As global temperatures rise, soil microorganisms play a key role in regulating terrestrial biogeochemical feedbacks by controlling carbon and nitrogen cycling. Microbial carbon use efficiency (CUE) and nitrogen use efficiency (NUE) are core indicators linking microbial metabolism to soil carbon and nitrogen cycling. However, whether the temperature sensitivities (Q₁₀) of these two efficiencies are coordinated across broad geographic scales remains unclear.

A new study published in Global Change Biology and led by Prof. WANG Chao from the Institute of Applied Ecology of the Chinese Academy of Sciences revealed a significant coupling between the temperature sensitivities of CUE and NUE, with higher Q₁₀ values at lower temperatures and a shift in the primary drivers from biotic to abiotic factors as temperature increased.

To investigate this, the researchers collected soil samples along a 4,000 km forest transect spanning eastern China. The scientists quantified microbial CUE, NUE and their respective Q₁₀ values using ¹⁸O and ¹⁵N isotope tracing techniques at 12 °C, 20 °C, and 28 °C.

The results showed that the temperature sensitivities of microbial carbon and nitrogen use efficiencies were closely related across temperature ranges. Notably, the researchers found that the Q₁₀ values of CUE and NUE were higher in the lower temperature interval (12-20 °C) than in the warmer interval (20-28 °C).

Further analysis highlighted the mechanisms driving these sensitivities. The temperature sensitivities of CUE and NUE were positively associated with the temperature sensitivity of microbial growth. Additionally, at lower temperatures, biotic factors such as microbial community properties governed the Q₁₀ values of CUE and NUE. However, as temperature rose, abiotic factors, including precipitation patterns and the soil nitrogen to phosphorus ratio, became the dominant regulators.

“Our research demonstrates that the environmental controls on microbial efficiency are not static,” Prof. WANG said. “By identifying how these drivers change with temperature, we can provide more accurate data to refine Earth system models and better predict how forest ecosystems respond to a changing climate.”

Figure 1. Study location, experimental design, and overview of the coupled temperature sensitivity of microbial carbon and nitrogen use efficiencies (Image by WANG Chao)