Impacts of morphological traits and temperature on fine root respiration during dormancy of Caragana korshinskii

Respiration of fine roots (R (fr)) plays a major role in belowground carbon cycles, but the relationships between R (fr) and biotic and abiotic factors during plant dormancy remain unclear. We used a standard chamber equipped with an infrared gas analyzer and configured as an open system to measure R (fr) of intact roots (< 2 mm) of Caragana korshinskii in situ in November 2013. Rates of R (fr) in C. korshinskii were closely related to root morphological traits, including mean root diameter (D (fr), mm), specific root length (SRL, root length per unit root mass, m g(-1)), and root tissue density (RTD, root mass per unit root volume, g cm(-3)). During dormancy of C. korshinskii, smaller-diameter fine roots had higher respiration rates than larger diameter fine roots, and R (fr) increased with increasing SRL and decreasing RTD. Meanwhile, R (fr) rates increased exponentially with increasing root temperature. Soil temperature (especially in the subsoil layer) did not play a role in controlling changes in R (fr). The results indicated that changes in root temperature and D (fr) were likely to determine rates of R (fr) in C. korshinskii during dormancy. Our results highlight the importance of assessing carbon loss from fine roots during the dormant period.