Soil moisture estimation in the transition zone from the Chengdu Plain region to the Longmen Mountains by field measurements and LANDSAT 8 OLI/TIRS-derived indices

Abstract

Soil moisture is a key element in hydrological processes, and the accessibility of the moisture in the soil controls the mechanisms thereof amid land surface and atmospheric progressions. Many studies have examined the role of the land surface temperature (LST) and normalised difference vegetation index (NDVI) in changes in soil moisture. Nevertheless, an understanding of the influence of the temperature vegetation dryness index (TVDI), which combines the LST and the NDVI, on soil moisture remains elusive, including in the transition zone area from the Chengdu Plain region to the Longmen Mountains (TZ). In this study, the TVDI was calculated based on the NDVI and LST, using LANDSAT 8 operational land imager/thermal infrared sensor (OLI/TIRS) images. From the TVDI, regression models were trained by using 96 observation points of in situ soil moisture measurements to calculate the soil moisture in the transition zone. The results revealed that there is a strong and significant negative correlation between the TVDI and the in situ measured soil moisture (P < 0.05, r = 0.710, R2 = 0.504). This indicates that the TVDI can reflect the soil moisture status in the TZ. The overall spatial patterns of soil moisture content were relatively high in the northwestern and central mountainous areas but were relatively low in the southeastern plains. Our study uniquely illustrates the spatial patterns of the relationship between TVDI variability and soil moisture variability in the TZ, western China and provides an approach for using remotely sensed soil moisture to optimise the parameterisation of soils in agricultural water management.