© 2005 Heron Publishing—Victoria, Canada
Determinants of biomass production in hybrid willows and prediction of field performance from pot studies
Martin Weih (1, 2) and Nils-Erik Nordh (1)
1. Department of Short Rotation Forestry, Swedish University of Agricultural Sciences, P.O. Box 7016, SE-750 07 Uppsala, Sweden / 2. Corresponding author (martin.weih@lto.slu.se) / Received September 15, 2004; accepted January 21, 2005; published online July 4, 2005
Summary
Pot experiments are often performed to assess plant physiological traits and relationships among growth traits under controlled
environments. However, the reliability of pot studies for predicting the growth and performance of trees in the field has
rarely been rigorously assessed. We evaluated the suitability of pot experiments for predicting field performance, measured
as shoot biomass production, by investigating determinants of growth in hybrid willows (Salix spp.) grown under various environmental conditions in the field, and by comparing the data with the results from a corresponding
pot study. Biomass production in six hybrid willow clones, bred for use as bio-fuels, was assessed in three field trials located
in central and southeastern Sweden throughout the first 3-year cutting cycle. The determinants of biomass productivity, measured
as biomass allocation and nitrogen (N) economy, were identified in one of the field trials. Key traits for shoot biomass production
in the field were total leaf area and total amount of N; plant N losses by shed leaves were only partly controlled by leaf-litter
N concentration. These key traits were also obtained from the pot study and related to shoot biomass production and abscission-leaf
N loss in the field. Total leaf area and total N pool of plants grown in pot experiments were good predictors of long-term
biomass production in the field, whereas shoot biomass production, specific leaf area and tissue N concentration of pot-grown
plants were less suitable as predictors of field performance. Relationships between the key traits and shoot biomass production
were clone-specific, indicating the need for analysis of growth traits at the clone level if field performance of trees is
to be evaluated based on data from pot studies. Nutrient loss components are important for tree performance in the long term
and evaluations of nutrient loss characteristics at the individual-tree level should focus on nutrient pools lost rather than
on nutrient concentrations in abscised plant parts.
Keywords:
bio-fuels, growth analysis, leaf abscission, nitrogen economy, Salix, Sweden.
