Abstract: The genetic diversity of the Frankia strains in the nodules of Alnus tinctoria,A.mandshurica and A.sibirica growing at different altitude in Changbai Mountain was studied by REP-PCR fingerprinting.The REP-PCR fingerprint patterns revealed that uncultured Frankia strains tested had a high genetic diversity.Host and altitude factors influenced the genetic diversity.Frankia strains from A.mandshurica showed greater specialization toward the host,and Frankia stains from A.sibirica and A.tinctoria had a closer affinity.The Frankia stains from the same alder distributing at different altitude belonged to different REP patterns,and the Frankia stains from A.sibirica and A.tinctoria at the same altitude showed promiscuity.

Key words: Black soil, Farmyard manure, Urease activity, Dynamic change, Soil nutrient