1. Soil Science and Agrifood Engineering Dep.; Laval Univ.; 2425 rue de l'Agriculture Québec QC G1V 0A6 Canada
2. Dep. of Geography; Univ. of Waterloo; Waterloo ON N2L 3G1 Canada
3. Plant Science Dep.; Laval Univ.; 2425 rue de l'Agriculture Québec QC G1V 0A6 Canada