Stable isotopes and soil water use efficiency as ecohydrological indicators of plant biomass productivity in Cerrado and Caatinga ecosystems, at different scale

Abstract

The project entitled "Transition to sustainability and the agriculture-energy-water nexus: exploring an integrative approach with case studies in the Cerrado and Caatinga Brazilian biomes" aims to build strategies that allow the transition to a sustainable future in these biomes through a participatory approach that integrates qualitative and quantitative methods of the natural and social sciences at multiple scales. In the context of the water - food - energy nexus, water scarcity is a crucial issue. Among many other impacts, it compromises the provision of one of the critical environmental services of forests, which is the cycling and maintenance of water quantity and quality. The research to be developed in the current project intends to characterize the water status and the mechanisms of water use by plants vegetation with a view to their impact on health, growth, and maintenance of natural ecosystems of the Caatinga and Savanna Brazilian biomes, and their respective environmental benefits. This project will be based on the combination of different methodologies - isotopic landscapes (isoscapes), Ecohydrology, Soil Physics and remote sensing - to answer the following scientific questions: I) where come from the water transpired by plants (surface or deep soil or water table?); II) which are the strategies of plants to deal with water stress?; III) what is the impact of land use on aquifer recharge (croplands/fallows/forests)? Soil Water Use Efficiency (SWUE) will be used as an integrative indicator. The WUE index has traditionally been derived from agricultural sciences and indicates the amount of water required by a given plant or ecosystem to produce a unit of carbon. In the present work, this index will be derived in multiple scales - varying from local to regional. The regional scale includes the Caatinga and Savanna biomes and the hydrographic regions of the Parnaíba and São Francisco Rivers. The local scale comprises the selection of the study sites under the aforementioned thematic project. Remote sensing of the landscape will be used as a tool for spatializing the data obtained at the various scales. We expect that the results obtained here can provide indications of the vulnerability/resilience of the principal vegetation remnants of the Brazilian Cerrado and Caatinga biomes, against the prospects of a drier and hotter climate, as well as indications of water demand of common local plant species for land degradation recovery purposes. (AU)