Switchgrass Leaf Area Index and Light Extinction Coefficients

Much of recent interest in biofuel species modeling has been for switchgrass ( Panicum virgatum L.). Such modeling requires accurate simulation of light interception. We investigated the stability of the light extinction coefficient ( k ) in Beer's Law with data from Temple, TX; Lincoln, NE; and Elsberry, MO. Variability in k values was not related to fraction of light intercepted, time of day, or incident solar radiation. Only the magnitude of leaf area index (LAI) showed a significant impact on the k value. The mean k value (−0.37) for the ‘Alamo’ switchgrass data at Temple was similar to the previously published k value (−0.33) and similar to Alamo k values in Nebraska (−0.38) and Missouri (−0.31). Compared to Alamo, other switchgrass cultivars had similar k values in Nebraska but were higher in Missouri. This study gave guidance as to which factors are important for quantifying k with Beer's Law for light interception of switchgrass.