13 

 A. fecunda recruitment by usurping space and light from 

 germinating seedlings. Gurevitch (1986) found that inhibition of 

 seedling establishment was an important effect of interspecific 

 competition on the grass, Stipa neomexicana , although she also 

 found that competition limited the growth and flower production 

 of mature plants. 



At Birch Creek, removal of Centaurea maculosa resulted in 

 increased recruitment and population growth for the first two 

 years, but by the third year the difference between treatment and 

 control plots had disappeared. This pattern suggests that A^_ 

 fecunda underwent a two-year period of competitive release 

 following removal of C^. maculosa but was approaching a new, 

 higher eguilibrium after two years. Put simply, removal of 

 Centaurea maculosa increased the carrying capacity of the habitat 

 for Arabis fecunda . 



The results of our study indicate that the main mechanism by 

 which Centaurea maculosa interferes with Arabis fecunda is 

 reduction of space available for seedling establishment. This 

 hypothesis suggests that competitive displacement of A_;_ fecunda 

 will not occur if density of C\_ maculosa stays near current 

 levels. The fact that eguilibrium growth rates were near 1.0 for 

 the study period lends support to this conclusion. If C. 

 maculosa increases in these habitats, the size of A^_ fecunda 



