Measurement and modelling ozone fluxes over a cut and fertilized grassland

Abstract

Abstract. During the GRAMINAE intensive field campaign between 20 May and 15 June 2000, ozone flux was measured and modelled above grassland in northern Germany, Braunschweig. Results of flux measurement and model calculations are presented in this study. Effects of agricultural activities (cut and fertilization) on ozone fluxes have also been analysed. A detailed deposition model for ozone is used to parameterise and to calculate the deposition velocity and flux of the ozone. Model calculations also provide an evaluation of the ratio of stomatal and non-stomatal fluxes. Measured and modelled flux and deposition velocity values have been compared for each period (before cut of grass, after cut, and after fertilization). Results show that agricultural activities hardly have any influence on total O3 fluxes, although both cutting and fertilization have complex impacts on different deposition pathways. Reduced vegetation decreased the stomatal exchange, while at the same time for this short canopy, the role of both soil emission of NO (promoting ozone loss close to the surface) and deposition of ozone to soil surface have increased. These effects demonstrate the importance of canopy structure and non-stomatal pathways on O3 fluxes.