Study Of The Seedling Establishment Patterns Of Castanopsis Fargesii In A Subtropical Evergreen Broad-leaved Forest On Jinyun Mountain

Castanopsis fargesii is one of the dominant species of the subtropical evergreen broad-leaved forests in China.This species plays an important role in the maintaining and functioning of forest ecosystems.Whether this species can regenerate in the wild directly affects the structure and composition of evergreen broad-leaved forests.While the seedling stage is the most important stage among a plant’s life-history stages,it is the key to the understanding of patterns of population regeneration for C.fargesii.In this study,a three-year in situ experiment was conducted in different types of habitat to investigate the seed germination,seedling demography and the differences in seedling traits in varied conditions for C.fargesii.The major findings were as follows:(1)Castanopsis fargesii seeds showed a delayed germination pattern.Although being sown in March,the seeds did not germinate until July.The germination rates under canopy,and in small gap,medium gap and large gap were 64.4 ± 4.6%,61.3 ± 4.5%,63.2 ± 3.8%,and 63.2 ± 3.5%,respectively.There were no significant differences in the germination rate under different canopy conditions,but the temporal patterns of seed germination were different.The time to reach germination peak in the gaps was later compared to that under canopies.The germination rates on the ridge,slope and in the gully were 71.8 ± 4.1%、64.4 ± 4.6% and 51.0 ± 5.0%,respectively.The germination rate was significantly lower in the gully than on the ridge and slope,but there were no significant differences in seed germination pattern across these three habitats.(2)The death of C.fargesii seedlings in the early stage was mainly caused by defoliation and physical damages.Seedling mortality rates under canopy,small gap,medium gap and large gap were 40.2 ± 4.1%,38.9 ± 4.5%,19.8 ± 3.0% and 20.3 ± 2.7%,respectively.Mortality rates were significantly higher under canopies and in small gaps than in the medium and large gaps.Seedling mortality rates on the ridge,and in the slope and gully were 23.5 ± 3.7%,40.2 ± 4.1% and 21.8 ± 3.9%,respectively.Seedling mortality rate was significantly higher on the slope than on the ridge and in the gully.(3)The seeding establishment rates under canopies,and in small gap,medium gap and large gap were 33.8 ± 3.4%,34.4 ± 3.6%,45.6 ± 3.7% and 47.0 ± 3.1%,respectively.Seeding establishment rates were significantly higher in the medium and large gaps than under the canopies and in small gaps.The seeding establishment rates on the ridge,and in the slope and gully were 49.8 ± 3.2%,33.8 ± 3.4% and 35.7±3.6%,respectively.Seeding establishment rates were significantly higher on the ridge than on slope and in the valley.(4)Canopy conditions had a significant effect on the growth of C.fargesii seedlings.The diameter,height,leaf number,root length and other growth indicators of the seedings were the largest in large gaps and the smallest under the canopies.The microtopography had no significant effect on the growth of seedlings(5)The root biomass ratio of seedlings decreased with the increase of seedling age,while the stem biomass ratio showed no obvious changes,with leaf biomass ratio increasing as the increase of seedling age.Canopy conditions had a significant effect on biomass allocation pattern of seedlings.The root-to-shoot ratio under gaps was significantly lower than under the canopies.The microtopography had no significant effect on the biomass allocation pattern of seedlings.