ENVIRONMENTAL CONSEQUENCES in rocky mountain coniferous ...

Night radiation values for the clearcuts on both sites were more negative than
they were on the uncut sites. This indicated a greater loss of energy from the
clearcut surface, resulting in cooler potential temperatures. The canopy of an uqcut
stand acts as a blanket holding in energy. McCaughey (1978) determined that net
radiation was reduced 10% by clearcutting, as compared to the daily total above the
coniferous canopy. The net effects of cutting differ above the canopy and at the
soi 1 surface.
Methods of seedbed preparation include leaving residues on site or removing
various amounts of them, and burning and mulching. Theoretically, each of these
a1 ternatives should have a different effect on net radiation vqlues. Preliminary
analysis of our data indicates that on unburned surfaces where residues were left,
net radiation was greater than where residue was removed. Net radiation is signifi-
cantly higher over dense residue surfaces than over burned surfaces. Treatment areas
with residues burned had higher net radiation values than unburned areas where residues
were removed or chipped or where mineral soil was left exposed. Net radiation over
areas where vegetation had grown back, however, was the same, whether previously
burned or cleared. Data from our Wyoming site (fig. 5). show that flux density of net
radiation was much higher on cleared and burned areas than in places scarified, or
where residues were chipped and spread over the surface.
Figure 5.-- Net radiation over severaZ surfaces in a dearcut at the
Wyoming site, ae noon on JuZy 22, 1979. fie differences between
burned and cleared and bekween scarified and chip spread probably
are not sign< f$cant.
Thermal characteristics of surface materials and soil influence the distribution
of the energy. The materials comnonly encountered at our sites, along with their
thermal properties, are listed in table 3. Our data allowed us to calculate approx-
imate energy fluxes, to get an indication of the overall energy balance. We used
Campbell 's (1 977) equations to calculate sensible heat flux, and subtraction to
estimate evaporative flux (fig. 6) for data on one day in a clearcut at Coram.