林業(yè)資源配置ppt課件-資料下載頁
2025-05-01 00:06本頁面
【正文】 the time needed for clear cutting all the forest in the management unit, and the new forest are grow up and ready to be harvested. Rotation and age of maturation is different (page 129), but the rotation is calculated from the age of maturation (see figure on next slide ) Rotation = age of maturation 177。 regeneration period 0 10 20 30 40 50 10 20 30 40 50 30 10 20 40 50 輪伐期 A、 更新期 =0 此圖為采伐后及時(shí)更新，因此 v=0，輪伐期 u=50（年） B、 更新期 =10 輪伐期 30 10 20 40 50 0 10 10 20 30 40 50 60 10 20 30 40 50 60 此圖為伐后更新， v=10（年），則 u=60年 30 10 20 40 50 0 10 20 30 40 50 0 10 30 40 50 20 0 10 20 30 40 50 伐前更新 輪伐期 此圖為伐前更新， v = 10，則 u=40年， 這種情況常見于漸伐作業(yè)的采伐更新 So the task to calculate rotation is trying to find the age of maturation, the following are methods to calculate the age of economic maturation 2. Calculation methods of age of economic maturation Net profit of forest Average profit per unit area: iTCTRFR iii??In which: FRi: profit of forest at year I TRi: Total momentary revenue of clear cutting at year i TCi: Total cost of forest cultivation until year I i: age of forest Using the above equation to calculate the profit of forest for different year, the year which has the highest value will be the age of economic maturation. Then using this value together with regeneration period, the rotation can be calculated. The expected value of forest land 1)1()1(????ttee iiVLIn which: Le: Expected value of forest land Ve: Net present value form harvest i: interest rate t: harvest age The age which has the highest value will the age of maturation Present value (worth) ?? ???ntttt PCRP NW0 )1(1)(In which: PNW: present value Rt: moary revenue at year t Ct: moary cost at year t t: the year when the revenue and cost happened P: interest rate, or discount rate Internal rate of return ???? ???ntttnttt PCPR00 )1(1)1(1In which: Rt: moary revenue at year t Ct: moary cost at year t t: year P: the interest rate which hold the equation (IRR)
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