Characteristics Of Soil And Water Loss And Nitrogen And Phosphorus Loss Of Cinnamomum Camphora Dwarf Forest At The Initial Stage Of Planting

In order to meet the market’s demand for natural camphor tree essential oil,the planting area of swarf Cinnamomum camphora in Jiangxi has been increasing year by year.At the beginning of its development,a large area of exposed ground caused serious soil erosion problems,and excessive fertilization caused serious problems due to the unilateral pursuit of economic benefits during the planting.The problem of non-point source pollution in China has become a severe ecological and environmental problem in the concentrated and contiguous development of land.In this paper,the 2-year-old Cinnamomum camphora forest is used as the research area,and the test method combining field monitoring and artificial simulated rainfall in indoor runoff troughs is adopted.After the general rule is proved in the field monitoring test,the artificial simulated rainfall test is set to 0.8mm/min,Three rainfall intensity gradients of 1.2mm/min,1.6mm/min and three fertilization gradients of 0.035kg/m²,0.1kg/m²,and 0.2kg/m² were used to study soil and water loss in the initial planting of Cinnamomum camphora under the condition of 60 minutes of rainfall.And the loss of nitrogen and phosphorus,in order to explore the characteristics of soil and water loss and the characteristics of vertical and horizontal migration of nitrogen and phosphorus in the initial planting of linden.The main results are as follows:（1）In natural rainfall,discharge and sediment yield are significantly related to rainfall,with correlation coefficients of 0.987 and 0.979,respectively.However,the intensity of daily rainfall has a greater impact on the amount of surface runoff carrying sediment.During the observation period,the content of total phosphorus in sediment is much greater than that in runoff.Nitrogen is more likely to be lost in surface runoff than phosphorus.Ten days after fertilization is a high risk period for nitrogen and phosphorus loss,and phosphorus is lost in surface runoff.After the risk period,only when the daily rainfall reached 49.0 mm,the loss of phosphorus concentration increased significantly.The concentration of nitrogen loss in soil flow was significantly higher than that in surface runoff,and was the largest in soil flow at a depth of 60 cm.The loss of phosphorus in soil flow at 20 cm and 40 cm was significantly higher than that in soil runoff at a depth of 60 cm.There is no significant difference in runoff between medium and surface.（2）In artificial simulated rainfall,when the rainfall intensity increased from 0.8mm/min to 1.2mm/min,the initial runoff time of surface runoff was shortened by 324s,and the proportion of surface runoff in the runoff trough increased from 32.98%to 87.74%,the main mode of slope runoff changed from infiltration to surface runoff,but the change was not obvious as the rainfall intensity continued to increase.During the rainfall process of the runoff trough that lasted 60 minutes,the correlation coefficient between sediment yield and rainfall was 0.892,and the correlation coefficient with discharge yield was 0.975;the loss concentration of total nitrogen and ammonium nitrogen decreased first,then increased,and finally tended to gradually A stable trend;the loss concentration of nitrate nitrogen and soluble phosphorus generally showed a downward trend during the whole rainfall process;the loss concentration of total phosphorus showed a peak when the rainfall intensity was1.6mm/min.Under the same artificial rainfall conditions,the amount of nitrogen loss in surface runoff was much greater than that of phosphorus.The loss of total nitrogen and total phosphorus increased significantly after the rainfall intensity increased from 0.8mm/min to1.2mm/min and 1.6mm/min.Moreover,the loss of nitrate nitrogen and soluble phosphorus is the largest when the rainfall intensity is 1.2mm/min,and the loss of nitrate nitrogen decreases as the rainfall intensity continues to increase.When the rainfall intensity is0.8mm/min-1.6mm/min,the proportion of soluble nitrogen and phosphorus in the loss of nitrogen and phosphorus gradually decreases with the increase of rainfall intensity.The loss of nitrogen and phosphorus is generally dominated by soluble nitrogen and phosphorus,But at 1.6mm/min,phosphorus loss is dominated by particulate phosphorus.The fitting effect of the nitrogen loss model is better.The regression model of total nitrogen loss is Y_TN=13.711I+64.015F+0.006V-19.436（R²=0.947）,and the regression model of ammonium nitrogen loss is Y_NH4-N=8.784I+15.751F+0.001V-8.494（R²=0.897）,the regression model of nitrate nitrogen loss is Y_NO3-N=-8.580I+3.863F+0.003V+5.842（R²=0.847）.The fitting effect of the phosphorus loss model is not good,and the R² of the regression model of total phosphorus loss and soluble phosphorus loss is lower than 0.8.（3）The total amount of fertilizer applied to camphor trees in a single runoff trough is0.2kg.Under the condition of a rainfall intensity of 1.6mm/min,the initial runoff time of soil runoff is 60min after the runoff from the surface runoff,and the flow rate of the surface runoff is the amount of the runoff from the soil.14 times.The loss of nitrogen and phosphorus in soil flow is mainly nitrate nitrogen and soluble phosphorus.The loss of nitrate nitrogen accounts for 72.43%of the total nitrogen loss,and the loss of soluble phosphorus accounts for 63.64%of the total phosphorus loss.The average concentration of nitrate nitrogen in the soil flow is 6.27 times that of the surface runoff,but the loss is 1/11 of the surface runoff.The soil nutrient loss was the largest when the rainfall intensity of Cinnamomum camphora was 1.2mm/min in the early planting period.