Stomatal uptake of SO2, NOx and O3 by spruce crowns (Picea abies) and canopy damage in Central Europe

Abstract

Stomatal uptake of SO2, NOx and O3 by Norway spruce canopies was integrated at six sites in central Germany. The following specific annual doses of stomatal trace-gas net uptake in the field (μmol m-2 total needle surface d-1 annual trunk growth period/(nPa Pa-1) annual mean of trace gas concentration) are obtained; SO2: (0.157 ±0.011) μmol m-2 d-1/(nPa SO2 Pa-1), NOx: (0.477 ±0.035) μmol m-2 d-1/(nPa NO2 Pa-1), O3: (0.474 ±0.034) μmol m-2 d-1/(nPa O3 Pa-1). There is an apparent NO2 compensation point at 7 nPa Pa-1 in the field if NOx (= NO2 + NO) fluxes are integrated; the individual NO2 compensation point equals 3.2 nPa Pa-1. There was a statistically significant correlation between observed damage to spruce canopies and ambient SO2 concentrations in air. No such correlation could be observed between spruce decline and concentrations of NO2 and O3. -from Authors