Hydropedology as support for water resources management in an experimental watershed at mantiqueira mountain range

Abstract

Hydropedology emerges with the aim of improving the studies of soil-water relations at spatial and temporal scales, from the interaction among pedology, soil physics, and hydrology. A key factor in the planning and management of water resources consists of knowledge of the properties and distribution of soils in the landscape, both to perform efficient experimental measures and to interpret the dynamics of water in the landscape. The present work was developed in the Posses subbasins, a pioneer sub-basin in the payment for ecosystem services in Brazil. The objectives of this work include: 1) to carry out the survey, classification and digital mapping of soil in the sub-basin and compare different algorithms; 2) to develop specific calibration equations of capacitance sensors for the soil classes and horizons monitored in the sub-basin and; 3) to obtain information about the temporal pattern of soil moisture in six depths of Argisols, according to the physic-hydric attributes of the soil, in pasture and reforestation areas. A soil survey was carried out and 74 soil profiles were described, sampled and classified for the production of the digital soil map. Three different algorithms were evaluated based on aggregated data from a proportional 5-fold crossvalidation procedure. Undisturbed soil samples were collected from the A and B horizons of the predominant soil classes in the sub-basin for the calibration of capacitance sensors in the laboratory and different regression models were investigated. Soil moisture temporal behavior was monitored in four Argisol profiles, under pasture and reforestation, with PR2 / profile probe sensors, from 08/2014 to 03/2018. Disturbed and undisturbed samples were collected from the A and B horizons of the four sites monitored for physical-hydric characterization. The random forest model including additional sampling showed the best performance among the three tested models and was selected to produce the soil map of the Posses sub-basin, where there is a strong predominance of Argisols. The capacitance sensors were calibrated by adjusting polynomial equations with an accuracy of 0.02 m 3 m -3 . Based on the analyses of the time series of soil moisture in the Argisol profiles, it was verified that the soil moisture was higher in the 10 and 20 cm soil layers in the reforestation area, when comparing to the pastures, and also that similarities in the soil moisture pattern, among the four sites, were higher as the depth of the soil increases. The greatest differences in the pattern of soil moisture variation were observed in periods of less rainfall. In soil depths below 30 cm, the soil moisture remained high throughout all the time series, reflecting the high water retention capacity of the Argisols of the Posses sub-basin and also the high and well-distributed rainfall.