Origin, molecular composition and fate of dissolved organic matter in intensive grazing and integrated livestock-forest systems

Abstract

Brazil plays a globally important role being the largest exporter of beef and the second largest bovine producer in the world. The biggest challenge for the country has been to increase the productive capacity of Brazilian soils based on the concept of sustainable agriculture. Within this scenario, conservation practices have shown both high productivity and sustainability in the agronomic world, highlighting both management, intensive grazing, and integrated livestock-forest systems. Dissolved organic matter (DOM) is an important reactive carbon pool in soils participating in many biogeochemical processes. Despite its importance to soil function, studies focused on its dynamics in Brazilian soils are scarce. Soil DOM contains molecular and stable isotopic signals from inputs derived from surface vegetation, as well as from the subsurface biotic and abiotic processes. Accordingly, to appreciate the role of soils inglobal productivity it is necessary to understand the connectivity between the various environmental processes that play a role in molding soil organic matter into an important global carbon reservoir. Considering the fact that studies have already commenced in Brazil, in long-term field experimental areas, the goal of this project is to investigate the origin, molecular composition and fate of soil DOM.These studies will take place in intensive grazing and livestock-forest systems, from the surface through the subsurface, using traditional Stable Isotope Analysis (´ 13C and ´ 15N), along with advanced molecular-level characterizations using Tetramethylammonium Hydroxide Thermochemolysis - Gas Chromatography/Mass Spectrometry (TMAH-GC x GC/MS) and Electrospray Ionization coupled withFourier Transform Ion Cyclotron Resonance Mass Spectrometry (ESI-FT-ICR-MS). The research group of Professor Patrick Hatcher has significant internationally recognized experience in the area of environmental chemistry and geochemistry. The achievement of these experiments under supervision of Dr. Hatcher, specialist in the techniques proposed, will facilitate the understanding and interpretation of results, allowing a better understanding of how pastures under different managements, including integrated systems, affect soil biogeochemistry.