Partitioning heterotrophic and rhizospheric soil respiration in a mature Dougals-fir forest.
Lalonde, Rachelle*,1, Prescott, Cindy1, 1 University of British Columbia, Vancouver, British Columbia, Canada
ABSTRACT- We partitioned belowground respiration to estimate a portion of CO2 originating from heterotrophic and rhizospheric organisms. As part of the Fluxnet Canada program, we investigated heterotrophic and rhizospheric respiration rates at a 55-year-old Douglas-fir forest on Vancouver Island, British Columbia. We used a root exclusion technique with fifty cylinders, 10 cm diameter by 50 cm long, with large windows cut out on either side. Half of the cylinders had a 0.5 m nylon mesh attached to these windows to create a barrier against roots and hyphae. The cylinders were then installed, extending to below the root zone (40 cm). These cylinders provided a measure of heterotrophic respiration; rhizospheric respiration was calculated as the difference between the open and mesh cylinders. Our results indicate that heterotrophic organisms are the dominant producers of CO2 during warmer months (June-Sept), but not during the spring and fall. Within the top 50 cm of this forest soil, 65% of the annual CO2 is from heterotrophic respiration and 35% is from rhizospheric respiration.
Key words: soil, respiration, forest
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