Climatic and Edaphic Drivers of Soil Organic Carbon and Pyrogenic Carbon Stocks Across Elevation and Disturbance Gradients in Colombian Andean Forests

Abstract

Understanding the drivers of soil organic carbon (SOC) and soil pyrogenic carbon (PyC) variation and their role in natural and managed ecosystems is increasingly important. However, PyC stocks in tropical Andean soils remain understudied. Here, we examined how edaphic and environmental factors affect PyC across elevation and disturbance gradients in 36 plots spanning natural forests and agrosilvopastoral systems in the Colombian Andes. Across the 0–100 cm soil profile, the mean SOC stock in the study region was 433.10 Mg C ha−1 (range: 67.97–1462 Mg C ha−1), while the mean PyC stock was 34.13 Mg C ha−1 (range: 2.29–305.70 Mg C ha−1), accounting for approximately ~8% of the total SOC. This PyC stock is approximately nine times greater than the Amazon-wide average. PyC (%) did not vary significantly with disturbance gradients or soil depths. However, both PyC (%) and SOC (%) varied significantly with elevation zonation (p < 0.001). The High Andes had the highest concentrations of PyC (1.3%) and SOC (14.6%), which were substantially higher than the Medium Andes (PyC = 0.17%; SOC = 6.7%) and Low Andes (PyC = 0.06%; SOC = 1.3%). Soil clay content and annual precipitation were the primary drivers of PyC, explaining 56% of the variability when combined with pH, Ca, and NDVI. PyC was positively associated with clay content (Estimate: 0.27, p < 0.001) and negatively associated with annual precipitation (Estimate: −0.18, p < 0.05). These factors may influence the physical and chemical processes that affect PyC formation and preservation in soils. This analysis provides insight into SOC and PyC variability in Andean forest soils, highlighting the substantial contribution of soil PyC to total soil carbon and its importance as persistent soil carbon under current and predicted warming conditions across the region.