Forest floor carbon dioxide fluxes within an upland-peatland complex in the Western Boreal Plain, Canada

This study examined the midday (10:00 to 16:00) growing season (April to October) surface cover CO2 relationships with different canopy closures in a forested upland-peatland-pond complex in the Western Boreal Plain (WBP), north-central Alberta. Canada. Large differences were observed among the forest floors of landscape units with different canopy covers with respect to midday total respiration [(Rtot) = vegetation respiration (Rveg) + soil respiration (Rsoil)] and gross ecosystem production (GEP), and the seasonal pattern of GEP and Rtot. Highest rates of Rtot followed the general progression of riparian > upland > open peatland > covered peatland, with high Rsoil contributions. Strong correlations were observed between C:N, soil temperature, moisture and Rtot. Photosynthetic active radiation (PAR) controlled the GEP, which was highest in the open and covered peatland. GEP and Rtot were highest in the middle of the growing season when soil and air temperatures were warmest; in addition Rveg contributed more to Rtot during this time. However. Rsoil dominated the flux. This study demonstrated that controlling environmental factors on CO2 exchange cannot necessarily be extrapolated among land cover units within a sub-humid region, such as Canada's WBP. In addition, forest floors of different land cover units, and microtopography should be taken into account when discussing understory contributions to CO2 exchange.