| Abies georgei var.smithii,as the dominant species in Sejila Mountain,southeast Tibet,has important ecological functions such as soil and water and soil conservation,beautifying environment and regulating climate.The ability of seedling settlement and community natural regeneration is closely related to root growth.Currently,the weak cognition of the response and adaptation mechanism of the growth and development process of seedlings of A.georgei var.smithii root system to various environmental factors has become the bottleneck of ecological conservation in Sejila Mountain,southeast Tibet.In this study,the seedlings of 1-10 years old of A.georgei var.smithii were studied at six elevations(3800,3900,4000,4100,4200,4300m)on the north and south slopes in Sejila Mountain,southeast Tibet.The growth characteristics of biomass allocation,root distribution,root functional traits,and root nutrient elements of seedlings of different ages at different altitudes and slopes were analyzed,and their relationships with soil factors and plant community factors were also analyzed.The main findings and conclusion were as follows:(1)Seedling age has a significant effect on above-ground biomass and root biomass of seedlings of A.georgei var.smithii(p<0.001),slope and altitude have a strong indirect effect on it.The seedlings may adapt to high altitude habitats by increasing the input of root biomass.Above-ground biomass and root biomass had a very high linear relationship with seedling age,and the best fit between above-ground biomass and seedling age was at 4000 m in the north slope(R2=0.921).The best fit between root biomass and seedling age was at4100 m in the north slope(R2=0.938).According to the allometric relationship analysis,the allometric indices(α)of above-ground biomass and root biomass were not equal to1,which was between 1.004 and 1.268 in the south slope and were between 0.913 and 1.046 in the north slope.(2)Seedling age had significant effect on the root growth of A.georgei var.smithii seedlings(p<0.05).With the increasing of seedling age,the ability to adapt to the habitat increased gradually,and the root growth traits of seedlings showed a linear function(y=ax+b,a≠0).Seedlings of A.georgei var.smithii may adapt to high altitude by changing their root tissue density,nitrogen and phosphorus content.In addition,drought conditions,soil conditions and plant community conditions may be the reasons for the differences in root dry matter content and root total carbon of seedlings between the north and south slopes.(3)According to the results of principal component analysis,the explanation rate of PC1 for seedling traits in 5 seedling age groups on the south slope(33.2%,34.3%,39.0%,31.3%,28.3%)was higher than that in the north slope(27.2%,24.6%,35.4%,35.1%,24.5%).The explanation rate of PC2 for seedling traits in 5 seedling age groups in the south slope(17.8%,19.2%,19.5%,25.6%,22.9%)was higher than that in the north slope(20.4%,17.1%,18.2%,20.3%,19.1%).Seedling root biomass and vertical root length of 5 seedling age groups in south slope(r=0.786;r= 0.717;r= 0.647;r= 0.701;r=0.763)had a significant positive relationship(p<0.05).Seedling root biomass were significantly positively correlated with horizontal root length(r=0.720;r=0.689)and vertical root length(r=0.511;r=0.563)in two seedling age groups(1-2 years,9-10 years)on the north slope(p< 0.05).(4)In the south slope,the contribution rates of soil factors to seedling biomass,root distribution,root functional traits and root nutrient elements were53.2%,17.2%,22.8% and 25.5%,and the contribution rates of plant community factors were 20.5%,33.1%,9.2% and 22.6%,respectively.The contribution rates of soil factors on the north slope were 21.5%,10.1%,11.2% and 20.7%,and those of plant community factors were 47.8%,46.5%,21.9% and 25.1%.In the south slope,the root growth of of A.georgei var.smithii was more affected by soil factors,while in the north slope,it was more affected by plant community factors(Because the higher stand density,litter thickness and species diversity index in the south slope may inhibit seedling growth,while soil nutrient and moisture conditions in the south slope are better than those in the north slope,so it the soil conditions are more suitable for seedling growth).(5)The main soil factors affecting seedling biomass and root growth characteristics were soil organic carbon,total potassium,total phosphorus,available phosphorus,available potassium,etc.The main plant community factors affecting seedling biomass and root growth characteristics were cover,canopy density,species diversity index,etc.In addition,soil factors and plant community factors may affect seedling root distribution,root functional traits and root nutrient elements through seedling biomass as the medium. |
PDF Full Text Request