不同放牧制度对土壤种子库的影响——以青藏高原东缘高寒草甸为例

以青藏高原玛曲地区高寒草甸为研究对象,通过对暖季牧场与冷季牧场不同放牧强度的比较分析,探讨了可萌发土壤种子库的密度、垂直分布规律及其与地上植被的关系。结果表明,1)暖季牧场土壤种子库中,轻度放牧有12种,种子密度为2 307.66粒·m~(-2),重度放牧有6种,种子密度为1 065.08粒·m~(-2),禁牧有5种,种子密度为828.38粒·m~(-2),轻度放牧的物种丰富度及密度都显著大于重度放牧草地(P0.05);冷季牧场轻度放牧有12种,种子密度为3 786.88粒·m~(-2),重度有8种,种子密度为5 621.15粒·m~(-2),禁牧有5种,种子密度为532.53粒·m~(-2),轻度放牧种子密度小于重度放牧。2)无论是暖季牧场还是冷季牧场轻度放牧土壤种子库的多样性指数、均匀度指数、优势度指数和丰富度指数均大于重度放牧,土壤种子库与地上植被的相似性在不同的放牧强度下都小于0.3,其中不放牧时的相似性最小,轻度放牧时的相似性最高。而暖季牧场和冷季牧场的轻度放牧和重度放牧两种放牧强度之间的相似性系数都最大,分别为0.63和0.67。3)土壤种子库在不同处理间随着土层的加深数量都呈现迅速减少的趋势,大部分集中在0-5cm。

Effect of grazing systems on soil seedbank:A case study of an alpine meadow in the eastern Qinghai-Tibet Plateau

In order to understand the response of soil seed banks to different grazing regimes,we investigated the seed density and vertical distribution of soil seed banks,and the relationship between soil seed banks and the aboveground vegetation change in the warm-and cold-season pasture of an alpine meadow in the Maqu area of the Qinghai-Tibet plateau.The results showed the following:1)In the soil seed bank of the warm-season pasture,there were 12 species subjected to light grazing,with seed density 2 307.66 seed?m-2;there were six species subjected to severe grazing,with seed density 1 065.08 seed?m-2;there were five species subjected to restricted grazing,with seed density 828.38 seed?m-2;the species richness and density of lightly grazed spe-cies were significantly higher than those of heavily grazed species.2)In the cold-season pasture,there were 1 2 species subjected to light grazing,with seed density 3 786.88 seed?m-2;there were eight species subjected to severe grazing,with seed density 621.15 seed?m-2;there were five species subjected to restricted grazing, with seed density 532.53 seed?m-2.The amount of light grazing was less than that of heavy grazing.3)The Shannon-Wiener,Pielow,Simpson and Margarlef indices of the soil seed bank under light grazing were higher than those under heavy grazing conditions.Both in warm-and cold-season pastures,the similarities between the soil seed bank and aboveground vegetation under different grazing intensities were lower than 0.3.4)The seeds were mainly concentrated in the shallow soil layer (0-5 cm),and the seed density decreased rapidly with an increase in soil depth.