金沙江干热河谷滇榄仁种子扩散与种子库特征研究

采用随机取样和跟踪调查的方法对滇榄仁(Terminalia franchetii)种子扩散规律、空间分布特征以及种子库动态进行了系统研究。结果表明,滇榄仁种子扩散受到较强的风力作用影响,具有明显的方向性,扩散距离是其树高的1.6倍以上。不同群落类型中,滇榄仁的土壤种子库存在较大差异,但不同时间段的变化趋势基本一致,即在雨季(6月、8月和10月)数量相对较少,12月到翌年4月,数量逐渐增加。滇榄仁植冠种子库从当年10月开始缓慢脱落,到翌年3月达到脱落高峰(15%以上种子此时脱落),然后再次进入缓慢脱落期,翌年6、7月的种子脱落速率最低,但直到翌年10月仍有部分种子(约15%左右)存在于植株冠层。总体来说,不同类型群落中,滇榄仁幼苗更新不良的原因不应是缺乏种源,可能与种子质量以及群落环境等影响群落天然更新的其它因子存在较大关联。同时,滇榄仁土壤种子库数量与植冠种子库的脱落过程存在紧密联系,而植冠种子脱落可能与该区域气候因子存在着较大依存关系,其中,与风力可能存在着正相关,与降雨量和空气相对湿度存在着负相关,这可能是滇榄仁长期以来对干热河谷环境的一种适应特征。

Seed Dispersion and Seed Bank Characteristics of Terminalia franchetii in Dry-hot Valley of Jinsha River

The seed dispersal pattern, spatial distribution characteristics and seed bank dynamics of Terminalia franchetii in Dry-hot Valley of Jinsha River were investigate by random sampling and follow-up survey. The seed dispersal pattern had obvious direction influenced by strong wind, and the dispersal distance was more than 1.6 times of tree height. There was significant difference in soil seed bank among the different community types, but the change trends were consistent during different time. The soil seed bank was relatively small in rainy season (June, August, and October), and it was gradually increased from December to April of next year. The canopy seed bank started to shed in October, and reached to peak in March of next year (more than 15% of seeds shedding), and then the seed shedding rate became slow again, and seed shedding rate was the lowest in June and July of next year. However, there were nearly 15% of seeds existed in the canopy until October of next year. In summary, the lack of seed sources should not be the reason of T. franchetii seedling regeneration failure, and it might be associated with other factors which influence the community natural regeneration, such as the quality of seeds and community environment. Simultaneously, T. franchetii soil seed bank was closely related to the shedding process of canopy seed bank. Canopy seeds shedding might be closely related to the climatic factors, and might be a positive correlation with wind power, and be a negative correlation with rainfall and relative humidity. This might be an adaptive characteristic to Dry-hot valley environment in a long time.