ORSAKER TILL AVRINNINGSÖKNING EFTER KALAVVERKNING / Cause to Run-off Increase after Clear-cutting
Earlier investigations have shown that the run-off from a forested area increases after clear-cutting. For Swedish conditions, values between 90 and 406 mm/year have been reported. On the bases of micrometeorological measurements above clearcut and forest areas and of theoretical discussions, light can be shed on the causes to the run-off increase. The present micro-meteorological measurements show that the influence on the surface resistance (or, resistance against evapotranspiration) is shifted from a biological to a climatic control. The results also indicate that the surface resistance is larger for the clearcut than for the forest area during dry conditions. The reflection of solar radiation and the daytime heat storage increase after clear-cutting, thus reducing the amount of energy available for evapotranspiration. Furthermore, the higher surface temperature during daytime at the clearcut area increases by definition the outgoing longwave radiation and hence the production of warm air. “Complete abstract not presented.”