4S 



PARAGRAPH XVI. 



TEMPERATURE. 



The air temperature is certainly more influenced by altitude, 

 latitude and proximity of ocean or gulf stream than by the proxi- 

 mity of the forest. 



Daily temperature: The forest air is warmer during the night 

 and cooler during the day than the field air. 



Mean temperature: In summer the forest air is by three degrees 

 cooler than the field air; in winter there is scarcely any difference. 

 Shade-bearing species show a greater influence on temperature 

 than light-demanding species. 



Extreme temperature: The extremes of temperature seem to 

 be considerably influenced by the forest, if observations by 

 Woeickof are correct. After him, the forest lessens the extremes 

 of temperature by about ten degrees. For Germany, the summer 

 extremes in the forests are about seven degrees lower than in 

 the field, the winter extremes about two degrees higher. The 

 radial posts of the meteorological stations now established in 

 Europe may throw additional light upon the subject. 



The soil t'emperalitre is "limping behind" the air temperature 

 by about two months, the difference increasing with increasing 

 depth. In the soil, during May, the temperature decreases with 

 the depth ; in October, it increases with the depth. 



The soil temperature in the toplayers of the field is almost 

 equal to the air temperature in the field. In the forest, there 

 is a difference of two degrees in favor of the air. 



The daily range of temperature is smaller in the forest soil 

 than in the field soil. The summer temperature in the field 

 soil is about six degrees higher than in the forest soil. , In winter, 

 there is almost no difference. 



The temperature of the bole of a tree ranges between soil 

 temperature and air temperature. The temperature of the inner 

 layers of the bole, during winter, is higher than that of the 

 outer layers. 



