Seasonal controls on net branch CO2 assimilation in sub-Arctic Mountain Birch (Betula pubescens ssp. czerepanovii (Orlova) Hamet-Ahti)
Poyatos, R.; Gornall, J.; Mencuccini, M.; Huntley, B.; Baxter, R.
Professor Robert Baxter email@example.com
Forests at northern high latitudes are experiencing climate-induced changes in growth and productivity, but our knowledge on the underlying mechanisms driving seasonal CO2 fluxes in northern boreal trees comes almost exclusively from ecosystem-level studies on evergreen conifers. In this study, we measured growing season whole-branch CO2 exchange in a deciduous tree species of the tundra-taiga ecotone, Mountain Birch (Betula pubescens ssp. czerepanovii (Orlova) Hamet-Ahti), at two locations in northern Fennoscandia: Abisko (Sweden) and Kevo (Finland). We identified strong seasonal and environmental controls on both photosynthesis and respiration by analysing the parameters of light response curves. Branch-level photosynthetic parameters showed a delayed response to temperature, and, at Kevo, they were well described by sigmoid functions of the state of acclimation (S). Temperature acclimation was slower (time constant, τ = 7 days) for maximum photosynthesis (βbr) than for quantum efficiency (αbr) (τ = 5 days). High temperature-independent values of the respiration parameter (γbr) during leaf and shoot expansion were consistent with associated higher growth respiration rates. The ratio γbr/βbr was positively related to temperature, a result consistent with substrate-induced variations in leaf respiration rates at the branch level. Differences in stand structure and within-site variation in the active period of C uptake determined the spatiotemporal patterns in net assimilation amongst branches. Growing season CO2 uptake of individual branches on a leaf area basis did not show a significant relationship with total incident photosynthetically active radiation, and did not differ across sites, averaging ca. 640 g CO2 m−2.
Poyatos, R., Gornall, J., Mencuccini, M., Huntley, B., & Baxter, R. (2012). Seasonal controls on net branch CO2 assimilation in sub-Arctic Mountain Birch (Betula pubescens ssp. czerepanovii (Orlova) Hamet-Ahti). Agricultural and Forest Meteorology, 158-159, 90-100. https://doi.org/10.1016/j.agrformet.2012.02.009
|Journal Article Type||Article|
|Publication Date||Jun 15, 2012|
|Deposit Date||Jun 25, 2012|
|Publicly Available Date||Oct 31, 2014|
|Journal||Agricultural and Forest Meteorology|
|Peer Reviewed||Peer Reviewed|
|Keywords||Arctic, Branch bags, Light response curve, Phenology, Photosynthesis, Respiration, State of acclimation.|
Accepted Journal Article
NOTICE: this is the author’s version of a work that was accepted for publication in Agricultural and Forest Meteorology. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Agricultural and Forest Meteorology, 158-159, 2012, 10.1016/j.agrformet.2012.02.009.
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