高寒干旱退化草地披针叶黄华群落土壤种子库

以石羊河上游高寒干旱退化草地披针叶黄华（Thermopsis lanceolate）群落为研究对象，采取现场植物测定与土壤采样分析相结合的方法，对祁连山北坡中山区的皇城盆地实验地土壤种子库的基本特征以及与地上植被的关系进行了对比研究。结果表明：植被物种共有14种，隶属于7个科，物种在植被群落中优势度的变化差异明显。在披针叶黄华盖度梯度下，可食草优势度之和始终不小于不食草，其它不食草都未稳定存在。土壤种子库中共检测出草本植物16种，隶属于11个科。可食草种类以禾本科、菊科和豆科为主，共10种，种子库密度为5 837±4 659个·m^-2，占21.1%，不食草种类以菊科为主，共6种，密度为21 727±14 514个·m^-2，占78.9%。在不同植被覆盖度梯度下，可食草土壤种子库密度明显小于各梯度不食草密度，功能群物种呈现单峰分布格局，可食草种子的物种数为明显的下降趋势，不食草种子的物种数变化趋势与可食草的相反。可食草相似性系数呈现降低的状态，由梯度I的0.545降为梯度V的0.286；不食草的相似性系数呈现升高的趋势，由梯度I的0升为梯度V的0.667。

Soil seed bank of Thermopsis lanceolata community in degraded alpine arid grasslands

Soil seed bank is an important indicator for plants responding to changes of the land utilization and climate，also an important tool for the understanding vegetation dynamics. In this paper，taking the Thermopsis lanceolata community in the upstream of Shiyang River，Gansu Province，China as a research object and adopting soil seed bank analysis combined with vegetation restoration determination，the soil seed banks and vegetation functional group structure，as well as their relationship are analyzed. Results show that there are fourteen vegetation species which belong to seven family. A majority of species have low dominance and the variation of dominance in vegetation community is evident. The sum of dominance of edible grass is not less than that of non-edible grass in different vegetation gradients and other non-edible grass is not able to exist stable. There are sixteen kinds of herbaceous plants in the soil seed bank of the Thermopsis lanceolata community which belong to eleven families such as composite，gramineous，leguminous and other families. The edible grass mainly belongs to composite，gramineous and leguminous family with ten total families. The density of the soil bank is 5 837±4 659 seeds·m^-2 as a percentage of 21.1%. Unedible grass mainly belongs to gramineous family in total of six kinds whose density is 21 727±14 514 seeds·m^-2 as a percentage of 78.9%. The functional group species of seeds bank presents uni-modal distribution with the variation of vegetation gradients. The number of species of edible grass seed appears descending tendency，on the contrary，the number of species of non-edible grass seed shows ascending tendency. The density of edible seed is apparently less than that of non-edible seed in different gradients. The similarity coefficient between edible grass shows reducing tendency which decreases from 0.545 in gradient I to 0.286 in gradient V. Meanwhile the similarity coefficient between inedible grass shows increasing tendency which increases from 0 in gradient I to 0.667 in gradient V. Because of the long-term and stable existing of unedible grass in the research area，the position of excellent gramineous grass is replaced，some species of edible grass are to be eliminated and the stability，productivity and nutrient dynamics of community ecosystem will be influenced. It is impossible to recovery excellent grass in a short time if the excellent gramineous grass to be totally destroyed.