黄土高原草地封育与放牧条件下土壤种子库特征

对半干旱区黄土高原草地在封育和放牧条件下土壤种子库种子密度、种子库组成、种子库物种多样性及均匀性进行了比较研究,并得出主要结论：1）封育提高土壤种子库的植物种类和密度，使优良禾草和多年生植物增加。2）种子库的垂直分布规律是随着土层的加深，种子在数量上递减的速度较快。3）坡向和坡位对土壤种子库有较大影响，种子库密度变化趋势是阴坡>阳坡；坡下部>坡中部>坡上部。4）从丰富度、Shannon Wiener多样性和均匀性3个方面比较分析封育和放牧样地土壤种子库多样性,得出封育样地Margalef丰富度指数和Shannon Wiener指数都高于放牧地，Pielou均匀性指数低于放牧地。

Characteristics of soil seed banks in grassland under fencing and grazing in Loess Plateau

Characteristics of soil seed bank,such as species composition,density and diversity in semiarid grassland on loess plateau under fencing and grazing conditions were investigated.The main inclusions were: 1) fencing greatly increased plant species and density of soil seed banks,palatable grass and perennial plant increased;2) with the increasing soil depth,seeds decreased quickly;3)Slope direction and position had a tremendous effect on soil seed banks.Density followed the order of southern slope > northern slope;slope bottom >medium > top;4) The results of the study indicated that the Margalef and the Shannon-Wiener diversity indexes of soil seed banks in fenced area were higher than enclosed grassland,while Pielou evenness indexes were higher in the latter.