1. College of Resources and Environmental Sciences, Agricultural Univ. of Hebei; Baoding 071001 China
2. Key Lab of Plant-Soil Interactions, MOE; College of Resources and Environmental Sciences, China Agricultural Univ.; 100193 Beijing China
3. Dep. of Soil Quality; Wageningen Univ.; P.O. Box 47 6700 AA Wageningen the Netherlands
4. Alterra Wageningen Univ.; P.O. Box 47 6700 AA Wageningen the Netherlands
5. Key Lab of Plant-Soil Interactions; MOE, College of Resources and Environmental Sciences, China Agricultural Univ.; 100193 Beijing China
6. Dep. of Soil Quality; Wageningen Univ., and Alterra, Wageningen Univ.; Research Centre; P.O. Box 47 6700 AA Wageningen the Netherlands