The effect of fractional vegetation cover on the relationship between EVI and soil moisture in non-forest regions

Surface soil moisture (SM) is critical for terrestrial ecological and hydrological processes, particularly in non-forested arid and semi-arid regions. On the large scale, the relationship of vegetation greenness to SM is often considered to be a reflection of spatiotemporal changes in SM. In this study, we investigated the empirical relationship between the remotely sensed enhanced vegetation index (EVI) and in situ SM, using observations from 16 Ameriflux sites in non-forest regions. The linear relationship between SM and EVI could be classified by the fractional vegetation cover (FVC), and the ratio of EVI to SM became higher as the FVC increased. In addition, multiple regressions for SM using both EVI and FVC showed a higher correlation than that of the single regressions using EVI or FVC separately. We found that EVI and FVC were critical parameters in representing the SM variations related with the surface vegetation changes, but further studies are necessary before the relationship can be applied.