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Acta Prataculturae Sinica ›› 2022, Vol. 31 ›› Issue (3): 1-15.DOI: 10.11686/cyxb2020573


Canopy scale characteristics of grassland under different grazing intensities based on UAV lidar and multispectral data

Jie SHEN1(), Lei DING1, Xiao-ping XIN1(), Xiang ZHANG1,2, Da-wei XU1, Lu-lu HOU1, Rui-rui YAN1   

  1. 1.Institute of Agricultural Resources and Regional Planning,Chinese Academy of Agricultural Sciences,Beijing 100081,China
    2.College of Geographical Science,Inner Mongolia Normal University,Hohhot 010028,China
  • Received:2020-12-23 Revised:2021-03-01 Online:2022-03-20 Published:2022-01-15
  • Contact: Xiao-ping XIN


Grazing activities not only affect ecological processes of grasslands, but also change the spatial pattern of grassland communities. This research utilized airborne lidar carried by an HS-600 unmanned aerial vehicle (UAV) with a RIEGL laser system and flying at a height of 119 m, and multi-spectral remote sensing to obtain grassland canopy data with sub-meter resolution. The grassland canopy spatial pattern and its scale characteristics under different grazing intensities were studied using wavelet analysis (i.e. the deconvolution of observed lidar waveforms to extract wavelet data), to quantify the spatial characteristics and scales of three canopy parameters: canopy height (CH), fractional vegetation cover (FVC) and normalized difference vegetation index (NDVI), in terms of their response to grazing intensity. It was found that the wavelet variances of grassland CH, FVC, and NDVI show a downward trend with increase in grazing intensity, indicating that the periodic fluctuation energy of its spatial pattern decreases, and the overall grassland canopy spatial structure tends to be more uniform at higher grazing intensity. The analysis of wavelet variance and the real part of coefficients showed that the spatial pattern of FVC and NDVI has two main characteristic scales of 116-140 m and 170-180 m, and a spatial variation period of about 110 m, and the spatial pattern scale characteristics were comparatively stable with change in grazing intensity. The spatial pattern of CH was more complicated. The larger-scale pattern described above was evident, but moderate and heavy grazing resulted in many smaller patches forming with comparatively larger variation in CH and vegetation cover on a smaller spatial scale.

Key words: spatial heterogeneity, spatial pattern, wavelet analysis, characteristic scale, grazing intensity, vegetation coverage