The effect of density on short rotation Populus sp. plantations in the Mediterranean area

In this study, the effect of density on poplar short-rotation forestry plantations was analyzed in the context of maximizing biomass production under Mediterranean conditions. Data from 12 experimental sites in Spain with densities ranging from 6666 to 33,333 cuttings·ha−1 were used. At the end of the first year, biomass production from the different poplar plantations differed significantly among sites and densities. Furthermore, after one year of growth, biomass production was found to increase exponentially with plot density. However, after three years of growth, at the end of the first rotation, significant differences were not found. When we analyzed the variables that affect the production, we found that weed control and therefore a reduction in competition explained much of the variability. The greatest biomass production was achieved in high density plots in more southern latitudes where high spring temperatures benefit trees growing in well-watered soils. Considering on the one hand the scope of current weed control methods and on the other, the cost of plantation and/or the difficulties associated with management and mechanisation, plantation densities of more than 15,000 plants ha−1 would not be recommendable.

► Production increased significantly with density after one year of growth.
► After three years of growth significant differences was not found.
► The production variability is mainly explained by weed control factor.