The Vegetation: 

 Pattern and Succession 



p. J. Webber, P. C. Miller, 



F. S. Chapin III, and B. H. McCown 



INTRODUCTION 



This chapter analyzes paths by which the environment acts upon 

 tundra plants and interdependence between environmental factors and 

 plant growth form characteristics (Figure 6-1). The analysis emphasizes 

 the distinguishing characteristics and the environmental distributions of 

 some of the principal growth forms recognized for tundra regions by 

 Webber (1978) (Figure 6-2). 



Although selection acts on whole individuals, growth form charac- 

 teristics follow environmental gradients (Mooney et al. 1974) somewhat 

 independently of each other. The objectives of this chapter are to iden- 

 tify the patterns of vegetation and plant growth forms in the coastal tun- 

 dra at Barrow, the principal factors controlling these patterns, and the 

 paths of influence between the major environmental controls and the 

 plant growth forms which lead to the patterns of vegetation observed in 

 the field. The major pathways of plant succession and the effect of 

 natural and other perturbations are also examined. 



To approach these objectives, the distribution of species, growth 

 forms, and plant characteristics was determined along environmental 

 gradients in the field, and the distribution of plant characteristics along 

 environmental gradients was predicted from the physical and physiologi- 

 cal information given in preceding chapters. The field distribution can be 

 regarded as the realized niche, the predicted distribution as an indication 

 of the fundamental niche (Hutchinson 1959). 



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