ANNUAL INCREMENT OF GROWING CROPS OF TIMBER. 1 67 



of falling to about the level of the mean annual increment. 

 When this point is reached it is usually time to cut the crop, as 

 no advantage can be served, unless timber of specially high 

 quality is being aimed at, in allowing the current to fall below 

 the mean annual increment. 



The Scots pine in the same plantation shows some rather 

 interesting results. The very low mean annual increment 

 (32 feet to 36 feet) indicates the struggle which the crop 

 probably had in its early stages to get established at all, and 

 it was very likely 20 or 25 years before the crop was even 

 measurable. Between the years 1910 and 1914 it certainly 

 appeared that this crop would be better cut for pit-wood, and a 

 more suitable species planted in its stead. The sudden increased 

 growth in the last few years has, however, contradicted that 

 conclusion, and the explanation is no doubt to be found in 

 the fact that the canopy is now fairly good, that the surface 

 conditions of the soil have become better, and that in all 

 probability the roots have opened up and penetrated the soil 

 to greater effect. A sudden change in the growth of a crop, 

 either for the better or the worse, would be difficult to detect 

 or estimate by mere inspection unless supported by actual 

 measurement. 



The Scots pine in Plantation I illustrates clearly the un- 

 suitability of most soils in the district for the growth of this 

 species. The soil and situation are good, but both mean and 

 current annual increment are disappointing. This is especially 

 so if the figures are compared with those which immediately 

 follow for the spruce growing in the same plantation. It may 

 be emphasised that, with the exception of the Japanese larch, 

 none of the crops under observation have been grown in the 

 past under the best possible conditions. The increment results 

 now obtained do not therefore show the utmost of which the soil 

 and species are capable under the best conditions of planting 

 and subsequent management. In spite of such drawbacks it 

 will be observed that in three different cases the current annual 

 increment for spruce is over 100 cubic feet per acre, with a mean 

 annual increment of between 70 and 80 feet. At a moderate 

 estimate it should be possible to increase these results by 

 20 per cent., which would represent a yield very substantially 

 beyond what is looked for at the present time in continental 

 forests. 



