INTRODUCTION 141 



Mathieu, Costa de Bastelica, and, finally, D^montzey, whose reforesta- 

 tion work for France will never be forgotten. 



There is always greater rainfall in the mountains than in the plains; ^ 

 this favors erosion on the one hand, but on the other is more favorable 

 to tree growth. This greater rainfall is due to the well-known effect of 

 the colder air on the moisture-laden atmosphere, as it is forced to rise 

 on meeting a mountain range. But, when an altitude of about 6,500 

 feet is reached, the rainfall begins to decrease again, and only scattered 

 trees or groups of trees are found. The distribution of this rainfall has 

 an important bearing on the problem of reforestation. Up to 45° north 

 latitude the rain is evenly distributed, whereas in the south there is 

 little moisture in summer, the rainfall being evenly distributed between 

 winter, spring, and autumn. But in the Alps the climate seems to have 

 become drier, a fact due, as some authors say, " to the intervention of 

 man" though others say it is because the air has really become drier 

 through climatic changes. Possibly these two views can be reconciled. 

 The Waters and Forests Service says : 



"The direct intervention makes itself felt in mountain regions by felling trees along 

 the forest limits, by unregulated grazing, and in certain places by too conservative 

 forest fellings, as M. Thirion has indicated." 



In the mountains the forester must avoid leaving too many trees 

 which would become overmature and at the next felling could not assure 

 the perpetuation of the forest, because, if the stand has not been opened 

 up while the trees are vigorous, it is certain that regeneration will not 

 be complete; and if at the same time, as happens only too often, the 

 forest has been opened to grazing, its ruin has been completed through 

 having too few trees and trees of very mediocre quality. To this fact 

 can be attributed the so-called receding of the forest growth in the high 

 moimtains. The stand not having been thinned when the trees were 

 vigorous and healthy and grazing not having been forbidden, surfaces 

 covered with old stands have not been able to reseed and the forest has 

 been forced to disappear. M. Flahaut says: 



"In the lower mountains the passage of the plains climate to that of the heights is 

 at first favorable to tree growth. As you rise, the pressure diminishes, the capacity 

 of the air in water content is less, the rains are less frequent and less abundant, the 

 heaviest winds increase the transpiration. These conditions are unfavorable to tree 

 growth; when extreme they become fatal and completely prevent it; they are on the 

 contrary favorable to herbaceous growth. Commencing at a certain altitude, which 

 varies according to the geographic situation of the mountains, according to the cli- 

 matic conditions, and even according to the topographic detail, the tree growth is 

 then impossible." 



■^ A brief summary of the campaign for forestation in its broader sense will help to 

 an understanding of French sensibilities on the deforestation caused by the Great 

 War, The statement by the French Government has been followed, for it gives the 

 official viewpoint. 



