Presently, a total of 104 species belonging to 87 genera under 38 families of flowering plants in exotic (Eucalyptus citriodora Hook.) and indigenous (Pinus roxburghii Sarg.) tree plantations were determined.  There were higher numbers of plant species under the indigenous plantations as compared to the exotic ones. InEucalyptus plantations 60% species were exotic, 36.92% indigenous and 3.08% obscure as compared to 44.44% exotic, 54.33% indigenous and only 1.23% obscure species under Pinus ones. The alpha diversity also decreased by 34.73% under the exotic tree plantations of Eucalyptus. Evidently, the exotic tree plantations become in-roads for the opportunistic and environmentally flexible species with wide ecological amplitude.

Key words:  Species diversity, exotic, indigenous, N.W. Indian Himalayas.