| The development of artificial mixed forest,especially the planting modes of artificial mixed forest of precious tree species,was one of important research directions in the forestry technology field in China.Phoebe bournei,as the preferred tree species for cultivating large diameter timber in Hunan,was long-life tree was mixed planting with fast-growing species Cunninghamia lanceolata.We studied functional traits of two tree species and the responses of phenotypic plasticity to the coexistence environment with two tree species mixed,our aims were to reveal the variation characteristics of functional traits,relationships between functional traits,phenotypic plasticity and adaptation strategies to the environment with mixed plantation.Exploring the responding mechanism of Phoebe bournei and Cunninghamia lanceolata to mixed mode and community assembly of Phoebe bournei-Cunninghamia lanceolate mixed forest,which provided theoretical basis for the sustainable management of artificial mixed forests,and technological support for the construction of China’s timber strategic reserve production base.An experimental investigation was carried out in the Jindong national forest farm in Yongzhou,Hunan province.We choosen 3 types of forest whose ages were about 10 years,including Phoebe bournei+Cunninghamia lanceolata mixed forest(MF),Phoebe bournei pure forest(PF)and Cunninghamia lanceolata pure forest(CF).In this study,we measured 12 kinds of functional traits of Phoebe bournei and Cunninghamia lanceolata,including:leaf thickness(LT),leaf area(LA),specific leaf area(SLA),leaf carbon concentration(LCC),leaf nitrogen concentration(LNC)and leaf phosphorus concentration(LPC),specific root length(SRL),specific root area(SRA),root tissue density these(RTD),root carbon content(RCC),root nitrogen content(RNC)and root phosphorus content(RPC),which were chosen because these functional traits were easily measurable and able to adequately refllect plant survival strategies.The main conclusions were as follows:(1)Compared with Phoebebournei pure forest,the leaves of Phoebe bournei in the mixed forest showed:the leaves were thinner,the leaf area was larger,and the leaf specific area and leaf nitrogen content were higher,while compared withCunninghamia lanceolata pure forest,the leaves of Cunninghamia lanceolata in the mixed forest showed:the specific leaf area decreased,the leaf area increased.Compared with Phoebe bournei pure forest,the specific root length,specific root area and root phosphorus content of Phoebe bournei in the mixed forest were significantly lower,root nigtrogen content significantly increased,while compared with Cunninghamia lanceolata pure forest,the specific root length,specific root area,root nigtrogen and phosphorus content of Cunninghamia lanceolata were significantly higher.(2)The slopes or intercepts of the SMA relationship between the five pairs of trait combinations,including SLA-LT,SLA-LA,SLA-LNC,LNC-RNC,and LPC-RPC,were significantly different between Phoebe bournei pure forest and Phoebe bournei-Cunninghamia lanceolata mixed forest.The slopes or intercepts of SMA relationship between the three pairs of trait combinations,including SLA-LCC,SRL-RNC,and RNC-RPC were significantly different between Cunninghamia lanceolata pure forest and Phoebe bournei-Cunninghamia lanceolata mixed forest.(3)The soil of organic carbon content and total nitrogen contentin in Phoebe bournei-Cunninghamia lanceolata mixed forest were significantly higher than those in Phoebe bournei pure forest and Cunninghamia lanceolata pure forest.The soil of total phosphorus content was significantly higher than that in Cunninghamia lanceolata pure forest,but significantly lower than that in Phoebe bournei pure forest.This indicated that the mixed forest could significantly improve soil C and N nutrients situation.There was a significant positive correlation between soil total nitrogen content and N content in leaf and root of Phoebe bournei.There was a significant positive correlation between soil total phosphorus content and P content in leaf and root of Phoebe bournei.There was a significant positive correlation between soil total nitrogen content and N content in root of Cunninghamia lanceolata.There was a significant positive correlation between soil total phosphorus content and P content in root of Cunninghamia lanceolata.In short total nitrogen content and total phosphorus content in soil showed a certain correlation with N content and P content in plant.(4)The plasticity indexs of nutrient characteristics of the leaf and root in Phoebe bournei were higher than that of the morphological characteristic,and the plasticity index of leaf was higher than that of fine root.Under mixed pattern,Phoebe bournei tended to maintain leaf higher plasticity.The plasticity index of root nutrient characteristics is greater than that of morphological characteristics.The plasticity index of nutrient characteristics of rootin Cunninghamialanceolata was higher than that of the morphological characteristic,and the plasticity index of root of Cunninghamia lanceolata was much higher than that of its leaf.Under mixed pattern,Cunninghamia lanceolata tended to maintain higher plasticity of fine root.In general,the plasticity index of Cunninghamia lanceolata was 0.19,which was higher than that of Phoebe bournei(0.15),indicating that the mixed pattern had a greater impact on Cunninghamia lanceolata.In summary,Phoebe bournei-Cunninghamia lanceolata mixed model was more favorable for the growth of Phoebe bournei,and the stress on Cunninghamia lanceolata was greater.Under Phoebe bournei-Cunninghamia lanceolata mixed model,Cunninghamia lanceolata had greater plasticity to adapt better to the mixed coexistence environment. |
