Microbial and organic matter composition jointly drive phosphorus cycling genes and phosphorus availability in Amazonian soils

Martins, G. L.; Monteiro, G. G. T. N.; Lange, M.; Freitas, A. S.; Barbosa, L. N. S.; van Leeuwen, J.; Soares, J. E. C.; Hanada, R. E.; Gleixner, G.; Tsai, S. M.

doi:10.1101/2025.10.14.682339

bioRxiv · 10.1101/2025.10.14.682339

Microbial and organic matter composition jointly drive phosphorus cycling genes and phosphorus availability in Amazonian soils

Martins, G. L.·Monteiro, G. G. T. N.·Lange, M.·Freitas, A. S.·Barbosa, L. N. S.·van Leeuwen, J.·Soares, J. E. C.·Hanada, R. E.·Gleixner, G.·Tsai, S. M.

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Abstract

Soil phosphorus (P) is a limiting factor for vegetation growth in the Amazon rainforest, where plants depend on microorganisms for organic matter cycling and nutrient uptake. However, forest-to-agriculture conversion changes plant-microbe-soil interactions, affecting P cycling, which may additionally changed by land-use intensity. This study examined the 30-year effects of converting a primary forest into two contrasting systems: a low-intensity agroforest and a high-intensity citrus plantation. We investigated how microbial and water-extractable organic matter (WEOM) composition interacted with soil physicochemical attributes and P fractions (labile, moderately labile, non-labile, and residual). Agroforest soils retained physicochemical and enzymatic attributes similar to the primary forest, while soils of the citrus plantation showed increased P in all fractions due to fertilization and reduced soil organic matter content, mainly in deeper layers. Microbial and WEOM composition patterns reflected land-use, with agroforest representing an intermediate state between primary forest and citrus plantation. Proteobacteria and nutrient-rich WEOM were more abundant in the agroforest, whereas Ascomycota and nutrient-poor WEOM predominated the citrus plantation. Genes related to "P acquisition" were more abundant in agroforest soils, while genes related to "P-compound synthesis" were more abundant in citrus plantation. Labile P was negatively correlated with genes related to microbial metabolism, suggesting that reduced P availability may induce a boost in microbial activity for internal P-cycling. These findings demonstrate that forest-to-agriculture conversion strongly affects microbial functions, with responses aligning with land-use intensity and WEOM resource availability. Nonetheless, microbes adapt by shifting strategies: prioritizing mineralization and solubilization or favoring biosynthesis depending on P availability.

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Martins, G. L., Monteiro, G. G. T. N., Lange, M., Freitas, A. S., Barbosa, L. N. S., van Leeuwen, J., Soares, J. E. C., Hanada, R. E., Gleixner, G., Tsai, S. M.. 2025-10-14. Microbial and organic matter composition jointly drive phosphorus cycling genes and phosphorus availability in Amazonian soils. https://doi.org/10.1101/2025.10.14.682339

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