Soil pyrogenic carbon in southern Amazonia: Interaction between soil, climate, and above-ground biomass

The Amazon forest represents one of the world’s largest terrestrial carbon reservoirs. Here, we evaluated role soil texture, climate, vegetation, and distance to savanna on distribution stocks pyrogenic (PyC) in intact forests with no history recent fire spanning southern Amazonia forest-Cerrado Zone Transition (ZOT). In 19 hectare plots, including three Amazonian Dark Earth (ADE, terra preta) sites high PyC, measured all trees lianas diameter ≥ 10 cm analyzed physicochemical properties, texture PyC stocks. We quantified as a proportion total organic using hydrogen pyrolysis. used multiple linear regression variance partitioning determine which variables best explain variation. For combined, ranged between 0.9 6.8 Mg/ha 30 depth (mean 2.3 ± 1.5 Mg/ha) average, represented 4.3% (SOC). most parsimonious model (based AICc) included clay content above-ground biomass (AGB) main predictors, explaining 71% After removal ADE 3.8 1.9 0.8 –1 ) continued represent ∼4% SOC. models without AGB sand having an inverse relationship, 65% Partial analysis did not identify any components (climatic, environmental, edaphic), pure or shared, important variation plots. observed substantial amount even excluding forests; however, contrary expectations, were higher nearer fire-dependent Cerrado than more humid regions Amazonia. Our findings that ZOT will help improve estimates SOC change further climatic warming.