Evaluation of isoprene light response curves for bryophyte-dominated ecosystems and implications for atmospheric composition

Langford, Ben ORCID: https://orcid.org/0000-0002-6968-5197; Cash, James M.; Vieno, Massimo ORCID: https://orcid.org/0000-0001-7741-9377; Heal, Mathew R.; Drewer, Julia ORCID: https://orcid.org/0000-0002-6263-6341; Jones, Matthew R.; Leeson, Sarah R.; Simmons, Ivan; Braban, Christine F.. ORCID: https://orcid.org/0000-0003-4275-0152; Nemitz, Eiko ORCID: https://orcid.org/0000-0002-1765-6298. 2023 Evaluation of isoprene light response curves for bryophyte-dominated ecosystems and implications for atmospheric composition. Environmental Research: Ecology, 2 (1), 011002. 15, pp. 10.1088/2752-664X/aca2ad

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Abstract/Summary

Isoprene is emitted from numerous plant species in response to light and temperature and parameterisations of these relationships, based on observations from a few vascular plant species, have been shown to be broadly applicable to many different vegetation types. Here, we investigate their performance when applied to an ecosystem dominated by bryophytes. Over a six-week period, emissions of isoprene were measured above a Scottish peat bog. The light response derived on the basis of both canopy-scale flux and whole-plant enclosure measurements, deviated from the classical response, showing no sign of saturation within the observed range. We attribute this response to the canopy architecture of moss hummocks, which may attenuate light differently compared to a grass canopy. Both existing big-leaf and canopy-level emission algorithms, developed for vascular plants but commonly used for moorland vegetation, failed to replicate the observed fluxes, overestimating at low light intensities (<1000 μmol m−2 s−1 photosynthetically active radiation) and underestimating during daytime clear sky conditions. The light response was optimised for bryophyte-dominated ecosystems using measured fluxes and incorporated into the EMEP4UK chemical transport model and applied exclusively to moorland. The revised parameterisation resulted in a small reduction in the average annual isoprene emissions in the northern latitudes (5%), but peak isoprene emissions and concentrations increased by up to a factor of two. Yet, no significant change in average or maximum surface ozone concentrations was observed, reflecting that the northern latitudes are in a chemical regime that is strongly NOx limited, in part due to the spatial segregation with the urban sources of NOx. We conclude that, the anticipated increase in isoprene emissions from the northern latitudes in response to climate change is unlikely to contribute towards ozone-related air quality issues, as long as NOx pollution does not increase. However, the non-saturating light response may be equally applicable to non-vascular plants elsewhere, including in the tropics.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	10.1088/2752-664X/aca2ad
UKCEH and CEH Sections/Science Areas:	Atmospheric Chemistry and Effects (Science Area 2017-)
ISSN:	2752-664X
Additional Information. Not used in RCUK Gateway to Research.:	Open Access paper - full text available via Official URL link.
Additional Keywords:	isoprene, ozone, bryophytes, eddy covariance
NORA Subject Terms:	Atmospheric Sciences
Date made live:	09 Jan 2023 16:40 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/533746

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