期刊
NEW PHYTOLOGIST
卷 173, 期 3, 页码 537-549出版社
WILEY
DOI: 10.1111/j.1469-8137.2006.01926.x
关键词
canopy profiles; chlorophyll; down-regulation; free-air CO2 enrichment; ( FACE); leaf mass area; light; nitrogen; photosynthetic capacity
The long-term response of leaf photosynthesis to rising CO2 concentrations [CO2] depends on biochemical and morphological feedbacks. Additionally, responses to elevated [CO2] might depend on the nutrient availability and the light environment, affecting the net carbon uptake of a forest stand. After 6 yr of exposure to free-air CO2 enrichment (EUROFACE) during two rotation cycles (with fertilization during the second cycle), profiles of light, leaf characteristics and photosynthetic parameters were measured in the closed canopy of a poplar (Populus) short-rotation coppice. Net photosynthetic rate (A(growth)) was 49% higher in poplars grown in elevated [CO2], independently of the canopy position. J(max) significantly increased (15%), whereas leaf carboxylation capacity (V-cmax), leaf nitrogen (N-a) and chlorophyll (Chl(a)) were unaffected in elevated [CO2]. Leaf mass per unit area (LMA) increased in the upper canopy. Fertilization created more leaves in the top of the crown. These results suggest that the photosynthetic stimulation by elevated [CO2] in a closed-canopy poplar coppice might be sustained in the long term. The absence of any down-regulation, given a sufficient sink capacity and nutrient availability, provides more carbon for growth and storage in this bioenergy plantation.
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