Modifying integrated nursery management through the lens of mycorrhizal ecology improves radiata pine seedling performance and reshapes root mycobiome structure at operational industry scale

Early management decisions in operational forestry are critical for plantation success because it strongly influences seedling quality at planting. Beyond shaping seedling morphology, nursery inputs can also restructure root-associated fungal communities which has consequences for nutrient acquisition, stress tolerance and disease suppression after planting. In this study, we altered nutrient and fungicide inputs based on mycorrhizal ecological theory and quantified the effects of these treatments on key dimensions of the growth performance of radiata pine seedlings. In parallel, we profiled the root-associated mycobiome, assigning fungal taxa to functional guilds and summarizing their richness, diversity, relative abundance and community structure. Using a composite performance index that integrates the key morphological and health measures into a single response variable, together with conventional statistical models with machine learning approaches, we identified management practises that promote both plant performance and a favourable root fungal community and determined the consistent microbiome changes linked to overall quality of the seedlings. These results suggest that microbial feedback loops occur even in highly managed nursery conditions. More broadly, by combining a composite performance index with predictive modelling, we provide a practical way to test complex management combinations and identify microbiome features associated with high-quality planting stock.