川西南山地高山栲种群种子雨和地表种子库研究

Seed Rain and Seed Bank of Castanopsis delavayi Populations in Mountainous Area of Southwest Sichuan

研究川西南山地区两个高山栲低密度种群的种子雨模式、种子雨过程中地表种子库动态和种群的幼苗状况,讨论种子产量、种子存留和种子对成苗的贡献。结果表明:1)种子雨持续时间超过2个月,但种子下落的高峰期存在样地间差异;2)该地区高山栲的种子产量很低,种子雨散落的密度不大(2.3～2.8个·m-2)。3)在种子雨过程中,地表种子库各组成的动态不同,霉烂种子和萌发种子为零,完好种子和虫蛀种子有轻微的波动,完好种子的存留密度为0.13个·m-2;和它们相反,地表的壳斗和败育种子存在积累效应。4)动物捕食是地表种子损失的主要原因,两种群分别占91.3%和97.83%,地表种子的存留率仅为8.7%和2.17%。5)研究样地的高山栲种群低的种子生产量、地表种子存留率和幼苗建成困难等3个环节都限制了高山栲种群的实生更新。

The arid hardwood forests in mountainous region is distributed in the upper edge of dry-hot valley of Jinsha River in Southwest Sichuan, in which, Castanopsls delavayi is one of the main constructive species. C. delavayi forest is typical arid hardwood forest. By the investigation of seed rain pattern and seed bank dynamics on the earth＇s surface during seed rain, and the seedling situation in two low density populations of C, delavayi in mountainous area in Southwest Sichuan, the seed productions, seed retentions and their contributions to seedling establishments were discussed. The results showed as follows： 1 ） the duration of seed rain was above 2 months, but there was a different top time of seed fall between the studied plots. 2） the seed production of C. delavayi was low in the studied area, seed rain had a low dispersing density （2,3 to 2.8 grain·m^-2 ）. 3） in the whole process seed rain, the decayed and germinating seeds in the seed bank were never found. The sound seeds and the damaged seeds by insects were slightly fluctuated. The retaining density of sound seeds was 0.13 grain·m^-2, on the contrary, there were accumulative effects of cups and aborted seeds on the earth＇s surface. Therefore, various constituents of soil seed bank had different dynamics. 4） the retention rate was only 8.7% and 2.17% of dispersing seeds, which was the main cause of soll seed bank losing, 91.3% lost in population 1 and 97.83% lost in population 2. 5） three key links i. e., the low seed production, the low seed retention in soil seed bank and difficult establishment of seedling, limit the population regeneration of C. delavayi