ENVIRONMENTAL CONSEQUENCES in rocky mountain coniferous ...

Wind speed modifies the exchange of heat moisture and gases. An increase in
wind speed decreases the thickness of the boundary layer, or cushion of air close to
a surface, and decreases the resistance to exchange. When the resistance to heat,
moisture, or gas exchange is reduced more heat, moisture, or gas is lost, Increases
in wind speed can be effective in removing heat and cooling an object. Removal by
wind of water vapor being transpired or evaporated from a surface increases water
loss. Often this has adverse effects, causing dessication and possibly death if the
supply of mi sture becomes inadequate. During periods of rapid photosynthesis wind
can be beneficial by keeping carbon dioxide levels higher near leaves. In still air,
carbon dioxide suppl ies may be depleted near 1 eaves, depressing photosynthetic rates.
Some wind near the ground can help prevent freezing at the surface. Mixing of the
air is more thorough, reducing radiative cooling. This principle is often used in
orchards to prevent frost.
PREDICTING ENVIRONMENTAL CONDITIONS AND CONSEQUENCES
Managers need facts about existing environmental conditions, about vegetative
requirements and how manipulation of vegetation will alter conditions. One way to
get such facts is to monitor and measure what goes on. This is becoming more feasible
in mqny cases, but we can't measure everything in all places. Modeling using
existing information and selective monitoring based on studies and experience constitute
another a1 ternative. While it is obvious that ma~y causal environmental
re1 ationships escape our description, we can predict some. Combining monitoring and
mathematical modeling to predict environmental conditions and biological consequences
offers some powerful management tool s.
It is beyond the scope of this paper to discuss the details of many models and
integrate them. I w ill, however, present some models and potentials for models that
may be of benefit to managers, listing the source and where specifics for use can be
obtained. Gonsior and Ullrich (1980) present a potential method for integrating
specific models and information.
Since all available energy comes from the sun, it is Important to know how much
is received. Solar radiation is comnonly measured at standard locations, but not in
mountainous terrain. Latitude, aspect, slope, and cloud cover are input variables
for a model described by Satterlund and Means (1978) for estimating solar radiation.
With their model mean daily totals can be estimated to within 8 percent of meqsured
values, The model uses estimates of potenti41 direct beqm solar radiation described
by Fons and others (1960) and cloud cover data from a nearby weather station. Topo-
graphical shading in mountainous terrain, and the sizes and shapes of openings, also
influence the amount of solar radiation received on the surface. Satterlund (1977)
deyelaped a way to predict shadow boundaries with a programmable calculqtor. The
output of this model can be used to adjust the model for incident solar radiatiou
(Satterl und and Means 1978).
Halverson and Smith (1974) also describe a computer model to calculate $hading
for any combination of date, slope and aspect at latitudes from the Mexicap to the
Canadian borders. Using this model one can estimate the increase or decrease in heat
or li ht to the snow surface or In the vicinity of seed1 ings, Fisher and Merritt
(19797 discuss the use of a model to calculate 1 ight distribution in small forest
openings. The inputs are coordinates and heights of trees on the boundary, slope,
aspect, latitude, day, time interval and point coordinates of interest in the opening.