Vegetation Type Does not Affect Nitrous Oxide Emissions from Riparian Zones in Agricultural Landscapes.

Abstract

Riparian zones provide multiple benefits in agricultural landscapes, but nitrogen (N) loading can cause N2O emissions. There is a knowledge gap on how different types of riparian vegetation influence N2O emissions. This study quantified N2O emissions from a rehabilitated riparian zone with deciduous trees (RH), a herbaceous (grassed) riparian zone (GRS), a natural forested riparian zone with deciduous trees (UNF-D), a natural forested riparian zone with coniferous trees (UNF-C), and an agricultural field (AGR). N2O fluxes were not significantly different (p > 0.05) among riparian zones (11-17 µg N2O-N m-2 h-1) and were not significantly different (p > 0.05) when comparing riparian zones to the AGR field (34 µg N2O-N m-2 h-1). Despite high N-loading, cumulative N2O emissions (1989 µg N2O-N m-2) in the riparian zones was significantly lower (p > 0.05) than AGR (13,278 µg N2O-N m-2). The main predictors of N2O fluxes were soil temperature and soil NO3--N for the riparian zones and the AGR field. We found that environmental conditions played a greater role than the type of riparian vegetation or age in predicting N2O emissions. We suggest that soil environmental factors created an anaerobic environment that favored N2O consumption via complete denitrification.