Reproductive Ecology Of Four Grasses In Xilingole Typical Steppe

The Multiplication and Recruitment characteristics of four grasses were studied in Xilingole typical steppe of Inner Mongolia between 1999 and 2000. They are Leymus chinensis (Trin.) Tzvel., Stipa grandis P. Smirn., Stipa korylovii Roshev., and Agropyron cristatum(L.)Gaertn. which are dominant species in the typical steppe. Two sites were selected for this study, one is located in Dongwu Banner and another in Taipusi Banner. Quantity characteristics of seed reproduction and vegetative reproduction were measured on both population levels and individual levels. Contributions to the population development and recruitment were analyzed. The main results are as follows:The populations potential seed production of L. chinensis, A. cristatum, S.glandis, and S. krylovii are 516.06±22.53kg/hm2, 2134.37±45.05kg/hm2, 301.78±32.73kg/hm2, and 435.96±24.63kg/hm2 respectively, while the present seed production are 61.28±18.56kg/hm2, 276.68±23.44kg/hm2, 199.18±21.35kg/hm2 and 257.22±17.94kg/hm2 respectively.The results of the vegetative production investigations showed that propagule are mainly produced after fruiting. The quantities of the four populations propagule are 548±28/m2, 102±12/m2, 457±34/m2, and 449±34/m2 respectively.The study on the characteristics of the seed production and vegetative production of the four grass populations indicated that the development of the population L. chinensis is mainly by vegetative production, while the other populations (A. cristatum, S. grandis, S. krylovii) are mainly by seed production.Biomass allocation and energy allocation of the four populations were analyzed using biomass and calories methods. The results showed that the proportion of biomass allocation on the seed production of L. chinensis is only 6.1%, S. krylovii with 18.7% biomass allocation, S. grandis and A. cristatum with 15.4% and 13.3%. The energy allocation proportions of the above populations are 6.6%, 20.8%, 17.5%, and 15.2% respectively. The biomass and energy allocation to the head module of L. chinensis are obviously high contrast with the three other grasses. Small investment to the seed reproductive organs is the key reason lead to low seed production of L. chinensis. The productive adaptation strategies of the four populations were analyzed. L. chensis mainly adopted K-strategy which win by quality under stabilizing conditions while opportunity of seed production would be increased under disturbed conditions. S. grandis, S. korylovii and A. cristatum Mainly adopted r-strategy by producing large amount of seeds which win by quantity.