1 



Introduction 



Competition is a difficult phenomenon to study effectively 

 (Harper 1977, Keddy 1989). Much of the literature on competition 

 is rife with circular reasoning and expositions of "the ghost of 

 competition past" (Connell 1980) . Experiments are often 

 phenomenological and non-mechanistic, measuring what happens 

 without examining how it happens (Tilman 1987). Tilman (1987, 

 1988) has urged a more mechanistic approach to the study of 

 interspecific competition. He argues that such studies more 

 often result in testable hypotheses, ultimately leading to more 

 useful predictive generalizations. 



Werner (1979) divided competitive interactions into two 

 mechanistic categories: (1) preemptive i.e., competition for 

 space and (2) interactive i.e., competition for water or 

 nutrients. Similarly, Tilman (1988) divided resources into two 

 broad groups: (1) space and light, and (2) nutrients and water. 

 Many researchers have recognized the importance of regeneration 

 in competitive interactions (Grubb 1977, Harper 1977, Grime 1979, 

 Werner 1979) . Nonetheless, most studies of plant interspecific 

 interference have focused on competition for light, nutrients, 

 and water during later life stages and have ignored the effects 

 of competition for space on seedling establishment (Schoener 

 1983) . 



