Carbon storage of soil-vegetation system under different land use patterns in saline coastal regions

Research on the coupling relationship between land use change and carbon sequestration potential in soil-vegetation systems in saline coastal plains has been of great theoretical and practical significance in terms of optimizing the implementation of land use with the purpose of vegetation restoration and enhancing carbon sink. This study used an abandoned bare saline-alkali land as the control to determine the dynamic changes in carbon storage in soil-vegetation systems under 3 years and 10 years old Tamarix chinensis plantations, 2 years and 8 years old Lycium chinense plantations, and frozen saline water irrigated cotton field with plastic mulching, and cotton field only mulched with plastic film. Based on continuous observation and quantitative description, we discussed carbon sequestration potential of soil-vegetation systems under the land use patterns and provided theoretical basis for increased regional carbon storage. The results were as follows:1) T. chinensis and L. chinense plantations and cotton cultivation with frozen saline water irrigation and plastic mulching significantly increased soil organic carbon content and reduced soil bulk density. T. chinensis planted for 10 years and L. chinense planted for 8 years had the highest carbon storage, 118.24 t·hm^-2 and 96.27 t·hm^-2, which recorded carbon storage increases of 58.51 t·hm^-2 and 36.54 t·hm^-2 respectively over cotton fields under frozen saline water irrigation with plastic mulching treatment. It also increased by 83.39 t·hm^-2 and 61.42 t·hm^-2 respectively over abandoned bare saline-alkali lands. 2) T. chinensis planted for 3 years and L. chinense planted for 2 years had the highest carbon sequestration rate, which was respectively 10.08 t·hm^-2·a^-1 and 2.71 t·hm^-2·a^-1. The rate of carbon sequestration was lowest (0.53 t·hm^-2·a^-1) for cotton field under frozen saline water irrigation with plastic mulching. T. chinensis planted for 10 years and L. chinense planted for 8 years had the weakest performance as carbon source and needed increased carbon storage by land use change or vegetation regeneration. The carbon storage of cotton field only with plastic film mulching decreased 0.86 t·hm^-2 per year due to remove of cotton straw. The abandoned bare saline-alkali land was a carbon source because not exogenous carbon input, whose carbon storage decreased 1.42 t·hm^-2 per year. By comparing the advantages and disadvantage of each land use type, T. chinensis and L. chinense cultivation was the most efficient way of increasing regional carbon storage in saline coastal regions.