Higher temperatures cause tundra vegetation to emit much more climate-relevant gas

27 September 2022

The sun sets over the Norwegian alpine tundra of Finse (1,222 m asl) at the end of May. The melting snow reveals the underlying vegetation and the growing season will start soon. This hut houses the instruments used for measuring biogenic volatile isoprene emissions from the nearby Eddy Covariance tower. Image credit: Roger Seco (IDAEA-CSIC)

A study led by the IDAEA-CSIC researcher Roger Seco together with scientists from the University of Copenhagen and published in the Proceedings of the National Academy of Science (PNAS) journal, has found that climate warming can strongly push tundra plants’ production of a lesser-known gas, isoprene. Isoprene is the volatile organic compound most emitted by vegetation worldwide. It is a key compound for climate monitoring, given the fact that it readily reacts with many other substances in the atmosphere and can, among other things, produce ozone or extend the life of methane in the air.

Up until now, scientists know that the emission of volatile organic compounds from plants is an important component of the interaction between the atmosphere and the biosphere with climate impacts. However, the response of isoprene emission to changes in temperature is not well understood in northern ecosystems.

Alpine tundra at the Finse flux tower during summer 2019. Image credit: Cleo L. Davie-Martin (University of Copenhagen).

On the other hand, current Earth system models mostly rely on temperature responses measured on vegetation from lower latitudes, which leaves the predictions in the Arctic regions highly uncertain.

In this study, the authors used a technique called “eddy covariance” to describe how isoprene emissions from the tundra vegetation respond to temperature.

“Eddy covariance allowed us to measure turbulent fluctuations of the air, coupling them with rapid measurements of isoprene concentration to calculate the exchange flux between the ecosystem and the atmosphere”, indicates Roger Seco, first author of the study and researcher at IDAEA.”This methodology requires quick-response scientific instruments that measure 10 times per second both the gas concentrations and the vertical wind speed”.

A subarctic peatland in Northern Sweden at the end of the growing season, during which the instrumented Eddy Covariance tower of the ICOS Abisko-Stodalen station has continuously measured the biogenic emissions of isoprene and their dependence on temperature. Image credit: Roger Seco (IDAEA-CSIC)

The scientific team measured the emissions of isoprene from two different tundra sites: one an alpine tundra site in south-central Norway and the other a subarctic peatland in Swedish Lapland. With four months of ecosystem isoprene emission data at each location, it is the longest dataset of isoprene emissions ever presented for tundra ecosystems.

The authors calculated the temperature response of isoprene emission, finding that the temperature dependence is 3.5 times higher than derived from model calculations and vegetation data from low latitudes. The revised temperature dependence, the authors indicate, suggests that an additional 2 °C of warming would enhance tundra isoprene emission by up to 41%, which is 46% more enhancement than predicted by previous models.

Our results show that tundra ecosystems may increase the emission of volatile organic compounds in response to climate warming at rates significantly higher than previously thought, and allow for improvement of models that currently underestimate this temperature dependence”, declares Seco.

These insights have implications for the atmosphere and climate in high-latitude regions where the climate is changing more than anywhere else on the planet.

Seco, R., Holst, T., Davie-Martin, C. L., and Rinnan R. 2022. Strong isoprene emission response to temperature in tundra vegetation. PNAS, 119 (38) e2118014119. DOI: 10.1073/pnas.2118014119

 

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