Study On The Species Diversity And Soil Nutrition Of Degraded Succession For Leymus Chinesis Meadow In Hulunbeier

Based on the investigation and analyses of properties of plant communities, the the change of vegetation and soil nutrients of Leymus chinesis meadow steppe under different degradation in Hulunbeier was studied in this study. The results were as follows:1. Along with the degree of degradation, the number of plant species gradually decreased, and the number of plant species in different families changed as well. With succession, the number of plant species in Gramineae decreased, and the change of the number of plant species in Leguminocae, Compositae and Cyperaceae were not significant, while the number of plant species of Potentilla with indicating function in Rosaceae significally increased.2. Along with succession process, the number of plant species in life forms changed. The species number in perennial herbaceous plants and semi-shrubs gradually decreased. As to annual-biennial herbaceous plant, the species number showed a trend of single peak curve(low-high-low) with succession process. As to ecological types,with succession process, the proportion of the number of plant species in the mesophytes gradually decreased, while the proportion of the number of plant species in intermediate xerads and the xerads increased.3. Along with succession process, the a–diversity significally decreased, in which the indices of species richness, diversity and evenness decreased by 27%, 62%, and 60.7% respectively compared with the light degradation. Theβ-diversity index showed that the similarity of community structure between the moderate and the heavy degradatted community was higher than others, and the similarity of community structure between light degradated community and others was lower. Along with the degree of degradation, the degradated community showed a regressive succession and it was Leymus+forbs, Leymus+Carex duriuscula, Carex duriuscula.4. In different degradated communities, there is an overall linear increase relationship in a–diversity -productivity pattern. Along with succession process, the significant difference of a–diversity index- productivity pattern changed, but the significant difference of species richness index-productivity pattern reached 1% significance levels in different degradated communities. 5. With the degree of degradation, both the aboveground biomass and underground biomass descreased.The underground biomass was 10.19, 19.53 and 23.54 times higher than the aboveground biomass in different degradated communities.It showed that the aboveground part degradated more seriously than the underground part.Along with vertical aspect, the underground biomass showed that most of it was in top-soil and descreased quickly along with depth.6. In the same depth soil, the soil organic matter and water content decreased gradually with the degree of degradation while the pH value increased gradually.Affected by grazing livestock, the total nitrogen, available nitrogen, available potassium showed"moderately degraded > lightly degraded > heavily degraded",and available potash increased.