The application of ETM and sample site statistics data to study distribution pattern of endangered rare plants in West Ordos Plateau

The endangered rare plants, mainly Tetraena mongolica, Helianthemum soongolicum, Reaumuria trigyna, Reaumuria soongorica, Potaninia mongolica, Ammopiptanthus mongolicus in the West Ordos Plateau located at the central part of the 250 nm precipitation rim and geographically in transaction of tow geographical scenery there are desert grassland and grassland desert. In Inner-Mongolia, in this context, are for a long time regarded as environment change indicators. These plants have also played very important role in maintaining the ecosystem in preventing desertification. Because the plants are endangered so as to be protected as the diversity plants in Asia. Since beginning 19^th century there have been extensively studies in the field of the functions of rare plants in the frame of retaining ecology system and roles of preventing desertification in region, including UNDP project