320 HORTICULTURE, FORESTRY, FLORICULTURE 



fully penetrate the ground. Again, more snow is caught and pre- 

 served under the forest cover than on the wind-swept fields and 

 prairies. 



All these conditions operate together with the result that larger 

 amounts of the water sink into the forest soil and to greater depths 

 than in open fields. This moisture is conserved because of the re- 

 duced evaporation in the cool and still forest air, being protected 

 from the two great moisture-dissipating agents, sun and wind. By 

 these conditions alone the water supplies available in the soil are 

 increased from 50 to 60 per cent over those available on the open 

 field. Owing to these two causes, then increased percolation and 

 decreased evaporation larger amounts of moisture become avail- 

 able to feed the springs and subsoil waters, and these become finally 

 available to the farm, if the forest is located at a higher elevation 

 than the field. The great importance of the subsoil water especially, 

 and the influence of forest areas upon it, has so far received too little 

 attention and appreciation. It is the subsoil water that is capable 

 of supplying the needed moisture in times of drought. 



The Forest Tempers the Farm. Another method by which a 

 forest belt becomes a conservator of moisture lies in its wind-break- 

 ing capacity, by which both velocity and temperature of winds are 

 modified and evaporation from the fields to the leeward is reduced. 



On the prairie, wind swept every day and every hour, the 

 farmer has learned to plant a wind-break around his buildings and 

 orchards, often only a single row of trees, and finds even that a de- 

 sirable shelter, tempering both the hot winds of summer and the 

 cold blasts of winter. The fields he usually leaves unprotected ; yet 

 a wind-break around his crops to the windward would bring him 

 increased yield, and a timber belt would act still more effectively. 



Not only is the temperature of the winds modified by passing 

 over and through the shaded and cooler spaces of protecting timber 

 belts disposed toward the windward and alternating with the fields, 

 but their velocity is broken and moderated, and since with reduced 

 velocity the evaporative power of the winds is very greatly reduced, 

 so more water is left available for crops. Every foot in height of a 

 forest growth will protect 1 rod in distance, and several belts in suc- 

 cession would probably greatly increase the effective distance. By 

 preventing deep freezing of the soil the winter cold is not so much 

 prolonged, and the frequent fogs and mists that hover near forest 

 areas prevent many frosts. That stock will thrive better where it 

 can find protection from the cold blasts of winter and from the heat 

 of the sun in summer is a well-established fact. 



The Forest Protects the Farm. On the sandy plains, where the 

 winds are apt to blow the sand, shifting it hither and thither, a 

 forest belt to the windward is the only means to keep the farm pro- 

 tected. In the mountain and hill country the farms are apt to suf- 

 fer from heavy rains washing away the soil. Where the tops and 

 slopes are bared of their forest cover, the litter of the forest floor 

 burnt up, the soil trampled and compacted by cattle and by the 

 patter of the raindrops, the water can not penetrate the soil readily, 



