40 Methods of Sylviculture 



The harvesting of the crop should be done in the most careful 

 manner, as upon this depends the longevity of the stools, and after 

 the cutting, the stools should be trimmed so that water will not 

 lodge. Oak, ash, sweet chestnut, and hazel are suitable species for 

 this method of culture. 



Pure and Mixed Woods. 



A pure wood is a wood composed of one species of tree only. 

 It is rare in practice, or else it shows a bad system of forestry ; for, 

 over an extensive area, there is sure to be some variation in the soil, 

 and so the probability is that one species cannot thrive efficiently 

 throughout the whole area. The consequence is that stunted and 

 diseased patches of trees are produced, and these form centres of 

 infection from which attacks by insects and fungi may spread to the 

 healthy portions of the wood. Further, an error in judgment may 

 have been made in the selection of the species for planting. Then, 

 if the wood consists of one species only, the whole is unsatisfactory 

 and is not likely to be remunerative ; whereas, if more than one 

 species is planted, the most unsuitable one can be cut out. Pure 

 woods of light-demanding species are permissible, however, when 

 the trees are to be cut at an early age — e.g., pit wood, or when no 

 other species will grow. 



Many species are not adapted to form pure woods, owing to the 

 opening out of their crowns at an early age, and to the consequent 

 deterioration of the soil. Again, when the soil is very good, valu- 

 able species may be grown pure, although, even then, there is a 

 likelihood of the soil deteriorating towards the end of the rotation. 



The term mixed wood is applied to a wood composed of two or 

 more species. The advantages are to a great extent analagous to those 

 of rotations in agriculture. They may be summarised as follows : — 



(i) Different trees make different demands on the soil; conse- 

 quently, the soil being fully utihsed, a larger amount of timber is 

 produced. 



(2) "Frost-tender" species are protected by the more hardy 

 ones. 



