Periodical Literature. 259 



15 years, showed a mean height advantage of .8 meters, (about i 

 yard), over closed stands. 



Volume increment depends on amount and energy of the leaf 

 apparatus. Both are induced by increasing the growing space. 

 As to amount of foliage, dormant buds and young sprouts are 

 stimulated, especially in deciduous trees, where the light in spring 

 reaches buds both in the periphery and interior of the crown. 

 This is shown by Prof. Cieslar's example of 60 year beech where 

 in 10 years the trees on the thinned half showed 8 times greater 

 leaf development than that of the unthinned half. 



The energy with which assimilation takes place varies with 

 light, warmth and soil. Minerally poor soil produces a mis-rela- 

 tion between increment and leaf apparatus. R. Hartig opines 

 for beech, oak and spruce that the light on trees set free calls forth 

 more leaves than are necessary for the manufacture of food- 

 Such leaves work sluggishly even in full enjoyment of light; 

 hence such trees can afford to lose some foliage by pruning or 

 natural clearing, without detriment to increment. Light alone 

 does not do it. Hartig found the increment for spruce on miner- 

 ally good as against poor soil to be as 2 to i. Therefore, the 

 growing space or thinning practice should be related to the char- 

 acter of the soil. Only on good soils does severe thinning pay. 

 On poorer soils the increased increment due to thinnings often 

 declines after a few years. R. Hartig and Hornberger say this is 

 on account of the using up of the humus stock, of which there 

 was only enough for temporary stimulation. 



The greater part of increment, as high as 90 per cent., falls to 

 the dominant trees. Comparing the work of the leaves of domi- 

 nant as against oppressed trees, R. Hartig found that for spruce 

 on best soil on dominant trees i kg. needles produced cdm., 

 on oppressed i cdm., showing only one-fifth as much wood pro- 

 duced for the latter. Such relations are more significant in de- 

 termining light influence than absolute amount of increment, the 

 latter being dependent, ceteris paribus, on the assimilation en- 

 ergy and amount of foliage of the particular species. Both fac- 

 tors can compensate in their influence. For instance, Lubimenko 

 found that with vertical light at 35° C, one gram of leaves de- 

 on best soil on dominant trees, ikg- needles produced 5 cdm., 

 for pine 7.5 ccm.; for larch 11.5 ccm. These figures exhibit the 

 smaller energy of fir and spruce as compared with pine and larch. 



