Arid Zone Research ›› 2019, Vol. 36 ›› Issue (4): 924-934.doi: 10.13866/j.azr.2019.04.17

• Plant Physiology • Previous Articles     Next Articles

Estimation of Chlorophyll Content of Typical Oasis Vegetation in Arid Area Based on Sentinel-2 Data

GU Feng1,2,3, DING Jian-li1,2,3, GE Xiang-yu1,2,3, GAO Shi-bao4, WANG Jing-zhe1,2,3   

  1. 1. College of Resources and Environment Sciences,Xinjiang University,Urumqi 830046,Xinjiang,China;
    2. Key Laboratory of Wisdom City and Environmental Modeling under Department of Education of Xinjiang Uygur Autonomous Region,Urumqi 830046,Xinjiang,China;
    3. Key Laboratory of Oasis Ecology under the Ministry of Education,Xinjiang University, Urumqi 830046,Xinjiang,China;
    4. School of Earth Sciences,Zhejiang University,Hangzhou 310027,Zhejiang,China
  • Received:2018-11-27 Revised:2019-03-07 Published:2025-10-18

Abstract: The Ogan-Kuqa River Delta Oasis,a typical oasis in the arid zone in China,was taken as the study area.The method of Random Forest with a comparative advantage in machine learning was chosen to model and estimate the relative contents of chlorophyll (SPAD values) of leaves from four kinds of representative vegetation (cotton,reed,poplar and jujube).The 23 broadband spectral indices of vegetation,which are sensitive to chlorophyll content,were obtained based on the reflectance of original Sentinel-2 image with rich spectral information in the “red edge” bands.These vegetation indices were extracted again in the original band order on the firstly-derived Sentinel-2 image and secondly-derived Sentinel-2 image.Three soil parameters (soil moisture content,SMC;soil organic matter,SOM;electrical conductivity,EC) related to vegetation growth were all conducted as the characteristic variables affecting SPAD values.According to the characteristic variables above,three modelling schemes could be developed to monitor the SPAD values of vegetation leaves in oasis.The results showed that: ① Vegetation indices obtained from the firstly-derived image played a more important role than the original vegetation indices in the SPAD estimation model. ② It could be concluded that SPAD-RF regression model,based on the Sentinel-2 satellite image data,could be used to effectively monitor the SPAD values of leaves of the four vegetation types.Especially for the estimation model of SPAD of reed leaves,R2 reached 0.926. ③ By analyzing and comparing the model prediction capability under the three schemes,the prediction capability of scheme 3 (including soil parameters) was excellent (2.143<relative percentage deviation (RPD)<2.692),and the prediction capability was ranked as scheme 3>scheme 1>scheme 2.There was a significant nonlinear correlation between the soil properties and the model prediction results.Holistically,Sentinel-2 data has great potential for predicting chlorophyll content of oasis vegetation.This study provided an efficient,low-cost,potentially high-precision solution to estimate SPAD.

Key words: oasis, Sentinel-2 data, SPAD, chlorophyll, vegetation index, random forest, Xinjiang