Persistence of soil microbial residuals and lignin phenols in forest ecosystems along the latitude gradient

Aims

Soil organic carbon (SOC) storage is mainly governed by inputs from plant and microbial sources. How the relative contributions of these two sources in forest soils vary along broad-scale environmental gradients is poorly understood. The contributions of these two carbon sources in different soil layers are also elusive.

Methods

We used amino sugar and lignin phenol as biomarkers to indicate microbial- and plant-derived soil carbon. The concentrations of amino sugar and lignin phenol in topsoil (0–10 cm) and subsoil (30–60 cm) of major forest types along a latitude gradient in China were investigated.

Results

The concentration of soil amino sugar decreased along the latitude in topsoil, which is mainly controlled by the variations in mean annual temperature and soil nitrogen. The concentration of lignin phenols decreased along latitude in topsoil, mainly controlled by soil carbon/nitrogen ratio. The microbial-derived carbon was mainly composed of fungi-derived in topsoil, while bacteria-derived dominated in subsoil. Climate and soil properties are primary factors controlling the persistence of microbial residues and lignin phenols in topsoil, and soil clay is the crucial factor in the subsoil.

Conclusions

Both microbial residuals and lignin phenols in topsoil showed a decreasing trend with increasing latitude, but controlled by different sets of environmental factors. Subsoil microbial residues and lignin phenols showed no trend along the latitude and are mainly influenced by soil clay content.These findings provide new insights on how climate and vegetation affect soil carbon persistence, revealing significant distribution patterns of forest soil microbial residuals and lignin phenols along a latitude gradient.