| Cupressus funebris is a major local timber species in Sichuan hilly area,and have high economic value.The species of soil in hilly area is purple soil,which has poor nutrient and the adaptability to environment and the stress resistance ability is relatively low.Combined with the awareness of forest unreasonable planting and harvesting,natural and man-made effects lead to inefficient low ecological function and low land productivity of Cypress forest,so people take measures to create a mixed forest to improve the overall ecological and economic benefits of Cypress forest.Fine root has the strongest root absorption and direct contact with the soil,and it not only can obtain a large number of required nutrients and water from the soil for their own growth,but also can transport them to the where required,so it has important significance to ensure the normal physiology of plant metabolic activity.Cupressus funebris,a light-loving species,whose root is shallow,taproot is not obvious,lateral root and fine root are developed,and then it also has a narrow crown,Therefore,we perforam a experiment chosing Cupressus funebris and Koelreuteria paniculata as mixed tree species,which are deep-rootedness,positive deciduous broad leaved tree species,and we set different mixed conditions(1:3,1:2,1:1,2:1,3:1)to measure the fine root biomass,shape index(average diameter,specific root length,specific space are)and nutrient allocation pattern of various species(nitrogen,phosphorus,kalium,calcium,magnesium),and by analyzing the correlation between different mixed condition and root physiological indexes we can select the most appropriate way of mingling,which can improve the comprehensive benefit of the mixed and provide theoretical basis and scientific reference for mixed cultivation.Results:(1)Whether mixed forest and pure forest,there is a same conclusion among three tree species of mixed:fine root morphological indexes can make regularity change by fine root level.The average diameter of fine root,would increase with root order,while specific root length and specific surface area decrease with root order.The fine root average diameter of level 1 is the smallest,but the specific root length(SRL)and specific surface area(SSR)is the largest.The fine root average diameter of level 5 has the largest specific root length and specific surface area.(2)A11 mixed treatments can decrease the average diameter ofCupressus funebris lower root(leverl-3),but Cupressus funebris mixed with Koelreuteria paniculata by 1:1 can significantly increase the average diameter ofCupressus funebrisat level 4,the specific root length at level land 5,and the specific surface area at level5,and then,it can also significantly improve the average diameter of Koelreuteria paniculataat level 2-5 and the specific root length of level 1 and.Cupressus funebris mixed with Toona sinensisby 1:2 will significantly improve the specific root length of Cupressus funebris at level5 and the specific surface area at level 1;also this radio can significantly improve the average diameter ofToona sinensisat level 2-3,the specific root length and the specific surface area at level 1.Above all,in terms of fine root morphology,Cupressus funebris and Koelreuteria paniculata mixed with the ratio of 1:1 is the best proportion,Cupressus funebris and Toona sinensis mixed with the ratio of 1:3 and 1:2 are the best proportion.(3)Mixing can make the grade 1-4 root biomass of Toona sinensis decreased and make Koelreuteria paniculata level 1,2,5 root biomass increased,besides,Cupressus funebris and Koelreuteria paniculata mixed by 1:2 mixed and Cupressus funebris mixed with Toona sinensis by 1:3 can also significantly increase level 2 and 4 root biomass.That is to say,these two methods can improve the total biomass of fine roots.(4)1:3 in the most suitable mixed ratio for Cupressus funebris and Koelreuteria paniculata root to improve the absorption of nutrients,because this proportion can significantly improve Cupressus funebris the total N content of level 2-4 root,the total P content of fine roots at all levels,the Ca content of fine root at level 1,the Mg content of fine root at level 3-5,and for all levels of total K content and other root order fine roots nutrient has no significant inhibitory effect.At the same time,the ratio can also significantly improve Koelreuteria paniculata the total N content of fine root at level 1-4,the total P content of fine root at level 3,the total K content of fine root at level 5,and the Ca content of fine root at level 1-3.Therefore,in order to improve the nutrient content of fine root,the best ratio of Cupressus funebris mixed with Koelreuteria is 1:3.(5)The effects of mixed with the same ratio on the content of N,P,K,Ca,Mg of Cupressus funebris and Toona sinensis at different levels are different,as well as their trends.Ratio at 1:3,1:2,1:1 all can significantly improve the Mg content of fine root at 3-5 level,the Ca content of fine root at 1 level,and the ratio at 1:1 can significantly increase the total P content of fine root at 1-2 level and the inhibition of total N and total K is lesser at the same time.Besides,mixing can reduce the content of total P,total K,Ca of Toona sinensis fine root at level 4-5 and the Mg content at level 5,but they can increase the Mg content at level 3 and the Ca content at all levels.So,in order to improve the nutrient content of fine root,the best mixed proportion of Cupressus funebris and Toona sinensis is 1:1.(6)In the same proportion of mixed treatment,the effect of Cupressus funebris mixed with Koelreuteria paniculata on improving fine root morphology,biomass and nutrient is bigger than mixed with Toona sinensis,and 1:3 is the most appropriate proportion.Using this mixed method,we can reform the low efficiency of Cupressus funebris,and at the same time improve paniculata the root’s ability of absorbing soil nutrients of Cupressus funebris and Koelreuteria,then it can also make full use of soil resources,improve the weak ecological function of pure forest,and increase economic benefits. |
