Root Competition And Allelopathic Effects Of Cunninghamia Lanceolata And Phoebe Chekiangensisunder The Simulated Nitrogen Deposition

In this study,Cunninghamia lanceolata and Phoebe chekiangensis were treated by two nitrogen treatments and three planting methods.By measuring plant biomass,root morphological characteristics,rhizosphere soil components and other indicators,we analyzed the overall plant competitiveness and root growth level,the interspecific competition between C.lanceolata and P.chekiangens and the importance of allelopathy in root competition,and the effects of simulated nitrogen deposition on interspecific competition and root competition.1.Simulated nitrogen deposition promotes root growth of C.lanceolata and P.chekiangensis.Under simulated nitrogen deposition,the biomass of C.lanceolata and P.chekiangensis was increased significantly in a non-competitive treatment.Among them,the root morphological characteristics of C.lanceolata were significantly enhanced.2.Root system of C.lanceolata has allelopathic competitive advantage,while root system of P.chekiangensis showed predatory competitive advantage.According to the level-overall competitiveness response of root growth,C.lanceolata is better at root allelopathic competition and P.chekiangensis.is better at root predatory competition under the background of no simulated nitrogen deposition.3.Simulated nitrogen deposition enhances the allelopathic competitive advantage of C.lanceolata,and intensifies the competition between C.lanceolata and P.chekiangensis,which causes the competition between C.lanceolata.and P.chekiangensis.to change from mutual promotion to mutual inhibition,and makes C.lanceolata dominate the competition.Under the background of simulated nitrogen deposition,as the intensity of root competition increases,the competition between C.lanceolata and P.chekiangensis is intensified,and the relationship between the two species is transformed from mutual promotion to mutual inhibition,which promotes the allelopathic competitive advantage of C.lanceolata and makes C.lanceolata dominate in root competition.In addition,the research on the composition of rhizosphere soil of C.lanceolata and P.chekiangensis suggests that the composition of rhizosphere soil of C.lanceolata is mainly affected by simulated nitrogen deposition,while the composition of rhizosphere soil of P.chekiangensis is mainly affected by the intensity of competition with C.lanceolata roots.The simulated nitrogen deposition may aggravate the interspecific competition between C.lanceolata and P.chekiangens by affecting allelopathy of C.lanceolata.4.The rhizosphere soil components of C.lanceolata and P.chekiangensis were correlated with the morphological characteristics of the root system of P.chekiangensis.and P.chekiangensis.After comparing with the results of previous studies,6 possible allelochemicals are selected for further analysis and research,which are: Ambrettolide,Carnosic acid,Actinidic acid,12-Hydroxydodecanoic acid,Cinncloval and All-cis-octadeca-6,9,12,15-tetraenoic acid,includes two terpenes,one unsaturated lactone,two long-chain fatty acids and one cinnamic acid derivative.