Eastern Gamagrass Model Simulation Parameters for Diverse Ecotypes: Leaf Area Index, Light Extinction Coefficient, and Radiation Use Efficiency

Abstract

Eastern gamagrass (Tripsacum dactyloides) is highly palatable, ideal for grazing and hay production in the United States. It is deep rooted and resilient, tolerant of flooding and drought. Objectives of this study were to develop plant parameters for different ecotypes of this grass. Data collected in field plots of diverse ecotypes included biomass, leaf area index (LAI), light extinction coefficient (k), and radiation use efficiency (RUE). Average LAI was 1.06 and average k was −1.05. The power response of k to LAI offers a new approach to simulating light interception at very low LAI values and throughout the range of LAI values of these ecotypes and similar grass species. The RUE values, which ranged from 1.16 to 4.31 g/MJ, highlight the immense diversity of eastern gamagrass. The high RUE values for the most productive ecotypes emphasizes the importance of this grass species for hay and grazing. While not as large as switchgrass (Panicum virgatum) values, it is still a prominent forage species that even is comparable to maize (Zea mays L.) in productivity when expressed as radiation use efficiency. These results are an important step in developing relationships and parameters to simulate the different ecotypes of this grass with process-based models.