PHOTOSYNTHESIS, LEAF-AREA AND PRODUCTIVITY OF 5 POPLAR CLONES DURING THEIR ESTABLISHMENT YEAR

The stem volume and biomass (stem + branches) production, net photosyn thesis of mature leaves and leaf area production of 5 poplar (Populus) clones, Populus trichocarpa x deltoides (Raspalje and Beaupre), Popul us x euramericana (Robusta) and P trichocarpa (Columbia River and Frit zi Pauley), were studied during the first year of growth in an experim ental high density plantation (15 600 plants ha-1). Significant differ ences were found in volume production, woody biomass production, total leaf area and net photosynthesis. Above-ground biomass production was 3.5 times higher in Raspalje than in Robusta. The best performing clo nes (Raspalje, Beaupre) were those with large leaves, high leaf area i ndex and high photosynethetic rates. A positive relationship between l eaf photosynthetic capacity and above-ground biomass production was al so noted for 4 of the 5 clones. The euramerican clone Robusta was an e xception, showing high photosynthetic rates, but low biomass productio n. This discrepancy was mainly due to the lower leaf area of this clon e, and possibly also due to a larger carbon allocation to below-ground biomass (Barigah, 1991). The root/shoot ratios at the end of the firs t season in the clones Raspalje and Robusta were 1.23 and 1.79, respec tively.