Photosynthesis And Light-Use Efficiency By Plants In A Canadian Boreal Forest Ecosystem

  • Sites: CA-Obs
  • Whitehead, D., Gower, S. T. (2001/08/01) Photosynthesis And Light-Use Efficiency By Plants In A Canadian Boreal Forest Ecosystem, Tree Physiology, 21(12-13), 925-929.
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  • Measurements of the photosynthetic response to midsummer irradiance were made for 11 species representing the dominant trees, understory shrubs, herbaceous plants and moss species in an old black spruce (Picea mariana (Mill.) B.S.P.) boreal forest ecosystem. Maximum rates of photosynthesis per unit foliage area at saturating irradiance, Amax, were highest for aspen (Populus tremuloides Michx.), reaching 16 μmol m−2 s−1. For tamarack (Larix laricina (Du Roi) K. Kock) and P. mariana, Amax was only 2.6 and 1.8 μmol m−2 s−1, respectively. Values of Amax for understory shrubs and herbaceous plants were clustered between 9 and 11 μmol m−2 s−1, whereas Amax of feather moss (Pleurozium schreberi (Brid.) Mitt.) reached only 1.9 μmol m−2 s−1. No corrections were made for differences in shoot structure, but values of photosynthetic light-use efficiency were similar for most species (70–80 mmol CO2 mol−1); however, they were much lower for L. laricina and P. mariana (15 mmol CO2 mol−1) and much higher for P. schreberi (102 mmol CO2 mol−1). There was a linear relationship between Amax and foliage nitrogen concentration on an area basis for the broad-leaved species in the canopy and understory, but the data forP. mariana, L. laricina and P. schreberi fell well below this line. We conclude that it is not possible to scale photosynthesis from leaves to the canopy in this ecosystem based on a single relationship between photosynthetic rate and foliage nitrogen concentration.