The Early High Spectral Diagnosis Model Of Cinnamomum Camphora Under Acid Stress

Along with Europe and the eastern North America,the southern China has become one of the most serious acid rain polluted regions in the world.Acid deposition has caused serious harm to the ecosystem.Hyperspectral remote sensing can identify the subtle change of the research object,thus has been used in the study that the change of plant under environmental stresses.Because of the acid rain contains N and S of plant nutrient elements,so acid stress is different from with other stress.Under the low concentration of acid rain,plants can grow better in a short time.With the increasing of contact time or acid concentration,physiological and biochemical indexes of plant began to change,which lead to the growth of plant restrained eventually.Therefore,monitoring the early variations of plants under acid stress is very crucial to the health recovery of plants.This paper aims to use hyperspectral remote sensing technology to detect the spectral change of leaves and canopy of Cinnamomum camphora caused by acid stress.According to element of the rainwater in Linan,simulated acid rain was configured(S042-:N03-=2:1),then diluted into four pH value of5.6,4.5,3.5 and 2.5.In this study,we have measured hyperspectral data of 16 stages in leaf scale and 14 stages in canopy scale for 419 days under acid stress.First,compare the spectrum and the first derivative spectrum of Cinnamomum camphora under different acid disposals after data preprocessing,analysis the changes of spectral reflectance.Next,typical bands were found out by the principle of plant response to acid stress and construct the difference of vegetation index.In the end,the early high spectral diagnosis model of Cinnamomum camphora under acid stress was constructed with the difference of vegetation index.The main conclusions are as follows:(1)In the spectrum of leaf,the typical bands that can best reflect the change of Cinnamomum camphora under acid stress are 470 nm?520 nm and565 nm?700 nm.The difference of blue edge index and the difference of yellow edge index in leaf are built with typical bands,which can indicate the level of acid stress.The diagnosis model of acid stress shows:under acid rain of pH4.5andpH 3.5,the growth of Cinnamomum camphora presents the trend of "first promote then inhibit" and the abrupt change time is the 100th day.With the increase of acid concentration,the inhibition for Cinnamomum camphora leaves also increased.The acid rain of pH2.5 inhibited the growth of Cinnamomum camphora at the beginning of spray acid,and then this inhibition has been strengthened over time,and finally the inhibition reached a high value that show acid rain have produced irreversible damage for Cinnamomum camphora.(2)In the spectrum of canopy,the typical bands that can reflect the change of Cinnamomum camphora under acid stress are570 nm?670 nm.The difference of valley-deep index and the difference of yellow edge index in canopy are built with typical bands,which can indicate the level of acid stress.The diagnosis model of acid stress shows:under acid rain of pH4.5,the growth of Cinnamomum camphora presents the trend of "first promote then inhibit" and the abrupt change time is the 270th day.Under acid rain of pH3.5,the growth of Cinnamomum camphora presents the trend of "first promote decrease then increase",which related to the temperature.The acid rain of pH2.5 inhibited the growth of Cinnamomum camphora at the beginning of spray acid and this inhibition has been strengthened over time.(3)Under different acid disposals,all difference of vegetation indices in leaf and canopy can better response the effects of acid rain.The spectrum of leaf is more sensitive than the spectrum of canopy under acid stress.The fit indices of difference of indices in leaf are higher than canopy and the abrupt change time are earlier.The spectrum of canopy can better reflect the whole of Cinnamomum camphorate,is highly consistent with the actual growth.This study shows that the resolution of hyperspectral remote sensing is high,which can well distinguish the tiny spectral changes of Cinnamomum camphorate under acid stress.The spectrums of different acid disposals are different,which suggests that remote sensing can monitor the change of vegetation under acid rain and provides the theoretical support for the widespread monitoring the change of vegetation under acid rain by remote sensing.