Enhanced priming effect in agricultural soils driven by high-quality exogenous organic carbon additions: A meta-analysis
Yuyao Zhang, Hongyu Hu, Yiguo Ran, Ping Huang, Yunlong Cai, Lin Chen, Congzhi Zhang, Xin Gao, Donghao Ma, Jiabao Zhang
Abstract
The addition of exogenous organic carbon (C) to soil can either accelerate or retard the soil organic carbon (SOC) mineralization, i.e., the priming effect (PE), which plays a crucial role in SOC sequestration and thus is significant in the context of global warming. However, the influence of exogenous organic C quality on PE remains poorly understood, potentially limiting our understanding of SOC dynamics. Thus, we conducted a global meta-analysis to reveal the effect of exogenous organic C quality on PE through compiling a data set of 2031 experiment trials. Our results revealed that the addition of organic C significantly enhanced SOC decomposition by 46.23 % in agricultural soils. Labile C compounds induced a stronger PE than both intermediate and recalcitrant C compounds. Organic C materials rich in labile C compounds or with low lignin/N ratios exhibited a greater PE than the resistant substrates. Notably, a threshold C/N ratio of 25 was associated with a higher PE in substrates with C/N < 25. Given the pronounced PE observed with high-quality organic C addition (characterized by C/N <25, low lignin/N ratio, and easy decomposability), we proposed that "stoichiometric decomposition" might predominate the PE in agricultural soils. Collectively, the current study underscores the significant role of exogenous organic C quality in modulating the PE, emphasizing the need for further research to inform effective SOC management strategies.