Estimating fractional cover of non-photosynthetic vegetation for various grasslands based on CAI and DFI

Abstract

Non-photosynthetic vegetation (NPV) is a vital component of terrestrial ecosystems and an important indicator of grassland degradation, therefore, it is of great significance to realize its accurate evaluation. Here, we analyzed spectral characteristics of NPV of different biomass types in undisturbed vegetation (herb, subshrub and shrub), and established relationship models among dead fuel index (DFI), cellulose absorption index (CAI) and fractional cover of NPV (fNPV) based on ground hyperspectral data; then, fNPV of four grassland types were evaluated based on the models. Our results showed that: (1) NPV reflectance exhibited similar change trends for herb, subshrub, shrub, and a mixed type, although there were significant differences among values, (2) DFI and CAI, CAI and fNPV, DFI and fNPV were significantly positively correlated (p < 0.001), (3) the maximum fNPV estimation accuracy of CAI was higher than that of DFI, and the values were 85 and 75%, respectively, (4) fNPV differed significantly among the four grasslands, with highest in meadow grassland (77%) and lowest in desert grassland (43%). We conclude that fNPV has obvious heterogeneity among different vegetation types, and both CAI and DFI can be used to reflect fNPV although there is difference in evaluation performance.