| The paper studied the Daxing'an Mountains low-quality broad-leaved mixed forest,replanted it and the seedlings were Larix gmelinii seedlings.The selected sample plots were BZ1,BZ2,BZ4,BZ5 and BZ6,and the corresponding planting densities were 400,500,600,700,800 and 900 tree · hm-2.The control plot was CK and it was not operated.The canopy structural parameters,seedling growth parameters and photosynthetic parameters were obtained by field work,the physical and chemical properties of the soil and the water holding performance data of the litter were measured in the laboratory.Firstly,the descriptive statistical analysis and the difference analysis were carried out.Then,35 indexes in the above indexes were selected to study.Establish the comprehensive evaluation model and the optimal transformation mode was selected by the principal component analysis method.The results could provide reference and basis for the follow-up cultivation of low-quality broad-leaved mixed forest in Daxing'an Mountains.(1)The organic matter mass fraction of BZ5 was 33.67 g · Kg-1,the pH value was 6.41,the available nitrogen content was 446.68 mg · Kg-1 which was the largest,and the available phosphorus and available potassium of BZ3 which were the largest.And the total phosphorus,total phosphorus and total potassium contents were all lower than those of the control plot.By the analysis of variance,total phosphorus and total potassium mass fraction were significantly different(P < 0.05);The non-capillary porosity of BZ4-modified plots was 32.01.And the noncapillary porosity of BZ1 was similar to that of BZ6,and the total porosity of BZ4 was 87.52%,and the non-capillary porosity of all modified plots were higher than those of control plot.(2)The natural water holding capacity of the untreated litter of BZ5 was 43.90%,the maximum water holding capacity was 828.86%,the maximum water holding capacity was 1098.25%,the maximum water holding capacity was 31.37 t · hm-2,the total maximum water holding capacity was 53.81 t · hm-2;The no-decomposed volume,semi-decomposed volume,total volume,the maximum water holding capacity of semi-decomposed litter,no-decomposed effective storage,semi-decomposed effective storage and total effective storage of BZ6 were the largest;The no-decomposed volume,the maximum water holding capacity of nodecomposed litter and no-decomposed effective storage of the selected sample plots were lower than those of semi-decomposing litter;the semi-decomposing litter of BZ1,BZ3 and BZ4 was lower than the control plot.The difference between the control and the control plot was significant(P <0.05).(3)The total leaf flux,the average leaf rotation angle,the total point factor,the total radiation flux on the crown,the direct radiation flux under the crown,the indirect radiation flux under the crown,the total radiation under the crown of BZ5 were the largest.And the leaf area index of BZ5 transformation plot was 5.76,which was higher than that of control plot 3.14.The total radiation flux of BZ3 was the highest,the transpiration rate of BZ4 was the largest and the net photosynthesis and environmental CO2 mole fraction of BZ3 were the largest.The results showed that the photosynthetically active radiation and the stomatal conductance of BZ5 were the largest,and the intercellular CO2 molar fraction of BZ6 was the largest.The seedling growth rate of BZ5 was the highest.(4)A comprehensively evaluate model was established on low-quality forest which was replanted by uing the principal component analysis method,and 35 evaluation indexes reflecting the effect of replanting and transformation were selected,the comprehensive score of each plot was calculated to evaluated the low-transformation effect.The results showed that the comprehensive score of BZ5(0.761)was the highest,indicated that BZ5 was the best,and the planting density was 800 tree· hm-2 was the most suitable for the cultivation of low-quality broad-leaved mixed forest in Daxing'an Mountains. |
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