Ecological Stoichiometry and Microbial Community Dynamics in the Rhizosphere of Parashorea chinensis: Implications for Ex Situ Conservation of Endangered Trees

Ex situ conservation of the endangered tree Parashorea chinensis, a national first-class protected species in China, hinges on the development of functional belowground ecosystems, a process that remains mechanistically unclear in restoration ecology. This study evaluated the development of conservation plantations by analyzing rhizosphere soil stoichiometry, enzyme activities, and microbial communities across four growth stages in natural forests and ex situ plantations. Results showed that ex situ plantations exhibited obvious soil acidification and persistently low N:P ratios, with phosphorus acting as the primary limiting nutrient. Fungal α-diversity was strongly correlated with stoichiometric imbalance in ex situ plantations. Artificial management drove microbial community shifts toward fungal-enriched assemblages, forming a distinctive functional microbial portfolio to tolerate combined stresses from acidification and nutrient stoichiometric imbalance. Crucially, these managed ecosystems maintain core nutrient cycling functions, and key microbial indicators show distinct developmental trends toward the conditions observed in natural forests as stands mature. In summary, ex situ conservation alters belowground biogeochemical processes rather than merely supporting plant survival. We propose targeted microbial management, particularly inoculation with native functional taxa from natural forests, to accelerate soil stoichiometry rebalancing and enhance nutrient cycling efficiency. These findings provide both evidence for the ecological feasibility of ex situ conservation and practical strategies for optimizing its long-term success through science-based belowground management.