93 Forestry Quarterly 



The necessity of opening up more freely in the pure conifer 



stands, in order to get sufficient light for regeneration, easily 



leads to weed-growth and failure of the regeneration, while in 



mixed stands the necessary light is secured by Hghter opening up. 



Spectrophotometrische Untersuchungen im Walde. Mitteilungen der Schweiz- 

 erischen Centralanstalt fur das forstliche Versuchswesen, XI, 1, 1914, pp. 1-93. 



The effect of the eclipse of the sun which 

 Sun Eclipse occurred last August 2 1st upon the tempera- 

 awe^ ture of trees has been studied by Danberg, 

 Temperature a Russian forester. He was particularly 

 of Trees prepared for such observations because he 

 was carrying them on for nine months 

 before the eclipse of the sun occurred. The observations were 

 conducted by means of specially devised thermometers inserted 

 in the trees. The trees under observation were three live pines, 

 one dead pine, one live spruce and one live birch. 



In the locality where the observations were made the sun eclipse 

 began at 1:24 P. M. and ended at 3:31 P. M. It thus lasted 

 two hours and seven minutes. The sun eclipse was not complete. 

 However, the sun disk's occultation reached its maximum to the 

 extent of nine-tenths at 2:29 P. M. During the sun ecHpse the 

 temperature of the air in the forest dropped 4^^° F., from 50" to 

 45.5°. The temperatiire of the living pines dropped 2.2", from 

 47.7° to 45.5°. The temperature of the spruce and birch dropped 

 1.1°, from 51.1° to 50°. Only the temperature of the dead pine 

 remained without change. The fall of the temperature of the air 

 was sudden. The drop of 43/^° occurred within thirty-five minutes. 

 The living pines responded also very rapidly to the sun eclipse 

 while the birch and spruce proved less sensitive and the dead 

 pine did not react at all. 



The observations conducted for the previous nine months have 

 established very conclusively that the temperature of the living 

 trees is characterized by comparative stability, that it does not 

 respond to slight fluctuations in the temperature of the air, while 

 radical changes produce only a gradual change in the temperature 

 of the trees. The marked sudden effect of the sun eclipse upon the 

 temperature of the trees must, therefore, be due to some other 

 still imknown influence connected with the eclipse of the sun. 



R. Z. 



