ENVIRONMENTAL CONSEQUENCES in rocky mountain coniferous ...

CLEARCUT
Rn E H
a* 15%
CLEARED Figure 7. -- Energy balance components: Rn = net
radiation; E: = evapotrampirat;on; H = sensibZe
heat flux; md G = soiZ heat flux at the Wyoming
site for chips spread, cZeared, broadcast burned
cmd uncut treatments Zrection of arrows shows
direction of flow and width indicates the reZa-
tive mount. "aM represents the albedo of the
surf ace.
Temperature
Midsunmer maximum surface temperatures were 25% higher in clearcuts &han an
uncut stands. Temperatures in partial cuts of varying intensities were 10 C-15 C
higher than in uncut areas. Temperature differences between clearcut and uncut
stands were ~ i mlar i in different study areas. However, mean maximum temperqtures
differ by 20 C or more among study arpas. Daily differences between temperatures of
clearcut and uncut stands exceeded040 C (fig. 8). Daily maximum tempgratures on our
study sites frequently exceeded 50 C, and were measured as high a8 70 C. Daily and
mean monthly maximum temperatures and the length of time above 50 C (fig. 9) indicate
potential harmful levels of heat for seedl ingso(table 4). Maximum temperatures in
uncut stands at Coram and Lubrecht exceeded 50 C but never lasted more than one
consecutive hour. Conversely, temperatures in the clearcut at Coram remained 50'~
for 4-5 hours. At Lubrecht, in theopartial cuts where the overstory was not removed,
temperatures frequently exceeded 50 C, but not for mgre than 2 consecutive hours.
Temperatures in the clea~cut at Lubrecht exceeded 50 C for 5-6 hours on clear days
and sometimes reached 66 C or mored Temperatures in the uncut stand at Solo Creek
(m~ture hemlock) never exceededo30 C, but in the Solo Creek clearcut they exceeded
50 C for 3-4 hours, reaching 56 C. Data from several days in Wyoming indicate
temperaturesoin the 9,000 foot clearcut exceeded 60 C for several hours, but remained
less than 25 C in the uncut stand.
50 -
41 -
Figure 8.-- DiurnaZ temperature variat-ion 40 -
-
of duff ~urface for dearcut and uncut
z 35 -
Icontro ll study areas, Corm Experimental g m -
Forest.
iap
- 2a
15 -
I0 ----
5 -
55
I
0 I I I I I
0 S 10 15 TLK e0 IliCwSl 24 6 11 IS