1. Institute of Intelligent MachinesChinese Academy of SciencesHefeiAnhui230031China
2. Dep. of Plants, Soils and ClimateUtah State Univ.LoganUT84322‐4820
3. Dep. of Soil, Water and Environmental ScienceUniv. of ArizonaTucsonAZ85719
4. Centre for Ecology and Hydrology, Environment Centre WalesDeiniol RoadBangorUK