Importance of considering the growth response after partial harvesting and economic risk of discounted net revenues when optimizing uneven-aged forest management

Abstract

Because of the very high complexity of modern optimization models based on single trees, uncertainties are often disregarded. In this study, we present a modelling approach that allows partial harvesting but is still simple enough to consider risk. Our modelling approach investigates whether the inclusion of timber price uncertainty influences the harvesting schedule. The model considers positive growth response to the density reduction that follows harvesting. Testing the impact of uncertainty, we define the discounted net revenues of each harvest operation as random variables. We compare harvest scheduling both with and without the inclusion of uncertainty. We first model growth response based on a partial-harvest schedule, without integrating uncertainty from timber price fluctuations. The results show that harvesting tree cohorts at different times is financially optimal. We run the same model again, including the risk of timber price fluctuations. The inclusion of risk leads to slightly greater differences in recommended harvest timings. Because of the small difference observed, we conclude that it is unlikely that risk arising from fluctuating timber prices would strongly affect the results for more complex forest economic models concerning the optimal harvest schedules.