with or without the price risk, what is the difference of
the NPV? To what degree can it increase or decrease the total NPV of the agro-forestry? In order to
answer it, we examined year 7, the minimum age of the rotation of agro-forestry based on Eq. (13).
The total net present value is examined under two cases: (1) with timber price risk in agro-forestry
system, and (2) without timber price risk. Under price risk the result is 300,625 yuan/ha (which is total
net present value of the whole rotation, with a minimum harvest age of 7 and a maximum harvest age
15) and this result is gathered from the stochastic dynamic program. Without price uncertainty the
value is 269,499.1. Therefore, we can draw a conclusion that considering price risk can increase the
total NPV of the agro-forest system by 11.55%.
For pure forest, the NPV determined using the reservation price model (when price risk is considered)
is 101,191.5 yuan/ha. The NPV is 85,682.92 if price risk is ignored when determining the
optimal harvest decision. The NPV is also increased under price risk at a rate of 18.1%. Therefore, our
conclusion is that under price risk, the total NPV is greater than without price risk. As a matter of fact,
it is wise and necessary for the manager to take risk into consideration, because uncertainty and risk
exists objectively during the long growth period of forest.