OLEOKESHST PRODUCTION. 43 



Chipping should progress up the tree at the rate of not more 

 than one-half inch a week. In experiments in which chips of an 

 average height of 0.40 ^ to 0.34 i5 inch were actually cut, a higher 

 sustained yield was produced than in comparable workings in which 

 the chip averaged one-half inch high. In the case of the double 

 chipping at Columbia, Miss., an average height of chip of 0.32 inch 

 was obtained with a 00 hack in 1916, and an average 0.26-inch chip 

 with a puller during 1917. During the second year these trees, 

 under this treatment, showed a smaller relative reduction in yield 

 of turpentine, when compared to the first year yield, than did the 

 half-inch chipping (standard). Using such a narrow streak means 

 chipping in the lightwood or region of maximum stimulation, at 

 least for a part of the season. It is yet to be determined whether the 

 height of the chip can be further reduced. 



Sufficient experiments to determine the most advantageous depth 

 of chipping have not been carried out. It appears probable that 

 the significant factor in this case, however, is the width of the sap- 

 wood, since, as has been shown, a considerable yield is obtained from 

 many of the outer sapwood rings. A layer of healthy moist sap- 

 wood should always be present behind each face to maintain at the 

 maximum the vital activities of the sapwood layers exposed at the 

 streak. With wide sapwood and deep chipping (about three-fourths 

 inch) very high yields may be obtained. 



The advantages to be gained by the practice of conservative nar- 

 row chipping were shown to be the following : 



1. Higher yields (40 to 50 per cent) per inch of height of chipped 

 surface. 



2. Higher sustained yields — that is, less reduction in yield from 

 year to year, approaching the optimum condition, confidently to be 

 expected, when the yields of subsequent years will surpass that of 

 the first year. 



3. Total annual yield approximating or even surpassing the yield 

 from heavier chipping. 



4. Little reduction, on the average, below the wood formation 

 of the round timber, either in amount or quality. 



f>. Vary high production of resiniferous tissue. This, for a 

 given year, was markedly greater about one foot above the early 

 streaks made thai year. Hence, narrow chipping enables the opera 

 tor to reap the full benefit from this region of maximum stimiila 

 tion am! re ponse by ihe practice known as chipping in the lightwood 

 instead of wasting the wood containing the greatest number of resin 



|,a ages by cutting it away with high chipping. 



44 K.-irly Fore«1 Service Experiments, page 'J7. 



irrow Chipping, roluinMii, MIhh., pa»?o 21. 



