Soil respiration following site preparation treatments in boreal mixedwood forest

The effects of experimental site preparation treatments on soil respiration were studied in a boreal mixed wood forest. The treatments were: (I) intact forest (uncut); (2) clearcut without site preparation (cut); (3) clearcut followed by mixing of organic matter with mineral horizons (mixed); and (4) plots from which all organic matter was removed (screefed). Soil respiration was measured as carbon dioxide (GO,) evolution from surface soil once a month from June to October, 1994 in the field using infra-red gas analyzer (IRGA). In addition, soil temperature and moisture content were determined once a month during the 1994 growing season and soil organic matter content was determined once in July 1994. Mixed plots had the highest soil respiration rates (0.86 to 0.98 g m(-2) h(-1)), followed by the clearcut (0.68 to 0.84 g m(-2) h(-1)) and uncut plots (0.56 to 0.82 g m(-2) h(-1)), with screefed plots having the lowest respiration rates (0.24 to 0.52 g m(-2) h(-1)) from June to September. Soil respiration of the cut plots was not significantly different from that of the uncut control. The site preparation treatments reduced soil moisture and soil organic matter contents significantly. Changes in soil temperature within treatment at 0, 5 and 10 cm depths and between the treatments were not significant. Observed soil respiration patterns were attributed to changes in soil moisture and organic matter content associated with the various treatments. A laboratory incubation experiment elucidated the effects of organic matter, soil moisture, and temperature on soil respiration rates. Site preparation treatments in boreal mixedwood forests affect soil respiration by modifying the moisture and organic matter content of the soil. (C) 1997 Elsevier Science B.V.