Study On Growth Physiological Characteristics And Nutritional Status Of Camellia Nitidissima Chi And Camellia Japonica L. In Different Canopy Density Conditions Under The Illicium Verum Forest

The development of under-forest economy is conducive to improving the comprehensive benefits of forestry,but also conducive to the protection of the ecological environment.Ilicium verum is an important economic tree species in South China.Planting under the Illicium verum forest can make full use of the natural resources of the South and improve the utilization rate of Illicium verum forest land.In this study,the research object were Camellia nitidissima Chi and Camellia japonica L.which were planted under Illicium verum forest.Using a single factor randomized trial,four levels(full illumination,canopy density of 0.5,canopy density of 0.7,canopy density of 0.9).The morphological,growth,physiological indexes,soil and leaf nutrient status,photosynthetic physiological characteristics were studied to explore the influence of different canopy density(full sunlight,canopy density 0.5,canopy density 0.7,canopy density 0.9)on Camellia nitidissima Chi and Camellia japonica L.,and to obtain suitable canopy density conditions which were good for the growth of Camellia nitidissima Chi and Camellia japonica L.under the Illicium verum forest,thereby enhancing the Illicium verum forest productivity and economic,ecological and social benefits.The main resultsare as follows:(1)Compared with full sunlight,the height,ground diameter and biomass of Camellia nitidissima Chi and Camellia japonica L.were increased under three canopy density conditions,and Camellia nitidissima Chi adds more than Camellia japonica L..The Specific leaf weight of the two plants decreased first and then increased with the increase of canopy density,and it was the largest under full sunlight.Under full sunlight,the leaf length and leaf width of the two plants were the smallest,and the leaf thickness was the largest.With the increase of canopy density,leaf area and specific leaf area increased first and then decreased.The values of two indicators were the largest when the canopy density was 0.7,and the smallest under full sunlight.(2)The soluble sugar and soluble protein content of Camellia nitidissima Chi and Camellia japonica L.decreased with the increase of canopy density,and both of them were the most under full sunlight.The content of malondialdehyde,relative conductivity,SOD activity and POD activity decreased with the increase of canopy density.The change of the free proline content of Camellia nitidissima Chi was not obvious,and the content of free proline in Camellia japonica L.decreased first and then increased with the increase of canopy density.The CAT activity of Camellia nitidissima Chi was larger under the canopy density of 0.7,0.9,which was smaller under full sunlight and canopy density 0.5.On the contrary,CAT activity of Camellia japonica L.showed a decreasing trend.(3)The content of chlorophyll a,chlorophyll b,and chlorophyll of Camellia nitidissima Chi increased first and then decreased,while Camellia japonica L.increased with the increase of canopy density,and the trend of chlorophyll a/b in the two plants was opposite to that of chlorophyll content.The net photosynthetic rate(Pn)of Camellia nitidissima Chi and Camellia japonica L.increased first and then decreased.The apparent quantum yield(AQY),maximum net photosynthetic rate(Pmax)and light saturation point(LSP)of Camellia nitidissima Chi leaves increased first and then decreased,light compensation point(LCP)and dark respiration rate(Rd)decreased compared to full sunlight.The AQY,Pmax and LSP in the leaves of Camellia japonica L.were the highest under canopy density 0.5,LCP was the largest in full sunlight,and Rd was the highest in canopy density 0.5.(4)The total nitrogen and total phosphorus contents in leaves of Camellia nitidissima Chi were the highest under canopy density 0.7,and the total potassium content was the highest under canopy density 0.9,and the total nitrogen,total phosphorus and total potassium contents of Camellia japonica L.increased with the increase of canopy density.The soil total nitrogen,total phosphorus and total potassium contents of the two plants increased with the increase of canopy density,and the content of organic matter was the lowest in full sunlight.The results of DRIS nutrition diagnosis showed that the order of fertilizer requirement of two plants was different under different canopy density conditions.(5)The results of comprehensive analysis showed that plant height,ground diameter,biomass were positively correlated with leaf area,chlorophyll content,Pn,total nitrogen,phosphorus and potassium content in leaves and soil,soil organic matter content,while negatively correlated with soluble protein,malondialdehyde,cell membrane permeability,SOD,POD,chlorophyll a/b.There was a strong correlation between most indicators.Camellia nitidissima Chi and Camellia japonica L.membership values were the lowest in full sunlight.Camellia nitidissima Chi had the largest membership value under canopy density of 0.7,and Camellia japonica L.had the largest membership value under canopy density of 0.5.In conclusion,the height,ground diameter and biomass of of Camellia nitidissima Chi was the largest under canopy density 0.7,the growth was the best,the stress was low and the leaf photosynthetic rate was high,the photosynthesis was strong.When the canopy density was 0.5,the growth of Camellia japonica L.was the best,the stress was low and the leaf photosynthetic rate was high.Compared with the Camellia japonica L.,the shade tolerance of Camellia nitidissima Chi was stronger.