Climate-sensitive, spatially explicit multi-objective thinning for stand-structure and living-biomass-carbon trade-offs

Thinning can improve stand spatial structure but removes living biomass carbon, creating a trade-off that may vary among stand types and future climate pathways. We developed a spatially explicit, climate-sensitive multi-objective computational framework that integrates an individual-tree growth model, five neighborhood-based spatial metrics, species-specific biomass equations, and Monte Carlo optimization. The framework was applied to 15 mapped plots comprising secondary Betula platyphylla forests, Larix principis-rupprechtii–B. platyphylla mixed forests, and L. principis-rupprechtii plantations in northern China. Stand development was projected from 2025 to 2030 under SSP1-2.6 and SSP5-8.5, and thinning was optimized under carbon-retention, balanced, and structure-priority objectives. Across stand types, the best-found thinning intensity increased from 5.0–12.0% under the carbon-retention objective to 32.1–41.0% under the balanced objective and 44.2–49.3% under the structure-priority objective. Mixed stands showed higher absolute spatial-structure improvement efficiency per unit of living biomass carbon removed than larch plantations. Under the balanced objective, SSP5-8.5 reduced best-found thinning intensity by 3.9 and 6.0 percentage points in secondary birch and larch stands, respectively, but increased it by 4.6 percentage points in mixed stands. Across the evaluated scenarios, variation among management objectives was greater than variation between climate pathways, while stand composition mediated the direction of climate effects. The framework provides spatially explicit, stand-specific decision support for evaluating thinning intensity and candidate harvest-tree locations while reconciling structural diversification with short-term living biomass carbon retention.