The amount of CO₂ released to the atmosphere through soil microbial respiration (Rs) is estimated to be 60 Pg C. Therefore, a small change in the response of Rs to elevated temperature will have great influence on soil organic C stock and atmospheric CO₂ concentration under a continuously warming scenario.

In recent years, temperature sensitivity (Q₁₀) of Rs or soil organic C decomposition has gained increasing concerns. However, most previous incubation experiments on the Q₁₀ were conducted at constant temperatures, resulting in the thermal acclimation of soil microbial community and the substantial differences in substrate availability, which greatly influence Q₁₀ values.

Furthermore, the previous studies at large scale is used the same incubation temperature for all soils collected from different sites, resulting in a deviation in estimated Q₁₀ values.

Thus, to advance the understanding of the spatial pattern of Q₁₀ values and its fundamental drivers, professor Wang Qingkui and his colleagues from the Institute of Applied Ecology of the Chinese Academy of Sciences conducted a novel incubation experiment with periodically changing temperature based on the mean annual temperatures of soil origin sites along a 3,800 km long north–south transect of forests in eastern China.

They had three important findings in this study. First, Q₁₀ values of Rs nonlinearly changed with latitude, showing low Q₁₀ in subtropical forests and high Q₁₀ in temperate forests. Second, coniferous forest soils had higher Q₁₀ values than broadleaved forest soils, and soil C:N ratio was positively related to the Q₁₀ values, supporting the “C quality temperature” hypothesis. Last, the dominant factors regulating the regional variations in Q₁₀ varied among the tropical, subtropical, and temperate forest ecosystems, although gram-negative bacteria exhibited the most importance in regulating the variation in Q₁₀ across all ecosystems, followed by the C:N ratio, fungi, and the fungi:bacteria ratio.

Their results suggested the non-linear latitudinal patterns of Q₁₀ values of Rs and highlighted the importance of C quality (C:N ratio) and microbial controls over Q₁₀ value in China’s forest ecosystems.

The results were published as the title " Carbon quality and soil microbial property control the latitudinal pattern in temperature sensitivity of soil microbial respiration across Chinese forest ecosystems " in Global Change Biology.

The work was supported by the National key R & D projects in China and the National Natural Science Foundation of China.