image: Conceptual illustration comparing China's current forest harvesting practices (business-as-usual, BAU, left) with an optimized management strategy (OPT, right). Under current management, restrictions on timber harvesting favor the accumulation of standing biomass but may also contribute to forest aging, increasing tree mortality and limited domestic wood production. The optimized strategy adjusts harvesting intensity, timing and location according to forest age, management objectives and ecological constraints. It also allows carefully regulated timber production in suitable multifunctional forests while maintaining restrictions in ecologically sensitive forests. Green plus signs indicate increases, red minus signs indicate decreases or reductions, and blue symbols indicate neutral effects in the conceptual framework. The illustration highlights how age-structured and spatially targeted harvesting could reduce aging-related mortality, improve domestic wood supply and enhance long-term carbon retention without compromising designated conservation functions.
Credit: ©Science China Press
Keeping trees standing is often seen as the best way to protect forest carbon. But as forests grow older, their growth slows and more trees die, raising a difficult question: does cutting less wood always lead to greater carbon storage over the long term?
A modeling study of China’s forests suggests that the answer depends on when and where harvesting takes place. Researchers found that carefully designed harvesting strategies could increase both total carbon storage and domestic timber production, even though they leave slightly less carbon in living trees.
The team, led by researchers from Nanjing University of Information Science and Technology and the Chinese Academy of Forestry, analyzed 15.5 million individual-tree records from China’s National Forest Inventory. They used a spatially explicit ecosystem model to simulate forest growth, harvesting, tree mortality and carbon stored in wood products through 2100 under changing climate conditions.
The researchers compared a business-as-usual scenario, reflecting current harvesting practices, with an optimized approach. The latter adjusted harvest timing and intensity to forest age and local conditions, and allowed carefully managed timber harvesting in suitable multifunctional forests while retaining ecological restrictions and excluding protected areas.
Historical inventory data showed that average harvested volume fell while tree mortality increased between the sixth and ninth national inventories. The simulations likewise indicated that, without management changes, aging forests could lose increasing amounts of wood through natural mortality. Harvesting selected stands earlier, before some trees die, could reduce these losses and support regeneration.
Under the optimized scenario, average annual timber production from 2020 to 2100 increased from 0.32 billion to 0.44 billion cubic meters, a rise of 38% compared with business as usual. Cumulative mortality-related volume losses fell by 1.82 billion cubic meters, or 6.7%.
The climate result was more nuanced. Greater harvesting reduced standing forest biomass relative to current management, but also increased the carbon retained in harvested wood products and reduced mortality losses. When forest and wood-product carbon pools were considered together, modeled total carbon storage was 4.2% higher, equivalent to an additional 0.52 ± 0.16 billion tonnes of carbon under the study’s wood-product assumptions.
The modeling also suggested that greater domestic timber supply could reduce reliance on wood imports. Under the optimized scenario, projected wood self-sufficiency rose from 59% to 81%, although future demand and trade will depend on economic conditions beyond the forest model.
The authors emphasize that these results do not support indiscriminate logging. The modeled benefits depend on forest age, management objectives, ecological limits, and the fate of harvested wood. The analysis did not explicitly resolve harvest-induced changes in soil carbon, and future climate simulations used one climate model across four emissions pathways.
Taken together, the findings suggest that forest carbon policy needs to consider more than the carbon held in standing trees at any one time. Managing the timing, intensity and location of harvesting may help sustain carbon storage while supplying timber, provided that ecological safeguards are maintained.
The research was supported by the National Key Research and Development Program of China, the National Natural Science Foundation of China, provincial science funding in Jiangsu, and Schmidt Sciences through the CLARiTy project.
Journal
National Science Review
Method of Research
Computational simulation/modeling