title: Monoterpene 'thermometer' of tropical forest-atmosphere response to climate warming.
abstract: Tropical forests absorb large amounts of atmospheric CO2through photosynthesis but elevated temperatures suppress this absorption and promote monoterpene emissions. Using13CO2labeling, here we show that monoterpene emissions from tropical leaves derive from recent photosynthesis and demonstrate distinct temperature optima for five groups (Groups 1-5), potentially corresponding to different enzymatic temperature-dependent reaction mechanisms within β-ocimene synthases. As diurnal and seasonal leaf temperatures increased during the Amazonian 2015 El Niño event, leaf and landscape monoterpene emissions showed strong linear enrichments of β-ocimenes (+4.4% °C-1) at the expense of other monoterpene isomers. The observed inverse temperature response of α-pinene (-0.8% °C-1), typically assumed to be the dominant monoterpene with moderate reactivity, was not accurately simulated by current global emission models. Given that β-ocimenes are highly reactive with respect to both atmospheric and biological oxidants, the results suggest that highly reactive β-ocimenes may play important roles in the thermotolerance of photosynthesis by functioning as effective antioxidants within plants and as efficient atmospheric precursors of secondary organic aerosols. Thus, monoterpene composition may represent a new sensitive 'thermometer' of leaf oxidative stress and atmospheric reactivity, and therefore a new tool in future studies of warming impacts on tropical biosphere-atmosphere carbon-cycle feedbacks.
authors.affiliation: Climate and Ecosystem Sciences Division, Lawrence Berkeley National Laboratory, 94720, Berkeley, CA, USA.
authors.forename: Kolby J
authors.initials: KJ
authors.lastname: Jardine
authors.affiliation: National Institute for Amazon Research (INPA), 69060-001, Manaus, Amazonas, Brazil.
authors.forename: Angela B
authors.initials: AB
authors.lastname: Jardine
authors.affiliation: Climate and Ecosystem Sciences Division, Lawrence Berkeley National Laboratory, 94720, Berkeley, CA, USA.
authors.forename: Jennifer A
authors.initials: JA
authors.lastname: Holm
authors.affiliation: Climate and Global Dynamics Laboratory, National Center for Atmospheric Research, 80307, Boulder, CO, USA.
authors.forename: Danica L
authors.initials: DL
authors.lastname: Lombardozzi
authors.affiliation: Climate and Ecosystem Sciences Division, Lawrence Berkeley National Laboratory, 94720, Berkeley, CA, USA.
authors.forename: Robinson I
authors.initials: RI
authors.lastname: Negron-Juarez
authors.affiliation: Harvard University, School of Engineering and Applied Sciences, 02138, Cambridge, MA, USA.
authors.forename: Scot T
authors.initials: ST
authors.lastname: Martin
authors.affiliation: Climate and Ecosystem Sciences Division, Lawrence Berkeley National Laboratory, 94720, Berkeley, CA, USA.|Joint BioEnergy Institute, Lawrence Berkeley National Laboratory, 94068, Emeryville, CA, USA.
authors.forename: Harry R
authors.initials: HR
authors.lastname: Beller
authors.affiliation: National Institute for Amazon Research (INPA), 69060-001, Manaus, Amazonas, Brazil.
authors.forename: Bruno O
authors.initials: BO
authors.lastname: Gimenez
authors.affiliation: National Institute for Amazon Research (INPA), 69060-001, Manaus, Amazonas, Brazil.
authors.forename: Niro
authors.initials: N
authors.lastname: Higuchi
authors.affiliation: Climate and Ecosystem Sciences Division, Lawrence Berkeley National Laboratory, 94720, Berkeley, CA, USA.|Department of Geography, University of California, 94720, Berkeley, CA, USA.
authors.forename: Jeffrey Q
authors.initials: JQ
authors.lastname: Chambers
mesh_terms: D001272:Atmosphere; D002244:Carbon / Q000378:metabolism; D002245:Carbon Dioxide / Q000378:metabolism; D002247:Carbon Isotopes; D002940:Circadian Rhythm / Q000502:physiology; D057231:Climate Change; D059000:El Nino-Southern Oscillation; D065928:Forests; D039821:Monoterpenes / Q000032:analysis*; D018515:Plant Leaves / Q000502:physiology; D012621:Seasons; D013696:Temperature; D014329:Tropical Climate; D055549:Volatile Organic Compounds / Q000378:metabolism
chemical_list: D002247:Carbon Isotopes; D039821:Monoterpenes; D055549:Volatile Organic Compounds; D002245:Carbon Dioxide; D002244:Carbon
keywords: 13CO2 labeling; El Niño; TPS synthase; drought; heat; photosynthesis: carbon reactions; secondary organic aerosols; volatile emissions