Electromagnetic-induction and spatial analysis for assessing variability in soil properties as a function of land use in tropical savanna ecosystems

Identifying spatial patterns in the variability of key soil properties to delineate the extent of land degradation could ensure efficient management of natural resources in terrestrial ecosystems. However, little is still known in tropical savannas that are subjected to indiscriminate land use. We evaluated the soil variability at the plot-scale in a terrestrial tropical ecosystem subjected to varying land use/land cover management to assess the impact of uncontrolled land uses on the soil natural capital. The non-invasive, time/cost efficient electromagnetic induction (EMI) technique was assessed for its potential, to determine the effect of land uses on soil spatial variability in a changing land use gradient from pristine land use/land cover conditions. The investigation was carried out in a natural tropical ecosystem in Aripo, Trinidad with soils of predominantly ultisols order and influenced by anthropogenic disturbances. EMI-based apparent electrical conductivity (ECa) measurements were obtained at two depth ranges (shallow = 0–0.5 m and deep = 0–1.5 m). Soil properties showed that the residential anthropogenic land use had a higher mean apparent electrical conductivity shallow (ECas) value (ECas = 305.9 mS/m) than all other land uses. Higher ECas values in the residential site suggest that human influences can increase the magnitude of electrical conductivity, which can alter the biogeochemical cycles of the soil affecting services provided by the ecosystem. Also anthropogenic land use/land covers exhibited lower coefficient of variation for soil texture (silt and clay) than natural land uses, indicating lower sensitivity of soil texture to land use due to the mixing of soils, which encourages uniformity in anthropogenic sites. Soil texture dominated the ECas signal in the natural land use/land covers with the relationship between ECas and silt in the Forest (r = 0.486) and Grass (r = − 0.495) significant at P < 0.05. Soil texture showed greater sensitivity to land use in natural sites than in anthropogenic sites. The dominance of soil texture in the natural sites indicates that in tropical soils that are predominantly light textured (clay content < 21%), silt content controls the EMI signal, which can become of low influence following disturbance. The magnitude of electrical conductivity can increase due to human influences. This can alter the biogeochemical cycles of the soil, affecting services provided by the ecosystem.