| Biodiversity is the substance foundation which people are lived on.However, with the fast developing of population and the increasing of human economical activity, eco-environment has been infinitly destroyed, continuous environment was divided into different patch communities, biodiversity was seriously intimidate. Leymus chinensis, Kalimeris integrifolia, Arundinella hirta and Hemarthria sibirica are four typical clonal plants on Leymus chinensis meadow of Songnen Plain. In this research, the botanical composition, the quantitative characteristics, life form, dominance and diversity were calculated and analyzed quantitatively for the above patch communities. Meantime corresponding the overground plants, the statistics and quantitative analysis of composition, quantitative characteristics and the diversity of bud banks were made under the ground on three different Leymus chinensis patches so that the environment fragmentation theory and biodiversity theory would be enriched and these would offer a theoretical guidance to the renovation of fragmented environment and the rebuilding of ecological system. The results are showed as follows:(1) With the patches from big to small, botanical composition of all communities changed differently. The number of L. chinensis plants changed univocally with the max 36 appearde on middle patch. The number of K. integrifolia and H. sibirica were decreasing with the patch from big to small, whose max 41 and 31 all appeared on big patch, while the max of A. hirta which is 30 also appeared on big patch, but its species on middle and small patch almost the same, which are 19 and 20 respectively. At the same time, with the patch from big to small, station of every dominant plant in the communities own different degree discrepancy, single dominance has disappeared, while presenting co-dominance of multi-plants contemporarily.(2) On big patch from middle to around, botanical composition of all communities all changed univocally. In L. chinensis, K. integrifolia and A. hirta communities, the max of species 24, 31 and 22 all appeared on the second around of big patch, while in H. sibirica community, the max 23 appeared on the first around. Besides, on middle and small patch of L. chinensis, botanical composition also changed similarly from middle to around, viz the max of species 28 and 19 appeared on the second around of middle patch and the first around of small patch respectively. Indicating: intermediate disturbance can create ecesis and development for more plants which greatly supported the Intermediate Disturbance Hypothesis.(3) With the patches from big to small, the ratio of plant fundational group in sense of life form in every community changed regularly. In L. chinensis community, the ratio of Chamaephyte and Hemicryptophytes decreased gradually, of the Hemicrypto-geophyte and Geophyte increased little by little, while the variety trend of Therophyte was first decrease and then increase. In K. integrifolia community, the ratio of Chamaephyte, Hemicrypto-geophyte and Geophyte also first decreased and then increased, while of Hemicryptophytes and Therophyte first increased and then decreased. In A. hirta community, with the patches from big to small, the variety trend of Chamaephyte and Hemicryptophytes was first decrease and then increase, while of Hemicrypto-geophyte, Geophyte and Therophyte was first increase and then decrease. To the contrary of A. hirta, in H. sibirica community, with the patches from big to small, the ratio of Chamaephyte and Hemicryptophytes first increased and then decreased, while the ratio of Hemicrypto-geophyte, Geophyte and Therophyte first decreased and then increased.(4) On big patch from middle to around, the functional group composition in sense of life form in every community changed differently. Though different life form fluctuated in specific circle, overall the variety trend of Hemicryptophytes was decline from middle to around on four patches. The ratio of Hemicrypto-geophyte descend on L. chinensis and K. integrifolia patch, while ascend on A. hirta and H. sibirica patch. On the contrary, the ratio of Geophyte ascended on L. chinensis and K. integrifolia patch, descend on A. hirta and H. sibirica patch. The ratio of Therophyte from middle to around decreased gradually on L. chinensis and H. sibirica patch, while increased little by little on K. integrifolia and A. hirta patch. Chamaephyte plant only appeared occasionally in specific circle. Futhermore the regular of L. chinensis on middle and small patch was rather different from big patch.(5) With the patches from big to small, species richness (Margaff index), diversity (Shannon-Weiner index) and evenness (Pielou index) all changed univocally, with the biggest appeared on middle patch simultaneously. Futhermore on big patch of all communities and the middle and small patch of L. chinensis, from middle to around, species diversity also changed regularly. On big patch of L. chinensis and H. sibirica, the biggest of diversity and evenness all appeared on the third circle, while the biggest of richness appeared on the second circle. On big patch of K. integrifolia and A. hirta, the first and the second circle owned the biggest of diversity, richness and evenness simultaneously. On middle patch of L. chinensis, the biggest of three indexs all appeared on the third circle. On small patch of L. chinensis, the second circle owned the biggest of diversity and evenness, while the biggest of richness appeared on the first circle.(6) The bud banks of L. chinensis consist of the tillering node buds and the rhizome buds. The bud banks of L. chinensis patch constituted majority in the tillering node buds in July, September and October. In August, the bud banks constituted majority in the tillering node buds on the first and the second circle, whereas on patch middle and the third circle, the ratio of tillering node buds and rhizome buds were comparative. Meantime with the patches from middle to around, the ratio of tillering node buds of all months first increased and then decreased, with the max appeared on the second circle. The rhizome buds of L. chinensis constituted majority in the node buds of rhizomes in July, August and September accept in October, with the max appeared on the first, second or the third circle respectively from patch middle to around in every month. Whereas the ratio of node buds of rhizomes and the topmost buds of rhizomes were comparative in October.(7) Considering by seasonal dynamics, diversity of bud banks of L. chinensis pacth changed regularly. Diversity and evenness first decreased and then increased, while richness first increased and then decreased, with the lowest in August and October individually. Analyzing bud banks of every month concretely, from patch middle to around, the seasonal change of richness was inconspicuous. Diversity and evenness first decreased and then increased in July and August, in September the change of diversity and evenness was first increasing then decreasing and then increasing again. In October the change of these two indexs was opposite to September rightly, with the lowest appeared on the first or the second circle individually, which greatly confirmed the overground results.
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