A New Field Instrument for Leaf Volatiles Reveals an Unexpected Vertical Profile of Isoprenoid Emission Capacities in a Tropical Forest

Journal Article · Fri Jul 09 00:00:00 UTC 2021 · Frontiers in Forests and Global Change

DOI: https://doi.org/10.3389/ffgc.2021.668228 · OSTI ID:1851074

Taylor, Tyeen C. ^[1]; Wisniewski, Wit T. ^[2]; Alves, Eliane G. ^[3]; Oliveira Junior, Raimundo C. ^[4]; Saleska, Scott R. ^[2]

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1. Univ. of Arizona, Tucson, AZ (United States); Univ. of Miami, FL (United States); Univ. of Arizona, Tucson, AZ (United States)
2. Univ. of Arizona, Tucson, AZ (United States)
3. Max Planck Institute for Biogeochemistry, Jena (Germany)
4. Embrapa Amazônia Oriental, Santarém (Brazil)

Both plant physiology and atmospheric chemistry are substantially altered by the emission of volatile isoprenoids (VI), such as isoprene and monoterpenes, from plant leaves. Yet, since gaining scientific attention in the 1950’s, empirical research on leaf VI has been largely confined to laboratory experiments and atmospheric observations. Here, we introduce a new field instrument designed to bridge the scales from leaf to atmosphere, by enabling precision VI detection in real time from plants in their natural ecological setting. With a field campaign in the Brazilian Amazon, we reveal an unexpected distribution of leaf emission capacities (EC) across the vertical axis of the forest canopy, with EC peaking in the mid-canopy instead of the sun-exposed canopy surface, and moderately high emissions occurring in understory specialist species. Compared to the simple interpretation that VI protect leaves from heat stress at the hot canopy surface, our results encourage a more nuanced view of the adaptive role of VI in plants. We infer that forest emissions to the atmosphere depend on the dynamic microenvironments imposed by canopy structure, and not simply on canopy surface conditions. We provide a new emissions inventory from 52 tropical tree species, revealing moderate consistency in EC within taxonomic groups. We highlight priorities in leaf volatiles research that require field-portable detection systems. Our self-contained, portable instrument provides real-time detection and live measurement feedback with precision and detection limits better than 0.5 nmol_VI m^-2_leaf s^-1. We call the instrument ‘PORCO’ based on the gas detection method: photoionization of organic compounds. We provide a thorough validation of PORCO and demonstrate its capacity to detect ecologically driven variation in leaf emission rates and thus accelerate a nascent field of science: the ecology and ecophysiology of plant volatiles.

• Research Organization: US Geological Survey, Boulder, CO (United States); Univ. of Arizona, Tucson, AZ (United States)
• Sponsoring Organization: National Science Foundation (NSF); USDOE Office of Science (SC), Biological and Environmental Research (BER)
• Grant/Contract Number: SC0008383
• OSTI ID: 1851074
• Journal Information: Frontiers in Forests and Global Change, Journal Name: Frontiers in Forests and Global Change Vol. 4; ISSN 2624-893X
• Publisher: Frontiers Media S.A.Copyright Statement
• Country of Publication: United States
• Language: English