Abstract
Leaf area index (LAI) is a factor for vegetative growth parameter. It is defined as leaf area per unit of ground area and could be used as a linkage between plant biophysical, biochemical and spectroscopic parameters. In this research, direct laboratory LAI measurements were tested versus different in situ field measurements for different parameters including LAI derived from LAI-2000 canopy analyzer and six hyperspectral vegetation indices (VIs) (normalized difference vegetation index (NDVI), chlorophyll index (CHI), photochemical reflectance index (PRI), triangular vegetation index (TVI), modified triangular vegetation index (MTVI)), that were generated from ASD-4 field spectroradiometer measurements. The objective is to calibrate the accuracy of LAI-2000 measurements and to examine hyperspectral vegetation indices as estimators of LAI through regression models. A strawberry cultivated area in the Nile delta of Egypt was selected as a study site. Linear regression models were used to calculate LAI through different variables with a high correlation coefficient (0.97, 0.93, 0.90, 0.90, 0.89 and 0.85) for LA optical , PRI, TVI, NDVI, MTVI and Chl. Respectively. The correlation coefficient between actual and predicted models wasused for validation assessment, the higher accuracy for validation showed high accuracy of all generated models, however, PRI index MTVI, TVI, LA optical , NDVI and Chl. Index showed relative higher accuracy 0.941, 0.927, 0.927, 0.906, 0.902 and 0.806 respectively. High similarity was found between optical and actual LAI. Generated models are valid during the maximumphase of vegetative growth of strawberry under local conditions of Egyptian Nile delta.
Highlights
Healthy plant canopy visually appears green because of the significant high absorption of leaf pigments to red and blue spectra with a strong reflectance of green spectrum
Regression analysis between laboratory measured LADirect as the dependent variable and each field measured factor as independent variable showed that all factors were highly correlated with laboratory measured LADirect as the correlation coefficient ranged from (0.85) to (0.97).This is clear evidence that spectral vegetation variables could be considered realistic indicators for canopy phonological, physiological and production parameters
(Mussche et al, 2001) reported high similarity between LAOptical and LADirect as long as no changes in the canopy structure are made (Jonckheere et al, 2005) reported that no significant difference was found between LADirect and LAOptical, correction for blue light scattering, clumping, and the non-leafy material is necessary when measuring leaf area index (LAI) for tree cover
Summary
Healthy plant canopy visually appears green because of the significant high absorption of leaf pigments to red and blue spectra with a strong reflectance of green spectrum. Red edge district has a solid retention because of the leaf chlorophyll, nitrogen fixation, and reflection due to mesophyll cells in developing plants (Datt, 1998). First defined LAI as the total one-sided area of the canopy per unit ground surface area (Chen and Black, 1992) It is a one-sided area of leaves per unit ground area. It mirrors the biochemical and physiological processes of vegetation; it is considered a perfect indicator of crop growth and productivity.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
