Hyperspectral Characteristics and Scale Effects of Leaf and Canopy of Summer Maize under Continuous Water Stresses

Meng Li, Ronghao Chu, Xiuzhu Sha, Feng Ni, Pengfei Xie, Shuanghe Shen and Abu Reza Md. Towfiqul Islam
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Meng Li: College of Resources and Environment, Anhui Agricultural University, Hefei 230036, China
Ronghao Chu: Anhui Public Meteorological Service Center, Anhui Meteorological Bureau, Hefei 230031, China
Xiuzhu Sha: The Weather Modification Center of Henan Province, Zhengzhou 450003, China
Feng Ni: College of Resources and Environment, Anhui Agricultural University, Hefei 230036, China
Pengfei Xie: College of Resources and Environment, Anhui Agricultural University, Hefei 230036, China
Shuanghe Shen: College of Applied Meteorology, Nanjing University of Information Science & Technology, Nanjing 210044, China
Abu Reza Md. Towfiqul Islam: Department of Disaster Management, Begum Rokeya University, Rangpur 5400, Bangladesh

Agriculture, 2021, vol. 11, issue 12, 1-21

Abstract: The scale effect problem is one of the most challenging issues in remote sensing studies. However, the research on the methodology and theory of the scale effect is scarcely applied in practice. To this end, in this study, 3 years of field experimental data of continuous water stresses on summer maize were used for this purpose. Furthermore, the Prospect and Sail models were employed to investigate the scale effects of reflectance characteristics and vegetation indexes. The results indicated that the spectral characteristics of canopy and leaf of summer maize were similar under continuous water stresses at various stages. The reflectance at the canopy level was distinct from that at the leaf level, considering the soil background differences. From leaf to canopy scales, with the increase in the leaf area index (LAI), the spectral reflectance of all treatments in the visible band decreased, but increased in the near-infrared band, and the reflectance was saturated when LAI increased to 5. The reflectance difference caused by LAI variation was enlarged as the drought stress intensified in the short-wave infrared band. The spectral reflectance in the near-infrared band was susceptible to leaf inclination angle (LIA) variation and changed significantly, especially in the closed canopy. With the increase in LAI, the difference vegetation index (DVI) and normalized difference vegetation index (NDVI) values under each treatment showed a gradually increasing trend. With the increase in LIA, the DVI value decreased gradually, and the DVI value under the saturated canopy was significantly higher than that under the unclosed canopy. However, the NDVI values of all treatments did not change with LIA, mostly under the closed canopy. Overall, the results demonstrated that LAI had a more significant influence on canopy reflectance than LIA. In addition, NDVI was not able to capture the LAI and LIA information when the canopy was closed, but DVI performed better.

Keywords: summer maize; continuous water stresses; spectral reflectance; scale effect; Prospect and Sail models (search for similar items in EconPapers)
JEL-codes: Q1 Q10 Q11 Q12 Q13 Q14 Q15 Q16 Q17 Q18 (search for similar items in EconPapers)
Date: 2021
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