ENVIRONMENTAL CONSEQUENCES in rocky mountain coniferous ...

understory biomass density, X2 represents soil nutrient concentration, Xg represents
average soil moisture content, and XI+, Xg, ... Xn represent the remainder of the
forest environment being considered. Suppose further that we know the level of soil
nutrients 1 imi ts understory growth in this situation, and that a1 1 other environmental
components that would promote growth are at or above critical levels while all that
would retard growth are at or below critical levels (e.g. , increasing soil moisture
would not accelerate growth). In this situation, we would simply conclude that the
change in XI, say AX1, over the ensuing time period, At, would be determined by the
level of nutrients, X2, during the same period. The amount of change, AX1 = AX129
would be based on data from the research literature or, in its absence, on profes-
sional opinion. This same thought process would be followed for each of the n
environmental components. resulting in an estimate of AXi for each, and a corre-
sponding estimate of its new status, or
where Xi is the status of the ith component at tine t; and Xi,t+At is the status
, t
of the ith component at some later time, t + At (fig. 11 ).
Figure 10. --Pt-edictions based on -
Zimitina interactions.
I I I
t t +at Time
-
x 1
Figure 11. --IZZustration of quat ti on 4.
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