Abstract

The aim of this thesis was to answer the question: Which processes should be included in a model to simulate willow production as a function of climate, soil and fertilisation conditions? Studies were carried out to determine: a) the radiation use efficiency of an unstressed willow stand; b) to which degree willow growth can be described as a function of absorbed radiation, shoot age and shoot mortality; c) to which extent model predictability is improved by further including soil water availability and d) nitrogen availability. Model simulations were tested against biomass production of 22 stands representing differences in location, soil type and fertilisation level. It was found that radiation use efficiency varies with shoot-age. This was attributed to differences in canopy development, and to mortality caused by self-thinning. The absorbed radiation, shoot age and shoot mortality could explain 70 to 85% of the observed variations in stem biomass at harvest and 32 to 48% of the observed variations in annual production. Incorporating simulations of soil water availability decreased model predictability except for production of three-years-old shoots. Including simulations of soil water and nitrogen availability improved the degree of explanation in some situations. For all stands, model predictability of biomass at harvest was improved from r2 = 0.70 to r2 = 0.82 and of annual biomass from r2 = 0.70 to r2 = 0.82. For low or not fertilised stands, only a slightly improvement was obtained in explaining variations at harvest and none for variations of annual biomass. For fertilised stands, model predictability was decreased except for production of three-years-old shoots. Predictability of three-years old shoots production was improved, for all situations, by including simulations of soil water and nitrogen availability. For willow stands growing on former arable land in southern Sweden, variations on biomass production at harvest, of stands with similar fertilisation level, can be simulated from the absorbed radiation and shoot mortality caused by self-thinning. Simulations of soil water and nitrogen availability are only worthy of including to explain yield variations of stands with different fertilisation levels. Variations in biomass production between years and sites are indicated to be poorly related to annual variations in solar radiation, shoot mortality or soil water and nitrogen availability.

Keywords

drought; growth; models; plant nutrition; salix viminalis; plant production; sweden

Published in

Acta Universitatis Agriculturae Sueciae. Silvestria
2003, number: 286
ISBN: 91-576-6520-6
Publisher: Dept. of Short Rotation Forestry, Swedish Univ. of Agricultural Sciences

SLU Authors

• Noronha Sannervik, Angela

  • Department of Crop Production Ecology, Swedish University of Agricultural Sciences
    

UKÄ Subject classification

Soil Science
Forest Science


Permanent link to this page (URI)

https://res.slu.se/id/publ/11798