Summer evapotranspiration trends as related to time after logging of forests in Sierra Nevada

The quantity of summer soil moisture lost from logged forest openings was related to the length of time since the creation of the opening, in the subalpine forest zone of the Sierra Nevada west side, near the Central Sierra Snow Laboratory, California, at an elevation of 6000 to 7000 feet. Soil moisture depletion was measured in forest openings which were created in 1959, 1955, 1950, and 1948, and in the forest surrounding these openings. Soil moisture was found to be uniformly near field capacity in all plots in early June. Later soil moisture was lost most rapidly from the forested parts of the plots and at progressively slower rates toward the center of the openings. The rate of moisture loss was greatest in early summer and then decreased as the availability of moisture decreased. Maximum soil moisture depletion occurred in early September, nearly all the available moisture being depleted from the forest. The quantity of residual soil moisture increased toward the center of the openings. At the period of maximum soil moisture depletion, openings 1 year old were found to have 6.9 inches more soil moisture per 4 feet of soil than the surrounding forest had, which is an expression of the quantity of moisture saved as a result of the logging operation. In openings 5 years old, the saving has decreased to 2.9 inches, after 10 years to 1.2 inches, and after 12 years to 0.7 inch. A projection of the regression indicates that the moisture saving at maximum depletion will become negligible 16 years after cutting.