Abstract:Growth status of reproductive individuals of Betula alnoides were investigated in an ecological ectone of two types of soils originated from limestone (site L) and granite (site G), respectively, at Jingxi County, Guangxi, and the relationships between reproductive modules and their allocation patterns in crown layer were discussed. The results showed that the diameter at breast height (DBH) in site L were remarkably smaller than that in site G, when plants started flowering and fruit setting. The number of flower buds, total number of inflorescences and ratio of male inflorescences were not significantly correlated with DBH and plant height (P>0.05). The number of male inflorescences increased with increment of total number of inflorescences by logarithm curve, and the trees trended to develop male inflorescences under lower reproductive investment, while mainly develop female inflorescences under larger reproductive investment. There were remarkable differences in characteristics of reproductive module between both sites, the number of male buds and number of inflorescences developed from each male bud at site L was significantly lower than that in site G (P<0.05), the ratio of the plants with male inflorescences less than female ones was much higher than that at site G, and the ratio of reproductive branches was also significantly lower than that at site G (P<0.05). Although the number of male inflorescences, female inflorescences, total inflorescences and ratio of male inflorescences at site L were smaller than those at site G, and ratio of female inflorescences at site L was larger than that at site G, there were no significant difference between them (P>0.05) due to high level of variation among individuals at each site. The majority of inflorescences were on upper and middle layers of crown, and above 90% of reproductive branches occupied on the surface of crown at both sites.
