The net ecosystem CO2, H2O and energy exchange of mountain grasslands : methodology, controls and modelling / presented by Albin Hammerle

• VerfasserIn: Hammerle, Albin
• Place / Publishing House: Innsbruck, March 2009
• Year of Publication: 2009
• Language: English
• Classification: 42.91 - Terrestrische Ökologie
• Physical Description: 78 Blätter; Illustrationen
• Notes: Im Titel ist 2 jeweils tiefgestellt.; Enthält: u.a. vier Veröffentlichungen des Verfassers aus den Jahren 2007-2009

ger: Using carbon dioxide (CO2) and energy fluxes measured continuously by means of the eddy covariance method since 2001 and associated measurements of the green area index and the major environmental driving forces at a grassland site, managed as a hay meadow, in the Stubai valley (Austria), we investigated the influence of (a)biotic factors and management activities on the energy partitioning and the CO2 exchange of this ecosystem. Moreover, an evaluation of the eddy covariance technique was conducted above a steep mountain grassland and possibilities of gap-filling based on remotely sensed broad-band reflectance indices were explored. The main findings of these studies were: (i) that eddy covariance measurements conducted above a steep meadow with low canopy height were, a rigorous quality control provided, of similar quality compared to those obtained over flat terrain; (ii) that compared to standard environmental parameters, the green area index explained similar, and partially larger, fractions of the variability in energy partitioning; (iii) that there were little, if any, indications of water stress effects on energy partitioning; (iv) that the role of environmental parameters regarding seasonal variation in the net ecosystem CO2 exchange was obscured by the strong response of gross primary production to changes in green area index; (v) that no single parameter or combination of parameters investigated were able to explain the interannual variability in the net ecosystem CO2 exchange; (vi) that broad-band reflectance indices were well suited to model several metrics of the net ecosystem CO2 exchange; (vii) and that a gap-filling method based on these reflectance indices resulted in net ecosystem CO2 exchange values well comparable to data derived from well-established gap-filling methods.

eng: Using carbon dioxide (CO2) and energy fluxes measured continuously by means of the eddy covariance method since 2001 and associated measurements of the green area index and the major environmental driving forces at a grassland site, managed as a hay meadow, in the Stubai valley (Austria), we investigated the influence of (a)biotic factors and management activities on the energy partitioning and the CO2 exchange of this ecosystem. Moreover, an evaluation of the eddy covariance technique was conducted above a steep mountain grassland and possibilities of gap-filling based on remotely sensed broad-band reflectance indices were explored. The main findings of these studies were: (i) that eddy covariance measurements conducted above a steep meadow with low canopy height were, a rigorous quality control provided, of similar quality compared to those obtained over flat terrain; (ii) that compared to standard environmental parameters, the green area index explained similar, and partially larger, fractions of the variability in energy partitioning; (iii) that there were little, if any, indications of water stress effects on energy partitioning; (iv) that the role of environmental parameters regarding seasonal variation in the net ecosystem CO2 exchange was obscured by the strong response of gross primary production to changes in green area index; (v) that no single parameter or combination of parameters investigated were able to explain the interannual variability in the net ecosystem CO2 exchange; (vi) that broad-band reflectance indices were well suited to model several metrics of the net ecosystem CO2 exchange; (vii) and that a gap-filling method based on these reflectance indices resulted in net ecosystem CO2 exchange values well comparable to data derived from well-established gap-filling methods.