Seed Ecology Of Subtropical Broad-leaved Evergreen Forest On Jinyun Mountain

The plant life cycle begins and ends with a seed. Seed production, seed dispersal and seed germination are key processes determining the spatial structure and dynamics of plant populations. The evergreen broad-leaved forest is widely distributed in the Yangtze River Basin area, and is the zonal vegetation type of the subtropics. Castanopsis fargesii, an evergreen and long-lived species, is one of the dominant species in the evergreen broad-leaved forests, and plays an important role in maintaining forest structure and ecosystem function. In this study, we set 172 seed traps in a 1 hm2 permanent monitoring plot on Jinyun Moutain, and conduct an ecological study of the seeds in a C. fargesii-dominated evergreen forest. We firstly investigated the temporal variation in seed rain and in seed trait at the community level. Then, we examined the germination and fate, and the spatial distribution of seeds for C. fargesii to infer species coexistence and the regeneration mechanism of the evergreen broad-leaved forests on Jinyun Mountain. The main results are as follows:1. A total of 20,207 mature seeds from 24 woody species was collected in 3 years. The average seed rain density was 117.48 seeds m-2 a-1. A total of 23 shared woody was found between the seed rain and the plant community, accounting for 32% of the total number of species in the community. Seed mass of 16 species ranged from 0.0096 g to 1.58 g, and differed among life form and dispersal mode.2. The seed rain of C. fargesii lasted from 1th November to 24 th December, totaling about 13 weeks. Annual variation in the fruit production was substantial, while the production of mature seed was stable. The total amount of mature seed was 48.24, 51.78 and 43.83 seeds m-2 in 2013, 2014 and 2015, respectively. There was no significant annual difference in the spatial distribution of mature seeds.3. Seed mass of C. fargesii ranged between 0.484 g and 0.589 g from 2013 to 2015. There were no significant differences between seed mass of seed rain and of seed bank. Indoor germination rate of C. fargesii seed was 76%, and medium seed had the highest germination rate.4. The key seed-killing agents for C. fargesii seeds were abortion and vertebrate attack, and only 2.46% to 3.7% of seeds can survive and germinate. We found notably aggregated spatial patterns for C. fargesii seeds during the seed dispersal stage, suggesting a decreased efficiency in secondary dispersal for C. fargesii within this evergreen broad-leaved forest. Density of newly germinated seedling was 5.8 to 7.04 seedlings m-2, and a majority of them aggregated under adult tree canopies.