Evaluation of poplar and willow clones on the experimental short rotation plantation in Kharkiv region: results of the second cultivation year

Purpose. To estimate the growth performance of poplar and willows clones on the 2nd vegetation year at short rotation plantation in the Kharkiv region, and to identify the most perspective clones for the establishing of bioenergy plantations. Methods. The growth characteristics of 2-year-old poplars (10 clones) and willows (3 clones) were analyzed on experimental plot established in 2014 due to common practice, with stem cuttings 20–25 cm long and 0.8–1.2 cm in diameter. During the analysis performed in October, diameter and height of the shoots were measured and the quantity of plants with 1, 2, and ≤ 3 shoots per plant was determined. Results. The investigations revealed significant interclonal variation in estimated growth parameters on the second vegetation year. The poplar clones ‘Huliver’, ‘Strilopodibna’, ‘Rohanska’, ‘Slava Ukrainy’ and willow clone ‘Pryberezhna’ demonstrated high growth rates. The shoot height of poplars ‘Rohanska’ and ‘Slava Ukrainy’ were 30% and 42% respectively, higher than average rates after two years of cultivation. The clones of poplars ‘Huliver’, ‘Strilopodibna’, and clone of willow ‘Pryberezhna’ had the largest diameters exceeded the average rates more than 20%. Poplars ‘Constanta’, ‘Lvivska’ and ‘Noctiurn’ demonstrated low growth. By the sprouting capacity the clones were divided into two groups: with a high level of sprouting capacity increasing significantly during the second growing season (‘Huliver’, ‘Rohanska’, ‘Druzhba’); and with low sprouting capacity within both vegetation seasons (‘Constanta’, ‘Noctiurn’ and ‘Lvivska’). In general, a comparison of the averaged growth parameters of poplars and willows revealed that the willows prevailed the poplars in height, but no significant differences in diameter and sprouting capacity were observed. Conclusions. The poplars ‘Huliver’, ‘Strilopo­dibna’, ‘Rohanska’, ‘Slava Ukrainy’ and the willow ‘Pryberezhna’ demonstrated high growth values, and poplar clones ‘Huliver’, ‘Rohanska’ and ‘Druzhba’ showed a high level of sprouting capacity. During the two growing seasons the clones of poplars ‘Constanta’, ‘Lvivska’ and ‘Noctiurn’ showed low growth rates and sprouting capacity. The results of experiments could be taken into account when establishing short-rotation plantations of bioenergy trees, in particular on plots without artificial irrigation.