Biomass production of poplar short rotation coppice over five and six rotations and its aptitude as a fuel

Abstract

Cultivations of poplar short rotation coppices (SRC) over five/six 3-year rotation cycles of three clones of Populus nigra and one interspecific commercial hybrid clone were studied in the Czech Republic at three sites with different environmental conditions. Two sites were planted in 1998 and the other was planted in 2002. This study focused on the evaluation of the growth and biomass yields, and on the biomass aptitude to be used as a fuel. Plant mortality, ranging between 10% and 100%, was found as a determinant variable for SRC management. Biomass yield decreased comparatively with earlier harvests, with only the commercial clone delivering productivity levels higher than 11 Mg ha−1.yr−1. The sixth harvest was applied to a single mid-level site quality profile, marginal to food cultivations. This site was subjected to an intensive management during the first four rotations with fertilization, herbicide application and soil discing. These treatments were central to assure the high plant survival rate after the sixth rotation with adequate biomass productivity. The number of shoots per plant was higher in the site chosen for extension of lifecyle, supporting the hypothesis that this variable, by facilitating resprouting, allows a cultivation to withhold further rotations. The harvested biomass was found appropriate to be used as a fuel. The results suggest that the sustainability of SRC poplar cultivations can be achieved under lifecycles longer than 20 years, under 3-year rotation cycles, with proper clones, site and management practices.