The Contribution of Roots, Mycorrhizal Hyphae, and Soil Free-Living Microbes to Soil Respiration and Its Temperature Sensitivity in a Larch Forest

Abstract

Soil respiration plays a critical role in driving soil carbon (C) cycling in terrestrial forest ecosystems. However, evidence to demonstrate the response of roots, mycorrhizal hyphae, and soil free-living microbes of soil respiration and their temperature sensitivity (Q₁₀) remains lacking. Here, we used a root exclusion method to assess the contribution and response of root respiration (R_root), mycorrhizal respiration (R_myc), and (soil organic matter) SOM respiration (R_som) to soil temperature in a larch forest. During the growing period, the contributions of R_root, R_myc, and R_som to soil respiration were 42%, 6%, and 52%, respectively. The respiration rates of all components increased exponentially with increasing temperature. Based on these constitutive respiration rates with soil temperature, the Q₁₀ values for R_root, R_myc, and R_som were 3.84, 5.18, and 1.86, respectively. The results showed that the response to temperature change was different among roots, mycorrhizal hyphae, and microbes in the soil, while the temperature sensitivity of autotrophic respiration was higher than that of heterotrophic respiration. Importantly, the R_myc at this site was extremely sensitive to temperature, although its overall emission was small. Mycorrhizal associations were identified as the key drivers of soil respiration and temperature sensitivity. A good understanding of the different soil CO₂ efflux components will provide useful information for determining soil C fluxes and predicting soil C dynamics under changing environments.