海南甘什岭白藤土壤种子库特征及幼苗更新能力

为探究海南甘什岭地区白藤土壤种子库的储备状况及幼苗更新能力,按公里网格设置样地30块(20 m×20 m),于各样地内沿对角线设置7个1 m×1 m小样方,对白藤种子和天然更新幼苗(≤40 cm)的分布状况进行调查,比较不同样地环境条件下种子储备和幼苗更新能力的大小,并采用随机森林方法,对影响种子和幼苗数量的立地环境因子进行分析。结果表明:甘什岭地区白藤土壤种子分布不均匀,土壤种子库种子主要集中在枯落物层;白藤更新幼苗中Ⅰ级(0~9 cm)幼苗占比最高,达61.63%,是更新幼苗的主体,但Ⅰ级幼苗、Ⅱ级幼苗间的转化率较低(39.18%),是制约白藤幼苗天然更新关键环节;立地环境因子中,林冠高度、林分郁闭度、凋落物厚度和林分密度是影响种子分布和幼苗数量的主要环境因子;总之,在自然状态下,白藤天然更新能力不足,应采用人工干预和调控措施促进更新;在白藤更新抚育过程中,应通过林内疏枝除冠、间苗等措施,调节立地环境因子,改善种子的着地环境,提高白藤幼苗转化率,达到促进白藤自然更新的目的。

Seed bank and seedling regeneration of Calamus tetradactylus in Ganzhaling,Hainan Province.

To reveal soil seed bank size and seedling regeneration capacity of Calamus tetradactylus in Ganzhaling of Hainan Province,we investigated seed distribution and natural regeneration seedlings of C.tetradactylus(≤40 cm)by setting up 30 grid plots(20 m×20 m)and seven 1 m×1 m quadrats in each plot along the diagonal.Random Forest method was used to analyze the effects of environmental factors on the abundance of seeds and seedlings.The results showed that seed distribution in soils was not uniform.Seeds in the soil seed bank were mainly concentrated in the litter layer.ClassⅠ(0-9 cm)of C.tetradactylus seedlings was the main component of the regenerating seedlings,with a contribution of 61.63%.The conversion rate of classⅠto classⅡseedlings was low(39.18%),which was a key factor limiting C.tetradactylus seedling’s natural regeneration.Among all the examined environmental factors,canopy height,canopy density,litter thickness,and stand density were the main ones affecting seed distribution and seedling quantity.In summary,natural regeneration capacity of C.tetradactylus was low under natural conditions,and thus manual intervention and control measures should be adopted to promote the regeneration.To promote the successful natural regeneration of C.tetradactylus,it is necessary to consider site-specific environmental factors,such as pruning tree crown and thinning seedlings,which would improve the bedding environment of seeds and the conversion rate of C.tetradactylus seedlings.