Acta Geographica Sinica ›› 2023, Vol. 78 ›› Issue (3): 729-745.doi: 10.11821/dlxb202303014

• Phytogeography • Previous Articles     Next Articles

Spatio-temporal dynamics of vegetation optical depth and its driving forces in China from 2000 to 2018

LIU Yue1(), LIU Huanhuan1, CHEN Yin1, GANG Chengcheng2,3()   

  1. 1. College of Grassland Agriculture, Northwest A&F University, Yangling 712100, Shaanxi, China
    2. Institute of Soil and Water Conservation, Northwest A&F University, Yangling 712100, Shaanxi, China
    3. Institute of Soil and Water Conservation, Chinese Academy of Sciences and Ministry of Water Resources, Yangling 712100, Shaanxi, China
  • Received:2022-05-09 Revised:2023-02-08 Online:2023-03-25 Published:2023-03-27
  • Contact: GANG Chengcheng E-mail:liu_yue@nwafu.edu.cn;gangcc@ms.iswc.ac.cn
  • Supported by:
    National Natural Science Foundation of China(31602004);Natural Science Foundation of Shaanxi Province of China(2021JQ-171)

Abstract:

Compared to traditional optical remote sensing indicators, the microwave remote sensing indicator vegetation optical depth (VOD) is less sensitive to clouds and atmosphere, and also less susceptible to saturation. The VOD is capable of monitoring changes in the total water content and biomass of vegetation. In this study, we analyzed the spatio-temporal dynamics of VOD in different regions of China and different vegetation types from 2000 to 2018 based on multiple frequencies of VOD datasets (VODCA C-VOD, X-VOD, Ku-VOD, and AMSRU X-VOD) using trend analysis and residual analysis. Then, the relative contributions of climate change and human activities at national and regional scales were quantitatively assessed. Results showed the following. (1) All of the VOD increased significantly over this period. AMSRU X-VOD had the fastest growth rate (0.062/10a), especially in eastern China. VODCA C-VOD increased at the lowest rate (0.013/10a), which showed the highest increasing rate in southwestern China. The fastest increasing trend of VOD was observed in grasslands, followed by needleleaf forests and scrubs. (2) The rising precipitation and radiation promoted the increase of VOD in northern and northwestern China. The temperature was closely related to the VOD changes in southern China and coastal areas. The contribution of radiation on Ku-VOD and X-VOD representing vegetation canopy was higher than that of precipitation and temperature. (3) According to different datasets, human activities were the primary factor for the increase in VOD. The contribution of human activities to VODCA C-VOD, Ku-VOD, X-VOD, and AMSRU X-VOD was 171%, 48%, 43%, and 30%, respectively, especially in the Loess Plateau, southwestern China, and Northeast China Plain. The outcomes of this study shed new light on the efficiency evaluation of ecological projects, which will provide guidance for future ecosystems management and environment protection in China.

Key words: vegetation optical depth (VOD), spatio-temporal variability, climate change, human activities