Preliminary Study On Plant Functional Characters Of Abies Georgei Var.smithii Community In Sejila Mountain Of Tibet

The research method based on plant functional traits has always been a hot topic in community ecology.The differences of plant functional traits can not only reflect the internal physiological processes of plants and their ecological strategies to cope with the differences of external environment,but also link the community structure with the community environment and ecosystem processes.Abies georgei var.smithii community plays an irreplaceable role in maintaining biodiversity and ecological balance in high altitude areas.A deep understanding of the structure and variation of plant functional traits in this region can provide basic scientific data for understanding the formation and maintenance mechanism of biodiversity in this region.Based on this,the structure of 7 functional characters（chlorophyll content,leaf area,specific leaf area,leaf nitrogen content,leaf phosphorus content,leaf potassium content,wood density）of 17 species（4 evergreen and 13 deciduous leaves）in the community were analyzed by using the method of character based on the typical 4 hm²permanent dynamic monitoring sample land with the rapid growth of Abies georgei var.smithii as the group species The following results are obtained:the correlation between functional characters,the inter species and intraspecies variation of functional characters,and the relationship between leaf functional characters and soil factors at community level（1）In the 4 hm²permanent monitoring sample plot in Sejila Mountain,where A.georgei var.smithii is used as the constructive species,the overall appearance structure of the community is characterized by small leaves（11.72 cm²）,leaf with medium chlorophyll content（33.77 SPAD）,medium specific leaf area(296.53 cm²·g^-1),moderate content of nitrogen,phosphorus and potassium（2.62%,0.35%）1.52%and trees had medium wood density(0.51 g·cm^-3).（2）From the whole community level,the specific leaf area,leaf nitrogen content,leaf phosphorus content,leaf potassium content and wood density of deciduous tree species were higher than evergreen trees.Evergreen tree species have smaller specific leaf area(106.82 cm²·g^-1)and lower wood density(0.39 g·cm^-3),and deciduous tree species have higher functional characteristics related to leaf nutrients(leaf area and leaf nitrogen,phosphorus and potassium content are 318.52 cm²·g^-1,2.82%,0.38%,1.64%).Evergreen and deciduous trees coexist through different ecological strategies.Evergreen trees adopt resource conservation acquisition strategy,while deciduous trees adopt resource acquisition ecological strategy.The differences of ecological strategies of different leaf habits effectively reduce the intensity of biological competition in this small-scale habitat,and promote species coexistence.（3）In this community,the vertical position of plants in the community is one of the main reasons for the difference of plant functional characters.The functional characters of the trees in the lower layer of the forest are much higher than those in the canopy,that is,the leaves of the canopy trees have lower chlorophyll content（11.70 SPAD）,the nitrogen,phosphorus and potassium content（1.82%,0.25%,0.99%）,the smaller leaf area（0.42 cm²）and the specific leaf area(112.28cm²·g^-1),and have a smaller wood density(0.32 g·cm^-3).The lower layer of the forest has a large leaf（18.66 cm²）,a higher chlorophyll content（34.84 SPAD）,a high content of nitrogen,phosphorus and potassium（2.73%,0.37%,1.59%）,and a hard trunk(0.53 g·cm^-3).But the wood density of the shrub species is higher than that of the lower forest,there is no significant difference between the other six plant functional characters.（5）There are variations in 7 functional characters at interspecific and intraspecies levels,which are caused by large variation among species and within species.Among them,the variation coefficient of leaf area in intraspecies and interspecific level was the largest than that of the other six characters,31.35%and 101.15%respectively.The variation coefficients of wood density were the lowest among species and species,19.37%and 11.10%respectively.The variation sources of plant functional characters are different,which reflects some ecological strategies of reducing competition in communities.The variation of leaf area,leaf potassium content,leaf nitrogen content,specific leaf area,chlorophyll content and wood density mainly came from interspecific variation,among which the variation of interspecific variation had great influence on leaf area（contribution rate was 93.39%）,while the variation of leaf phosphorus content was from species.However,it is very important to understand the mechanism of community construction and dynamic change of the community,whether it is interspecific variation（contribution rate is 56.90%）or intraspecies variation（contribution rate is35.08%）.（6）The functional characters of plants,whether at community level,on different leaf habits or individual level,often show a certain degree of correlation（P<0.05）.There is a general correlation between the characters,which shows that species are subject to similar environmental impact and tend to evolve.In addition,at 20 m×20 m spatial scale,the community weighted mean of leaf functional traits at community level were correlated with soil nitrate nitrogen and soil temperature,indicating that the distribution of leaf functional traits at community level was driven by soil nitrate nitrogen and soil temperature.