Estimation of leaf area index, light interception and biomass accumulation of Miscanthus sinensis ‘Goliath’ from radiation measurements

A field study of Miscanthus sinensis ‘Goliath’ was conducted in 1996 in a four year old crop. The objectives of the study were to derive the parameters of mathematical relations between spectral vegetation indices (VI) and the fraction of intercepted photosynthetically active radiation (fipar) and between VI and the green leaf area index (GLAI). Also the purpose was to estimate the dry-matter:radiation quotient ( ) and to discuss the use of VI for energy crop development. Good estimates of fipar were obtained from spectral reflectance measurements over crop and bare soil, when used as the only input to a theoretical model. GLAI was better related with normalised difference vegetation index than ratio vegetation index during the same period. Leaf area index determined by the plant canopy analyzer was highly correlated (R2=0.91) with destructive measurements of GLAI, during periods when growth was not affected by soil water deficit. A robust estimate of of 1.90±0.01 gDMMJ−1 PAR was obtained for the period of dry-matter accumulation, based on the relationship between VI and fipar, which excluded PAR-interception by senesced leaves. This low value was a result of drought stress, low temperatures and low plant density which together with a low fipar during parts of the season resulted in a low yield when compared to yield in 1997. Light interception and energy conversion efficiency are key selection parameters for energy crop genotype screening, and we propose to utilise the fast and reliable method of spectral reflectance measurement for their determination.