1. Department of Biology; University of Regina; 3737 Wascana Parkway Regina Saskatchewan S4S 0A2 Canada
2. Laboratory of Geo-Information Science and Remote Sensing; Wageningen University; P.O. Box 47 6700 AA Wageningen The Netherlands
3. Laboratory of Tree-Ring Research and Department of Ecology and Evolutionary Biology; University of Arizona; Tucson Arizona 85721 USA