Variation in growth and resource utilisation among eight poplar clones grown under different irrigation and fertilisation regimes in Sweden

Growth, biomass allocation and nutrient economy of eight clones of poplar (Populus balsamifera L., P. trichocarpa Hook.) and hybrid poplar (P. trichocarpa Hook. × P. deltoides Bartr.) of north-American origin were studied in a full-factorial pot experiment in Sweden, using the approach of classical growth analysis. The clones were compared in terms of relative growth rate (RGR), biomass production, biomass allocation, nitrogen accumulation and productivity, and ability to withdraw nitrogen from senescing leaves (leaf nitrogen proficiency). The clones differed significantly among treatments by means of several variables, and for some of them also clone × treatment interaction effects were significant. The components of RGR, i.e., leaf area ratio (LAR) and unit leaf rate (ULR), shifted in their importance to explain differences between treatments and genotypes. The results are discussed in the context of growth characteristics particularly important for the selection of clones for multi-purpose poplar plantations grown under the cool-temperate, high-latitude climatic conditions typical for large parts of Sweden.