Sara Lopez

Isolating Bacterial and Fungal Contributions to Nitrous Oxide (N2O) Emissions from Nitrogen Fertilized Grasslands 

Although effects of nitrogen fertilizer additions to soils has been recognized since the 1970’s, a high uncertainty still remains mostly due to the difficulty of integrating all possible interactions among soil biota, land use and cover, soil characteristics and climatic conditions in a single study. Despite the fact that both fungi and bacteria transform nitrate through a similar pathway under hypoxic conditions [i.e. oxygen is replaced by nitrate as electron acceptor at the end of the electron transport chain and reduced products are excreted rather than being incorporated into cell material], evidence suggests that their relative abundance and therefore the origin and amount of N2O produced is strongly limited by soil condition and climatic regime. Hence, the main objectives of this project are to determine the relative contributions of bacteria and fungi to denitrification in a semi-arid fertilized grassland in relation to soil depth and water content, and to develop a standardized protocol for simultaneous measuring of N2O and CO2 using Tunable Diode Laser Spectroscopy.