On the importance of digital soil mapping scale for ecosystem service assessment and policy - A study involving soil sediments dynamic and direct aquifer recharge

Abstract

Soil is crucial for many ecosystem services. Among them, direct aquifer recharge and sediment dynamic have the soil as a fundamental basis for interpretations to improve territorial and environmental planning. This study assessed the importance of improving the scale (details) of soil maps and the impact it has on the correct interpretation and quantification of ecosystem services related to aquifer recharge and sediment dynamics. Fuzzy logic was applied to four watersheds from the Pontal do Paranapanema region, Brazil. Knowledge-based models were used to upscale soil maps, later validated and then adopted to derive information on direct water recharge and sediment dynamics. Effects of upscaling were evident when comparing the soil maps produced by fuzzy logic at low cost with the existing maps. Incorporating terrain attributes and legacy data effectively predicted soil spatial distribution in the studied watersheds, delivering overall accuracy and Kappa index values of 69–74 % and 0.51–0.63, respectively. Latossolos and Argissolos persist as the main soils in the watersheds, but their spatial distribution drastically changed. Another remarkable improvement on the soil maps by fuzzy logic was the detailed distinction of floodplain soils, which were not reported in previous maps. Aquifer discharge interpretations was severely affected by the soil maps scale. Trade-offs or synergies among ecosystem services were spatially detected since soil-landscape relations that foster water infiltration, storage, and direct aquifer recharge are those that also prevent soil loss (sediment retention). More detailed soil maps identified places where ecosystem services were more prominent in each watershed, showing the impact of using more detailed soil maps in this process. Knowledge-based process under the fuzzy logic approach allowed such maps upscaling at relatively low cost. Future studies should incorporate other environmental data (e.g., land use/land cover, relief variation, lithology, etc.) to further improve soil maps and, hence, the assessment of ecosystem services, supporting detailed interpretations and decision-making towards environmental sustainability.