Clearcutting effects on streamflow in coppiced Eucalyptus globulus stands in Portugal

Two Eucalyptus globulus catchments in Central Portugal were instrumented to gain some understanding of the hydrological effects of coppicing forest stands of this fast-growing species. Suspected increases in total flow, quick flow and delayed flow after clearcutting were tested statistically using the R-Student statistic for outlier detection. Under normal climatic conditions, significant annual flow increases were found only during the water-year immediately after clearcutting. However, when the water-year following harvesting was extremely dry, no flow increase occurred during that year although flow increases were found during the second water-year. Nevertheless, owing to the rapid regrowth of the stands, the hydrological effects of clearcutting were always short lived. Depending on the dominant runoff-generating processes, increases in total flow were due to increases in both the quick and delayed flow components or to increases only in the quick flow component.