444 Forestry Quarterly. 



Finally, we may note that the Middle Forest system will pay 

 only on very moist soils, and to these it is nowadays confined. 



5. The Pine Forests on the Rhine. Of this type are the forests 

 in the first uplands in the valley of the Rhine. The soil here con- 

 sists of a somewhat older formation than that occupied by the 

 previous two types, and is diluvial sand and gravel. 



These forests are now almost entirely composed of Scotch Pine, 

 but this was not always the case. Years ago they were beautiful 

 broadleafed forests of Oak, Beech and Hornbeam, with Linden 

 and Elm in addition. However, owing to the drying up of the 

 soil caused by the regulation of the river and consequent soil 

 changes of which we have already spoken, Scotch Pine is the only 

 workwood tree which it now pays to grow here. 



This change has been so complete that the present generation 

 has no idea that anything but Scotch Pine ever grew in this dis- 

 trict. Nevertheless, about 20 years ago the last of the old broad- 

 leafed trees were cut and there were then to be found beautiful 

 Oaks as much as 30 meters (100 feet) high, but already stag- 

 headed and showing signs of decay, and Beech as much as 42 

 meters high (138 feet). Such trees were only to be found on 

 the moister soil and as the ground gradually rose so did the height 

 growth fall off. 



The soil higher up the Rhine is loam and coarse gravel, whilst 

 lower down towards Mannheim it is a very sandy loam, in some 

 cases almost pure sand, and consequently unless the water level 

 is rather near the surface will not support any good forest growth. 



The present Pine forests extend from Rastadt to Mannheim 

 and are treated under a rotation of 100 years, but owing to the 

 amount of snow breakage many stands are cut over much sooner 

 whilst others in good condition are left for a longer period to 

 acquire a heartwood. 



The immediate efl;ect of svibstituting coniferous trees for the 

 broadleafed ones was to lower the revenue, as the old Oaks 

 fetched very high prices. In order to bring the revenue up to its 

 former figure heavier thinnings were made and it was found that 

 these thinnings so far from deteriorating the stands, on the con- 

 trary, improved them. 



Natural regeneration is excluded here, and clear cutting and 

 planting is everywhere practiced. The system adopted in most 



