1910] ROBBINS—VEGETATION IN COLORADO 265 
above 10,000 feet having a mean annual temperature below 35°. 
Isotherm 35 follows approximately the upper limit of lodgepole pine, 
Separating the montane from the subalpine zone. The mean autumn 
and spring temperatures are very nearly the same as the annual mean. 
As a rule, the fall mean is somewhat higher and the spring mean lower 
than the annual mean. Fig. 6 gives the mean summer temperatures 
A ERE SEU, EET NL ARSE NG IAN NONE 
— 60 SS SS Yeas * SrepeoaaaSremmeay aS en 
i 
t-———! 
Pt. Collins ET ad 
a "$$ \ 
' eter eee: ! 
' 
—_—— - — 1 I 1 
Meeker—— reculder 7” | 
a =DENVER 
65 SS ee : , 
a ae | 5 
f 1 cr 1 
Wd ot ! 
2 \ 
79 rand roe = ~---=4 
Junction =| lorado 
7 z * Springs—F= ! 
ae = unnison 1 i 
4 I at ee Ga ee 
n 
ae _| Pueblo t 
E os e i ! 
* 1 i ' ! 
— fe i t 
—----. Tatty : ' 
—- — [ERPS pomp q ee if H | 
i ae f ‘| | 
7 : ] 
Trinidad I 
s 
1 ———4durango~ . 
Meee i Rene ane se ceoiags : wo 
a is 
Te Ree eee eee 
Fic. 6.—Mean summer temperatures. 
of Colorado.- Its general appearance is similar to the mean annual 
temperature map. On the eastern slope isotherm 65 marks the lower 
limit of the foothill zone. Isotherm 60 on both slopes follows the 
lower limit of the montane zone and isotherm 55 the lower limit of 
the subalpine zone. No data are at hand to show the temperature 
conditions at timber line. 
RANGE OF TEMPERATURE.4—For the state as a whole the mean 
annual range (difference between the mean temperature for the 
Warmest month and mean temperature for coldest month) is great 
(see table IV). Inthe Arkansas Valley, Platte Valley, Grand Valley, 
4 Hany, |. c., Pp. 273. 
