Spatial relationships of carbon dioxide exchange in an upland forested wetland complex in the Western Boreal Plain, Alberta, Canada

This study examined the midday (10:00--16:00) growing season (April--October) surface cover CO2 relationships with different canopy closures and microtopography (lawn and depression) in a forested upland-peatland-pond complex in the Western Boreal Plain, north-central Alberta, Canada. A dynamic-closed chamber technique was used to: evaluate the relative contributions of heterotrophic and autotrophic respiration and photosynthesis and assess the relative roles of substrate, plant communities, hydrology, and microclimates on CO2 exchange.; 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 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 R soil dominated the flux.; Small differences were observed between lawn and depression sites in terms of net ecosystem CO2 exchange (NEE). The general trend was for warmer, drier lawn sites to have higher GEP and Rtot than the topographically lower, cooler and wetter depressions. The moisture and temperature differences between microtopography drove differences in the productivity of species but did not drive differences in vegetation distribution.; This study demonstrated that degrees of spatial and seasonal temporal variability as well as controlling environmental factors on CO2 exchange cannot necessarily be extrapolated to a sub-humid region, such as Canada's Western Boreal Plain. In addition, forest floors of different land cover units, and microtopography should be taken into account when discussing understory contributions to CO2 exchange.