水分条件对滇榄仁种子萌发及幼苗早期生长的影响

摘要

Terminalia franchetii community is one of the important and rare natural vegetations occurring in Yuanmou basin where the ecotope is typically fragile in the dry-hot valley of Jinsha River in southwestern China.In order to provide theoretical basis for artificially promoting vegetation restoration in this region,effects of water supply on seed germination and early seedling growth of T.franchetii was studied initially to understand the natural regeneration barriers of T.franchetii.The seed germination and early seedling growth characteristics of T.franchetii were observed under different levels of water supply by indoor control method.The seed germination percentage was 55％ to 90％ under the soil water content (SWC) of 15％ to 40％,and the SWC of 15％ to 25％ was suitable for the seed germination,but the seed germination was restrained seriously even completely unable to germinate when the SWC was lower than 10％ or higher than 50％00.The results showed that water supply affected significantly the early seedling growth.With the increment of water supply,the seedling height,basal diameter,branch number,main root length,leaf number in main stem,maximum leaf length,total leaf area,specific leaf area and dry mass increased,but root to shoot ratio decreased.The results of this research indicated that the water supply was the key obstruction factor for the natural regeneration of T.franchetii population,which suggested that the conservation of community species diversity and improvement of degraded soil in the dry-hot valley of Jinsha River should be enhanced to create the water retention environment for the survival of T.franchetii in seedling stage to implement self-renewing.%元谋盆地是中国西南金沙江干热河谷生态脆弱区的典型区域,滇榄仁(Terminalia franchetii)种群为该区域仅有的几种重要天然植被类型之一.研究水分条件对滇榄仁种子萌发及幼苗早期生长的影响,以了解其天然更新中的限制因子,为人工促进植被恢复提供理论依据.采用室内控制试验方法研究不同水分条件对滇榄仁种子萌发特征及幼苗早期生长特征的影响.结果表明,滇榄仁种子能够在含水量为15％～40％的土壤中萌发,种子发芽率＞55％,适宜的土壤含水量为15％～25％,种子发芽率＞70％.当土壤含水量＜10％或＞50％时,种子萌发受到严重抑制,甚至完全不能萌发.水分条件对滇榄仁幼苗早期生长具有显著影响.随着施水量的增加,幼苗株高、基径、萌枝数、主根长、主茎叶片数、最大叶片长、单株叶面积、比叶面积、生物量均出现了显著增加.随着水分胁迫的加剧,根冠比呈逐渐上升的趋势.综上,滇榄仁种群天然更新的主要影响因子是土壤含水量,应加强群落物种多样性保育及退化土壤的改善,使之形成集水、保水环境,使萌发幼苗安全度过脆弱期从而有效补充幼树以实现种群自我更新.