Studies On The Felling Age Of Chinese Fir Plantation

With the theory of forestal sustainable development, national forestry policies on the guidelines has been changed from the tradional forestry to the sustainable forestry gradually. The felling age is the fundamental index of forestry production, it is not only an important basis which is used to confirm the forest management cycle and assess the value of forestry enterprise, but also an important measure indicators of the cutting operation and the cutting quota. How to determine the felling age reasonably, so that people can gain the maximum benefit from the forest resources which is not based on damaging any forest resources, has become the important part of sustainable forest management.To confirm the forest economic mature age, we should estimate the growth law of forest firstly, that must combine the growth law of trees and the data of their main measuring factor (such as the age, height, diameter and height, volume, the site quality, etc.), so that we can estimate the rule of the volume, the average diameter, the average height and the distribution of diameter grade. Therefore, this paper is based on the collection of the sample data of Chinese fir, fitting by the professional statistical software, and finally choosed the growth equations which are the most accurate as the forest harvesting model of forestal every factors by comparing and analyzing their accuracy. To estimate the growth condition of Chinese fir plantation,this papper has established the site index model, the average dimater model, the volume model, the average height model and the distribution of diameter grade model,etc.After established growth model, we need to research the monetary income when the forest is on the felling age. So we must know the relevant economic value evaluation index of forest (wood price, taxes, etc.). With China's forestry policies updated constantly and the rapid development of economy, the economic indicators in past now no longer applies to the forest of the monetary income, so this paper will introduce the related concepts about updated replacement cost in the assets assessment, and according to the current economic policy of forestry (i.e., the cost of forest culture will be calculated by 10% of the sale price,and delete the dimension cost in this tax computation), calculated the price of one tree, and finally established the net monetary income model of Chinese fir plantation, so as to estimate the condition of the monetary income in different site conditions and different age when the trees is going to be cut.Finally, this paper has chosen the proper formula of calculating economic mature to calculate the economic mature age of Chinese fir plantation. But there are too many formulas of calculating economic mature, and many experts also puts forward a lot of experience equations, so based on comprehensive consideration of sustainable forest management and the time value of money situation, this paper choosed NPV method, the internal rate of return method and land expectation value method to calculate the economic benefit of the Chinese fir plantation in different felling ages and different site conditions, and figured out the economic mature age of Chinese fir by comparing and analyzing them at last.Due to the calculation of the economic mature age is based on economic evaluation index, so it need to be in certain social economic conditions to finish. However, with the development of society, social economic condition is changing constantly, economic mature age stand will be influenced by relevant factors either. Therefore, this paper has conducted the sensitivity analysis with the relevant factors which are influenced on the calculation of the economic mature age of Chinese fir.