Energy balance differences and hydrologic impacts across the northern treeline



Energy balance measurements were made over wet tundra and a nearby open conifer forest near Churchill, Manitoba during the summer periods of 1989 and 1990. Little difference was found between net radiation, Q*, and ground heat fluxes, QG, for the two sites: Q* at the forest exceeded Q* at the tundra by only 2–5 per cent; QG averaged 9 and 12 per cent of Q* for the forest and tundra, respectively.

The sensible, QH, and latent, QE, heat fluxes showed the greatest differences between the sites. When surface moisture was not limiting, QE was largest for the tundra and QH was largest at the forest. During a drying cycle in 1989 the energy balances for the two sites were similar. An analysis of wind direction on energy partitioning suggests that the tundra was more responsive to meteorological changes than the forest. The implications of this study for surface water balances in the subarctic are discussed.