PERMFILE67186

• Permit No: C1981028
• IBM Index Class Name: Permit File
• Doc Date: 6/15/2006
• Doc Name: Revegetation Success Criteria
• Section_Exhibit Name: Appendix TR-37
• Media Type: D
• Archive: No

• reclamation azeas and the two precipitation regimes revealed that the September-July
precipitation regime produced a higher correlation coefficient by more than fifteen percent
(Figures 4 and 7). As was the case with the Osgood sand reference azea plots, the curve
shape for total vegetation cover and precipitation was as expected, while that for total
herbaceous production showed unexpected variation within the data range. Further, no
significant difference in correlation between the two precipitation regimes was observed
for the cover data, while a significant difference was observed for the production data.
It was hypothesized that the age of the reclamation areas might be confounding the
relationships between vegetation parameters and precipitation regimes. The reclamation
area data were divided between the older azeas (1985, 1986, and 1987) representing areas
seven to thirteen yeazs old and the younger azeas (1995, 1997, and 1998) representing
areas two to six years in age. Comparisons between both age classes and both
precipitation regimes were made for both vegetation pazameters. Significant variation in
response of the two parameters to precipitation was observed between the age classes.
The older reclamation azeas showed high correlation of best-fit curves for total vegetation
cover and total herbaceous production for both precipitation regimes (Figures 9, 11, 13,
IS). The younger reclamation areas showed highly variable individual correlations
between the parameters and precipitation regimes, and lower overall correlations than the
older reclamation areas (Figures 17, 19, 21, 23).
3.6 Common Sense Curve Fitting
• The goal of calculating the best-fit curve for each vegetation parameter, age class, and
precipitation regime was to identify those curves and equations that produced the greatest
level of variation explanation as identified by the correlation coefficient. As has been
noted, the best-fit equations produced curves that did not reflect expectations in the real
world in some cases. This was often the case with third order polynomial equations that
produced inflection points within the data range indicating, for example, that the value of
total herbaceous production would decrease between eight and ten inches of precipitation
(Figure 15). This is certainly not the result predicted by vegetation science, in cases where
there are no significant limiting factors.
One further analysis was conducted with the data. Plots of the two vegetation parameters
in the older reclamation areas for the two precipitation regimes were undertaken again,
this time selecting a curve that was not best-fit, but more closely fit the theoretically
predicted response of the parameters to precipitation. The objective was to determine
whether these equations and curves would yield correlations that, while not best-fit or the
highest correlation, were significant and useful over the data range. Figures 25 through 32
illustrate these plots.
Plots of total vegetation cover in the 1985, 1986, and 1987 reclamation areas for both
precipitation regimes reveal curves reflecting increasing cover with increasing precipitation
. over the data range with no inflection points (Figures 25 through 28). The rate of increase
in cover decreases with increased precipitation, as is theoretically predicted, and
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