参数。地面实测高光谱遥感数据能以更高的空间分辨率及更高的光...植被叶面积指数(Leaf Area Index,LAI)是重要的生态学参数,被广泛用于指示植被密度、生物量、碳、氮物质循环以及气候变化对生态系统的影响,也作为生态过程模型的重要输入参数。地面实测高光谱遥感数据能以更高的空间分辨率及更高的光谱分辨率监测植物的光谱特征,为精准反演LAI提供了基础。本项研究以武夷山国家公园黄岗山顶的亚高山草甸为研究对象,通过建立多种高光谱植被指数和拟合多光谱植被指数反演叶面积指数的统计模型,并比较高光谱与多光谱对叶面积指数反演的效果,阐明用于反演高覆盖率亚高山草甸的最适高光谱和拟合多光谱植被指数。结果表明:高光谱新植被指数(NVI)对于反演LAI有最好的效果,R^(2)=0.85,P<0.01;依据高光谱NVI拟合而成的多光谱NVI反演结果次之,R^(2)=0.82,P<0.01。几种常用比值植被指数NDVI、MSR、RVI和GNDVI在高光谱和拟合多光谱反演结果中相差不大,表现较好,R^(2)都在0.65以上。通过对比高光谱和拟合Sentinel-2A和Landsat-8两种多光谱卫星波段的反演结果发现,光谱响应函数中具有更窄波段范围的近红外、红、绿、蓝波段构成的植被指数可以得到更好的反演结果,而固定波段的高光谱植被指数未必在每种植被指数中都具有最好的反演效果。同时,发现当某种植被指数反演LAI的线性回归方程的斜率越大,说明这种植被指数越有可能随LAI的增大而出现饱和现象,相反的,斜率越小则说明该种植被指数没有出现饱和现象。此外,在研究区内使用高光谱和拟合多光谱波段植被指数法反演LAI,NDVI都获得了较好的效果,存在很好的线性关系,之前的很多研究和判断都认为NDVI不适用于反演高覆盖植被的LAI,这个发现是具有意义的,表明高覆盖植被的叶面积指数在一定范围内是能够被NDVI(应用最广泛的植被指数)较好的反演,进一步扩展了NDVI反演LAI的适用性和可能性。展开更多
The alpine treeline ecotone is defined as a forest-grassland or forest-tundra transition boundary either between subalpine forest and treeless grassland,or between subalpine forest and treeless tundra.The alpine treel...The alpine treeline ecotone is defined as a forest-grassland or forest-tundra transition boundary either between subalpine forest and treeless grassland,or between subalpine forest and treeless tundra.The alpine treeline ecotone serves irreplaceable ecological functions and provides various ecosystem services.There are three lines associated with the alpine treeline ecotone,the tree species line(i.e.,the highest elevational limit of individual tree establishment and growth),the treeline(i.e.,the transition line between tree islands and isolated individual trees)and the timber line(i.e.,the upper boundary of the closed subalpine forest).The alpine treeline ecotone is the belt region between the tree species line and the timber line of the closed forest.The treeline is very sensitive to climate change and is often used as an indicator for the response of vegetation to global warming.However,there is currently no comprehensive review in the field of alpine treeline advance under global warming.Therefore,this review summarizes the literature and discusses the theoretical bases and challenges in the study of alpine treeline dynamics from the following four aspects:(1)Ecological functions and issues of treeline dynamics;(2)Methodology for monitoring treeline dynamics;(3)Treeline shifts in different climate zones;(4)Driving factors for treeline upward shifting.展开更多
文摘植被叶面积指数(Leaf Area Index,LAI)是重要的生态学参数,被广泛用于指示植被密度、生物量、碳、氮物质循环以及气候变化对生态系统的影响,也作为生态过程模型的重要输入参数。地面实测高光谱遥感数据能以更高的空间分辨率及更高的光谱分辨率监测植物的光谱特征,为精准反演LAI提供了基础。本项研究以武夷山国家公园黄岗山顶的亚高山草甸为研究对象,通过建立多种高光谱植被指数和拟合多光谱植被指数反演叶面积指数的统计模型,并比较高光谱与多光谱对叶面积指数反演的效果,阐明用于反演高覆盖率亚高山草甸的最适高光谱和拟合多光谱植被指数。结果表明:高光谱新植被指数(NVI)对于反演LAI有最好的效果,R^(2)=0.85,P<0.01;依据高光谱NVI拟合而成的多光谱NVI反演结果次之,R^(2)=0.82,P<0.01。几种常用比值植被指数NDVI、MSR、RVI和GNDVI在高光谱和拟合多光谱反演结果中相差不大,表现较好,R^(2)都在0.65以上。通过对比高光谱和拟合Sentinel-2A和Landsat-8两种多光谱卫星波段的反演结果发现,光谱响应函数中具有更窄波段范围的近红外、红、绿、蓝波段构成的植被指数可以得到更好的反演结果,而固定波段的高光谱植被指数未必在每种植被指数中都具有最好的反演效果。同时,发现当某种植被指数反演LAI的线性回归方程的斜率越大,说明这种植被指数越有可能随LAI的增大而出现饱和现象,相反的,斜率越小则说明该种植被指数没有出现饱和现象。此外,在研究区内使用高光谱和拟合多光谱波段植被指数法反演LAI,NDVI都获得了较好的效果,存在很好的线性关系,之前的很多研究和判断都认为NDVI不适用于反演高覆盖植被的LAI,这个发现是具有意义的,表明高覆盖植被的叶面积指数在一定范围内是能够被NDVI(应用最广泛的植被指数)较好的反演,进一步扩展了NDVI反演LAI的适用性和可能性。
基金The National Natural Science Foundation of China(41901361)The Six Talent Peaks Project of Jiangsu Province(TD-XYDXX-006)+1 种基金The Natural Science Foundation of Jiangsu Province(BK20180769)The Major Basic Research Project of the Natural Science Foundation of theJiangsu Higher Education Institutions(18KJB180009).
文摘The alpine treeline ecotone is defined as a forest-grassland or forest-tundra transition boundary either between subalpine forest and treeless grassland,or between subalpine forest and treeless tundra.The alpine treeline ecotone serves irreplaceable ecological functions and provides various ecosystem services.There are three lines associated with the alpine treeline ecotone,the tree species line(i.e.,the highest elevational limit of individual tree establishment and growth),the treeline(i.e.,the transition line between tree islands and isolated individual trees)and the timber line(i.e.,the upper boundary of the closed subalpine forest).The alpine treeline ecotone is the belt region between the tree species line and the timber line of the closed forest.The treeline is very sensitive to climate change and is often used as an indicator for the response of vegetation to global warming.However,there is currently no comprehensive review in the field of alpine treeline advance under global warming.Therefore,this review summarizes the literature and discusses the theoretical bases and challenges in the study of alpine treeline dynamics from the following four aspects:(1)Ecological functions and issues of treeline dynamics;(2)Methodology for monitoring treeline dynamics;(3)Treeline shifts in different climate zones;(4)Driving factors for treeline upward shifting.
