CLEARCUTTING EFFECTS OF STREAMFLOW IN COPPICED EUCALYPTUS-GLOBULUS STANDS IN PORTUGAL

Two Eucalyptus globulus catchments in Central Portugal were instrument ed to gain some understanding of the hydrological effects of coppicing forest stands of this fast-growing species. Suspected increases in to tal flow, quick flow and delayed flow after clearcutting were tested s tatistically using the R-Student statistic for outlier detection. Unde r normal climatic conditions, significant annual flow increases were f ound only during the water-year immediately after clearcutting. Howeve r, 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 regrow th of the stands, the hydrological effects of clearcutting were always short lived. Depending on the dominant runoff-generating processes, i ncreases in total flow were due to increases in both the quick and del ayed flow components or to increases only in the quick flow component.