石羊河上游干旱草原阴山扁蓿豆群落土壤种子库

Soil Seed Bank of Melilotoides Ruthenicus var.Inschanicus Community on the Arid Grassland in the Upstream Area of Shiyang River

土壤种子库是地上植被补充更新的源泉，土壤种子库的研究已成为植物种群生态学研究中相当活跃的领域。在石羊河上游干旱草原选择阴山扁蓿豆草地群落，研究了草地土壤种子库的物种组成、密度、多样性特征以及与地上植被的关系。结果表明，阴山扁蓿豆草地群落土壤种子库共有20个物种，分属12科。随阴山扁蓿豆分盖度减小，土壤种子库密度和种类在水平方向上增加，种子库密度垂直分布呈现O-5cm〉10—15cm〉5-10cm土层，物种数量随深度而减少；在阴山扁蓿豆分盖度〉60％的草地群落未发现其种子库的存在。土壤种子库的Margalef丰富度指数、Shannon--Wiener多样性指数和Pielow均匀度指数随阴山扁蓿豆盖度减小呈上升趋势，生态优势度由0．46下降至0．24；各草地群落土壤种子库与地上植被的相似性系数在0．29～0．58之间。

Soil seed bank is the renewal source of standing vegetation and researches on it become quite active in the area of plant population ecology. This paper studies the species composltion, density, diversity, and the relationship between seed and standing vegetation about soil seed bank of Melilotoides ruthenicus vat. in- schanicus community on the arid grassland in the upstream area of Shiyang River. Results showed that a total of 20 plant species belonging to 12 families were found in the soil seed bank. The density and specie of soil seed bank increased with the decrease in Melilotoides ruthenicus var. inschanicus＇ s coverage in the horizontal distribution. The vertical distribution of density changed in the order of 0 5 cm 〉 10 15 cm 〉 5--10 cm soil depth, but the species decreased with the increased depth. There was no seed exist in the grassland com- munity where the Melilotoides ruthenicus var. inschanicus＇s coverage is more than 60 %. With the decrease in Melilotoides ruthenicus var. inschanicus＇s coverage, the Margalef richness index, Shannon Wiener diversity index, and Pielow evenness index of the soil seed bank showed a rising trend, but ecological dominance showed a descending trend, decreasing from 0.46 to 0.24. The similarity coefficient of the soil seed bank and standing vegetation varied from 0.29 to 0.58.