Assessment of regional willow coppice yield in Sweden on basis of water availability

The aim of this paper is to assess the limitations by water on yield in sou thern Sweden on the basis of long-term records of precipitation and known w ater relations of willow. Data concerning relationship with water comes fro m a field experiment in central Sweden and data on yield, obtained in comme rcial cultivations, comes from a number of locations in southern Sweden. A simple water-limited yield model based on the concept of water-use efficien cy was used to estimate regional production. The model showed good agreemen t with the actual yield at a large number of locations in southern Sweden. The model was then used to produce a map of average maximum stemwood produc tion and it showed that the annual production would be 8-9 t ha in the nort heastern part of southern Sweden, 9-10 t in eastern Sweden, 11-12 t in the very south and reach a maximum of 16-17 t in a narrow belt along the west c oast. Relating these yield values to data, reported in literature regarding economics of short-rotation forestry, shows that water will be a critical factor in order to obtain good profitability in short-rotation forestry in Sweden. (C) 1999 Elsevier Science B.V. All rights reserved.