Strong isoprene emission response to temperature in tundra vegetation

Abstract

<p>Biogenic emissions of volatile organic compounds (BVOCs) are a crucial component of biosphere-atmosphere interactions. In northern latitudes, climate change is amplified by feedback processes in which BVOCs have a recognized, yet poorly quantified role, mainly due to a lack of measurements and concomitant modelling gaps. Hence, current Earth system models mostly rely on temperature responses measured on vegetation from lower latitudes, rendering their predictions highly uncertain.</p><p>We used Proton Transfer Reaction -Time of Flight- Mass Spectrometry (PTR-TOF-MS) and eddy covariance to measure ecosystem-level isoprene fluxes at two contrasting ecosystems in Sweden and Norway during an entire growing season. Measured fluxes showed that tundra isoprene emissions responded vigorously to temperature increases, with Q<sub>10</sub> temperature coefficients of up to 20.8; that is 3.5 times the Q<sub>10</sub> derived from the equivalent model results. Our results demonstrate that tundra vegetation possesses the potential to substantially boost its isoprene emissions in response to future rising temperatures, at rates that exceed the current Earth system model predictions.</p>

Optimizing the Isoprene Emission Model MEGAN With Satellite and Ground‐Based Observational Constraints

“…The posterior 𝜸 T is more than 5 times more sensitive to temperature ( Q 10 = 9.29) than the a priori ( Q 10 = 1.74). This heightened temperature sensitivity is consistent with previous studies, which have found that the a priori MEGAN 𝜸 T parameterization underestimates emissions at high temperatures for Australian eucalypt species (Emmerson et al., 2020) and Arctic vegetation (Angot et al., 2020; Kramshøj et al., 2016; Seco et al., 2020, 2022). Figure 7b shows that the median posterior 𝜸 T is also consistent with the observed $${\boldsymbol{\gamma }}_{\boldsymbol{T}}^{\prime }$$ as calculated with daily top‐down GlobEmission fluxes, indicating that the top‐down and eddy covariance constraints are consistent with respect to the temperature dependence of emissions.…”

“…Isoprene emissions can be estimated from tower‐ or aircraft‐based eddy covariance measurements (Guenther & Hills., 1998; Karl et al., 2009). This approach is useful for constraining the diurnal variability of isoprene emissions, making it well‐suited for characterizing the temperature response (Misztal et al., 2014; Seco et al., 2015, 2022; Yu et al., 2017). In this study, we use tower‐based eddy covariance isoprene flux measurements from the AmeriFlux site BR‐Sa1 in Brazil's Tapajós National Forest (2.86°S, 54.96°W) (Sarkar et al., 2020, 2022), as well as isoprene mixing ratio measurements from the 2018 Wytham Isoprene iDirac Oak Tree Measurements (WIsDOM) campaign in Wytham Woods near Oxford, UK (51.46°N, 1.20°W) (Ferracci, Bolas, et al., 2020, Ferracci, Harris, et al., 2020).…”

“…MEGAN's temperature response algorithm, which simulates the exponential increase in emissions with temperature up to an optimum value (Guenther et al., 1993, 1995), is another source of uncertainty. Recent experiments with Arctic vegetation (Angot et al., 2020; Kramshøj et al., 2016; Seco et al., 2020, 2022) and Australian eucalypt trees (Emmerson et al., 2020) have found that MEGAN significantly underestimates isoprene emissions from these species at high temperatures. Updating the parameterization of the temperature response with species‐specific measurements in Australia has been shown to improve MEGAN isoprene emissions estimates, with significant consequences for predictions of future ozone pollution in a warming climate (Emmerson et al., 2020).…”

“…Model performance is generally good when accurate driving variables are used (Situ et al., 2014; see also Filella et al., 2018; Sarkar et al., 2020), but significant sources of uncertainty remain. These include the empirical parameterization of the standard emission rates and the dimensionless scaling functions, particularly the temperature and drought stress responses (Angot et al., 2020; Guenther et al., 2006; X. Jiang et al., 2018; Kramshøj et al., 2016; Potosnak et al., 2014; Seco et al., 2015, 2020, 2022).…”

Satellite-derived constraints on the effect of drought stress on biogenic isoprene emissions in the southeastern US

“…These relationships provide the basic framework of isoprene emission models that are capable of coupling with meteorology and the land biosphere, with the most widely used being the Model of Emissions of Gases and Aerosols from Nature (MEGAN) (Guenther et al, 1993(Guenther et al, , 2006(Guenther et al, , 2012(Guenther et al, , 2017. Recent work has shown stressed conditions -such as drought, heat waves, and high winds -can induce large changes in isoprene emissions, in contrast with model predictions in the absence of those stress factors (Potosnak et al, 2014;Huang et al, 2015;Kravitz et al, 2016;Seco et al, 2015;Otu-Larbi et al, 2020;Seco et al, 2022). As stressed conditions are rarely sampled by field campaigns due to their infrequent and irregular nature, they are poorly constrained; hence, stress impacts on isoprene emissions are among the least understood aspects in our predictive ability with respect to BVOC-chemistry-climate interactions.…”