Determination And Analysis Of The Daily Vaiiation Of Photosynthetic Characteristics On Zenia Insignis Young Plantations In Different Seasons

Eucalyptus plantation interplanting Tephrosia candida is an excellent model for improving soil fertility and promoting forest growth.We through regular monitoring to understand the growth difference of eucalyptus about different Eucalyptus and Tephrosia candida compound model,to make clear the spatial distribution characteristics and interspecific competition mechanism in the niche overlap of root biomass,total root length density,root average diameter and absorption root length density about Eucalyptus and Tephrosia candida compound systempr.It can provide theoretical basis for agroforestry management,to optimize the management pattern and management measures for Eucalyptus plantation.The main results are as follows:(1)The volume size order for interplanting A(space between Eucalyptus plants were 2 m x 3 m),interplanting mode B(space between Eucalyptus plants were 2 m x 6 m)and pure forest CK mode of Eucalyptus was B>A>CK,pattern A increased 0.0059 m3 than CK each strain,model B increased 0.0103 m3 than CK each strain;Due to the difference in planting density between the modes,the model A increased 9.6849 m3 than CK per hm2 after 3 years of planting,the unit stock volume of model B decreased by 2.8758 m3 than CK per hm2.The yield per unit area of the edamame soybean was 82.1%and 78.4%in the first two years of the model A and B than CK,respectively,in the third year,it was down to 23.4%and 32.1%.(2)After interplanting Tephrosia candida,the root biomass of eucalyptus increased significantly,in which the fine root biomass of model A was 1.99 times than that of pure CK.The root biomass of model A and CK is concentrated in the soil layer of 0-40 cm,accounting for 87.23%and 85.05%of the total root biomass respectively.In the vertical distribution,the middle roots and fine roots of pattern A are all grown in deeper soil,and the order of biomass is 20-40 cm>0-20 cm>40-60 cm.On the horizontal distribution,the order of the total root biomass of pattern A and pure forest CK are location 1>location2>level 3,the root biomass of row is bigger than strains,and model A's fine root biomass mainly concentrated in the location 2.In vertical direction,the sorting size of the root length density of mode A and pure forest CK are 20-40 cm>0-20 cm>40-60 cm,the total root length density of model A decreased by 5.4%than pure CK,and the model A's fine length density decreased by 5.0%than pure forest CK in 20-40 cm soil layer.On the horizontal direction,the root length density of eucalyptus showed single change type,the maximum length density of fine root about model A and pure forest CK appeared at 1.0 m and 1.25 m,the density peak of coarse root appeared at 0.75 m and 1.0 m,the root length density of model A distributed in the range of 1 m distance of eucalyptus.The average diameter of pattern A is greater than that of pure forest CK.In the vertical distribution,the average diameter size of eucalyptus eucalyptus in model A and pure forest CK is 40-60 cm>20-40 cm>0-20 cm.On the horizontal distribution,the mean diameter of the root system decreased.In general,the root biomass and average diameter of eucalyptus trees in mode A was bigger than that of pure forest CK,but the total root density is less than CK.Compared with eucalyptus pure forest,while interplanting Tephrosia candida for 3 years,the root of eucalyptus tree was increased in vertical distribution,and its absorption roots were concentrated in 20-40 cm soil layer.It decreased in the horizontal direction,and the main concentration is within the range of 1 m of eucalyptus tree trunk,corresponding to the boundary of the planting belt on Tephrosia candida.(3)The total root biomass and root density of the Tephrosia candida in the model A was significantly smaller than that of the single model.In the vertical direction,the biomass density and root density of the Tephrosia candida of model A had been shifted to the shallow soil,which is more concentrated in the 0-20 cm soil layer.In A horizontal direction 0 m to 1.5 m,the root biomass and root length density of the Tephrosia candida of model A were gradually increase density,and in the distance of 0.25 m and 0.5 m position far away from eucalyptus,there was no Tephrosia candida root.(4)In the compound system about Eucalyptus(2 m x 3 m)and Tephrosia candida,the root biomass of Eucalyptus accounts for 81.2 percent of the total root biomass.In vertical direction,with the increase of soil depth,the proportion of the root biomass of Eucalyptus gradually increased,but the Tephrosia candida proportion decreases gradually,from 23.1%(0-20 cm soil layer)reduce to 6.3%(40-60 cm soil layer).On the horizontal direction,the line of Eucalyptus planting soybean planting zone extends to the Tephrosia candida,the total root length density of Eucalyptus reduced gradually,the root length density at 0.25 m,0.5 m,0.5 m,1.0 m,1.25 m and 1.5 m position respectively accounted for 100.0%,100.0%,96.3%,92.3%,87.6%and 92.3%;93.2%of the total root length of Eucalyptus,which was distributed in a space of lm between Eucalyptus lines and in the planting belt of the Tephrosia candida,only 6.8 percent of the Tephrosia candida roots competed with Eucalyptus of the compound system in the underground.