First Measurements of Saturated Hydraulic Conductivity From Peats of the Central Congo Basin

The peat swamp forests of the central Congo Basin represent the largest, most carbon-rich peatland complex in the tropics. The maintenance of peat carbon stocks and accumulation relies on persistent soil saturation, yet the hydrological functions of tropical peatlands remain poorly understood, particularly in the central Congo Basin. We report the first measurements of saturated hydraulic conductivity (Ksat) from Congolese peats. We used Mini Disk tension infiltrometers to estimate Ksat at depths of 0 and 10 cm across three study areas in the Democratic Republic of the Congo. Ksat ranged from 1.55 × 10−5 to 5.75 × 10−4 m s−1, with a mean of 1.78 × 10−4 m s−1. A general linear model revealed significantly higher Ksat at the surface than at 10 cm depth, while Ksat is negatively related to degree of peat humification. However, Ksat did not vary between palm, hardwood and mixed forest types, or with proximity to rivers (a proxy for flooding regime). Although our linear model is not sufficiently skilful to predict Ksat reliably, our findings suggest that a generalisable model for tropical peat Ksat may be attainable with larger datasets that span greater ranges of depths and levels of decomposition. Notably, our surface Ksat values are lower than those from deeper layers in Southeast Asia and the Americas, implying lower depth-integrated permeability in peats of the central Congo Basin. This may reflect low rainfall and deeper water tables in the region, which would enhance decomposition and reduce pore space more rapidly.