02 TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 



As experimental areas twenty- to twenty-five-year old pine 

 thickets {i.e. approaching the pole stage) were selected in the 

 Eberswalde State forest. These grew on very uniform soil on 

 a perfectly flat area (diluvial valley sand). For the object in 

 view there were chosen a fully-stocked and undisturbed {i.e. 

 unthinned) area, and two similarly stocked areas, which were 

 then thinned. In the one case the thinned-out material was 

 removed; in the other case the thinnings were left as a twig 

 and branch covering of the forest floor. In these three 

 contiguous areas soil tests were made from three different 

 places in each area every week during two periods of vegetation 

 (1912 and 1913)- The soil samples were taken from an upper 

 layer 20 cm. (7-8 inches), and also from a deeper layer 

 40 cm. (i5'7 inches), and the water-content investigated. The 

 results in both years of the investigation were similar, and 

 showed that the reduction in the number of stems had in itself 

 an appreciable and lasting influence on the increase in the water- 

 content of the soil. Still more favourable was the eff^ect of the 

 thinning combined with the twig and branch covering of the 

 soil, in that it had a considerable eff'ect in raising the water- 

 content of the soil, which is apparently to be explained by the 

 reduction in evaporation from the surface covered with branches. 

 The increase in soil moisture was not confined to the upper 

 layers only, but was distinctly marked in the deeper layers also. 

 In the thinned area covered with branches the water-content of 

 the upper layer was, for example, in the experimental year 1912, 

 8-07 per cent., while for the unthinned area it was only 6'3i ; 

 for the experimental year 1913, similarly the figures were 6'24 per 

 cent, and 4^42 per cent, respectively. In such light sandy soils 

 an increase in the water-content cannot fail to have a beneficial 

 influence. The early thinning of pine woods approaching the 

 pole stage of growth and the leaving of the practically valueless 

 thinnings on the ground is an extremely rational operation, 

 which will benefit both the soil and the trees. The poorer the 

 soil the greater the need for this treatment. This treatment is 

 especially suitable for all woods formed on hitherto waste land 

 or deteriorated agricultural land. The author was able to 

 conclude definitely in many localities that by the timely adoption 

 of this method of treatment, the failure, in groups, of pine 

 approaching the pole stage, which otherwise seems unavoidable 

 on such kinds of soil, can be entirely prevented. The author 



