Abstract:

Aims Quercus liaotungensis forest, which occurs on shaded, semi-shaded and semi-sunny slopes at an elevation of 1 700-2 300 m, is the main natural secondary forest and zonal climax community in China’s Liupan Mountains. It is essential for forest management to better understand the natural regeneration processes and limiting factors in the restoration of degraded Q. liaotungensis shrubs and secondary Q. liaotungensis forest. Our objectives are to (a) investigate the important ecological processes associated with recruitment and seedling regeneration (seed production, seed bank composition, seed storage and seed/cotyledon predation) and (b) analyze potential bottlenecks limiting seedling regeneration.
Methods We surveyed the seed production of Q. liaotungensis shrubs and soil seed bank composition of secondary Q. liaotungensis forest in Daliang Mountain and Qiuqianjia forest region of Liupan Mountains, respectively. We also investigated the effects of moist sand and natural air-dry storage on seed life-span and the effects of cotyledon predation (by excluding animals) on seedling establishment.
Important findings The percentage of viable seeds of Q. liaotungensis shrubs was 27.51%, and the rate of seed predation/removal (41.51%) was significantly higher than that of other seed types (P < 0.01). The rate of germination and insect infection in soil seed bank of secondary Q. liaotungensis forest was 35.16% and 38.29%, respectively, while only 13.65% of seeds were viable in the soil seed bank. Seed predators played an important role in influencing the density of the soil seed bank by removing and hoarding seeds. Storage in moist sand for 60 d resulted in germination of 96.67% of Q. liaotungensis seeds, and both short-term moist sand and air-dry storage led to accelerated germination timing and enhanced germination percentage and germination index. However, with the extension of the storage period, germination was delayed and germination percentage, germination index and vigor index were decreased. Survival rates of seedlings treated by predator elimination caged seedlings were 80% and 83% in forest gap and under canopy, respectively, while only 25% and 31% of survival rate, respectively, were found for uncaged seedlings, indicating the important role of cotyledons in seedling establishment. The predation rate of cotyledons in forest gaps (85.00%) was higher than that under canopy (71.00%). Although the survival rate of seedlings with cotyledons in forest gaps (6.00%) was higher than that under canopy (15.50%), the survival rate of cotyledon-predated seedlings in forest gaps (18.50%) was similar to that under canopy (18.00%).

Key words: predation, Quercus liaotungensis, seed production, seed storage, soil seed bank