Description:
<p> • Variation in root respiration and total soil respiration measured in the field in an alder (Alnus glutinosa) forest is reported here, complementing previous studies of below-ground carbon relations. • A novel technique, involving minimum disturbance to the roots, was used to measure tree fine-root respiration, while soil respiration was measured in an open system using infrared gas analysis. Calculations by process models of both rhizomicrobial, and bulk soil, respiration were compared with measurements of total soil respiration. • The rhizomicrobial respiration rate was strongly temperature dependent, with the variation determined by fine root structural parameters. The data were used to calibrate a soil respiration model comprising mineralization and rhizomicrobial respiration submodels. The calculated annual rhizomicrobial respiration (1234 g m<sup>-2</sup>) matched the carbon balance of the alder trees calculated in earlier studies; however, the calculated total annual soil CO<sub>2</sub>efflux (1754 g m<sup>-2</sup>) was very high compared with other European forest sites. • The modelled total soil respiration fitted well to measured values; a changing ground-water table and modified carbon partitioning of the alder trees might account for deviations during early summer. </p>