91 



show. He found in pines 147 years old which had been standing free for 

 seventeen years, that the growth had been doubled in the first ten years, 

 especially in the lower part of the trunk, where the amount of wood, that is 

 the dry weight, had also increased. But he also demonstrated that the in- 

 crease fell to the earlier amount, when the food in the soil was taken 

 up by spruces which were set out there. In trees whose roots are exposed 

 on one side, there is a less water content of the soil which also retards the 

 absorption of foods and the influence of light is scarcely able to cause an 

 increase of growth. But even if a considerable increase of growth is ob- 

 tained by the sudden thrusting of the trees into the light, no agricultural ad- 

 \antage is constantly connected with it. In the first place, the branching is 

 increased and, in the second, the wood due to the rapidly increased growth 

 is coarse grained. This is deduced from the observations of Cieslar and 

 Janka^ who investigated the spruce wood produced by long-standing 

 cultivation. Produced in great quantity the wood was of strikingly low 

 specific gravity because the autumn wood made a scanty growth and the 

 tracheids, in the main part of the annual ring, were unusually wide. On 

 the other hand, the danger of drying of the top, or blight of the tip, often 

 becomes greater. This applies also to deciduous trees grown in dense plan- 

 tations. The crowns are suddenly freed, their leaves, in structure and func- 

 tion, are adapted to a moderate amount of illumination, can not endure 

 the increased transpiration and the excess of light so that the tips of the 

 branches partially die back. Therefore it is urgently advised in the interest 

 of retaining old tracts of woods, specially in sandy soil, to avoid cutting 

 through the hills to lay out roads, preferably to lay the road out around the 

 hill. According to Hartig- the shock of the sudden opening may also 

 lead to injury if, with the increased supply of light, the top is stimulated 

 to too active growth. This continues some years, while The a\ ailable quanti- 

 ty of nutriment in the soil lasts. Because the leaf material is increased as a 

 result of the intensity of the light, much larger amounts of mineral stuifs 

 naturally are required than with growth in dense tracts. Hov/ever, when 

 parts of forests are exposed, soluble mineral food material can not be pro- 

 vided in sufficient quantity by the influence of the atmosphere, consequently 

 after a good growing period there is a decrease in growth due to the "im- 

 poverishment of the soil." Following a scarcity of material, however, no 

 matter whether due to an actual lack of the substance or to its insufficient 

 absorption on the part of the tree, as a result of injuries to the roots or a 

 lack of water, there is not only a decrease of growth but also the constitution 

 of the wood is weakened. As when growth is forced, only the thin-walled 

 spring wood, the vascular tissue, is formed and but little or no strengthening 

 tissue, which is present in late wood. 



1 Cieslar, A. und Janka, G., Studien liber die Qualitat rasch erwachsenen Fich- 

 tenholzes. Centralbl. f. d. gesamte Forstwesen 1902. Part 8. 



-' Hartig, R., Ueber den Einflufs der Kronengrofse und der Nahrstoffzufuhr aus 

 dem Boden auf die Grclfse und Form des Zuwachses etc. Forstl. naturw. Zeitschrift 

 VII, 1898, p. 78. 



