FURTHER INTERCEPTION STUDIES OF HEATHER USING A WET-SURFACE WEIGHING LYSIMETER SYSTEM

Measurements have been made of the four canopy parameters required by A. J. Rutter type interception models for heather (Calluna vulgaris). The values obtained are 5. 13 and 0. 00085 for the drainage parameters b and k, respectively, (0. 13 plus or minus 0. 09) for the free throughfall coefficient p, and values of 1. 1 plus or minus 0. 1 and 0. 85 plus or minus 0. 1 mm for the canopy capacity S, derived from independent drainage and evaporation experiments, respectively. It is suggested that the difference between the two values of S is significant and represents a real difference between the canopy storage at which drainage ceases and the smaller canopy storage necessary for a completely wet canopy. Studies of the wetting behavior of heather provide evidence to support this hypothesis.