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This thesis consists of analysis of three different data sets: (i) Aircraft-based eddy correlation data collected above irrigated and non-irrigated agricultural land in Southern California during the California Ozone Deposition Experiment (CODE) summer 1991; (ii) micrometeorological tower data, collected over grape and cotton canopies as part of CODE; (iii) aircraft-based eddy correlation flux data above two grid sites in the Canadian boreal forest during the Boreal Ecosystem-Atmosphere Study (BOREAS), spring and summer of 1994 and 1996. / Results from the CODE aircraft data document composition and size of the dominant structures, which transport heat and gases (H2O, CO 2 and ozone) over water stressed and non-water stressed surfaces, and the relative frequency with which structures carrying only a single scalar, or given combinations of scalars, were encountered along the flight paths. Interpretation of results provides further evidence for the existence of a second (nonphysiological) sink for ozone. The relative preponderance of structures that carry moisture, carbon dioxide and ozone simultaneously, particularly in the gradient-up mode, reflects the importance of vegetation as co-located source/sink for these scalars. The detrending procedures described in this study may help to define a more effective separation between local and mesoscale events in biosphere-atmosphere interaction. / Results from the CODE tower data indicates a single vegetated ozone sink for the grape site, but a vegetated as well as a non-vegetated sink for the cotton site. For both sites, structures simultaneously transporting significant flux contributions of CO2, H2O, heat and ozone dominate during unstable conditions. During stable conditions, unmixed single flux structures dominated over cotton but not over grape. The results of this study contribute empirical evidence about the relationship between ozone uptake and the physical and physiological state of vegetation, as well as the limitations placed on eddy scales in simulation models. / Results from the BOREAS aircraft data shows a decoupling between the surface and the atmosphere, where the patterns of vegetation, greenness and surface temperature may be quite dissimilar to those of the fluxes of sensible heat, latent heat and---to a lesser degree---CO2. Reasons for this lie in the extraordinary boundary layer conditions, high vapour pressure deficit, moist soil and hot canopies, and the response of the vegetation to these conditions. Analysis of the coherent structure compositions to some extent permits the characterization of the different sources and sinks. Overall, this study shows the importance of understanding the various interacting components of soil, vegetation and atmosphere when attempting to design process-based models for predictions in 'micrometeorologiacally' complex ecosystems.

Black spruce (Picea mariana (Mill.) B.S.P.)-feathermoss forests are a common subtype of the northern boreal forests. These forests are associated with large accumulations of mor humus, which is regarded as an important source of nutrients, contributor to soil structure, moisture retention and vital to the long-term sustainability of these forests. Harvesting with protection of advance regeneration (CPRS) is currently used in northwestern Quebec as the method for sustainable management, which reduces soil compaction and protects advance regeneration, and genetic diversity. We examined the effects of CPRS on organic matter and advance regeneration 6 years after harvesting. During the summer of 2002, a humus classification based on observable field characteristics was developed and applied to six CPRS sites in the northern Abitibi claybelt region of Quebec. At each site 75 humus profiles were surveyed and classified by order and thickness of horizons present. Humus horizons were easily observed using morphological features, and master horizon classes were distinguished by their nutritional and biochemical attributes with differences occurring as a result of the natural process of decomposition. Individual humus horizon and total profile thickness was the variable that most affected profile nutrient mass. High forest floor disturbance was associated with shallow profile depth, resulting in low humus profile nutrient mass and low density advance regeneration. Lower forest floor disturbance resulted in deeper profiles associated with higher available nutrients in humus profiles and higher density of advance regeneration. These results suggest that disturbance caused by harvesting may reduce overall stand productivity in the short term due to the effect of low tree density and possibly in the long-term due to loss of nutrients.

Mémoire (M.Ress.Renouv.)--Université du Québec à Chicoutimi, 1996. / Document électronique également accessible en format PDF. CaQCU

Mémoire (M.Ress.Renouv.)--Université du Québec à Chicoutimi, 1996. / Document électronique également accessible en format PDF. CaQCU

Mémoire (M.Ress.Renouv.)--Université du Québec à Chicoutimi, 1996. / Document électronique également accessible en format PDF. CaQCU

Mémoire (M.Ress.Renouv.)--Université du Québec à Chicoutimi, 1997. / Document électronique également accessible en format PDF. CaQCU

Mémoire (M.Ress.Renouv.)--Université du Québec à Chicoutimi, 2000. / Document électronique également accessible en format PDF. CaQCU

Mémoire (M.Ress.Renouv.)--Université du Québec à Chicoutim, 2000. / Document électronique également accessible en format PDF. CaQCU

Mémoire (M.Ress.Renouv.)--Université du Québec à Chicoutimi, 2001. / Document électronique également accessible en format PDF. CaQCU