CHAP, viii.] Formation of Timber Crops 163 



market may account for the comparatively low prices. The 

 monetary returns available in general from the softwoods 

 depend to a very great extent on local conditions of the 

 timber market ; whilst the Beech usually yields comparatively 

 poor returns, despite its being the best, and the most heat- 

 producing kind of fuel obtainable from woodlands. Its timber 

 is, however, now coming largely into demand again. 



Whilst the advantages derivable from mixed forests in- 

 cluding conservation of the productive capacity of the soil by 

 the shade-bearing, ruling species ; better utilization of the soil 

 through differences in root-system, and of the light, air, and 

 warmth by the crowns being generally at slightly different 

 levels ; protection against insect enemies, fungoid diseases, and 

 damage from inorganic causes, &c. are only attainable to the 

 fullest degree when the admixture of genera occurs in indi- 

 vidual stems, yet the casual differences in the physical properties 

 of the soil can only be fully availed of when admixture takes 

 place in patches or groups varying in extent with the variations 

 in the soil. The general principles guiding the choice of species 

 in mixed crops, apart from the fundamental rule regarding 

 conservation of the soil applicable alike in the formation of 

 pure and of mixed woods, are, broadly stated, that the conditions 

 of soil and situation must suit all the kinds of trees to be inter- 

 mixed, and that the more or less normal development of each 

 species should be interfered with as little as possible by the 

 others. Hence mixtures of trees with similar requirements as 

 to light, or nearly equal capacity for bearing shade, usually re- 

 commend themselves only when one kind can be utilized so 

 much earlier than the other as to permit of underplanting (e. g. 

 Oak, with Ash, Maples, and Elm on good soil), or when, besides 

 producing a greater quantity of timber with a higher percentage 

 of technical and consequently of monetary value, other advan- 

 tages are gained in protection against violent storms or the 

 ravages of insects (e. g. when Spruce is mixed with Beech and 

 Silver Fir). Thus, on soils and situations suitable for the Silver 



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