Soil karstification intensity and carbon sink effect of plum plantation in karst rocky desertification areas

The study of soil karstification intensity under artificial economic forest in karst rocky desertification area is not only related to the estimation of karst carbon sink, but also to the accurate assessment of land carbon source/sink in karst area. In order to make clear the contribution of artificial economic forest to karst carbon sink in the process of rocky desertification control, the soil of different planting ages of plum forest in the National Sustainable Development Experimental Area of Ministry of science and technology in Gongcheng County, Guilin City was selected as the research object. The soil CO2 concentration of different soil depths was monitored in situ with different planting ages of plum forest, and the limestone corrosion rate under the soil was monitored by standard corrosion test piece method, and the carbon sink intensity caused by karstification was analyzed according to the monitoring results. The results showed that at the same planting age, the soil CO2 concentration in 50 cm depth was greater than that in 20 cm depth, and the order from large to small of soil CO2 concentration between different planting ages in the same soil layer was 20, 2 and 5 years. In addition, the variation of soil CO2 concentration was obvious with seasons change, especially the monthly dynamic change of soil CO2 concentration had good correlation with the monthly average air temperature and precipitation in the study area. Therefore, planting ages, soil depth and climate conditions (temperature and precipitation etc.) of the study area had important effects on soil CO2 concentration of plum forest. The research results of limestone corrosion rate under plum forest soil with different planting ages were consistent with the order of soil CO2 concentration. Generally, limestone corrosion rate under plum forest soil in the same soil depth was the largest in 20 years, followed by 2 years, and the minimum in 5 years. This is mainly due to the nutrients and the surrounding environment have reached a dynamic balance, and there are a lot of root exudates returned by both fertilization and self-return after 20 years' growth. For the plum plantation planted for 2 years, due to the main vegetative growth in the initial stage of planting, the root system is in the vigorous growth and metabolism period. The plum plantation planted for 5 years changed to reproductive growth, mainly the fruit growth of aboveground part. Therefore, in addition to the CO2 concentration, the limestone corrosion rate under the soil of different planting ages is related to the growth status and soil environment of plum forests. The corrosion amount of plum plantation with different planting ages ranged from 42 to 136.3 t/(km2•a), and the carbon sink ranged from 5 to 16.4 t/(km2•a). The results showed that planting artificial economic trees in the process of rocky desertification control can not only produce forest carbon sink in the aboveground, but also the karst carbon sink in the underground. The results have important reference value for accurate prediction of underground karst carbon sink potential in karst area. © 2020, Editorial Department of the Transactions of the Chinese Society of Agricultural Engineering. All right reserved.