Canopy fluxes of 2-methyl-3-buten-2-ol over a ponderosa pine forest by relaxed eddy accumulation: Field data and model comparison

Canopy level flux measurements of 2-methyl-3-buten-2-ol (MBO) were made ove r a 7 year old ponderosa pine plantation in the Sierra Nevada range of Cali fornia using the relaxed eddy accumulation method. Fluxes peaked in late af ternoon (1600 LT), at an average rate of 1.11 mg C m(-2) h(-1). This corres ponds to the time of peak temperatures. MBO fluxes were strongly correlated with both temperature and photosynthetically active radiation (PAR). Model calculations of MBO flux from this site using a model developed for isopre ne provide an accurate simulation of the diurnal emissions pattern but over estimate the measured flux by a factor of 2. Discrepancies between the meas urements and the model predictions are likely due to the uncertainties in c hoosing model inputs. These results indicate a significant flux of reactive carbon in the western United States where MBO-emitting pines are the domin ant forest vegetation.