Hydroclimatic factors controlling net carbon dioxide exchange in managed peatland ecosystems (Quebec, Canada).

摘要

This thesis investigates ecosystem scale measurements of the atmospheric exchange of water and carbon dioxide (CO₂) from a restored vacuum harvested peatland in eastern Québec, Canada, using the eddy correlation measurement approach.; Results indicate that the adopted restoration practices reduced the loss of water from the peat. Evapotranspiration from the restored site was 20 and 25% less than that from an adjacent abandoned comparison site in 2000 and 2001 respectively. However, CO₂ emissions to the atmosphere remained large during the non-snow period (478 and 468 g C m−2 in 2000 and 2001, respectively). The bunds and blocked drainage ditches and the application of a mulch cover at the restored site kept the moisture and thermal conditions more or less constant. Consequently, the CO₂ flux, which is predominantly soil respiration, was strongly controlled by peat temperature fluctuations.; Soil moisture, vegetation and peat temperature data were collected at two contrasting spatial scales (90,000 m2 and 1,200 m 2 grids, at intervals of 30 and 2 m, respectively) and at three different times in the snow free season from a cutover peat bog in Cacouna, Québec. Analysis of statistical structure, variance and spatial autocorrelation were conducted on the soil moisture data at different sampling resolutions and over different grid sizes determined increasing the scale of interest without adequate resolution in the measurement can lead to significant inconsistency in the representation of these variables.; Finally, a simple SVAT model and empirical CO₂ exchange model were used to determine the ability to simulate the complex interactions in an impacted peatland as well as illustrate the long term effects of the restoration process on the peatland's role as a carbon sequestering system. Results indicate that accurate representation of the vegetation (vascular and moss) layer is essential in the realistic representation of such a system. Given the simplifications used in simulating this system in this thesis the system was predicted to become a net carbon sink within approximately six seasons of restoration.