Soil health and ecosystem services related to water recharge in the Cantareira system

Abstract

The concept of soil health/quality is directly linked to ecosystem services and has been increasingly used to incorporate environmental sustainability into the integrated governance of natural resources. The assessment of soil functions is based on soil properties and processes correlated with these functions of interest. However, most soil quality assessment protocols focus on crop production and their conservation management, and vital soil functions such as water recharge lack studies to be incorporated in the monitoring of impacts on environmental quality. Around 12 million people in the most economically developed region of Brazil depend on the water supplied by the Cantareira Water Production System. In this region, most of the agricultural activity is with pasture and eucalyptus forests for food and energy production, in addition, it is a hotspot of the Atlantic Forest preserved. Three studies were carried out to evaluate soil quality/health in the Cantareira System in three soil classes representative: Typic Hapludult, Typic Dystrudept, and Typic Usthortent. The objective of the first study was to evaluate, through the nexus approach- water, energy, and food, the soil physical properties that are directly linked to the ecosystem services: water recharge, biomass production, and erosion resistance in the predominant soil use and management. Soil samples were collected in the 0-5 cm and 30-35 cm layers and subsequently analyzed in the laboratory and then calculated additive soil functions using soil physical properties. Overall, the conversion of the native forest for anthropic use (eucalyptus and pasture) reduced the soil's physical quality and water recharge capacity. The intensification of pastures replacing continuous grazing with rotational grazing had little effect on promoting the ecosystem services of the Cantareira System. Typic Dystrudept obtained the highest value of the Soil Physical Quality Index (SPQI) for the native forests when compared to Typic Hapludult and Typic Usthortent. The second study was to monitor soil water content over three years using the soil electrical resistivity technique. The native forest in Typic Hapludult did not retain much water in the evaluated profile, suggesting that the water was absorbed by plants (evapotranspiration process) and/or replenished groundwater. For Typic Dystrudept, the study found that soils under native forests had higher hydraulic conductivity than eucalyptus and pastures. The young Typic Usthortent soil maintained higher soil water content in pastures associated with a low rate of water infiltration, resulting in stagnant water in the surface layer. Soil health was assessed in the third chapter through the Comprehensive Assessment of Soil Health (CASH) in order to compare with SPQI. CASH, which has a database mostly of American soils, was not able to accurately assess the effect of management and use for the studied soils. It is necessary importance of the database and better resolution of maps of Brazilian soils for the creation of indicators that are representative and capable of evaluating the health and soil functions of Brazilian soils.