10 THE PRODUCTION OF MAPLE SIRUP AND SUGAR. 



the ground is kept heavily matted with leaves and humus, so that 

 the sun and drying winds will have little access to it, and a Com- 

 paratively uniform degree of moisture and coolness may be main- 

 tained under all conditions. Commercial sugar making is confined 

 to a small part of the botanical distribution of the sugar maple, 

 because of a peculiar climatic requirement. It is the gradual north- 

 ern spring, with the slow yielding of the frost by the ground, which 

 makes the sap flow long and continuously enough to give a paying 

 production of sugar. A sudden thaw affects both the quality and 

 the duration of the sap flow. On this account it is always desirable 

 to maintain forest conditions in a sugar grove, for if the ground 

 has a heavy carpet of leaves and humus, it will be less sensitive to 

 changes in temperature. 



Altitude is one of the most important factors in determining the 

 necessary density of the sugar grove. High up in the mountains, 

 where the summer is moist and the spring long, and in the North, the 

 necessity of an unbroken cover is not so great as where the summer 

 is hotter and the spring less gradual in its transition from winter to 

 warm weather. In mountainous regions the forest can be more open, 

 and in every large grove a section on a southern exposure will insure 

 an early sugar season. In lower altitudes the close grove of full- 

 crowned trees will have an advantage over a scattered stand of field 

 trees exposed to the effects of a variable spring. It should not be 

 forgotten, however, that trees which have developed from their youth 

 in very open groves have stronger root systems than forest trees, and 

 that they draw their water supply from the moist subsoil (see p. 7) ; 

 but such groves have a relatively limited production per acre, and, 

 while serviceable for a small home production, would cover too large 

 an area to be profitable for a large undertaking. 



The model grove should satisfy the following requirements as far 

 as possible. 



(1) It should contain the greatest number of trees per acre con- 

 sistent with fully developed crowns. 



(2) The forest cover should be unbroken, so that in summer little 

 sunlight falls upon the ground. 



(3) There should be a complete litter of humus and leaves, to the 

 exclusion of grass and light-demanding weeds. 1 



(4) Young trees should be kept in reserve to take the place of those 

 that fail, and to fill other openings in the cover. 



(5) No grazing should be allowed in the grove, except in special 

 cases where the cover is perfect and no reproduction is needed. Cattle 

 not only keep back all reproduction, but also do harm by trampling 

 and breaking the ground, so that it dries out. 



(6) The grove should be made accessible by a system of roadways 

 to facilitate the collecting of sap. If the network is complete no 

 difficulty will be found with the underbrush, which hinders sap 

 gathering little in the early spring when the woods are devoid of 

 foliage. 



The first three points vary in importance with the latitude and 

 altitude of the grove, but they are always worthy of consideration. 



1 French and German experiments have demonstrated that a heavy growth of grass 

 dries the soil, and interferes with the entrance of water even during a heavy rain. 

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