1. NERC Centre for Ecology and Hydrology, Banchory Research Station, Hill of Brathens, Banchory, AB31 4BW, Scotland, UK
2. E‐mail
3. Biomathematics and Statistics Scotland, Environmental Modelling Unit, Macaulay Institute, Craigiebuckler, Aberdeen, AB9 2QJ, Scotland, UK; E‐mail