Methodology Comparison for Effective LAI Retrieving Based on Digital Hemispherical Photograph in Rice Canopy

The paper investigates methodology comparisons for retrieving effective leaf area index (LAI) using digital hemispherical photograph(DHP) in rice canopy. A set of self-making DHP instrument equipped with a fish-eye Len is utilized to acquire DHP in rice canopy, and some self-developing DHP processing procedures are utilized to pre-process DHP and extract effective LAI from DHP (LAIDHP) rapidly. Based on Beer-Lambert’s law and gap fraction that computed from DHP, four methods of single zenith angle (SZA), Lang, Mill formula(Mf) and iterative formula(IF) are used to derive LAIDHP(effective LAI from them are called LAISZA, LAILang LAIMf and LAIIF ,respectively). LAISZA, LAILang, LAIMf and LAIIF are inter-compared and are also compared with from AccuPAR LP-80(LAIAPAR) and direct manual method (LAIdirect). It is found that, in general, LAISZA, LAILang LAIMf and LAIIF are similar to LAIAPAR, but slightly lower than LAIdirect. During their intercomparsion, LAILang is more similar to LAIAPAR than other three and LAIMf is more similar to LAIdirect, while LAISZA and LAILang are almost the same. It is implied that Lang method outperformed the other three when compared with AccuPAR LP-80 and Mill formula method outperformed the other three when compared with direct manual measure.