Heatwave‐Period Temperature Response Parameterizations Amplify Modeled Isoprene Emissions From Temperate Trees

Abstract

Abstract Heatwaves can alter temperature responses of biogenic volatile organic compound emissions, yet these effects remain poorly constrained for temperate trees. We measured leaf‐level isoprene temperature response curves for Platanus occidentalis and Populus deltoides in central China during a July heatwave period (daily maximum air temperature exceeding 35°C for at least three consecutive days) and a later‐season non‐heatwave comparison period, and fitted MEGAN2.1 response functions. Relative to the September reference, July heatwave‐period measurements showed higher optimum temperatures for isoprene emission ( T opt ) and maximum normalized emission capacity ( E opt ) in both species. T opt rose from 313.15 to 317.56 K in P . deltoides and from 314.80 to 316.28 K in P . occidentalis , while E opt increased from 1.81 to 3.25 and from 2.01 to 2.63, respectively. In a model sensitivity experiment using common July leaf‐temperature and PAR forcing, July heatwave‐period parameterizations produced higher simulated daytime leaf‐level isoprene fluxes, especially during afternoon heat peaks. The enhancement varied between P . deltoides and P . occidentalis and between earlier and later heatwave sampling windows. The results indicate that non‐heatwave temperature‐response parameterizations may not capture high‐temperature isoprene responses during heatwave periods, highlighting the need for broader replicated observations to constrain emission‐model parameterizations.