Simulation of long-term peat accumulation dynamics & vulnerability: Insights from a Pole Forest and Palm Swamp in Amazonia

Abstract. Peruvian peatlands represent one of the largest reservoirs of carbon in Amazonia. This heterogeneous landscape exhibits several types of ecosystems, including pole forest (PF), palm swamp (PS), open peatlands (OP), and seasonal flooding forest (SFF). We apply the HPMTrop_EcoTy model, a novel development that represents ecological succession via bespoke parametrisations of ecohydrological mechanisms, to gain insights into long-term peat accumulation dynamics across these ecosystems and to assess their vulnerability to carbon gain and loss. Model results suggest that carbon accumulation rates in Amazonian peatlands are similar to or greater than those reported for the Congo Basin and Southeast Asia. Peat and carbon accumulation in Amazonia are particularly sensitive to local-scale changes, especially those driven by ecosystem succession. Amazonian peatlands appear less sensitive to precipitation changes, likely due to the extremely high rainfall across the Peruvian Amazon. However, reducing rainfall to levels similar to those of the present-day Congo Basin (45 % reduction) produces an exponential decline in peat and carbon accumulation, suggesting a critical tipping point. Sensitivity analysis shows that PF, the most carbon-dense ecosystem, is the most sensitive, likely because it is rain-fed and therefore more vulnerable to ecohydrological changes, whereas SFF, the least carbon-dense, is the least sensitive. Considering the exceptionally high precipitation in the region, peatland formation appears mainly controlled by local processes such as river migration, which drives vegetation succession linked to peatland development.