The use of remote sensing to detect the consequences of erosion in gypsiferous soils

Tillage practices on sloping ground often result in unsustainable soil losses impairing soil functions such as crop productivity, water and nutrients storage, and soil organic carbon (SOC) sequestration. A sloping olive grove (10%) was planted in shallow gypsiferous soils in 2004. It was managed by minimum tillage; the most frequent management practice in central Spain. The consequences of erosion were studied in soil samples (at 0–10, 10–20, and 20–30 cm depths) by analyzing SOC, available water and gypsum content, and by detecting spectral signatures using an ASD FieldSpecPro® VIS/NIR-spectroradiometer. The Brightness index (BI), Shape index (FI), and Normalized Difference Vegetation Index (NDVI) were derived from the ASD spectral signatures and from remote sensing (Sentinel-2 image) data. The development of these young olive trees was estimated from the measured diameter of the trunks (17 ± 18 cm diameter). In 20–30 cm of the soil, the carbon stock (38 ± 18 Mg ha^?1) as well as the available water content (12 ± 6%) was scarce, affecting the productivity of the olive grove. The above-mentioned indices obtained from the laboratory samples and the pixels of the Sentinel-2 image were significantly (p < 0.01) correlated, with a correlation coefficient of around 0.4. The BI was related to the gypsum content and the slope of the plot. The FI was related to the carbon and water contents. The NDVI derived from the satellite image identified the influence of soil degradation on the trees and the carbon content. The spatial-temporal changes of the indices might help in tracking soil changes over time.