Roots affect the response of heterotrophic soil respiration to temperature in tussock grass microcosms

Aims and Background

While the temperature response of soil respiration (R_S) has been well studied, the partitioning of heterotrophic respiration (R_H) by soil microbes from autotrophic respiration (R_A) by roots, known to have distinct temperature sensitivities, has been problematic. Further complexity stems from the presence of roots affecting R_H, the rhizosphere priming effect. In this study the short-term temperature responses of R_A and R_H in relation to rhizosphere priming are investigated.

Methods

Temperature responses of R_A, R_H and rhizosphere priming were assessed in microcosms of Poa cita using a natural abundance δ¹³C discrimination approach.

Results

The temperature response of R_S was found to be regulated primarily by R_A, which accounted for 70 % of total soil respiration. Heterotrophic respiration was less sensitive to temperature in the presence of plant roots, resulting in negative priming effects with increasing temperature.

Conclusions

The results emphasize the importance of roots in regulating the temperature response of R_S, and a framework is presented for further investigation into temperature effects on heterotrophic respiration and rhizosphere priming, which could be applied to other soil and vegetation types to improve models of soil carbon turnover.