CLIMATE AND SOIL 33 



be attempted on limy soils, as it is said that they do not grow 

 to large size on such soils. On peats, alder, birch, beech, white 

 poplar, willows, larch, Sitka spruce, spruce, Austrian pine, 

 and Scotch pine will do well if the peat is first drained and 

 if a little mineral soil is mixed into each hole at the time of 

 planting. On loams and sandy loams most species will succeed 

 and grow to a large size, and naturally the most valuable will 

 be chosen. 



Species which will accommodate themselves to various 

 soils and which will do fairly well on poor soils are called 

 accommodating trees ; such are Austrian pine, Corsican pine, 

 Scotch pine, Weymouth pine, birch, poplars, most willows, 

 false acacia, mountain pine, white alder, and red cedar. 



Species which must have a good soil to produce large size 

 timber are called exacting trees ; such are silver fir, beech, 

 chestnut, oak, sycamore, ash, and elm. Intermediate between 

 the two classes are certain species which do not require the 

 best class of soil, and yet which will not grow in the poorest 

 soils. These may be called moderately exacting trees ; this 

 class includes spruce, Sitka spruce, larch, alder, lime, osiers, 

 hazel, hornbeam, Norway maple, and Douglas fir. Whenever 

 the soil to be planted does not appear exactly suitable to any 

 particular species, it will be safest to plant one or more of 

 the accommodating trees, as the risk of failure is then reduced 

 to a minimum. 



It must always be the first aim of a woodman to improve 

 the physical properties of the soil and to maintain its fertility. 

 Fortunately there is a simple way of doing this by encouraging 

 a heavy fall of leaves to form humus, and by preserving this 

 when formed. By keeping a dense cover overhead, a heavy 

 fall of leaves will be obtained which will slowly decompose 

 into an excellent leaf mould ; on the other hand, if sun and 

 air are let into the woods by overthinning the humus will 

 decompose rapidly, and will disappear, with the result that the 

 soil will gradually deteriorate. Humus improves the soil in 



