PROTECTION AGAINST HEAVY RAIN. 555 



less secure against windfall. Clay soils are also injuriously 

 affected by heavy rains, as a crust forms on their surface 

 excluding air from the roots of plants. 



2. Protective Rules. 



(a) Maintain the forest growth and natural soil-covering of 

 herbage, moss, and dead leaves on all steep slopes exposed to 

 denudation. 



In high forest, it is best to have natural regeneration 

 under a shelterwood, but on slopes, coppice is less heavy 

 than high forest, and protects the soil as well. In plant- 

 ing up such localities, the slopes may be terraced with 

 advantage, and planting, which is preferable to sowing, 

 should be in horizontal lines commencing at the top of the 

 slope. For dry calcareous slopes the Austrian pine is most 

 suitable. 



(h) Establish a system of horizontal leaf-catching trenches, 

 or -protective trenches on dry slopes. 



These trenches differ from one another by their dimensions. 



The protective trenches are from 10 to 12 inches deep and 

 25 to 33 feet apart ; they should be in lengths of 12 to 30 feet, 

 to prevent the formation of drains. These trenches retain 

 the excess water after heavy rain, and part with it gradu- 

 ally to the soil, the permanent moisture of which is increased. 

 Leaves are washed and blown into them and the soil is 

 thus enriched with humus and rendered more porous and 

 deeper. In oak and beech forests, they catch the acorns 

 and beech-nuts which are rolling downhill, and thus natural 

 regeneration may be secured. Even the spoil-heaps from 

 the trenches afford suitable sites for the germination of 

 seeds. 



If, however, the trenches are intended merely as leaf-catchers, 

 they are shallower and closer to one another than the protec- 

 tive trenches. Excellent results have been obtained in the 

 Hessian district, Lindenfels, by the use of leaf-catching trenches. 

 They cost about 9(/. to Is. per running meter. 



(c) All measures which cause or favour loosening of the 

 soil should ho abandoned in steep places ; these are : — 



