330 



PLANT SOCIOLOGY 



comparison of existing bits of vegetation of different ages or the 

 presence of relict societies or pioneers gives convincing evidence of past 

 or prospective changes of vegetation. 



If, for example, we find in a pine wood on an old sandy bank dying 

 and dead Salix incana and tussocks of Hippophae, and at the same 

 time find that in neighboring vigorous stands of Hippophae a young 

 growth of pines is established, it does not require a permanent quadrat 

 to make plausible the succession from the Hippophae- Salix incana 

 association to Pinus silvestris forest. 



Fig. 166. — Permanent quadrat (1 sq. m.) in the Brachypndium ramosum-Phlomis 

 lychnitis association at Villeneuve-Ies Maguelonne in January. Surface covered by 

 vegetation, 80 per cent. {Photo by Braun-Blanquet and Keller.) 



Another important example illustrating the significance of pioneer 

 trees as syngenetic indicators is found in the Pinus montana forest in the 

 Ofen Pass region. The limestone talus is prepared for the coming of 

 trees by the stabilizing effect of such low shrubs, as Ardostaphylos 

 uva-ursi and Dryas. Protected by these, in the absence of disturbance, 

 there may come into the undergrowth an Erica carnea-Juniperus com- 

 munity with few mosses, to be followed in turn by a more mesic and 

 more mossy type with Erica carnea, Rhododendron hirsutum, Vaccinium 

 uliginosum, and V. vitis idaea. In this mossy community P. cembra 



