神农架巴山冷杉种子雨的时空格局

Spatial and temporal pattern of seed rain of Abies fargesii in Shennongjia Nature Reserve,Hubei

巴山冷杉(Abies fargesii)是我国特有树种,其分布区以秦巴山地为中心。在湖北神农架自然保护区选择不同的巴山冷杉群落设置样地,通过布设种子收集器结合室内实验分析,对巴山冷杉的种子雨进行研究。各样地巴山冷杉种子雨开始和持续时间大致相同,始于10月初,持续超过2个月,但是不同的巴山冷杉种群表现出不同的种子雨时空格局。巴山冷杉-箭竹(Fargesia nitida)群落种子雨的平均强度为167.93±111.14粒/m2,有活力种子比例占22.31%,落种高峰期集中于10月27日到11月2日间,种子雨呈现聚集分布。巴山冷杉-茵芋(Skimmia reevesiana)群落的种子雨强度在3个样地中最小,只有16.41±14.41粒/m2,有活力种子仅占3.05%。对巴山冷杉-陕甘花楸(Sorbus koehneana)群落,沿等高线方向和垂直等高线方向布置收集器带,收集器自群落内中心母树延伸至林冠范围之外(距中心母树的距离>18m)。收集结果表明种子雨落种高峰为10月15–21日,种子雨主要集中在林冠范围内,林冠内种子雨数量占到了收集总数的87.95%。方差分析结果显示各方向的种子雨数量不存在显著差异,按照远离中心母树的距离进行分段比较,0–6m区段内的收集数量和其他各区段间(6–12m,12–18m,>18m)存在显著差异,扩散的种子数量与离开中心母树的距离间的关系近似正态分布。研究结果说明巴山冷杉种子雨的强度大但种子质量不高,而且种子雨的扩散距离有限。这些特征将影响到巴山冷杉种群的分布格局和种群更新。

Abies fargesii is endemic to China and its distribution center is located in Qinling-Bashan Mountains. To study the spatial and temporal pattern of seed rain of Abies fargesii,we conducted experiments from 9 October to 24 November in Shennongjia Nature Reserve,Hubei in 2005. The results showed that patterns of Abies fargesii seed rain were different in three communities. In Abies fargesii-Fargesia nitida community,the average seed rain intensity was 167.93±111.14 seeds per m2,in which the proportion of viable seed was 22.31%; and the seed rain pattern mainly showed clump distribution which peaked in 27 October to 2 November. In Abies fargesii-Skimmia reevesiana community the seed rain intensity was just 16.41±14.41 seeds per m2 in which viable seed only accounted for 3.05%. In Abies fargesii-Sorbus koehneana community,seed traps were set up in four lines at 90°intervals,of which two lines run directly up and down the hill slope. In this community,the seed rain intensity peaked from 15 October to 21 October. And the most quantity of seed rain was concentrated under the crown,which accounted for 87.95% of the total amount. One-Way ANOVA analysis showed that no significant differences existed among four directions but significant difference existed between 0-6 m and other distance from the center mother tree in terms of seed rain quantity. The distribution pattern of seed rain in Abies fargesii-Sorbus koehneana community fitted the equation y=ae^-bx2. The result showed although Abies fargesii had high seed rain intensity,but inviable seeds accounted for a large proportion,and the dispersal distance of seed rain was limited. These characteristics would influence the pattern and regeneration of Abies fargesii population.