The first three-year development of ALASIA poplar clones AF2, AF6, AF7, AF8 in biomass short rotation coppice experimental cultures in Latvia
Latvian State Forest Research Institute Silava, 111 Rigas str., LV2169 Salaspils, Latvia; *Correspondence: email@example.com
Hybrid aspen and willows are the fastest growing tree species used for biomass production in short rotation coppice (SRC) cultures in Latvia. Poplars are suitable for cultivation in Latvia, however, their potential for this purpose as SRC in Latvia and North Eastern Europe has not yet been investigated. There is an increasing interest in using poplar clones to establish short rotation plantations. The aim of this study is to analyse the productivity of the Italian poplar clones AF2, AF6, AF7, AF8 and their potential use for biomass production, as well as the effect of fertilization on the development and survival of trees. The experimental plot consisted of drained mineral soil with the initial spacing of trees ranging from 9,000 to 10,000 trees ha-1 (1.5 m x 0.7–0.5 m). Weed management has been carried out on the plantation once per season every year. Four management methods were tested – control (no fertilization), fertilization with waste water sludge 10 t DM ha-1, wood ash 6 t ha-1, mineral fertilizer NPK (12:5:14) 100 kg ha-1. In the second year, the height of the trees ranged from 0.2 to 2.64 m, on average 1.12 ± 0.005 m. The annual increments during the third year ranged from 0.01–2.14 m, on average 0.787 ± 0.004 m. At the end of the third season, the tree diameters at breast height of all clones varied greatly from 0.36 cm to 4.4 cm. The trees reached average diameters of 1.48 ± 0.007 cm; the tree heights ranged from 0.36 m to 4.24 m and were 1.99 ± 0.01 m, on average at the end of the third season. Depending on the clone and treatment, the amount of fresh biomass was 1.57–10.67 t ha-1(planting density 10,000 trees), and one fifth of the biomass, on average, was located in branches. Sewage sludge fertilizer contributed to the development of the micropatogen Venturia sp., resulting in lower initial retention and delayed development. Mineral fertilizers were the most effective. No animal and frost damages were observed. Overall, the results indicate a significant potential for us for using poplar for bioenergy production, with the optimal rotation age for bioenergy production being more than 3 years.