Optimizing rotation lengths for maximizing carbon balance of larch plantations in northeast China

Abstract

Achieving the carbon neutral targets before year 2060 is one of the important commitments for mitigating global climate change by Chinese government. However, the manner in which one would maximize the carbon sequestration of the planted forests is still unclear. Estimating accurately the carbon balance in forestry depends highly on the dynamics of numerous delay-released carbon pools (e.g., harvest residues, wood products), thus the strategies used to account for the carbon emissions of these components may have great influences on the decision-making and profitability associated with planted forests. This study developed a tool that allows forest managers and policy makers to analyze the effects of alternative accounting strategies for recognizing carbon emissions on the optimal rotation lengths and profitability of planted forests. The considered carbon balance not only refers to the within-forest pools, e.g., living biomass, harvest residues, annually generated litters and dead trees, but also refers to the outside-forest pools that include wood products, biofuel, operating process and substitution effect. The obtained results indicated that the lengths of optimal forest rotation decreased significantly with increases in site index, planting density and discount rate, while they increased dramatically with increases of carbon price. The gaps in rotation lengths were as large as 13.5 years, 6.9 years, 27.6 years and 11.0 years, respectively for the ranges of site index (10–18 m), planting density (2500–4444 trees per hectare), discount rate (1%–5%), and carbon prices (0–880 CNY/ton CO2) assumed. The effects of delay-released carbon pools on the optimal rotation lengths were not significant, when the substitution effects of wood products and biofuels were considered under the current carbon trading markets; however, some exceptions were observed when a very high carbon price (880 CNY/ton CO2) was assumed.