SOIL RESPIRATION FOLLOWING SITE PREPARATION TREATMENTS IN BOREAL MIXEDWOOD FOREST

The effects of experimental site preparation treatments on soil respir ation 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 hori zons (mixed); and (4) plots from which all organic matter was removed (screefed). Soil respiration was measured as carbon dioxide (GO,) evol ution from surface soil once a month from June to October, 1994 in the field using infra-red gas analyzer (IRGA). In addition, soil temperat ure 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 plot s having the lowest respiration rates (0.24 to 0.52 g m(-2) h(-1)) fro m June to September. Soil respiration of the cut plots was not signifi cantly different from that of the uncut control. The site preparation treatments reduced soil moisture and soil organic matter contents sign ificantly. Changes in soil temperature within treatment at 0, 5 and 10 cm depths and between the treatments were not significant. Observed s oil respiration patterns were attributed to changes in soil moisture a nd organic matter content associated with the various treatments. A la boratory incubation experiment elucidated the effects of organic matte r, soil moisture, and temperature on soil respiration rates. Site prep aration 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.