Summary: Using 60-year records of daily streamflow from eight paired basins in the H.J. Andrews and South Umpqua experimental forests the authors found that average daily streamflow in summer in basins with 34-43 year old plantations of Douglas fir was 50% lower than streamflow from reference basins with 150-500 year old forests.
- “Together, the paired basin and experimental gap results indicate that even‐aged plantations in 8 ha or larger clearcuts are likely to develop summer streamflow deficits…”.
- “Long‐term paired‐basin studies extending over six decades revealed that the conversion of mature and old‐growth conifer forests to plantations of native Douglas‐fir produced persistent summer streamflow deficits of 50% relative to reference basins, in plantations aged 25 to 45 years.”
- “Widespread transformation of mature and old‐growth forests may contribute to summer water yield declines over large basins and regions around the world, reducing stream habitats and sharpening conflict over uses of water.”