A COMPARISON OF 6 METHODS FOR MEASURING SOIL-SURFACE CARBON-DIOXIDE FLUXES

Measurements of soil-surface CO2 fluxes are important for characterizi ng the carbon budget of boreal forests because these fluxes can be the second largest component of the budget. Several methods for measuring soil-surface CO2 fluxes are available: (1) closed-dynamic-chamber sys tems, (3) closed-static-chamber systems, (3) open-chamber systems, and (4) eddy covariance systems. This paper presents a field comparison o f six individual systems for measuring soil-surface CO2 fluxes with ea ch of the four basic system types represented. A single system is used as a reference and compared to each of the other systems individually in black spruce (Picea mariana), jack pine (Pinus banksiana), or aspe n (Populus tremuloides) forests. Fluxes vary from 1 to 10 mu mol CO2 m (-2) s(-1). Adjustment factors to bring all of the systems into agreem ent vary from 0.93 to 1.45 with an uncertainty of about 10-15%.