The Effects Of Environmental Factors On Seed Germination And Seedling Growth Of Metasequoia Glyptostroboides

Metasequoia glyptostroboides Hu & Cheng,a kind of plant belong to Metasequoiaisa,rare relict plant in the world and specialties in China.Due to human's excessive exploitation,the habitats of natural M.glyptostroboides forests degenerates so seriously that the regeneration of the forests is not good.Braun-Blanquet method was applied to investigate three forestry communities in Gangchang wan,Deng jia wan and Youjiawan,in Lichuan region of Hubei.M.glyptostroboides forest.Based on the results of the investigation,three environmental factors,i.e.,light,litter layer and water level were chose,and additionally the influence of three different gradients of the factors on germination of the Metasequoia glyptostroboides was studied.The results of the native community's research indicate that the community type of the observed plot in Gangehangwan is Metasequoia glyptostroboides-Camellia caudata-Thelypteris japonica,and the total kinds of species accounting to 78;the one in Dengjiawan is Metasequoia glyptostroboides-phyllostachys bambusoi-Impatiens siculifer,with 81 kinds of species;the one in Youjiawan is Metasequoia glyptostroboides-Eurya hebeelados-Chrysosplenium macrophyllum,with 58 kinds of species.By the 20 years's succession,each layer cover of the nature M.glyptostroboides is inereaseing.On the species composition,there is no significant varirty in the species composition of shrub layer and herb layer.On the study of influence of different sunlight on germination of seeds and seeding growth of Metasequoia glyptostroboides,by the field seeds experiment,we set five light gradient treatments(100%,52.3%,34.7%,26%,and 8%natural light).The results show that under 100%natural light treatment,the seeds germinated earliest than those of the other light treatments,and the ratio of germination is low,only 18.3%.For the condition of 8%natural light,the germination and survival ratio of M.glyptostroboides's seeds are highter than other light conditions,but it didn't facilitate the seedlings growth; on the conditions of 26%natural light,seedlings grow best than other conditions.This shows that low light condition helps M.glyptostroboides's seeds germination and that middling light condition is propitious to seedlings's growth.Litter layer is important to forest regeneration.We conducted a greenhouse experiment to study the influence of different litter layer on seed germination of Metasequoia glyptostroboides,the result shows that the seeds in litter layer cannot germinate;when the litter depth was 1cm the seed germination ratio was 21.3%;it's significant different with the seeds in litter layer which depth was 2cm and 3cm(p＜0.05). When cover the litter layer,the beginning and ending of seed germination delayed 3 days.Water is necessary for seeds germination,on different light conditions investigate seeds germination of the Metasequoia glyptostroboides,water level influences seeds' germinate ratio,germinatetion index and the days of the first seeds' generate.The result showed that the best water level for the seeds germination is 0cm～-1cm.with the water level depress,seeds' germinate ratio,germinate index are all depress,the days of the first seeds' generate also delay.