The atmospheric concentration of CO₂ has increased significantly as a result of the anthropogenic activities. Land use change, such as deforestation, can lead to a rapid loss of soil carbon (C), accelerating CO₂ emission from soil to the atmosphere. However, its effect on CO₂ emission remains a widely debated topic due to large variability in soil CO₂ emission caused by specific site conditions.    

Under the supervision of Prof. CHENG Xiaoli, ZHANG Qian and WU Junjun from Wuhan Botanical Garden made a field experiment in Danjiangkou Reservoir area which experiences the land use change from croplands to afforestation over a span of 30 years. This group explored the seasonal variation in co₂ emission and its δ¹³C-CO₂ signatures following agriculture land use change, and assessed the correlations between biotic and abiotic factors and CO₂ emission and δ¹³C-CO₂ signatures.  

The soil CO₂ emission in woodland and shrubland was significantly higher than that in cropland, reflecting that afforestation enhanced soil respiration due to an increase in the availability of soil C and a decrease in fluctuation of soil moisture and soil temperature. The soil CO₂ flux showed a typical seasonal pattern which was higher in the summer than other seasons due to higher temperature in the summer stimulating microbial decomposition thus enhancing soil respiration. Whereas, the δ¹³C-CO₂ was negatively related to soil temperature and positively correlated with the δ¹³C of microbial biomass due to its strongly relationship with the isotope signature of plant litter inputs. 

This research was financially supported by the National Natural Science Foundation of China, and the “Strategic Priority Research Program B” of the Chinese Academy of Sciences. Results have been published in Soil & Tillage Research entitled “ Agricultural land use change impacts soil CO₂ emission and its ¹³C-isotopic signature in central China ".

The monthly variations (a, c) and annual averages (b, d) of soil CO₂ flux and its carbon isotope signature within three land use types (Image by CHENG’s group)