 The study proposes an approach for estimating photosynthetic vegetation, senescent vegetation, and bare soil fraction in North America's mixed grasslands using Landsat-8 imagery and a constrained linear spectral unmixing model. The DFI index performs better than the SWIR-32 in predicting NPV from spectral unmixing, and index selection and equation setup have significant effects on estimation accuracy. This article was authored by Cialau, Qingxiaogua, Cheji Chen, and others.