THINNING AND PRUNING 139 



left and leaving a good many misshapen and worthless 

 individuals, and the mixed plantation, in nine cases out of 

 ten, will remain mixed until the end. In many cases even 

 it is better forestry to let the conifers remain altogether, and 

 let the hardwoods take their chance, than to leave a crop of 

 the latter which are more or less ruined already. 



On good deep soils which suit them, oak and ash may be 

 raised in mixed plantations with fair success, and on dry 

 soils beech will often fight its way through and succeed 

 at the end. But the species mixed with them must be 

 selected with some judgment, and on the lines recommended 

 in Chapter IV. To mix Corsican or Austrian pine, black 

 Italian poplar, etc., with oak can only end in failure, unless 

 they are taken out at an age at which they are perfectly 

 useless, and none with any knowledge of forestry would 

 think of planting them together. But those with any 

 knowledge of forestry do not plant indiscriminate mixtures. 



A frequent cause of outcry in connection with thick 

 plantations is the condition of certain crops which have been 

 grown thickly for a number of years, and then suddenly 

 thinned under the idea that the remainder of the trees are 

 going to develop in the way in which those gradually thinned 

 from the start are accustomed to do. Such a proceeding is of 

 course usually fatal. A large number of the trees are either 

 blown down with the first strong wind, or, in the case of oak 

 or most hardwoods, develop a mass of adventitious shoots all 

 up the stem, and remain in a stunted condition ever after- 

 wards. Such cases constitute no argument against the self- 

 thinning system, as it will invariably be found that one or 

 the other of the conditions necessary has not existed. No 

 one with any acquaintance of arboreal physiology would 

 expect anything different from that which actually occurs. 

 In the first place, the surface of the soil is exposed to the 

 sun and wind, which dry up or carry away the humus layer 

 that accumulates during the close order of the crop. This 

 humus layer, or the soil immediately below it, is full of roots 

 which supply most of the food available for the trees, and its 

 destruction means the starvation of these roots. But the 

 influence of sun and light upon the bare stems of the trees is, 

 in the case of certain hardwoods, even worse. The oak is 



