Study On The Spatial Distribution Pattern Of Plants On The Different Degradation And Desertification Sequence In Hulunbeir Steppe

Resent years, due to the influences of environmental factors and human activities, the eco-environment of the Hulunbeier steppe was gradually worsen.The evaluation of the number distribution and the association of different species in different degrees of degraded and desertification grassland had significantly importance and value for the fast recovery of degraded grassland and desertificated grassland. Major analysis of this study was on the distribution patterns of community, the diversity of different species and the association of species and the stability in different degrees of degraded and desertification grassland. Results were as following:(1) With the increase of the degradation's degree, dominant species occupied gradually eased.The number of species began to reduce, dominant species owned more prominent position in the lightly degraded grassland and non-degraded grassland.However, with the deepening of desertification degree, the changing range of variation of species quantity was more, and the diversity indices lowered quickly.(2) Different degrees of degraded and desertificated grassland communities were all in the state of instability.Among them all, the stability of non-degraded grassland was the best, the stability of severe desertification grassland was the worst.(3) In the varying degrees of degraded grassland, the distribution patterns of forage population were aggregated distribution in the lightly degraded grassland. The gathering strength was stronger in the species of perennial grass and compositae weeds, but the strength of legumes and rosaceae was relatively weak. However, in the moderate and severe degraded grassland, random distribution of different species had emerged.In the desertificated grassland, the plant communities were constituded of dominant species, and the most common pattern of distribution was aggregated distribution.(4) In the lightly degraded grassland, the amount of species of negative connection was more than that of positive connection.The species were performed more on the competition of environmental resources.The constructive species and dominant species did not show significantly interspecific association in the moderate degraded grassland. In the severe degraded grassland, the association of dominant species was more significant, but the association of accompanying species was weaker.Under the sequence of desertification, the replacing rate of species in the grassland varied quickly, moreover, the quantity of species decreased rapidly, drought-tolerant species existed independently, and the strength of interspecific association of these species were stronger than other accompanying species.