REFORESTATION AREAS 427 



toithe north and formed, for the most part, by gneiss and mica schists with granite on 

 about half its drainage area. . . . The upper basin of la Sioule occupies about 

 25 miles of circumference. . . . The highest altitudes are those of the Puy-de- 

 Dome, 4,806 feet. The lowest altitude is where the Sioule leaves the department, 

 1,037 feet. 



Climate. The climate of the region is severe, despite the moderate altitude of the 

 plateau, and is characterized by rapid changes in temperature. The spring rams are 

 very abundant and result in sudden floods. During the summer violent storms are 

 succeeded by prolonged droughts. The winter is long and vigorous and is marked by 

 heavy falls of snow in the mountain forests. 



Basins. The basin of the Sioule is divided into two regions (the grazing area ex- 

 tends over about one-fourth of the total area). The natural mountain zone, which 

 bounds the basin on the southeast and comprises all the volcanic soil from the Domes 

 chain to Mont Dore. The agricultural area occupies the plains. It extends into the 

 plateau region and produces fruit, rye, barley, grain, oats, and potatoes. A considerable 

 proportion (about 20 per cent) of the uncultivated land belongs to the State and is 

 covered by heather, which is open to sheep grazing. The forest occupies about 10 per 

 cent of the area and comprises simple oak coppice and pole stands of conifers. 



Administrative Situation. The part of the basin included in the department of 

 the Puy-de-D6me extends over twenty-one communes of the Clairmont district and 

 fifty-six communes of the Riom district. The area is about 339,769 acres and the popu- 

 lation about 72,600. 



State of Soil Erosion. The soil erosion as yet is not very important. Because of 

 the solid nature of the rock the surface water flows from the gentle slopes without cut- 

 ting in. Once in the bottom of the thalweg, it ... is almost unerodable. The 

 solidity of the rock facilitates the different correction work; forestation aims almost 

 entirely at forming a cover. 



Composition and Area. The Sioule area was laid out by Art. 16 of the law of 

 April 4, 1882. It includes eight working groups, but a total of only 1,453 acres. 



Work. The forestation undertaken under the law of July 18, 1860, had as its first 

 objective the creation of important forests capable of retaining the soil on the slopes and 

 of regularizing the general waterflow , . . the work has been both by means of 

 sowing and of plantations. In the case of the Scotch pine the seed has been sown broad- 

 cast on land covered with a short growth of heather (see page 133). The pedunculate 

 oak has been sown in seed spots. The species used in plantations have been the fol- 

 lowing: Scotch pine, spruce, pedunculate oak, beech, and birch. Usually the two 

 methods of forestation sowing and planting have been employed together. The 

 work has been finished for some time and the stands obtained are now making excellent 

 growth. 



Cevennes Region (Lozere, Ardeche Departments Chassezac Forestation Area). 

 The Chassezac is much the most important tributary of the Ardeche. With a total 

 length of about 47 miles it rises in the Lozere and extends to Alfigere, but it flows in to 

 the Ardeche River at the Sampzon rock, not far from the confluence with the Beaume. 

 It flows, to start with, in very narrow but extremely deep gorges, then in a valley of 

 increasing width. It has a length of 27 miles in the Ardeche department with an average 

 slope of 2 per cent, and an average width of 148 feet. Its flow per second in the lower 

 parts of its course is 1.5 cubic yards at low water, 8 cubic yards under average condi- 

 tions, and 2,500 cubic yards during floods. Bounded on the north by the CeVennes 

 (which separates it from the Allier basin) and by Mt. Tanargue (which separates it 

 from the upper Ardeche), this basin reaches at the hamlet of Bez an altitude of 4,072 

 feet; in the State forest of Tanargue, 4,462 feet; and on the plateau of the Borne work- 

 ing group (near Tanargue), 4,951 feet. 



