THE DEVELOPMENT OF COMMUNITIES 



335 



II. Communities of bacteria, fungi, and algae— inadequately known and little 

 investigated. 



3. Competition primarily for space and light. 



III. Lichen seres. In high mountains above the limits of grasses and in arctic 



regions lichens often form the climax community. 



IV. Moss seres. In cold, moist regions such as parts of Siberia, Lapland, and 



the Faroe Islands and Spitzbergen, moss communities may form the climax 

 Fhacomitriitm heath {cf. Fig. 17, p. 38). 

 B. Two- or more-layered terminal communities. ^ 



4. Competition for space, light, and food (root competition). 



Fig. 170. — Artemisia steppe (Artemisia barrelieri, Thymus capitatus, etc.), between 

 Alicante and Elche. Chamaephyte sere or climax. (Photo by Uehlinger and Braim- 

 Blanquet.) 



V. Therophyte seres. Common on desert and desert steppe, probably also as 

 chmax.- 



VI. Turf seres. The climax of the alpine heights of many mountainous regions, 

 savanna and natural prairie. 



1 Root layers included. 



2 An association of Arislida acutiflora and Echium humile in the sands of the 

 Sahara near Nefta, southern Tunis, contains 74 per cent therophytes, 14 per cent 

 chamaephytcs, 7 per cent hemicryptophytes and tussocks, and 5 per cent bulb 

 geophytes. 



