Study On Natural Regeneration And Seed Germination Characteristics Of Betula Albo-sinensis At MT.Taibai, China

Betula albo-sinensis occurs in the middle to high elevations of Taibai Mountain, China where its forests have regeneration barriers.We studied the germination and physiological characteristics of B.albo-sinensis seeds to investigate natural regeneration.We studied the number of the seeds and seed viability before and after winter.We also studied the effect of aquatic extract from B.albo-sinensis's pericarp and shrub's roots,light,day/night temperature,different pericarp treatments,culture media,mulch,store time,chilling injury on the seed germination.We found the seed density in seed rain is 5978±3733 ind/m²,and the seed density in upper level is 8801±1166 ind/m²,the seed density in lower level is 7698±1261 ind/m²,and we observed 2400 seeds of B.albo-sinensis without pericarp and recorded germination rates found that 54.29%is full in the seed rain.There is on effect of aquatic extract from Betula albo-sinensis's pericarp and shrub's roots on the seed germination rates.We studied germination rates under different photosynthetic active radiation(PAR)and photoperiod(high light:PAR=464.7μmol·m^-2·s^-1,12h·d^-1; middle light:PAR=233.8μmol·m^-2·s^-1,12 h·d^-1;low light:PAR=233.8μmol·m^-2·s^-1, 0.5 h·d^-1),different day/night temperatures(25/20℃,20/15℃and 15/10℃)and different pericarp treatments(without pericarp,open the pericarp,mechanical injury, CK),We also recorded germination rates without light,wen found that the optimum germination temperature is 25/20℃,and few seeds germinated under 15/10℃. Germination rates under middle light were highest,and there was no seed germination under no light.Pericarp treatment could improve germination rates.Seed low temperature dormancy could broked by mechanical injury treatment.Germination rates declined in the groups Covered with mulch(broad leaf,needle leaf and mixed leaf),shoot longth and shoot/root improved.There was no significant difference among culture media(soil and sand),the shoot/root in soil is higher than in sand.The germination rates in leaf(broad leaf and mixed leaf)declined,shoot and root longth improved,the improve of shoot/root is not obvious.Results indicated that the germination rates of the seeds which stored in 4℃were high..The viability of the seeds stored in leaves is high except the seeds stored in wet leaves at -20℃;the viability of the seeds stored in soil is high at 0℃and -7℃.In other conditions,the seed viability is high under 0%soil moisture.The germination rates of the seeds declined under 10%,40%,50%soil moisture.The seeds which stored in 20%,30% soil moisture hardly germinated.The germination rates of the seeds stored at -20℃for 2d,4d,6d is also high under 0%soil moisture,declined under 10%,40%,50% soil moisture,no germination under 20%,30%soil moisture.We collected seeds form 4 type environments(in forest,in gaps,road side and in leaf layer)before and after winter.We found that no seed germinated in leaf layer after winter and the germination rates of the seeds collected from forest and gaps declined after winter,the germination rates of the seeds collected from road side is high,and we found some seedlings in forest and road side.Few seeds in the seed bank could germinate,more than half of the seeds in seed rain could germinate.The limit facter of seed germination is temperature.Many seeds died for chilling injury in forest and gap which has high humidity,and more seeds living in dry area.So we conclude that B.albo-sinensis seed germination depends on disturbances in its natural environment.