A Study On The Pattern Of Plant Community Characters Change During The Succession In Abandoned Croplands Of Sub-meadow

As a topical focus in ecology, succession has drawn much attention of ecologist. During the researching on community succession ecologists laid out many theories to explain the succession process, but no one perfect theory that could explain all processes has been found. Here, we established experiment plots in the sub-alpine meadow of the Southern Gansu province, China to explore the plant community character dynamics during the succession. There were 5 year,9 year,14year,19year, 30year abandoned croplands and climax plant communities. According to the succession gradient, we surveyed the changing characters of plant community to analysis the change model of the succession process, and to explore the reason which lead to those shifting characters. We hope that we could provide a theoretical basis to sub-alpine meadow restoration and protection.The results showed:1) During the succession, the plant community changed from simple to complex. In early stage forbs are the mainly group, then grasses and legumes take a large proportion in middle and upper stages. A significant increase in the proportion of clonal plants were shown during the succession and reached the peak in the climax plant community.2) The biodiversity showed a unimodal curve, indicating the number of species increased first and decreased later along the succession gradient. In the early stage of succession, productivity enhanced rapidly and reached the highest with the mean of 183.77g/m2 in the 19years-plots, and it then kept in a stable level. In the process of succession, biodiversity was positively related to productivity, although such a relationship disappeared in the climax community;3) As the succession proceeded, the community pattern was gradually changed into a species log-normal distribution from the early niche-preemption;4) In the early stage of succession, N:P ratio enhanced rapidly and reached highest in the 21 years-plots. After that it kept in a stable level. During the succession, N:P ratio always under 14. Based on the fertilization experiment on the climax plant community we thought that plants growing in climax might be limited by N and P.