478 "HEARING OF THE ESTABLISHED CROP. 



Indeed, there are in all only two cases in -which thinnings may 

 have to be delayed : firstly , when the component species clear their 

 boles with difficulty or require to be forced up in height, and, 

 secondly, when small wood possesses too little value for the produce 

 of the thinnings to at least cover the cost of the operation. This 

 second reason for delaying the first thinning is, however, often 

 entirely illusory, as the accelerated growth of the fostered stems, 

 and hence their increased money-value, may prove more than a 

 set-off against any small excess of expenditure over the immediate 

 money-return of the thinnings, 



IV. How frequently thinnings should be repeated. 



If the crop under treatment is required to produce only small 

 wood, the rotation may be too short to admit of more than a single 

 thinning, or there may be no time even for this one thinning. 

 Otherwise more than one thinning must be made in order to allow 

 the more promising individuals of the crop to continue their 

 growth unchecked. Whenever, therefore, the crop begins to pre- 

 sent again a crowded appearance, a fresh thinning must be made. 

 The frequency of repetition will be in direct proportion to the rapi- 

 dity of growth of the overtopping and dominant trees. This will 

 itself depend on the nature of the soil, locality and species, and, 

 for one and the same soil, locality and species, on the age of the 

 crop. All crops grow most rapidly during the first half of their 

 life, particularly during the pole stage. In India we have still to 

 ascertain the periodicity suitable for our various species at different 

 ages and under different conditions of soil and locality. 



The interval between one thinning and the next will also, to a 

 slight extent, depend on the severity of the former, for it is obvi- 

 ous that the more open a crop is, the longer, cceteris paribus, will it 

 take to become crowded enough to require being thinned again. 

 This remark must not, however, be construed into a justification 

 for making heavy thinnings solely in order to lengthen their 

 periodicity and thereby save expense ; the severity of each thin- 

 ning must be determined on entirely different grounds, which have 

 already been considered in their proper place. 



Crops of shade-avoiding species should be thinned lightly and 

 frequently, so that they may always have sufficient light and yet 

 never be opened out too much to the detriment of the soil and the 

 future reproduction. 



V. Season for making thinnings. 



In the interior of the Himalayas where snow lies on the ground 



