Defining the relationship between bulk density and organic carbon content in forest soils using generalised linear mixed-effect models.

backgroundIn this study, we used a generalised linear mixed-effects model (GLMER) to establish a predictive pedotransfer function defining the relationship between forest soil bulk density and total organic carbon. More than 950 soil samples were obtained from four forested areas with a wide range of bedrock (limestone, loess, crystalline volcanic, sandstone, alluvial loam, polygenic loam and transported materials rich in organic carbon) and soil types (Leptosols, Cambisols, Fluvisols, Podzols and Technosols). Model validation was performed by testing against 10% of the data randomly selected from the original dataset (10% dataset) and an independent dataset from the Czech national forest inventory (NFI2 dataset).

resultThe GLMER including sample origin locality as random effect displayed a highly accurate predictive capacity. Subsequent analysis avoided model simplification by excluding sample origin and retaining the global GLMER only. For all samples, the final model covered a range from 0.16 to 27.70% for total organic carbon and from 0.27 to 1.94 g cm

conclusionThe pedotransfer functions produced, particularly that based on global GLMER, can be used to express bulk density via total organic carbon content, or vice versa, with high accuracy. While based on a wide range of bedrock/soil types, further studies may be needed in other regions to validate the model for general application.