Close-to-nature management enhances functional traits in Masson pine plantations by regulating stand states

Close-to-nature management (CTNM) is a silvicultural paradigm that seeks to emulate natural forest developmental trajectories in plantation systems. Although increasingly applied to subtropical conifer plantations such as Pinus massoniana, the extent to which CTNM alters the coupling between stand states and community-level functional traits remains poorly resolved. This study evaluated CTNM effects in P. massoniana plantations on the Qianzhong Plateau (Guizhou, southwestern China). Paired managed and control plots were surveyed twelve years after intervention across young, middle-aged, and near-mature stands. Nine stand indicators and nine community-level functional traits were quantified. CTNM significantly increased stand dominance (the proportion of dominant canopy tree count to the total tree count in a forest), tree health, and tree species diversity, particularly in middle-aged and near-mature forests, while young stands showed limited responses, reflecting lagged structural adjustment. Functional traits also shifted in a stage-specific manner: older stands exhibited higher leaf biomass and foliar nitrogen content, consistent with enhanced nutrient retention and foliar productivity, whereas young stands showed few consistent changes. Multivariate analyses indicated stronger coupling between stand indicators and functional traits under CTNM, though the key structural drivers varied with stand age. In young stands, tree health and species evenness were associated with higher leaf nitrogen content and leaf thickness. In middle-aged stands, species composition and evenness were linked to greater specific leaf area and leaf biomass. In near-mature stands, species diversity was associated with leaf dry matter content and phosphorus concentration. These findings demonstrate that CTNM strengthens the alignment between structure and functional traits, supporting the long-term ecological sustainability of subtropical P. massoniana plantations.