126 FORESTRY WORK 



If pitwood is in greatest demand, Scots and Corsican 

 Pines, Larch or Spruce, can be profitably grown on 

 rotations from 35 to 45 years, according to the size of 

 props required. 



Some pits use short props, which need not be very 

 thick; others use very long and strong ones. Forty 

 years is a good average rotation for pitwood. If the 

 butts are too big for props, they may be sawn for other 

 uses at the pits, such as sleepers or used for estate pur- 

 poses. For larger timber the following rotations are 

 usually considered most profitable on soils suited to the 

 different species: 



Oak, 120 to 150 years. 



Beech, 100 to 120 years. 



Ash, Spanish Chestnut, Sycamore, Elm, 70 to 80 years. 



Scots Pine, Larch, Douglas Fir, Spruce, and Silver Fir, 

 70 to 80 years. 



Poplars and Willows, 40 to 50 years. 



On soils less suited to their requirements, a rotation 

 shorter by 10 to 15 years may be more profitable. 



If exceptionally large timber is in demand, a proportion 

 of the final crop may be left standing at the end of the 

 first rotation, and the area restocked, using shade- 

 bearing and soil-improving trees near the standards, and 

 leaving the more open spaces for light- demanding trees. 



Underplanting. 



Soil improving and protecting trees not only provide 

 a heavy leaf-fall, but their dense shade keeps the leaves 

 damp, hastens their decay and the formation of a layer 



