封育对“黑土滩”垂穗披碱草栽培草地群落结构和特征的影响

在三江源区对3龄和7龄垂穗披碱草Elymus nutans栽培草地进行围栏禁牧封育，封育期为3年，在每年8月中旬进行群落调查，以冷季放牧利用的垂穗披碱草栽培草地作为对照，分析围栏内外样地的群落特征以及逐年草地群落演替过程。结果表明：1）物种多样性指数为放牧>封育，且随草龄的增长，群落多样性指数有缓慢增加趋势；2）放牧、封育2种处理样地的总盖度和优势种的盖度及高度的变化基本趋于一致, 即随建植年龄逐步变小，与放牧相比，封育草地的各值显得较低一些；3）地上植物量变化随着演替年限的增加，呈现持续下降趋势。

Impact of enclosure on community characters of sowed Elymus nutans grassland in black soil Land

The third-year and seventh-year sowed Elymus nutans grassland in black soil land in the Three-River region were fenced for 3 years,and the community was surveyed during the middle August in each year.The same grassland outside the fence which was grazed in winter was used as the control.The results showed:1)the species diversity index of fenced grassland was higher than the grazing grassland,and with the increase of sowed age,the diversity index gradually increased;2)the change of total coverage,coverage an...