PARENT SESSION
Poster Session 2: Forest Ecology
Monday, August 8, 5:00 PM - 6:30 PM, Exhibit Hall 220 A-E, Level 2, Palais des congrès de Montréal

A field comparison of two dynamic chamber instruments for measuring forest soil respiration.

Brown, Susan^*,1, Burton, Andrew¹, Piket, Angela¹, Pregtizer, Kurt¹, ¹ Michigan Technological University, Houghton, MI

ABSTRACT- Soil respiration is an important C flux in the global carbon cycle and plays an important role in determining if forest ecosystems are sources or sinks for atmospheric carbon. Several methods and devices are commonly used to measure soil respiration. Understanding the differences between measured values from different techniques is critical to those attempting to synthesize data from multiple sources for assessing environmental controls on soil respiration or estimating soil CO₂ efflux rates at regional and global scales. A field comparison of two common instruments used in recent studies (EGM and LI-6400) was made in five common northern forest types, and in experimental plots examining the effects of chronic N additions and elevated CO₂ and O₃. Objectives were to gain a more detailed understanding of the differences between the two devices and to determine if it is necessary or possible to produce correction factors to convert between measurements taken by the two devices. Respiration rates measured by the EGM were higher than corresponding rates from the LI-6400. Forest type and soil temperature affected soil respiration rates for both instruments, but did not alter the relationship between the instruments. A linear regression across all forest types predicted EGM efflux rates to be 1.35 times those measured by the LI-6400 (r² = 0.76, P < 0.001). Nitrogen additions and elevated O₃ significantly depressed soil respiration rates, an effect that was detected by both instruments. Similarly, both instruments detected an increase in soil respiration in a young, growing aspen forest exposed to elevated CO₂. For the sandy-textured forest soils common in the upper Great Lakes, it appears that a consistent relationship exists between soil CO₂ efflux rates measured by these two common devices.

Key words: soil respiration, elevated carbon dioxide and ozone, chronic N additons, northern forest ecosystems