Yang Lanfang

Effects of maize (Zea mays L.) growth and photosynthesis on δ13C in soil respiration

As a safe, stable and practical labeling method, the natural abundance of 13C has been widely used in a carbon cycle in the soil-plant system. In order to understand the effects of maize growth and photosynthesis on the value of δ13C in soil respiration, the value of δ13C in soil respiration was determined by mass spectrum after being trapped in a NaOH solution under a closed static chamber and then turned into barium carbonate in a pot experiment. The results showed that maize growth and photosynthesis significantly affected the value of δ13C in the soil respiration. In maize-planted soil, the value of δ13C in soil respiration had a clear seasonal variation. It changed with maize growth in the range of −14.57‰ to −12.3‰ and decreased during the period of trumpeting > ripening > flowering stages. The difference of δ13C in soil respiration during various maize growth stages added up to about 2.3‰ However, in bare soil, δ13C in soil respiration ranged from −19.34‰ to −19.13‰ and did not change significantly over time. The δ13C in soil respiration in the maize-planted soil was the lowest at flowering stage. This was mainly due to the decline of the input in assimilates into soil and the decrease in root activity. However, the δ13C increased at ripening stage, due to the decomposition and ingestion of senescent and died roots by soil microorganisms. In the planted soil, δ13C in soil respiration was significantly higher during daytime than at nighttime at flowering and ripening stages. The difference of δ13C in soil respiration between day and night periods added up to about 1.4‰ and 2.1‰ at flowering and ripening stages, respectively. Shading maize plants at the trumpeting stage decreased the value of δ13C in soil respiration significantly. The difference of δ13C in soil respiration between the treatment of non-shading and shading plants added up to 2.85‰ It was concluded that δ13C in soil respiration was remarkably controlled by the maize growth and photosynthesis in planted soil. Soil respiration was mainly derived from the recent assimilates during maize growth.