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Photosynthetic capacity of loblolly pine ( Pinus taeda L.) trees during the first year of carbon dioxide enrichment in a forest ecosystem
Author(s) -
MYERS D. A.,
THOMAS R. B.,
DELUCIA E. H.
Publication year - 1999
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1046/j.1365-3040.1999.00434.x
Subject(s) - photosynthesis , carboxylation , loblolly pine , carbon dioxide , photosynthetic capacity , botany , growing season , rubisco , chlorophyll fluorescence , photorespiration , chemistry , horticulture , zoology , pinus <genus> , biology , ecology , biochemistry , catalysis
Our objective was to assess the photosynthetic responses of loblolly pine trees ( Pinus taeda L.) during the first full growth season (1997) at the Brookhaven National Lab/Duke University Free Air CO 2 Enrichment (FACE) experiment. Gas exchange, fluorescence characteristics, and leaf biochemistry of ambient CO 2 (control) needles and ambient + 20 Pa CO 2 (elevated) needles were examined five times during the year. The enhancement of photosynthesis by elevated CO 2 in mature loblolly pine trees varied across the season and was influenced by abiotic and biotic factors. Photosynthetic enhancement by elevated CO 2 was strongly correlated with leaf temperature. The magnitude of photosynthetic enhancement was zero in March but was as great as 52% later in the season. In March, reduced sink demand and lower temperatures resulted in lower net photosynthesis, lower carboxylation rates and higher excess energy dissipation from the elevated CO 2 needles than from control needles. The greatest photosynthetic enhancement by CO 2 enrichment was observed in July during a period of high temperature and low precipitation, and in September during recovery from this period of low precipitation. In July, loblolly pine trees in the control rings exhibited lower net photosynthetic rates, lower maximum rates of photosynthesis at saturating CO 2 and light, lower values of carboxylation and electron transport rates (modelled from A–C i curves), lower total Rubisco activity, and lower photochemical quenching of fluorescence in comparison to other measurement periods. During this period of low precipitation trees in the elevated CO 2 rings exhibited reduced net photosynthesis and photochemical quenching of fluorescence, but there was little effect on light‐ and CO 2 ‐saturated rates of photosynthesis, modelled rates of carboxylation or electron transport, or Rubisco activity. These first‐year data will be used to compare with similar measurements from subsequent years of the FACE experiment in order to determine whether photosynthetic acclimation to CO 2 occurs in these canopy loblolly pine trees growing in a forest ecosystem.