Biomass production of 17 poplar clones in a short-rotation coppice culture on a waste disposal site and its relation to soil characteristics

This study describes the above ground biomass production of 17 poplar (Populus spp.) clones after a 4-year rotation in a short-rotation coppice culture. In addition, the link with soil characteristics was studied. In April 1996, an experimental field plantation with 10,000 cuttings ha-1 was established in Boom (province of Antwerp, Belgium) on a former waste disposal site. A randomised block design was used with three replicate plots (9m x 11.5 m). At the end of the establishment year, all plants were cut back to a height of 5 cm to create a coppice culture. At the end of the fourth year after coppicing, shoot diameters of all living and dead shoots were measured, and biomass production was estimated with an allometric power equation. A composite soil sample was taken for all plots, and pH, organic matter, water content, bulk density, content of nutrients, minerals and heavy metals were determined. Highest production was found for P. trichocarpa x P. deltoides hybrids Hazendans and Hoogvorst, P. trichocarpa clones Fritzi Pauley, Columbia River and Trichobel, and native P. nigra clone Wolterson with mean annual biomass production ranging between 8.0 and 11.4 Mg ha-1 per year. Lowest performance was observed for P. trichocarpa x P. deltoides hybrid Boelare, P. deltoides x P. trichocarpa hybrids IBW1, IBW2 and IBW3, and P. deltoides x P. nigra hybrids Gaver and Gibecq with a mean annual biomass production ranging between 2.8 and 4.7 Mg ha-1. Mean dead biomass accounted for less than 2% of total standing biomass for all clones. Some clones exhibited a uniform production across replicates, implying low susceptibility to soil heterogeneity; other clones showed a high inter-replicate variation. However, no cause for this interreplicate variation was identified. A cluster analysis enabled identification of two groups of plots with significant differences in soil characteristics and in biomass production. But a Spearman's rank correlation test showed only a negative correlation between biomass production and plant available magnesium and potassium in the soil. A principal component analysis and multiple regression could not reveal an unambiguous impact of soil either, caused by the low variance in soil characteristics, the high genotypic variation and/or the impact of non-identified (environmental) factors. © 2003 Elsevier B.V. All rights reserved.