Population structure and dynamic characteristic of Ulmus pumila sparse forest in sandy land, China

The vegetation, as one of positive factors for desertification control, has received extensive attention of scholars from different research fields. In this paper, the structure and dynamic characteristic of Ulmus pumila L. sparse forest in Horqin sandy land and Otindag sandy land were investigated. The results showed that Ulmus pumila L. sparse forest was monodominant community, and had simple structure in both two sandy lands, of which the stand density was separately 34 plants/hm² in Horqin sandy land and 105 plants/hm² in Otindag sandy land. In addition, Ulmus pumila L. populations in both sandy lands had declining age structure, and were suffering serious degradation due to deficiency of seedling renewal. Therefore, we concluded that there might be twice degradations in Horqin sandy land in recent years, separately happened in recent 20 years and the period during 40 to 30 years ago; the degradation of Otindag sandy land happened from 30 years ago. The death rate of young individuals was lowest, and the highest death rate occurred in the age of 50-60 in Horqin sandy land and of 80-90 in Otindag sandy land. Their survival curves both tend to be Deevey 1 type.