| In order to clarify the nutrient absor:ption and distribution rules and soil nutrient characteristics of Paulownia plantation,it is expected to provide a theoretical basis for scientific fertilization and provide a scientific basis for the promotion and planting of Paulownia plantation in Hunan Province.In this paper,through the four standard forests of 4 different forest ages and secondary forest control of different forest ages,a total of 20 standard plots were used to determine 35 physical,chemical,enzymatic activity indicators and microbial organisms in the soil.Quantitative indicators,and various organs of Paulownia forest:root,stem,branch and leaf 12 nutrient indicators,and using standard wood method to investigate the biomass of various organs of different forest ages,using factor analysis,canonical correlation analysis and stepwise regression analysis,etc.The nutrient absorption and distribution rules and soil nutrient characteristics of Paulownia plantation were studied.The main conclusions are as follows:(1)With the increase of forest age,the diameter of the breast,the height of the tree,and the dry biomass of each organ gradually increased,and the trunk biomass accounted for a high proportion.The total biomass of Paulownia forests in 1 year,3 years,9 years and 12 years was 1.28kg/plant,16.87kg/plant,72.22kg/plant and 100.42kg/plant,respectively,of which the proportion of trunks was 57.68%.57.68%,59.38%and 59.49%.(2)Various organs of Paulownia forest between different forests:nutrient indicators of roots,stems,branches and leaves:carbon,nitrogen,phosphorus,potassium,calcium,magnesium,sulfur,iron,manganese,copper,zinc and boron Significant difference(P<0.05).The accumulation of nutrients in the organs of Paulownia forest had the highest accumulation of carbon and nitrogen.With the increase of forest age,the cumulative amount of nutrients absorbed by various organs increased continuously.In general,the absorption and accumulation of nutrients in different forest ages were the same.Both carbon>nitrogen>calcium>potassium>phosphorus>iron>zinc>manganese>copper>boron>magnesium>sulfur.(3)There were significant differences in nutrient use efficiency between different organs of Paulownia plantation.Among them,roots had the highest utilization efficiency of potassium,magnesium,sulfur,iron and manganese,respectively:413.87g/g,616.50g/g,1099.48g/mg 11.06g/mg and 43.55g/mg,the highest utilization efficiency of dry nitrogen,phosphorus,calcium,zinc and boron are:307.10g/g,2420.58g/g,295.68g/m,14.89g/mg and 98.28g/mg,the utilization efficiency of copper to the highest is 41.91g/mg,the utilization efficiency of leaf to carbon is up to 1.89g/g,and the lowest efficiency of nutrient utilization is concentrated in the leaves except for carbon,and the utilization of carbon Efficiency is not significantly different in different organs.With the increase of forest age,the nutrient use efficiency of the whole tree of Paulownia forest increased first,then decreased and gradually stabilized.The comprehensive utilization efficiency of the three-year-old Paulownia forest was 1.86g/g,and the first-year nutrient utilization efficiency was only 1.65g./g,the total efficiency of nutrient utilization of Paulownia forest in 9 and 12 years was not much different,both were 1.76g/g,but both were lower than the average.(4)In addition to soil available phosphorus and soil acid phosphatase,there are significant differences in soil properties between different soils.Among them,the soil water content,water holding capacity and porosity of the 12-year-old Paulownia forest were significantly higher than other forests.The soil aeration of the 1-year-old Paulownia forest was significantly higher than that of other forests.The soil density and non-capillary porosity of the secondary forest of Tung oil tree were significantly higher than other woodland.The content of pH,available iron,available manganese and microbial biomass N in the secondary forest of Tung oil tree was significantly higher than that in Paulownia forest.In the Paulownia forest,the organic matter,total nitrogen,total phosphorus and ammonium nitrogen in the 1-year-old Paulownia forest were effective.Sulfur,invertase activity and microbial biomass P are abundant.The content of total potassium,nitrate nitrogen,available potassium,urease and catalase in 9-year-old Paulownia forest is abundant.The cation exchange capacity,effective calcium and effective in 12-year-old Paulownia forest Copper and available boron are abundant.(5)There was a significant correlation between the soil properties of Paulownia forests in different forest ages(P<0.05).Among them,the correlation between soil physical and chemical properties is significant and presents different correlations.Soil enzyme activity and microbial biomass are also significantly correlated with soil physical and chemical properties,including:soil total porosity,minimum water holding capacity,capillary porosity and Soil aeration,as well as organic carbon,total nitrogen,nitrate nitrogen,available magnesium and available manganese are sensitive factors for soil enzyme activity and microbial biomass changes.(6)With the increase of the age of Paulownia forest,the comprehensive score of soil fertility decreased rapidly and then gradually recovered.Among them,the secondary forest of tung tree>12-year-old Paulownia forest>9-year-old Paulownia forest>1-year-old Paulownia forest>3-year-old The average comprehensive scores of Paulownia forest were:0.285,0.2625,0.1775,0.1445 and-0.87.(7)There was a significant correlation between the nutrient content of various organs in Paulownia forest and soil available nutrients(P<0.05),among which:root nutrient carbon,nitrogen,sulfur and zinc and soil organic carbon,nitrate nitrogen,available sulfur and available zinc the correlation between dry nutrients nitrogen,mafgnesium,manganese and copper is related to soil organic carbon,nitrate nitrogen,available sulfur,available manganese and available zinc.The nutrients are carbon,nitrogen,iron and copper and soil.The correlations among organic carbon,nitrate nitrogen,available calcium,available sulfur and available manganese are high.Leaf nutrients carbon,sulfur,iron,manganese and boron and soil organic carbon,nitrate nitrogen,available calcium,effective magnesium,effective The correlation between manganese and available zinc is large.(8)The soil properties are significantly correlated with the nutrient use efficiency of carbon,nitrogen,phosphorus,potassium,calcium,magnesium,sulfur,iron,manganese,copper,zinc and boron in the roots,stems,branches,leaves and whole trees of Paulownia forest.(P<0.05).Among them,soil ammonium nitrogen,available sulfur,available magnesium,urease activity and microbial biomass phosphorus are the most significant factors affecting the utilization efficiency of Paulownia forest nutrients. |
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