Ecological And Economic Risk Assessment Of Cunninghamia Lanceolata And Eucalyptus Robusta Smith In Guangxi Area

With the continuous development of social economy,the demand for wood is greatly increased,and the contradiction between supply and demand of wood is becoming more and more prominent.In the face of the present situation,all countries take the development of artificial forest as a response to solve the contradiction between supply and demand of wood and improve the economic and ecological benefits of wood.Among all kinds of plantation tree species,Cunninghamia lanceolata and Eucalyptus robusta Smith are popular and widely planted in Yunnan,Guangxi and Guangdong because of their high wood value,strong adaptability and high economic benefit.However,in the process of planting artificial forest,the phenomena of land decline,economic benefit decline and vulnerability to natural disasters caused by multiple generations of continuous cropping have been widely studied by many scholars.But domestic and foreign scholars mainly focus on the mechanism of continuous cropping effect and the condition of forest growth.Wind damage is most common in natural disasters,but the research is limited to the principle of wind damage and the qualitative description of wind damage.Based on the continuous inventory data and field investigation of forest resources in Guangxi region,the net present value and internal rate of return economic index were used to evaluate the benefits from different site conditions and continuous cropping states,respectively,considering carbon sink and not considering carbon sink,and price sensitivity analysis,profit and loss threshold analysis and profit probability analysis were carried out without considering carbon sink.The results show that:?1?The economic benefit of Cunninghamia lanceolata and Eucalyptus robusta Smith plantation under different site conditions,the profit space of economic benefit gradually decreases with the continuous decline of site conditions.When the land use index of Cunninghamia lanceolata is higher than 13 and the forest land use index of Eucalyptus robusta Smith is higher than 17,the income can be obtained under the general market conditions,while the Eucalyptus robusta Smith with poor site conditions?SI=13?is no longer suitable for commercial planting because of its economic loss,and only when the market price of Eucalyptus robusta Smith wood is higher than 874.65 yuan·m^-3.If the market price of Cunninghamia lanceolata under the same conditions is higher than 2123 yuan·m^-3,it can reach high investment capital return,this return probability is only 9.65%,the ability to resist economic risk is low.?2?Under different site conditions,the carbon sink compound benefit of Cunninghamia lanceolata and Eucalyptus robusta Smith plantation increased significantly,even if the site conditions of Cunninghamia lanceolata and Eucalyptus robusta Smith plantation can get high income,but at this time the ecological benefit occupies the main share,and the value of Cunninghamia lanceolata and Eucalyptus robusta Smith as commercial forest will be lost.?3?The economic benefits of continuous cropping of Cunninghamia lanceolata and Eucalyptus robusta Smith under different site conditions,the profit space and probability of continuous cropping of three generations decreased gradually with the gradual increase of generation under the same site condition.Under different site conditions,with the continuous decline of site conditions and the rise of continuous cropping,the profit space gradually decreased,until the poor site conditions of the second and third generations of Cunninghamia lanceolata,Eucalyptus robusta Smith plantations were not profitable.The profit ranking of Cunninghamia lanceolata is:19F1>16F1>19F2>13F1>16F2>16F2>19F3>13F2>16F3>13F3.After continuous cropping for the third generation on the basis of good site conditions?SI=19?,it is no longer profitable.Only the wood price higher than 1133 yuan·m^-33 can be profitable,with a probability of 83.58%.The profit ranking of Eucalyptus robusta Smith is21F1>19F2>17F1>19F3>17F2>13F1>17F3>13F2>13F3.After the first generation with poor site conditions?SI=13?,there is no profit.Only when the Eucalyptus robusta Smith wood price is higher than 874.65 yuan·m^-33 can it be profitable.?4?Under different site conditions,the carbon sink compound benefit of Cunninghamia lanceolata and Eucalyptus robusta Smith plantation was much higher than that of Chinese fir forest.With the increase of generation,the quality of site becomes worse and the benefit of carbon sink is improved obviously.?5?After normalization,multiple linear regression was used to test the influence factors of wind damage.The results show that the wind damage grade model is that Cunninghamia lanceolata is Y=2.97059-0.15350X₁+0.10750X₂-0.11576X₃-0.30893X₄+0.29475X₅.The meaning of each factor is that Y—Chinese fir wind damage grade;X₁—age group;X₂—elevation;X₃—slope direction;X₄—slope position;X₅—management grade.Eucalyptus robusta Smith is Y=4.1966+0.2061X₁-0.5213X₂+0.2890X₃-0.2847X₄-0.1312X₅.The meaning of each factor is that Y—eucalyptus wind damage grade;X₁—slope;X₂—age group;X₃—management grade;X₄—soil thickness;X₅—the total vegetation coverage.In order to calculate the wind damage grade according to the situation,so as to remind the corresponding forest farm to prevent the loss of economic benefits caused by wind damage.