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Carbon dioxide, water vapour, and energy fluxes vary spatially and temporally within forested environments. However, it is not clear to what extent they vary as a result of variability in the spatial distribution of biomass and elevation. The following study presents a new methodology for extracting changes in the structural characteristics of vegetation and elevation within footprint areas, for direct comparison with eddy covariance (EC) C[O.sub.2] flux concentrations. The purpose was to determine whether within-site canopy structure and local elevation influenced C[O.sub.2] fluxes in a mature jack pine (Pinus banksiana Lamb.) forest located in Saskatchewan, Canada. Airborne light detection and ranging (lidar) was used to extract tree height, canopy depth, foliage cover, and elevation within 30 min flux footprints. Within-footprint mean structural components and elevation were related to 30 min mean net ecosystem productivity (NEP) and gross ecosystem production (GEP). NEP and GEP were modeled using multiple regression, and when compared with measured fluxes, almost all periods showed improvements in the prediction of flux concentration when canopy structure and elevation were included. Increased biomass was related to increased NEP and GEP in June and August when the ecosystem was not limited by soil moisture. On a daily basis, fractional cover and elevation had varying but significant influences on C[O.sub.2] fluxes. Le dioxyde de carbone, la vapeur d'eau et les flux d'energie varient dans l'espace et le temps dans les environnements forestiers. Cependant, nous ne savons pas dans quelle mesure ils varient en fonction de la variation des gradients de biomasse et d'altitude. Cette etude presente une nouvelle methode pour extraire les caracteristiques de la structure de la vegetation et les changements d'altitude a partir d'empreintes pour etablir des comparaisons directes avec des concentrations de flux de C[O.sub.2] calculees par la methode de covariance des turbulences. Le but de l'etude etait de determiner si la structure de la canopee a l'interieur d'une station et 'altitude locale influencent les flux de C[O.sub.2] dans une foret mature de pin gris situee en Saskatchewan, an Canada. Un lidar aeroporte a ete utilise pour estimer la hauteur des arbres, la profondeur de la canopee, la couverture foliacee et l'altitude dans des empreintes de flux de 30 minutes. Les composantes structurales moyennes et l'altitude issues de ces empreintes ont ete reliees aux valeurs moyennes sur des periodes de 30 minutes de la productivity nette de l'ecosysteme (PNE) et de la production brute de l'ecosysteme (PBE). La PNE et la PBE ont ete modelisees a l'aide d'une regression multiple et, lorsqu'elles on ete comparees aux flux mesures, la prevision des concentrations de flux a ete amelioree pour presque toutes les periodes quand la structure de la canopee et l'altitude etaient incluses dans le modele. L'augmentation de la biomasse etait reliee a des augmentations de PNE et de PBE en juin et en aout lorsque la teneur en eau du sol ne limitait pas le fonctionnement de l'ecosysteme. Sur une base journaliere, la proportion de couverture et l'altitude avaient une influence variable, mais significative, sur les flux de C[O.sub.2]. [Traduit par la Redaction], Introduction The eddy covariance (EC) method is commonly used to measure the direction and movement of energy and trace gas (e.g., water, C[O.sub.2]) concentrations throughout ecosystems (Baldocchi 2008). Networks of [...]

Abstract: Light detection and ranging (lidar) is becoming an increasingly popular technology among scientists for the development of predictive models of forest biophysical variables. However, before this technology can be [...]

An analysis of the positional accuracy of NAVSTAR Global Positioning System (GPS) data obtained in static mode and differentially rectified confirmed that the resulting precision adhered to the standards of general medium- and large-scale mapping projects. A circular map accuracy standard of 3.62 meters was observed. Low-cost GPS receivers in static and kinetic modes were applied to the data collection procedure for a region of rapid rural-to-urban land-use change.