Relationships between vegetation indices, radiation absorption, and net photosynthesis evaluated by a sensitivity analysis

摘要: Abstract A two-stream approximation to the radiative transfer equation is used calculate vegetation indices (simple ratio and normalized difference), fraction of incident photosynthetically active radiation (PAR) absorbed by canopy, daily mean canopy net photosynthesis under clear sky conditions. The model calculations are tested against field observations over wheat, cotton, corn, soybean. relationships between absorption or generally found be curvilinear, changes in soil reflectance affected these relationships. curvilinearity relationship difference PAR decreases as magnitude increases. might provide fractional with some a priori knowledge about reflectance. must distinguished for C 3 4 crops. Effects spatial heterogeneity discussed.