RELATION OF LIGHT-INTENSITY TO ADVANCE GROWTH. 1 49 



and they were practically confined to compartments 25, 33, 34 

 and 38, constituting the remains of Selection forest {Plenterii'ald) 

 which at one time extended over the whole district. They 

 lie approximately between the contour lines 1270 feet and 

 807 feet, on the southern slope of the Kling Bach Valley. 

 The gradient is gentle and the aspect ranges from north to north 

 north-east. The soil in all cases overlies and is derived from 

 Bunter sandstone, and, judgingfrom the height-developmentofoak, 

 would appear to be of uniform first-class quality for that species. 

 The density of stocking is on the whole fairly regular, the oak 

 tending to form small pure groups surrounded by pure beech. 

 In addition to this, the contour of the land is more or less 

 regular, and the range in elevation is not sufficient to bring 

 about any marked difference in the local climate. The growing 

 stock at present on the area consists of oak and beech, the 

 former varying in age from 120 to 350 years and forming about 

 60 % of the crop, while the remainder consists of beech, ranging 

 from 100 to 200 years in age. 



As already stated, the two species form more or less pure 

 groups, and since their seeds are comparatively heavy, and 

 therefore have a dissemination which is almost vertical, the 

 advance growth occurs in practically pure groups. It is of 

 interest to note that in the majority of cases the beech groups of 

 advance growth present a much better height-development than 

 the oak groups of the same age. As regards the persistence of 

 advance growth, groups of oak were observed which, although 

 they had remained for about fifty years under a shelter wood 

 without any appreciable increase in height, were still capable of 

 almost normal development. Again, as in the case of oak full 

 seed years generally occur once every decade, but in the case 

 of beech at intervals of about five years only, it may be safely 

 assumed that the seedlings comprising the advance growth have 

 persisted for some time and are likely to persist. The formation 

 of these groups of advance growth is doubtless largely due to 

 the natural thinning of the canopy, as the trees reach maturity. 

 The process, however, may have been assisted in some cases by 

 windfalls, disease, and the hand of man. Thus, as the various 

 conditions appear fairly uniform over the experimental areas, it 

 seems reasonable to assume that any variation in the advance 

 growth will be due principally to a difference in the light-intensity 

 with its accompanying effects. 



