高寒草甸植物多样性与营养的关系

以青藏高原典型高寒草甸为例，研究了施肥对植物群落生产力和物种多样性的影响。本文报道了这个实验的初步结果，就施肥对草地生产力和物种多样性的影响进行了分析，结果如下：(1)施肥提高生产力．施肥第1年和第2年，植物群落生产力显著增加；施肥第3年，生产力是施肥前的2倍多；(2)施肥使物种多样性降低，施肥第1年物种丰富度变化不显著；第2年施肥梯度上物种多样性差异显著；第3年最高施肥水平物种丰富度为对照的1／4；(3)施肥使草地质量提高．因为草地质量和生物量以及优良牧草比例直接相关，施肥使地上生物量明显增加，毒杂草比例降低，禾草比例增加，所以草地质量提高，说明施肥对改良草地有显著作用；(4)群落结构发生了明显的变化，施肥水平高时群落结构接近于生态位优先占领假说．随着施肥水平增加，各个物种重要值的最大值从0．107，0．183，0．585一直增加到0．775．不施肥时有10个物种地上生物量超过最大单种生物量的一半，最高施肥时只有一个。(5)对6个优势种进行的分析表明，只有垂穗鹅观草的生物量随着施肥水平的增加持续增加，其它物种都是减少的趋势，说明垂穗鹅观草的急剧增加可能是导致物种丰富度降低的原因。

The relation of nutrients and plant species diversity in an alpine meadow

A two-year (2000, 2001) fertilizing experiment in an alpine meadow of east Qinghai-Tibet Plateau showed that the plant species diversity decreased significantly while the aboveground net primary production increased significantly along the 4 levels of fertilization created using (NH4)2HPO4. The plant community structure changed- the number of species that weighed more than half of the greatest one changed from 10 to 1 along the fertilization levels, with the biggest relative importance varing from 0.107,0.183, 0.585 to 0.775. We grouped the species into 5 groups: graminoids, sedges, legumes, forbs, poison forbs, and found that graminoids increased significantly with fertilization while other groups all decreased.At the highest fertilization level, graminoids increased from 33% to more than 94% but other groups all decreased to less than 1%, except the forbs group, which was 3%. Since the grassland was grazed in winter and early spring, which removed the litter, the litter did not affect the experimental results. So fertilization may affect biodiversity without increasing litter.