三峡地区柏木林种子雨和种子库的研究

柏木种子雨在8月底开始降落,10月达到顶峰,翌年5月结束,历经9个月左右。整个过程呈单峰曲线,10~11月的种子雨量占全年的67.5%。种子雨时间变化格局差异极显著,而水平空间分布格局没有显著差异。种子雨中柏木种子的年均密度为5 982.2粒.m-2。63.4%的柏木种子直径大于2.5 mm,构成了柏木种子雨的主体。由于这一级别柏木种子的萌发能力较强,因此三峡地区柏木林的更新能力强。柏木林中非柏木种子的种子雨每年主要发生在1月和5月,形成2个高峰,年均种子雨密度为1 842.8粒.m-2。土壤种子库中柏木种子的平均密度为608.8粒.m-2。柏木种子在土壤种子库中垂直分布格局差异极显著。0~2 cm土壤层所分布的柏木种子占种子库中柏木种子的80.49%。其它土壤层次所含有的种子比例很低,且萌发能力较低,因此,柏木林的更新主要依赖于表层土壤种子库的种子。柏木种子在种子库中的水平分布格局虽然随坡位的不同而有所变化,但是差异不显著,表明整个柏木林的更新能力在水平格局上无显著差异。

Seed rain and seed banks of Cupressus funebris forest in the Three Gorges region

Study on the seed rain and seed banks of Cupressus funebris forest in Three Gorges indicated:(1) Seed rain of Cupressus funebris,beginning from the end of August,reaching peak in October and ending in next May,covered nearly 9 months and showed a single-peak pattern.Seed rain rainfall in October and November accounted for 67.5% of the annuall seed rain.There were great significant differences in seed rain as the time change,but no difference in level space change.The average seed rain density of Cupressus funebris in a year was 5 982.2 seeds·m-2.63.4% of Cupressus funebris seeds in the seed rain were bigger than 2.5 mm in diameter and dominate the seed rain.Cupressus funebris forests in Three Gorges renewal well because this kind of big seeds have good germination ability.Seed rain of other species reached peaks twice in January and May respectively.Their average seed rain density was 1 842.8 seeds·m-2.(2) The average seed density of Cupressus funebris in seed banks in the soil was 608.8 seeds·m-2.There were great significant differences in vertical distribution for Cupressus funebris seeds.Most of Cupressus funebris seeds distributed on the 1～2 cm surface of soil seed bank,accounting for 80.49%.Other layer soil had less proportion of seeds,also low germination ability,so the renewal of Cupressus funebris forests relied on surface soil seed bank.Although the level distribution of Cupressus funebris seeds of seed banks varied from different slopes,there was not significant difference,which indicated the renewal ability of whole Cupressus funebris forests had not significant difference in level distribution.