Isoprene measurements in an oak-dominated forest during the recent summer heatwave in the UK

Valerio Ferracciaa, Conor G. Bolasbb, and Neil. R.P. Harrisaa

a)Centre for Environmental and Agricultural Informatics,Cranfield University, College Road, MK43 0AL, UK

b)Centre for Atmospheric Science, Department of Chemistry, University of Cambridge, Lensfield Road, CB2 1EW, UK

Isoprene represents one of the largest biogenic emissions on the planet (estimated 300-700 TgC year-1, cf.~500 TgC year-1 from CH4) and it is expected to be profoundly influenced by global change (increasing temperatures, enhanced CO2 and land use change) over the next decade. A better understanding of its emissions and global distribution is therefore crucial for an accurate characterisation of the composition and oxidising capacity of the atmosphere. In particular, an improved description of the canopy-to-atmosphere exchange is highly desirable to establish a link between single-leaf emission measurements (a well-established practice in plant science) and isoprene flux into the boundary layer.

In this work an autonomous, portable gas chromatograph with photo-ionisation detection (GC-PID) was deployed to measure isoprene in Wytham Woods (UK), a research forest facility dominated by oak trees (quercus robur), one of the strongest isoprene emitters in mid-latitude/temperate regions. Isoprene abundances were measured at four heights within and above the canopy for the whole summer, encompassing periods of severe weather (unusually high temperatures and long dry spells).

The preliminary results from this deployment are presented and their implications for the transport of isoprene from the canopy into the atmosphere, as well as for the impact of more frequent heat waves in the future are discussed.