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Chinese Journal of Applied Ecology ›› 2024, Vol. 35 ›› Issue (3): 659-668.doi: 10.13287/j.1001-9332.202403.025

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Phenological characteristics of net ecosystem carbon exchange of Stipa krylovii steppe in Inner Mongolia, China and its remote sensing monitoring

WANG Jin1, ZHOU Guangsheng2,3,4*, HE Qijin1,3,4, ZHOU Li2,4   

  1. 1College of Resources and Environmental Sciences, China Agricultural University, Beijing 100193, China;
    2Hebei Gucheng Agricultural Meteorology National Observation and Research Station/State Key Laboratory of Severe Weather, Chinese Academy of Meteorological Sciences, Beijing 100081, China;
    3Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters (CIC-FEMD), Nanjing University of Information Science & Techno-logy, Nanjing 210044, China;
    4CMA-CAU Jointly Laboratory of Agriculture Addressing Climate Change, Beijing 100081, China
  • Received:2023-09-18 Revised:2024-01-19 Online:2024-03-18 Published:2024-06-18

Abstract: To accurately monitor the phenology of net ecosystem carbon exchange (NEE) in grasslands with remote sensing, we analyzed the variations in NEE and its phenology in the Stipa krylovii steppe and discussed the remote sensing vegetation index thresholds for NEE phenology, with the observational data from the Inner Mongolia Xilinhot National Climate Observatory’s eddy covariance system and meteorological gradient observation system during 2018-2021, as well as Sentinel-2 satellite data from January 1, 2018 to December 31, 2021. Results showed that, from 2018 to 2021, NEE exhibited seasonal variations, with carbon sequestration occurring from April to October and carbon emission in other months, resulting in an overall carbon sink. The average Julian days for the start date (SCUP) and the end date (ECUP) of carbon uptake period were the 95th and 259th days, respectively, with an average carbon uptake period lasting 165 days. Photosynthetically active radiation showed a negative correlation with daily NEE, contributing to carbon absorption of grasslands. The optimal threshold for capturing SCUP was a 10% threshold of the red-edge chlorophyll index, while the normalized difference vegetation index effectively reflected ECUP with a threshold of 75%. These findings would provide a basis for remote sensing monitoring of grassland carbon source-sink dynamics.

Key words: Stipa krylovii steppe, net ecosystem carbon exchange, phenology, remote sensing monitoring, Inner Mongolia