The early growth and fall frost damage of poplar clones in Latvia
Latvian State Forest Research Institute ʻSilava’, Rigas 111, LV 2169 Salaspils, Latvia
The early growth and frost damage of Populus spp. was studied in two sites. The height of 23 five-year-old poplar clones was measured in the central part of Latvia; and the early-fall frost damage of 19 one-year-old and two-year-old poplar clones were assessed in the eastern part of Latvia. The relation between the height growth and frost damage of 16 clones, which were common for both sites, was assessed. The phenologically dormant stage was denoted for three clones, among which two are collected across Latvia (the origin un-known; introduced in 1960s). All the other clones had trees with damaged leaves and two clones had stem damage. The height of the clones ranged from 273.3 ± 60.2 to 711.0 ± 32.0 cm. The 3 most productive clones (LV3, LV1 and LV4) significantly (P < 0.01) exceeded others, by 34 and 65% for height and biomass, respectively. The mean height of these clones was 649.0 ± 21.5 cm and stem biomass varied from 33.7 ± 4.2 to 55.0 ± 6.4 tfresh=ha-1 (planting density 6,500 trees=ha-1). The clone had significant (P < 0.01) effect on the phenological stage, leaf and stem frost damage, as well as on the height and stem biomass. No relation (P > 0.05) between the frost damage of leaves and both tree height and stem biomass was found. The results suggest that fast-growing frost-tolerant clones might be selected.