扁秆藨草种群内禀增长率的研究

采用“定期起苗”法，从６ 月１０ 日—８ 月３０ 日止，分别统计从越冬块茎上萌发出的再生苗及其后代蔓生枝系再生苗的数量，从而得出扁秆藨草再生苗各旬株数增长的指数方程；又用“定株观察”法，对１２ 株越冬块茎上的再生苗及其全部后代植株开花、结实数量进行统计，探讨扁秆藨草有性繁殖的能力，然后进行综合计算，求得扁秆藨草种群的内禀增长率ｒ＝７．２４，阐明了扁秆藨草很高的内禀增长率是其种群过度生长的根本原因；通过对其过度生长关键时刻的判断，选择灭草的关键期，有效地灭杀此种恶性杂草

A STUDY ON THE INTRINSIC GROWTH RATE OF SCIRPUS PLANICULMIS POPULATIONS

Field experiments were conducted, using "Fixed Interval technique for sampling seedlings", to determine the rules of asexual reproduction of Scirpus planiculmis population. Counts were recorded for the number of re emerged plants on the overwintering stem tubers and of the re emerged seedlings from the trailing branch system, from June 10 to August 30 at a 10 day interval. In this way, the exponential equation was established for describing the increase of the re emerged plants of Scirpus planiculmis per 10 day period. The technique of "observation on specific individual plants" was also used to determine the rule of sexual reproduction of the plant, i. e. to investigate the ability of sexual reproduction by counting the number of seed sets from the re emergeed seedlings on 12 overwintering stem tubers and all their progenies (2640 re emerged plants). Then, pooled caloulation was made to obtain the intrinsic growth rate of the Scirpus planiculmis population as r=7 24. Thus, it is indicated that the ultimate reason for the over grown of the species population is the high intrinsic growth rate. On the other hand, since the critical period of both the weed and rice was already estimated, it could be used (1) to determine the critical time for weeding and (2) to control the weed effectively, and (3) to provide sound basis for high grain yield of rice.