28 



MISC. PUBLICATION 61, U. S. DEPT. OF AGRICULTURE 



Table 7. — Record of thinning experiments in Old Orchard and Apiary plantations, 



1916-1928 * 





Old Orchard plantation 





Apiary plantation 



Date of record 



Volume per acre 



Trees per acre 



Volume 



per acre 



Trees per acre 





Plot la 



Control 2 



Plot la Control * 



Plot 4a 



Plot 4b 



Plot 4a Plot 4b 



Before first thinning, 



October, 1916 



After first thinning _. 



Cubic feet 

 2,710 

 1,980 



2,670 



1,760 



2,570 



Cubicfeet 

 2,710 



Number Number 

 2,304 2,580 

 1,136 



1, 056 1, 904 



508 ■ 



504 1, 284 



Cubic feet 

 4,680 

 3, 550 



4,290 



2,530 



3,460 



Cubicfeet 

 4,680 



Number Number 

 1,760 1,425 

 952 



Before second thin- 

 ning, January, 1923 . 



After second thin- 

 ning 



3,186 



5,060 



832 962 

 336 



Last examination, 

 September, 1928 



3,345 



5,980 



336 725 



1 Volumes were computed by the use of an assumed form factor of 0.5. 



2 Average of plots lb and lc. 



The difference in growth rate between the thinned and control 

 plots in the Old Orchard white pine is very marked. In the thinned 

 plot the annual growth between the first two thinnings was at the rate 

 of 115 cubic feet per acre, while in the six years following the second 

 thinning it amounted to 135 cubic feet. In the two control plots, 

 combined, the annual growth for the corresponding periods was at 

 the rate of only 79 and 27 cubic feet per acre, respectively. In the 

 thinned plot, also, there was removed in the two thinnings a useful 

 volume of wood equivalent to 1,640 cubic feet per acre; in the control 

 plots, of course, there was a total loss of at least some of this wood 

 volume through death and decay. The thinned plot, with 504 trees 

 per acre in 1928, and an increase in total yield of 865 cubic feet per 

 acre, is in a much more efficient condition for growth than the iin- 

 thinned, overdense control plots with 872 and 1,696 trees per acre, 

 respectively. 



In the Apiary white pine, the annual growth rate between the first 

 two thinnings (123 cubic feet per acre), was about double that for 

 the corresponding period in the unthinned plot (63 cubic feet per 

 acre) ; but for the six years following the second thinning the growth 

 rate of the thinned and unthinned plots was about equal (150 cubic 

 feet per acre per year in round numbers). Evidently the second 

 thinning was considerably too heavy and left the stand too thinly 

 stocked for efficient production. It should be noted, however, that 

 the growth of the unthinned stand was distributed among small trees 

 at the rate of 725 to the acre, while that of the thinned stand was 

 concentrated on carefully selected thrifty trees at the rate of only 336 

 to the acre. The thinned plot as it appeared after the heavy thin- 

 ning of 1923 is shown in Plate 10. Sample plots J^a and Jfi contained 

 0.125 and 0.08 acre, respectively. 



The mixed pine stand in the Ferry Farm plantation was 17 years 

 old when the thinning experiments were begun. In this stand the 

 shortleaf pine had considerably outgrown most of the white pine 

 without killing it, and one object of the experiment was to attempt 

 to preserve the mixed character of the stand. Of the taller trees in 

 the thinned plot, 95 per cent of the white pines were therefore left 

 standing and only 74 per cent of the shortleaf pines, while of the 



