割草干扰对典型草原土壤种子库种子数量与组成的影响Ⅱ具有生命力的种子数量及其垂直分布

The Influence of Mowing on the Seed Amount and Composition in Soil Seed Bank of Typical Steppe Ⅱ The Amount of Seed Having Vitality and Its Vertical Distribution

对具有生命力的种子数量及其垂直分布进行了研究，结果表明：刈割对土壤种子库中的种子数量有一定的影响，其中对照具有生命力的种子数量，１９９７ 年和１９９８ 年分别为２４１５ 和２２５３粒／０．１２ｍ ３，割一年休一年的处理分别为对照的９３．１３％ 和７８．３８％ ，一年割一次的处理分别为对照的８３．２３％ 和５８．５０％ ．从以上数值可见，同一处理内部种子的数量亦有下降．不同处理种子数量的垂直分布有共同趋势，有７５．４８％ ～８７．７８％ 分布在０～４ ｃｍ 土层内，有１４．９２％～１８．４２％ 分布在４～８ ｃｍ 土层内，有０．００％ ～６．１０％ 分布在８～１２ ｃｍ 土层内．连续刈割４５年和４６ 年的草地，种子数量分别为对照的２２．５７％ 和３５．９８％ ．单位面积上具有生命力的种子数量远低于降落下的种子数量，这是由于刈割时尚有大量种子未成熟和其它因素引起的．

This paper deals with the amount of seed having vitality and its vertical distribution,the result is that mowing has some influence on the seed amount of soil seed bank.In 1997 and 1998,in the contrast area,the amount of seed having vitality is 2 415 grain/0.12m 3 and 2 253 grain/0.12m 3,in the area of mowing a year and stopped next year,it is 93.13% and 78.38% of the contrast area,in the area of mowing once a year,it is 83.23% and 58.50%.From above data,it is certain that the seed amount in the same treatment decrease from 1997 to 1998.The vertical distribution of seed amount of different treatment has same trendence.That is 75.48~87.78% seed amount distributes in the soil horizon of 0~4 cm,14.92%~18.42% seed amount distributes in the soil horizon of 4~8 cm,0~6.10% seed amount distributes in the soil horizon of 8~12 cm.The continous long term mowing has great influence on the amount of seed having vitality in soil.To the grassland mowing continously 45 years and 46 years,the seed amount is 22.57% and 35.98% of the contrast area.In addition,the grazing on the medium degeneration grassland is benefit to the increase of seed amount of soil seed bank.The amount of seed having vitality in unit area is lower than the amount of falling seed,it is because a lot of seed hasn′t matured when mowing and other factors.