不同滞尘量对城市植物冠层光谱的影响

Effect of Different Dust Weight Levels on Unban Canopy Reflectance Spectroscopy

为了探索不同滞尘量对植被冠层光谱的影响,以位于上海市中心城区的上海师范大学徐汇区校园为研究样区,选取并使用ASD FieldSpec 3地物光谱仪测定校园内龙爪槐、紫荆、红叶石楠及蔓长春等植物不同滞尘量等级下的冠层反射光谱,然后在实验室中使用万分之一电子分析天平测定相应植物的滞尘量并计算各植物的滞尘能力。在此基础上,分析不同滞尘量对植物冠层光谱特征变化的影响。结果表明:(1)植物在710~1 350nm之间光谱反射率会随着滞尘量的增减而减小而且三条曲线之间的差值较大;滞尘量的变化对各植物在350~710和1 450~1 750nm之间的光谱影响较复杂,三条曲线之间的差值虽小但差值比并不小。(2)滞尘对植物冠层光谱的影响不仅与滞尘量有关还与树种有关,不同植物或同种植物不同波长的光谱曲线对滞尘量的灵敏度不同。(3)各植物在"绿峰"和红边附近的光谱曲线的斜率会随着滞尘量的增加而减小。(4)滞尘不会引起红边位移现象,但会消弱红边一阶导数的"双峰"现象,表现为"主峰"值与"次峰"值之间的差随着滞尘量的增加而减小,红边位于719nm处。找到滞尘或不同滞尘量对植被冠层光谱的影响关系,对高光谱遥感在这一领域的应用具有重大意义。

In order to explore the effect of different dust weight on vegetation canopy spectrum,we selected Shanghai Normal university as the study area located in the center of Shanghai and determined the canopy spectral reflectance under different grades of foliar dust including Sophora japonica,Bauhinia,Photinia fraseri,Vinca etc using ASD FieldSpec 3.Then we weighed the foliar dust of corresponding species using electronic analytical balance in the laboratory and calculated dust catching of each plant.On this basis,we analyzed the influence of different foliar dust weight on canopy spectral characteristics of plants.After analyzing the different spectral curves,we got some conclusions.The spectral reflectance of plant canopy between 710～1 350 nm reduced as the foliar dust increasing and the difference among the three curves was large.The different dust weight impacting on the reflectance spectrum of vegetation was more complicated in 350～710 and 1 450～1 750 nm.The difference between the three curves was small in 350～710 and 1 450～1 750 nm bands but the ratio of difference was not small.The influence of foliar dust on canopy spectral of plants was not only related with the weight of dust but also related with species of plants.In the vicinity of the ＂green peak＂ and ＂red edge＂,the slope of the plants reduced with the increasing of the amount of dust.The sensitivity of the spectral curves of different spieces or different wavelengths of the same plant to the dust was different.The foliar dust did not led to the phenomenon of red edge displacement,but it weakened the ＂twin peaks＂ phenomenon of the first derivative of red edge.The difference between ＂peak＂ and ＂secondary peak＂ reduced as the dust weight increasing and red edge was located in 719 nm.Finding the relationship between foliar dust or different dust weight and vegetation canopy spectrum will be of great significance for hyperspectral remote sensing application in this field.