STUDIES IN LAKE AND STREAMSIDE VEGETATION 



145 



for any special dryness of the air and evaporation is slower than at 

 lower altitudes. This fact was clearly shown by the fragmentary 

 records of the evaporimeters maintained in a forest opening east of the 

 lake for a period of a few weeks. 



Table I. Temperatures at Redrock Lake and at Boulder, Colo., for 1908 



{Degrees F.) 



Redrock Lake 



Boulder* 



Difference 



Mean Temperature June. 



July- 



Aug.. 



Mean Minimum June. 

 July- 

 Aug. 



Mean Maximum June. 



July- 



Aug. 

 Absolute Minimum June. 



July. 



Aug. 

 Absolute Maximum June. 



July. 



Mean Daily Range 



Last Frost in Spring. 

 First Frost in Autumn. 

 Period without Frost . . 



Aug. 

 June. 

 July. 

 Aug. 



Mean Annual Temperature . 



46 



52 



5i 



35 



40 



41 



58 



63 



61 



26 



3° ■ 



34- 



70. 



63- 

 73- 

 23- 

 22.7 

 19 6 

 July 7 



Sept. 1 

 56 days 



36| 



62.2 

 67.6 

 65.6 

 48.7 



55-7 

 54-o 

 75-6 

 80.1 



77-3 

 41. 



45- 

 46. 

 91. 



93- 

 92. 

 27. 

 24.4 



23-3 

 May 21 

 Sept. 26 

 128 days 



5°-9t 



15-7 

 15-3 

 14.2 



!3-7 

 14.6 

 12.4 

 17.6 



16. S 

 16. 1 



is- 



15- 



II . 



21 . 



30. 

 19. 



4- 



i-7 



3-7 



47 days 



25 days 



72 days 



14.9 



* At University campus, 

 f Estimated (see p. 142). 

 X Government Record, 1 1 years. 



Wind. — From a botanical standpoint wind is of interest chiefly 

 because of its effect on transpiration. There can be no doubt that 

 winds at Redrock Lake are high, especially in winter. The dwarfed 

 and contorted "wind timber" at the east of the lake is sufficient evidence 

 on this point. In summer, so far as the writers could judge without the 

 use of instruments, the winds are no more severe than at lower altitudes. 

 Hence the influence of high wind is exerted on the shrubs and trees which 

 are exposed in winter and not upon the herbaceous vegetation. The trees, 

 especially, show wind influence in their dwarfed form and profuse 

 branching and slow growth. The shrubs, where exposed to high wind, 



