Platte River Ecology Study

Tables

Table 12. Comparison of radial growth of cottonwood, red cedar, and willow during a period of low mean discharge (1967-70) and a period of high mean discharge (1971-74). Adjusted 1971-74 radial growth (corrected for changes in radial growth with age) was used in the t-test.

Species/          Mean      Mean     Regression equation   T-values
site             radial   adjusted    (growth [Y] vs
                 growth   1971-74      tree age [X])
                 1967-70   radial
                  (mm)     growth
                            (mm)

COTTONWOOD

Upland (33)       10.00     9.34                            -1.41
Lowland (164)     15.68    16.43      Y=-0.3953X + 26.3      1.35
Total (197)       14.73    15.24                             1.09

RED CEDAR

Upland (28)       14.68    13.29                            -2.43(P < 0.05)
Lowland (38)      16.47    15.50      Y=-0.2847X + 21.2     -1.60
Total (66)        15.71    14.56                            -2.71(P < 0.01)

WILLOW

Lowland (13)      13.15    17.92      Y=-0.4052X + 30.1      4.03(P < 0.005)
Total (16)        13.25    16.94                             3.23(P < 0.01)