Forest Influences on Climate and Water Resources at the Landscape to Regional Scale - Landscape Ecology for Sustainable Environment and Culture - page 310

a long-term repeated cutting experiment starting from 1939 (Watershed 13 on
north facing slope; Watershed 17 on north facing slope). The first year following
treatment in Watershed 13, water yield increased by 36 cm (60 %) (Meginnis
1959 ) (Fig. 15.5 ). In 1964, the 24-year-old stand on Watershed 13 was re-cut. The
first year water yield increase for the second cutting was 38 cm, a 40 % increase in
water yield. On watershed 17, water yield was 41 cm (65 %) higher than the effect
of the south facing watershed. The differential hydrologic response to the same
forest cutting activity was explained by the energy availability in the two water-
sheds. For the south facing watersheds, the changes in received solar energy for
evapotranspiration were small before and after tree removal. In contrast, for the
north facing watershed, the solar energy was only effective for evapotranspiration
prior to removing the fore canopies when taller trees at the bottom of the slope
transferred energy received to the soil reservoirs (Black, 1996 , p. 126).
Both Watershed 13 and Watershed 17 were low elevation watersheds (outlets at
725 and 760 msl) where temperature was significantly higher and precipitation
was significantly lower than the high elevation watersheds. Watershed 37, a steep,
high elevation (watershed outlet at 1,033 msl) watershed was clear-cut in 1963

40

First Treatment
Second Treatment
First Treatment
Second Treatment

35

30

25

20

15

10

5

0

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

Years Post-Treatment

Fig. 15.5 Effects of clear-cutting on annual water yield (Watershed 13). All woody vegetation
cut in 1939 and allowed to regrow until 1962 when the watershed was again clear-cut; no
products removed in either treatment (Data from Coweeta Hydrologic Lab, USDA forest service)