Rhizospheric soil as a means of maintaining the survival of Melanoxylum brauna Schott seedlings, an endangered tree species

The species Melanoxylum brauna Schott is considered vulnerable due to intensive logging and lack of replanting. Several challenges affect its propagation, including seed viability, predation, and difficulties in commercial seedling production caused by substrate, fertilization, and excessive watering, which can lead to mortality. This study aimed to evaluate the survival and quality of M. brauna seedlings produced in different soil/substrate compositions and under treatments expected to alter microbial viability, seeking to identify a suitable reference substrate for seedling production under nursery conditions. Seedlings grown in soil collected near the mother tree exhibited the greatest survival and growth after 150 days. Enzyme activities, including β-glucosidase and arylsulfatase, were highest in the organic substrate, followed by the soil near the parent tree, indicating their potential as biochemical markers for soil quality. However, high enzyme activity alone was insufficient to ensure seedling survival in the organic substrate. These findings indicate that soil collected near parent trees is an effective reference substrate for maintaining M. brauna seedling survival and quality under nursery conditions. The maintenance of seedling survival in autoclaved parent-tree soil may indicate a possible rhizosphere memory, understood as the persistence of soil properties generated by previous interactions among the mother trees, their roots, microorganisms, and the surrounding soil. However, for large-scale production, future studies should develop sustainable strategies based on low proportions of rhizospheric soil, microbial extracts, selected microbial consortia, or optimized mixtures with nursery substrates.