Net present value and iso-net present value curves for a sugi (Cryptomeria japonica D. Don)-plantation
1993
Ejiri, Y. (Iwaki Meisei Univ., Fukushima (Japan))
The NPV (Net Present Value) for a stand can be expressed by the functions of the two variables of discount rate and the rotation when the prices of goods are supposed to be constant. This paper considers the general relationship between the curves of NPVs and the curves of iso-NPVs, which represent the rotation dependency of NPV at a constant discount rate, and the rotation dependency of the discount rate that bring out a constant NPV, respectively, by drawing these curves in a three-dimensional coordinate space. The optimum rotation and the mean annual net revenue as the flow values, which are related to the production function, are explored based on these curves which actually were drawn for a sugi (Cryptomeria japonica D.Don)-plantation in the Iwaki district, Fukushima prefecture. As a result, the following facts were confirmed. The rotation which maximizes the NPV of a thinned stand is longer than that of an unthinned stand. The mean annual net revenue from a thinned stand is 1.6-1.7 times greater than that from an unthinned stand, when it is an upper site class, the rotation is longer than 80 years, and a demand for large diameter logs of great unit value exists. The mean annual net revenue from a stand of a lower site class is only about 30-40% of that of an unthinned stand of the upper site class
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