Ulums pumila, a typical anemochorous plant, is the single dominant species of many woodlands in the Keerqin Sandy Land, China. To understand habitat differences in the characteristics of seed deposition and seedling distribution in U. pumila, we randomly surveyed the numbers of seed and seedlings in the habitats of both understory and the wooland gaps. We also measured the abundance of seed and / or seedlings along transects of different directions starting from the woodland edges and the bases of isolated trees to illustrate differences and regulation of seed dispersal directions on the woodland edges and isolated trees. For the understory habitats, U. pumila seed densities on either shady or sunny slopes were significantly higher than both at the top of sand dunes or on the bottom of sand dunes. For the canopy gaps, seed densities on the bottom of sand dunes were greater than at the top of sand dunes. The number and distance of seed dispersal differed apparently among directions with the least amount of cumulative number of seed dispersal and the nearest dispersal distance were observed in the southwest direction (southwesterly winds are prevailing winds for the studied area) ; whereas the greatest amout of cumulative number of seed dispersal and the farthest dispersal distance were observed in the northeast direction for both woodland edges and isolated U. pumila trees. In the six sampled directions, seed dispersal patterns of both woodland edges and istolated trees can be discribed by density functions of the Weibull distribution and the Log鄄normal distribution (X 2 (琢) <0. 500). For the understory habitats, the seedling densities on the shady slope were higher than on the

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Rhizome bud development was studied in two populations of Phragmites australis: one from an area with typical meadow soil and another from an area characterized by saline鄄alkali soil. Soil samples were taken from each site and the number of rhizome buds in different age classes was recorded. The aim of this research was to determine the age structure, output regularity and vegetative propagation characteristics of P. australis rhizome buds in heterogeneous habitats. Results showed that P. australis rhizome bud banks are composed of six age classes, the age structure was expansive from June to October in the meadow soil habitat. In contrast, in the saline鄄alkali soil habitat it declined from June to July, was stable in August and was expansive from September to October. The number of rhizome bud at the 1st to 4th is generally higher in meadow soil habitat than that in saline鄄alkali soil habitat, while the number of rhizome bud at the 5th to 6th is generally higher in saline鄄alkali soil habitat than that in meadow soil habitat. There was a significant linear correlation (P < 0. 05) between the number of rhizome buds and month. As the age class increased, the proportion of dormant buds declined, and the proportion of germinating buds rose. There was also a significant linear correlation (P < 0.01) between the percentage of dormant buds and germinating buds in the growing periods and age classes. The rate of bud dormancy for each age class was http: / / www.ecologica.cn relatively stable, the output rate of rhizome dormancy buds in the meadow soil habitats was about 11% per year,and the output rate of rhizome dormancy buds in salinealkali soil habitats was about 7% per year. To conclude, there were significant differences in the age structure and age spectrum of P. australis population rhizome buds in heterogeneous habitats; however, they showed similar seasonal patterns ensuring new rhizome bud formation for vegetative propagation.

收稿日期：２０１３• ０６• ０８； 网络出版日期：２０１４• ０５• １６ * 通讯作者 Ｃｏｒｒｅｓｐｏｎｄｉｎｇ ａｕｔｈｏｒ．Ｅ•ｍａｉｌ： ｙａｎｇｙｆ＠ ｎｅｎｕ．ｅｄｕ．ｃｎ ＤＯＩ： １０．５８４６ ／ ｓｔｘｂ２０１３０６０８１４５９ 李程程， 李海燕， 杨允菲．松嫩平原野古草种群构件结构动态．生态学报，２０１５，３５(８) ：２６０９• ２６１５． Ｌｉ Ｃ Ｃ， Ｌｉ Ｈ Ｙ， Ｙａｎｇ Ｙ Ｆ．Ｄｙｎａｍｉｃｓ ｏｆ ｍｏｄｕｌｅ ｓｔｒｕｃｔｕｒｅｓ ｏｎ Ａｒｕｎｄｉｎｅｌｌａ ｈｉｒｔａ ｐｏｐｕｌａｔｉｏｎｓ ｉｎ Ｓｏｎｇｎｅｎ Ｐｌａｉｎｓ ｏｆ Ｃｈｉｎａ． Ａｃｔａ Ｅｃｏｌｏｇｉｃａ Ｓｉｎｉｃａ，２０１５，３５ (８) ：２６０９• ２６１５．