作者: Ruijun Su, Tingxing Hu

Abstract:

Objectives: Research of soil seed bank pays close attention to regeneration of plant populations to better predict the direction of population regeneration after environmental changes. At the same time, existence of canopy seed bank is an important reproductive strategy for plants to deal with unfavorable environments.

Methods: This paper studies characteristics of soil seed bank and canopy seed bank of D.involucrata population in Bainigang plot of Sanjiang Town, Wenchuan, Sichuan. Six mother trees were selected from the sample plot, the number of intact seeds (with complete kernels) and damaged seeds (with damaged kernels) in each layer of soil samples is counted for the surface layer, 0-3 cm soil layer, and soil layers below 3 cm. While counting, year of the seed (2016, 2015, 2014) is identified based on newness degree of the seed shell, with number and location recorded respectively. All seeds trapped in the canopy were counted when D.involucrata bloomed in May 2016, and their positions on the canopy were recorded. From May 1, 2016 to August 1, 2016, seeds were collected once every other month to study dynamics of the canopy seed bank.

Results: The results show that: soil seed bank of D.involucrata has narrow horizontal distribution, which is concentrated in the crown diameter +5 m range; time dynamics of the seed bank shows gradually decreased number of seeds, seed viability and germination rate; the seed bank spatial structure shows that D.involucrata seeds are concentrated in the soil seed bank at ground surface and 3 cm below the ground; D.involucrata canopy seeds have a retention time of 6 months, with effective seeds continuously input into the soil seed bank to reach 51% seed germination rate.

Conclusions: Studies have shown that the horizontal, vertical, and age-level distribution of seeds in the seed bank is stratified. As time goes by, seed germination is accelerated in vertical distribution, but with increased animal feeding and rottening in horizontal distribution and age, which reduces the germination of seeds, and at the same time, decreases density of the seed bank, reducing competition among seedlings. The existence of canopy seed bank diversifies the seed storage, and increases the possibility of maintaining seed viability. Seed bank of endangered species, as an important link in their life history, plays an important role in natural regeneration of their populations, which is one important mechanism in natural population regeneration.

Keywords: soil seed bank, canopy seed bank, D.involucrata, population regeneration;