Sprouting ability of two-year-old Betula pendula stumps exposed to different light intensities during five years
1991
Johansson, T. (Sveriges Lantbruksuniv., Garpenberg (Sweden). Inst. foer Skogsproduktion)
Altogether 1080 two-year-old silver birch (Betula pendula Roth) were planted in groups of 36 plants at a spacing of 20X30 cm in spring 1983 on a nursery field at lat. 60 deg 15 min N and long. 16 deg 00 min E. In spring 1984 all plants were cut with 10 cm high stumps and light screens were arranged on the stump groups. Relative irradiance (RI) 5, 10, 25, 50, 75, and 100% of full sunlight were used. After five growing seasons, all stumps exposed to 5 or 10% light intensity were dead, and 64-94% of stumps exposed to 25-100% RI were alive. 1.3-1.4 sprouts per living stump were living five years after cutting. The mean height of sprouts was highest on stumps exposed to 100% light. Also dry weights of leaves and sprouts, number of leaves per sprout, and leaf area were highest on stumps exposed to full sunlight. Stumps producting only one sprout five years after cutting have higher height and dry weight values than stumps with more sprouts. The biomass production per hectare and year for silver birch sprouts at a spacing of 0.2 m and with 90% survival was calculated as 5.4 tonnes. The biomass of leaves was 8.1 tonnes per ha and year five years after cutting.
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