Seedling-Stage Responses of Lumnitzera littorea to Substrate Type and Salinity-Structured Irrigation Regimes in Can...

Reliable nursery production is essential for producing ex situ planting stock of the locally threatened mangrove Lumnitzera littorea in Can Gio, Vietnam. We evaluated 12-month seedling performance using two nursery substrates-CTI (topsoil) and CTII (mixed substrate)-and salinity-structured irrigation regimes: C, a dynamic river/tidal water plus freshwater reference regime and seven fixed-salinity treatments (E1-E7: 0, 10, 15, 20, 25, 30, and 35‱). Each substrate-regime combination comprised three replicate cells of 40 seedlings (N = 1920). The primary endpoints were month 12 survival (SR12), seedling height among survivors (H12), and root collar diameter among survivors (Do12). Statistical inference was confined to E1-E7; C was retained as a descriptive operational reference. For E1-E7, substrate and regime significantly affected SR12 and H12, whereas Do12 varied by regime but not by substrate; no substrate × regime interaction was detected. SR12 declined sharply at 30-35‱, especially under CTI, and the high-salinity H12 and Do12 estimates were based on few survivors. CTII outperformed topsoil alone, particularly for survival and survivor-conditioned height. The findings support conservative nursery guidance for Can Gio: use a mixed substrate and avoid sustained high fixed-salinity irrigation, without extending the inference to a species-wide salinity optimum or post-planting field performance.