<div>Isoprene and 2-methyl-3-buten-2-ol (232-MBO) are the dominant</div> <div>biogenic \{VOCs\} released throughout the US, thus requiring simultaneous</div> <div>measurements. Recent measurements suggest the presence of isoprene</div> <div>in 232-MBO dominated ecosystems, however analytical difficulties</div> <div>make it problematic to detect both species independently. Based on</div> <div>a new chemical ionization scheme we use eddy covariance measurements</div> <div>to selectively measure fluxes of both species without analytical</div> <div>interference at the Manitou Experimental Forest (MEF) in Colorado.</div> <div>Our measurements show a concentration ratio between isoprene and</div> <div>232 \{MBO\} of 0.24 (ppbv/ppbv), and a flux ratio of 0.10 ([ppbv m/s]/[ppbv m/s]).</div> <div>Daytime average emission factors of isoprene and 232 \{MBO\} were</div> <div>1.4 +/- 0.3 and 16.0 +/- &nbsp;3.0 mg/m^2/h respectively.</div> <div>Both compounds exhibit light and temperature dependent fluxes. These</div> <div>findings suggest that isoprene is both locally produced and transported</div> <div>to the measurement site dominated by ponderosa pine. This makes it</div> <div>difficult to use \{MVK\} and \{MAC\} as tracers for estimating the</div> <div>photochemical age of isoprene chemistry at this site. Further our</div> <div>measurements suggest that isoprene can contribute to about 15% of</div> <div>the \{OH\} reactivity relative to 232 MBO.</div>