Agricultural land abandonment promotes soil aggregation and aggregate-associated organic carbon accumulation: a global meta-analysis

Abandonment of agricultural land is a common type of land-use change worldwide. Nevertheless, there is currently no consensus on how soil aggregates and aggregate-associated organic carbon (C) vary with agricultural land abandonment on a global scale.

We synthesized the global responses and controlling factors of distribution, stability, and associated organic C concentration of soil water-stable aggregates under the influence of agricultural land abandonment using meta-analysis.

On average, agricultural land abandonment significantly enhanced the mass proportion of large macroaggregates (LMA) and mean weight diameter (MWD) by 89.9% and 51.1%, respectively, while leading to a significant reduction in the proportion of silt-clay particles (SC) (−26.6%). By contrast, the proportions of both small macroaggregates (SMA) and microaggregates (MIA) showed no response to agricultural land abandonment. Overall, agricultural land abandonment significantly increased the aggregate-associated organic C concentrations by 23.3–24.8%, and the highest increase was observed for LMA. In most cases, the responses of soil aggregates to agricultural land abandonment did not differ significantly between subgroups of mean annual temperature, mean annual precipitation, soil texture, and abandonment duration (AD). We found that the dynamics of MWD and associated organic C concentrations were positively related to AD according to redundancy analysis.

Our findings suggested that the formation and C accrual of LMA, which could be improved with the increase of AD due to a more favorable environment for plant and microbial growth, played crucial roles in both soil structural rehabilitation and soil C sequestration during agricultural land abandonment.