Effect of tea plantation age on the distribution of glomalin-related soil protein in soil water-stable aggregates in southwestern China

Glomalin-related soil protein (GRSP) is crucial for the accumulation of soil organic carbon (SOC), and contributes to the formation of soil aggregates. However, it remains unclear whether GRSP is involved in altering the stability of soil aggregates in the long-term tea planting process. The relationship between the distribution of GRSP and soil aggregates in tea plantations is poorly studied. We compared the distribution of SOC and GRSP in aggregates in tea plantations of different ages (18, 25, 33, and 55years) and those in an abandoned land and investigated their potential contribution to the soil aggregate stability. Tea plantation was found to be beneficial for the accumulation of SOC and GRSP compared to the abandoned land. The content of SOC significantly increased after tea plantation, especially in surface soil (0-20cm), and the increase range was 21.79%-46.51%, due to the centralized management of tea plantations. The content of total glomalin-related soil protein (T-GRSP) and easily extractable glomalin-related soil protein (EE-GRSP) varied with the increasing tea plantation age. The T-GRSP content was higher in 25-year-old tea plantation, while EE-GRSP was gradually decreased with the increasing age of the tea plantation, and T-GRSP had better correlation with SOC than EE-GRSP. Long-term tea plantation (after 33years) was not conducive to the preservation of GRSP. The distribution of GRSP in the tea plantation soils differed greatly among the aggregates, with the 0.25-1-mm aggregate having less GRSP, which might be related to the distribution of soil fungi in the aggregates. There was a significant correlation between T-GRSP and mean weight diameter (MWD; P<0.05) in the whole soil, whereas EE-GRSP had no correlation with the MWD of the aggregates. The T-GRSP content was correlated closely with the stability of soil aggregates in the tea plantations, and their relationship was dependent on the aggregate scale. Our results show that the T-GRSP content in the tea plantation soils has important effects on the formation and stability of aggregates in this region, which was one of the factors affecting the structure and quality of tea plantation soil. Improving GRSP is an effective way for the both SOC sequestration and soil health after long-term tea plantation.