| Camellia oleifera,as one of largest woody oil crops in the world,is an important woody oil tree species in China.Young Camellia yield of 5 to 6 years planting,come to high-yield period in 8 to 10 years,which leads to a low land use efficiency in early stage,and severe Camellia industry restriction.Therefore,setting crops in the Camellia young plantation can not only meet the requirements of ecological management,but also effectively improve the soil structure and increase the soil nutrient content,Herein,in this experiment,we chose two-year-old Camellia young trees as the test objects,selected two models of intercropping(pepper and peanut),and set the nitrogen content at 50mg/kg soil(N1),250mg/kg soil(N2)and Omg/kg as control.To study the growth and nutrient dynamics of Camellia under different intercropping patterns,15N tracer technique was used to analyze the characteristics of nitrogen absorption,distribution and utilization of Camellia.It provides a reference for technical specifications formulation for efficient management of Camellia agroforestry ecosystem.The main results are as follows:(1)Research on the growth and development of Camellia under different intercropping patterns showed that:in the early intercropping period,pepper and peanut both significantly increased the photosynthetic rate of Camellia oleifera,and reached the maximum value under the N1 nitrogen level(4.15μmol CO2 m-2 s-1 and 5.71 μmol CO2m-2 s-1 respectively);at the nitrogen level of N0,the biomass of Camellia planted in intercropping pepper and peanut increased to 13.01g and 14.27g respectively,which increased 47.51%and 61.9%than single cropping mode;at N2 nitrogen level,when intercropping peanuts,the minimum biomass of aboveground,underground,and individual plant of Camellia were 5.06g,2.77g,and 7.82g,respectively.At N1 level,in Camellia single cropping mode,leaf photosynthesis rate,biomass of aboveground,underground and individual plant were 3.18μmol CO2 m-2 s-1,7.07g,3.48g and 10.55g,which were significantly higher than NO and N2 levels.In the late intercropping period,the highest photosynthesis rate of oil tea of intercropping pepper and peanut were 3.49μmol CO2 m-2 s-1 and 3.53μmol CO2 m-2 s-1,which were significantly higher than the single cropping mode.The biomass of Camellia was 16.16g and 17.53g,which were 32.79%and 44.04%higher than the single cropping mode.At N1 level,the highest photosynthesis rate of intercropping pepper and peanut was 7.26μmol CO2 m-2 s-1 and 9.81μmol CO2 m-2 s-1.At N2 level,when intercropping peanuts,the minimum biomass above ground,underground and individual plant of Camellia oleifera were 6.24g,4.30g and 10.54g respectively.At N1 level,the maximum photosynthesis rate of Camellia oleifera leaves was 6.21μmol CO2 m-2 s-1,and biomass of aboveground,underground,and individual plant were 10.28g,6.09g,and 16.37g,which were significantly higher than those of NO and N2.(2)The changes of nitrogen content and accumulation of Camellia under different intercropping patterns showed that the total nitrogen content of Camellia oleifera leaves ranged from 12.81g/kg to 18.03g/kg in the early stage of intercropping.When pepper and peanut were intercropped at the NO level,the total nitrogen content of Camellia oleifera leaves was 15.46g/kg and 15.44g/kg,which was significantly higher than that of single cropping mode.And the nitrogen accumulation of Camellia leaves was 0.076g and 0.072g,respectively.It was also significantly higher than the single cropping mode;the highest total nitrogen content of Camellia leaves was 18.03g/kg when intercropping peanuts at the N2 level,but the minimum nitrogen accumulation of Camellia leaves was 0.039g.The maximum amount of nitrogen accumulation in Camellia oleifera leaves was 0.060g at N1 level.In the late intercropping period,the total nitrogen content of Camellia leaves ranged from 11.70g/kg to 24.35g/kg,and when pepper and peanut were intercropped at the NO level,the total nitrogen content of Camellia leaves were 12.89g/kg and 13.36g/kg,and the nitrogen accumulation of Camellia oleifera leaf were 0.050g and 0.058g,which both significantly higher than the corresponding single-cropping mode of Camellia.But at N2 level,when intercropping with peanut,the maximum amout of nitrogen in Camellia leaves was 24.35g/kg while minimum amount of nitrogen accumulation in Camellia oleifera leaves was 0.036g,in single Camellia model,the maximum amount of nitrogen accumulation in leaves was 0.087g at N1 level.(3)Research on the nitrogen absorption,distribution and utilization of Camellia under different intercropping patterns showed that:in the early intercropping,the Ndff value of Camellia root system was higher than that of other organs;when intercropping peppers,the 15N distribution rate increased along with nitrogen application rate increasedwhilethe 15N distribution rate decreased with the increase of nitrogen application rate in all organs of the tree when intercropping peanuts;at NO level,the 15N utilization rate of Camellia,when interplanting peppers and peanuts,were respectively 14.47%and 20.33%,which was significantly higher than the single Camellia mode.In the late intercropping period,the Ndff value of Camellia leaves increased significantly compared with the early period.The two intercropping modes,the 15N distribution rate of Camellia leaves were less than that of single cropping.And the 15N distribution rate of the leaf increased,ranged from 39.43%to 48.53%,along with the increase of nitrogen application rate in single Camellia;at NO level,when intercropping pepper and peanut,the 15N utilization rate of Camellia were 16.23%and 17.25%respectively,which were significantly higher than single Camellia intercropping mode.Whether in the early or late intercropping period,in single Camellia model,the 15N utilization rate of Camellia at N1 level was significantly higher than that under NO and N2 level.in two intercropping models,the 15N utilization rate of Camellia along with nitrogen levels increasement both showed a significant decrease trend.In summary,from the perspective of planting models,the two intercropping models showed strong intercropping advantages only at NO level,which significantly promoted Camellia growth,nitrogen absorption and accumulation,and 15N utilization rate,And with the increase of nitrogen application rate,the intercropping advantage gradually weakened.From the perspective of nitrogen application level,in single Camellia model at N1 level Camellia biomass and and 15N utilization rate improved most,which means it can promote the growth of Camellia and its absorption of nitrogen,but inhibitory effects showed at N2 level. |
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