Water balances of contrasting land covers in the southern boreal forest

The boreal forest plays an important role in the earth's hydrologic cycle. The boreal forest landscape is a mosaic of contrasting land covers resulting from the interplay of topography, drainage, soil water holding capacity, disturbance history and ecological succession. The spatial pattern of its climax vegetation is controlled by soil drainage and available soil moisture, with peatlands in the poorly-drained deeper depressions, black spruce treed wetlands in the more subtle lowland depressions, jack pine forests on the well-drained sandy uplands, and mixedwood and aspen forests on the well-drained loamy uplands. Superimposed is the spatial pattern of disturbance history. The subtle topographic relief and heterogeneous land covers of the boreal forest landscape make it hydrologically complex, with fundamental differences in the hydrologic functioning of its upland, lowland and wetland ecosystems. This study reports water balance measurements over nine hydrologic years (Oct 1999 to Sept 2008) at seven sites in the Boreal Ecosystem Research and Monitoring Sites (BERMS) network in central Saskatchewan, Canada. The sites include one wetland, three mature forests (upland aspen, lowland black spruce and upland jack pine), and three younger jack pine stands following harvesting. The study period includes a severe three-year drought followed by three years of extreme high precipitation. The presentation will compare and contrast the annual stand-level water balances of representative boreal forest land covers (mature deciduous, lowland-coniferous and upland-coniferous forests, young forests following harvesting, and wetlands, and characterize the hydrologic responses of the contrasting land covers to extreme wet and dry years.