Germination of Forest Trees 27 



It is quite natural to wonder how these values compare with 

 values that have been obtained in the woods. Probably the com- 

 parison of the light values obtained in the dense shade with some 

 of the lowest values obtained in the woods would be most interest- 

 ing - . Clements (2) found light values from 0.12 to 0.05 under 

 mature lodgepole pine in Colorado. He observed that Douglas 

 fir occurred very rarely in densities below 0.05. Wiesner found 

 the same value in this case. Pearson in Arizona found that 

 western yellow pine seedlings grow fairly well in a light intensity 

 from 0.309 to 0.414. White fir was found in good condition in 

 light intensities of from 0.027 to 0.068 and healthy young growth 

 of Engelmann spruce was found in intensities of from 0.033 to 

 0.062. In Oregon Pearson found such tolerant species as alpine 

 fir, Engelmann spruce, western hemlock, and Lowland fir grow- 

 ing in light intensities from 0.021 to 0.029. The western larch 

 however showed only poor development in a light intensity of 

 -353- This will be sufficient to indicate that the light in the 

 dense shade tent compares with some of the lowest light intensities 

 that have been measured in our western forests. In this con- 

 nection it is interesting to note that white pine, black locust, red 

 oak, and western yellow pine lived for two to four mouths in the 

 dense shade tent, as is evidenced by the fact that stem and root 

 measurements were taken on these species during the last days of 

 these investigations. 



In connection with the light experiments a very important fact 

 soon became evident. In spite of the fact that all three cultures 

 were watered every evening at the same time and in the same 

 degree, it soon became evident from mere observation that the 

 top layer of soil by the following evening had dried out to very 

 different degrees in the three cultures. The open light culture 

 was noticeably the driest and the dense shade culture the moistest 

 so far as the top layer was concerned. This fact led to taking 

 systematic moisture samples to determine the exact difference 

 in moisture content. These samples were taken once a month, 

 three evenings in succession and these readings were averaged 

 into one reading. The table of soil moisture contents is given 

 below : 



