Clonal variation in growth, chemistry and calorific value of new poplar hybrids at nursery stage

Bioenergy from plants could make a substantial contribution to alleviation of global problems in climate change and energy security. The rapid growth rates of hybrid poplar (Populus spp.) exhibit a great potential for biofuels and selecting superior clones is critical to increase biomass production and ecological effects. Variation in growth, chemistry and calorific value of the 25 poplar clones were examined at nursery stage. The significant clonal differences in growth, leaf traits, wood basic density, chemical compositions and calorific values were observed among the 25 clones. Total leaf area per plant varied along a two-fold range (7146.7–18065.0 cm2), mean single leaf area varied between 273.4 and 496.9 cm2 and specific leaf area ranged from 158.7 to 204.9 cm2 g−1. After one growing season, the mean stem biomass production per plant ranged from 173.5 g to 485.8 g, while the average wood basic density varied from 224 kg m−3 to 310 kg m−3 among the tested clones. Mean gross calorific value of the stem on an oven-dry weight basis was within the range of 18.5–19.1 kJ g−1, while mean ash free calorific value varied between 18.7 and 19.3 kJ g−1. All the chemical compositions measured both in stem wood and stem bark also presented a broad variation and clonal effects. Based on a comparison of component score coefficients, twenty-five hybrid clones were classified into four distinct groups by means of hierarchical cluster analysis, and clones 208, 328 and 75 showed excellent growth and combustion traits. Clones for further long-term trials in large-scale were also recommended to reduce loss of superior genetic material and risks of maladaptation.