Balancing individual growth and stand carbon dynamics: optimizing age-dependent density management for Larix principis-rupprechtii plantations in semi-humid to semiarid regions

Planted forests serve as critical carbon sinks in climate mitigation strategies, yet balancing individual growth with stand-level carbon storage through age-specific density regulation remains a key knowledge gap. By integrating dendrochronological analysis (1003 increment cores from 532 trees) with longitudinal stand development data (50 permanent plots), we quantify moisture-mediated thresholds governing carbon dynamics in Larix principis-rupprechtii plantations. Our results showed that tree biomass dominated ecosystem carbon storage, accounting for over 95% of aboveground pools, with stand development exhibiting distinct phases: a linear carbon accumulation phase persisting until 70,000 tree-years/ha, followed by a carbon saturation plateau. Optimal balance between tree growth and carbon storage occurred at 27,000 tree-years/ha under baseline conditions, increasing to 34,000 tree-years/ha during normal/wet years but showing 20–35% reductions under drought stress. Moisture availability mediated these thresholds, with drought intensity exacerbating growth-carbon tradeoffs and significantly lowering operational targets. Our findings establish age-stratified density management curves that reconcile tree-level productivity with stand-level carbon storage across moisture gradients, providing actionable guidelines for adaptive silviculture in climate-sensitive plantations. These quantitative relationships enable forest managers to optimize stand density thresholds based on both stand age and projected climate conditions, offering a framework to maximize ecological and economic benefits in water-limited environments.