During the study at the University of Guelph(May to Nov.,2001), the auther took part in the ecological and environmental investigations in the tree based intercropping system in the southern Ontario, Canada. Through a series of studies on nitrogen mineralization, soil respiration and carbon sequestration, the competitive and complementary relations between trees and crops in the tree_based intercropping system are revealed. The impacts of the system on the environment, such as greenhouse gases emission reduction and carbon balance in the globe, are brought to light as well. N 2O emission from the tree_based intercropping system is 0 69?kg·hm -2 a -1 less than the monocropped agricultural field. The carbon storage of poplar_based intercropping system by age 14?a reaches 12?t·hm -2 The leaf litters from poplar will add 1 3?t·hm -2 a -1 organic carbon to the soil. As compared to monocropped wheat farm, the carbon sink of tree_wheat intercropped system is 1 776?t·hm -2 a -1 , whereas the wheat farm is just 0 264?t·hm -2 a -1 .
