Radon 222 tracing of soil and forest canopy trace gas exchange in an open canopy boreal forest

A set of continuous, high‐resolution atmospheric radon (222Rn) concentration time series and radon soil flux measurements were acquired during the summer of 1990 at a micrometeorological tower site 13 km northwest of Schefferville, Quebec, Canada. The tower was located in a dry upland, open‐canopy lichen‐spruce woodland. For the period July 23 to August 1, 1990, the mean radon soil flux was 41.1±4.8 Bq m−2 h−1. Radon surface flux from the two end‐member forest floor cover types (lichen mat and bare soil) were 38.8±5.1 and 61.8±15.6 Bq m−2 h−1, respectively. Average total forest canopy resistances computed using a simple “flux box” model for radon exchange between the forest canopy and the overlying atmosphere range from 0.47±0.24 s cm−1 to 2.65±1.61 s cm−1 for daytime hours (0900–1700 LT) and from 3.44±0.91 s cm−1 to 10.55±7.16 s cm−1 for nighttime hours (2000–0600) for the period July 23 to August 6, 1990. Continuous radon profiling of canopy atmospheres is a suitable approach for determining rates of biosphere/atmosphere trace gas exchange for remote field sites where daily equipment maintenance is not possible.