黄土高原典型草原区草地土壤种子库的动态分析

Dynamic Analysis of the Soil Seed Bank for Grassland in a Typical Prairie on the Loess Plateau

采用野外调查取样和室内试验相结合的方法,研究了黄土高原典型草原区草地土壤种子库的物种组成、密度、时空格局和物种多样性等特征。结果表明,(1)土壤种子库中共统计到37个物种,隶属于16科,其中禾本科、菊科、唇形科、豆科和毛茛科的植物占优势。(2)从返青期到枯黄期,种子库中豆科、禾本科、堇菜科所占比例呈下降趋势,唇形科和菊科所占比例明显提高,种子库的密度也显著提高。(3)种子库中种子数量在垂直分布上呈现出由表层土壤向深层逐层减少的变化规律;在水平分布上的变化规律为:封禁>放牧;阴坡>阳坡;下坡>中坡>上坡。(4)封禁地土壤种子库中的Margalef丰富度和Shannon—Wienner指数都高于放牧地,Pielou均匀性指数低于放牧地。从返青期到枯黄期,封禁地和放牧地土壤种子库的Margalef丰富度、Shannon—Wienner指数、Pielou均匀性指数都呈下降趋势。

Field survey and laboratory experiment were conducted to study the characteristics of soil seed bank for the grassland in a typical prairie on the Loess Plateau, such as species composition, density, spatial and temporal pattern distribution, and diversity. Results showed that there were 37 species in the seed bank, which belongs to 11 families. For the species of seed bank, Gramineae, Compositea, Labiatae, Leguminosac, and Panunculaceae were dominant. From green up stage to withering stage, the percentage of Legurninosae, Gramineae, and Violaceae decreased and however, the percentage of Cornpositea and Labiatae increased greatly. Density of soil seed bank increased significantly. For the vertical distribution, the number of seeds took on a decreasing trend with soil depth increasing. In terms of the level distribution of soil seed bank, landforms were in the descendant order of fenced grassland and grazed grassland; lunar slope and solar slope; and top slope, middle slope, and bottom slope. Results from the study indicated that the Margalef and the Shannon--Wiener diversity indexes of soil seed bank were higher in the enclosed grassland, and Pielou evenness index was higher in the grazed grassland. They all decreased from green up stage to withering stage.