According to ICPP report, extreme climate event such as heavy precipitation, long-term drought will steadily increase and this will induces variations of soil moisture and soil dry and wet alternation. The changes will deeply affect underground ecological process such as soil Carbon input. Changes in exogenous Carbon input may alter the degradation rate of organic Carbon. This is priming effect. Positive priming effect promotes the rate and reduces soil Carbon pool while negative priming is beneficial to the ecosystem Carbon storage. The difference in δ¹³C values between exogenous Carbon and soil organic Carbon can be used to evaluate such priming effect.

Prof WANG Qingkui in the Plantation Ecology Research Group, IAE investigated the priming effect of changes in soil water content in subtropical forest plantations. He took soil samples with various water content, added litters marked with ¹³C, then incubated in a lab, measured CO₂ release rate and δ¹³C value s of released CO₂ to discriminate the CO₂ from soil samples and added litters. The results show that adding Chinese pine (Pinus massoniaana) litters into soil samples with 69% water content induced maximum priming effect, but the percentage was not affected by soil water content. Analysis showed that the ratio of Galanz positive bacteria/Glanz negative bacteria is correlated to the priming effect. The results promoted our knowledge in soil Carbon cycling of terrestrial ecosystem and how to better manage plantations in order to increase its functions in Carbon storage under the background of global climatic changes. The work was supported by NNSFC (31570466) and Science and technology pilot project B (XDB15010301) CAS. The results were published in Ecosystems (2016, 19: 450-460, DOI: 10.1007/s10021-015-9941-2) entitle as Soil Moisture Alters the Response of Soil Organic Carbon Mineralization to Litter Addition.