关键词: 青钱柳, 种子雨, 林分密度, 季节动态, 土壤种子库, 天然更新

Abstract:

【Objective】 This study investigated the role of succession and regeneration for populations of Cyclocarya paliurus; in particular, seasonal dynamics of seed rain and soil seed bank characteristics were investigated.【Method】 Investigation of seasonal dynamics of seed rain was performed in plantations of C. paliurus with three densities (C1: 1 050 plant/hm², C2: 720 plant/hm², and C3: 525 plant/hm²), which were planted in Dashishan, Liyang, Jiangsu Province; the traits of seeds were also analyzed. In addition, we surveyed and dissected the soil seed banks dispersed in five natural populations located in Jiuling Mountain, Jiangxi Province. The soil seed banks in two layers, named as litter layer (Ⅰ) and soil layer (Ⅱ), were separately analyzed.【Result】 According to the density of seed rain, the duration of seed falling was divided into three stages: early stage (8.20-9.20), medium stage (9.20-12.10), and late stage (12.10-12.30); two peaks of seed rain were recorded at 9.10 and 12.20, respectively; the amount of seed rain during these two peaks in the early and late stage accounted for 42.4% and 43.5% of the whole annual production, respectively. The differences of seed rain and number of viable seeds at various stages were significant, but the other seed traits were insignificant. Moreover, the effects of plantation density on the number of full seeds and 1 000-seed weigh were significant, but no effect on the other seed traits was detected. In five natural populations of C. paliurus, the density of soil seed bank in the Ⅰ layer (37.4 grain/m²) was higher than that in the Ⅱ layer (17.9 grain/m²), and this parameter presented an obvious divergence among populations. Moreover, the seed diameter, thickness and volume from the Ⅱ layer were all smaller than those from the Ⅰ layer. More importantly, seed fullness and viability from the soil seed banks were lower by 13.0%-27.1% and 0%-10.4%, respectively. However, these indicators of seeds from the Ⅰ layer were generally higher those from the Ⅱ layer, indicating a descending tendency in seed quality as duration increases. 【Conclusion】 There were two peaks of seed rain in plantations of C. paliurus, and stand density affected the density of seed rain and 1 000-seed weigh more than seed fullness or viability. Both the quantity and quality of seeds in the soil banks from the Ⅰ layer were superior to those from the Ⅱ layer. The dormancy of seeds stored in soil is relieved in favor of regeneration and succession of C. paliurus populations.

Key words: Cyclocarya paliurus, seed rain, stands density, seasonal dynamics, soil seed bank, natural regeneration