Thermally labile Carbon dominates Amazonian deep soils

Beneath the towering canopy of Amazonian rainforest, where life has evolved in exquisite balance for millennia, the soil holds a deeper story still. Here, carbon is not merely stored — it is transformed, shielded, and sequestered within ancient mineral matrices. Understanding these dynamics is no longer a scientific curiosity; it is a vital key to predicting Earth’s changing climate and safeguarding its most enduring reservoirs.

The transition from forest to pastures alters not only what enters the soil, but how carbon persists, transforms, or is lost. By tracing these shifts through the deep profile, we uncover the hidden consequences of land‑use change. The loss of deep rooting trees scavenging for nutrients and water sources, is likely to reduce carbon inputs, changing biogeochemical processes in the deep.

In order to shed light on the carbon storage and dynamics in the deep Amazonian soils, samples (17 sites at 4 farms) were taken up to 6 m depth under native forest, pastures and secondary forests in eastern part of the state of Acre.

First results showed that carbon over the whole soil profile was thermally labile, meaning >90% of the carbon is oxidized <400 °C. We believe that this result is associated with higher sand contents in the sampled sites, and with kaolinite predominance in the soils of Acre. Potential enzymatic activity indicates a shift from investing in phosphorus acquisition to nitrogen acquisition in secondary forests, whereas β-glucosidase was lowest in native forests