The contributions of soil biochemical characteristics and soil organic carbon (SOC) structure to SOC mineralization rate during forest succession on the Loess Plateau, China

Soil organic carbon (SOC) mineralization is a process driven by microorganisms and is considered to be one of the main forms of carbon loss in land restoration. However, the interaction of SOC structures and bacteria that drive SOC mineralization remain unclear. Therefore, four forest succession stages were investigated on the Loess Plateau of Northern China: (1) primary stage Betula platyphylla (BP); (2) transitional stage which were two mixed communities of Populus davidiana and Quercus wutaishanica with different proportions (PQ1); (3) (PQ2) and (4) the late stage was climax communities of Quercus wutaishanica (QW). The Illumina sequencing of the 16S rRNA gene and Fourier transformation infrared (FTIR-ATR) spectroscopy were used to clarify the regulation mechanism of microbial activity on SOC mineralization during forest succession through the perspective of SOC structures. Our results indicated higher aromatics-C in QW contributed to decreased SOC mineralization ratio (SMR). Redundancy analysis confirmed SOC structures-bacteria interaction and revealed the groups Acidobacteria correlated with recalcitrant SOC structures while Proteobacteria and Bacteroides correlated with labile SOC structures, respectively. Moreover, the partial least squares path model revealed that the SOC and C:N ratio act on soil bacteria community characteristics, and the higher abundance of Acidobacteria and the increase of aromatics-C decreased SMR. Collectively, these findings highlight the importance of bacteria-SOC structures interaction in decreased SMR and contribute to an improved understanding of how forest succession regulates carbon mineralization.