The Recovery of Net Ecosystem Productivity and Water Use Efficiency of a Harvested Aspen Forest in the Western Boreal Plain, Alberta, Canada

The Utikuma Region Study Area (URSA) is located in north-central Alberta, Canada, in a region where aspen (Populus Tremuloides Michx.) dominate the upland vegetation of the Western Boreal Plain (WBP). Due to the heterogeneity of the surficial geology as well as the sub-humid climate where the water balance is dominated by evapotranspiration, the carbon balance across this landscape is highly variable. Moreover, the upland aspen regions represent significant stores of carbon. More recently, aspen stands have become valuable commercial resources for pulp and paper processing. These stands are harvested through clear cutting and are generally left to regenerate on their own, a process which occurs rapidly in clonal species like aspen. At URSA, three eddy covariance towers were setup during the length of the growing seasons of 2005-2009 to investigate the CO2 exchange under natural conditions and the rate of recovery after harvest. In 2007, the south facing slope of URSA was harvested and the north facing slope in 2008. This study examines the inter-annual variability and recovery (after harvest) of net ecosystem productivity (NEP) and water use efficiency (WUE) as controlled by environmental variables such as air temperature, precipitation, soil moisture, growing season length and LAI.