WATER LEVEL 21 



plantations after cutting were badly frosted two years out of three, while 

 the plantations under scattered seed trees were not damaged. 



The frost penetrates the soil about one-half as far in the forest as on the 

 outside. According to four experiments (quoted by Huffel) the average 

 soil depth of frost outside the forest was 17 inches, while inside the ground 

 was frozen only to the depth of 11^ inches. 



Hail. — Hailstorms are less frequent in the forest than outside. Huffel 

 quotes Riniker (1881 Die Hagelschage), who says: "In general hailstorms 

 stop at the border of well-stocked mature forests. Both on the plains and 

 in the mountains one often sees hailstorms cut in two or divided when 

 they pass above wooded stands . . . small coppice would not do 

 this." France had studied the effect of hailstorms on forests and vice 

 versa, but by the decree of January 20, 1892, the work was discontinued 

 and no decisive results were obtained. Jacquot notes the fact that of the 

 eighteen departments where hail does the most damage fourteen are the 

 least forested. 



Humidity and Rainfall. — Huffel^ says that "the relative humidity 

 of the air is greater under a stand than in the open, not, as one would sup- 

 pose, because the atmosphere of the forest holds more vapor, but because 

 it stands at a lower temperature and is nearer its saturation point." 

 According to Fautrat's experiments in the Ermonville Forest in 1876 the 

 air under the stands showed 7 per cent to 12 per cent greater moisture 

 content than in the open. 



French foresters believe that forests mean more rainfall and, as Huffel 

 puts it, "The rain increases according to the progress of forestation," and 

 "it rains more, all things being equal, in the center of a large stand than 

 on its border, and more on the border than a few miles away, that the 

 difference appears to be independent of the season of the year, but is 

 slightly greater during rainy years and less during a drought." The 

 French viewpoint is given more fully under "Springs" (in the Appendix, 

 p. 361), but French statistics collected near Nancy are at least significant. 

 If the rainfall (a) in the forest is represented by 100, the rainfall (6) near 

 the forest and (c) well outside would, on the average, be (6) 93,3 per cent 

 and (c) 76.5 per cent. It is at least safe to assume that forest tends to 

 increase rainfall. 



Water Level. — Experiments ^^ show that the water level the year 

 round is unquestionably lower in the forests than in openings, and that 

 there are smaller fluctuations in the water level in the forests than else- 



^ Vol. I, pp. 67-81, especially p. 75. It should be stated here that the theory that 

 forests increase rainfall (except under rare circumstances) is not accepted by American 

 meteorologists. 



1" E. Henry and A. Tolsky. Les Forets de Plaine et les Eaux Souterraines. Annales 

 de la Science Agronomique frangaise et etrangere, 1902-03. 



