P. Lesica et Js. Shelly, COMPETITIVE EFFECTS OF CENTAUREA-MACULOSA ON THE POPULATION-DYNAMICS OF ARABIS-FECUNDA, Bulletin of the Torrey Botanical Club, 123(2), 1996, pp. 111-121
We used a perturbation experiment coupled with demographic analysis to
study competition between two short-lived taprooted perennial plants,
the rare native Arabis fecunda and an aggressive exotic, Centaurea ma
culosa. Centaurea maculosa was removed from randomly selected plots at
two sites where these species occur together and the fate of mapped A
. fecunda individuals was followed in treatment and control plots for
two years at one site and four years at the other. We analyzed differe
nces between treatment and control in recruitment, survival, individua
l growth and fecundity separately. Estimates of equilibrium population
growth (lambda) were obtained from matrix projection models to evalua
te the overall competitive effects of C. maculosa on A. fecunda. Over
the course of the study lambda was significantly higher in treatment p
lots compared to controls, indicating that C. maculosa had a negative
effect on A. fecunda populations. Recruitment was significantly higher
in treatment plots during the first two years of the study. Survival,
growth and fecundity did not differ between treatment and control. Th
ese results indicate that the main effect of removing C. maculosa on p
opulations of A. Secunda was enhanced recruitment resulting from incre
ased seedling establishment. Competitive effects of C. maculosa on A.
fecunda varied between sites and among years, indicating that long-ter
m studies are required to fully understand the effects of competition
on population dynamics.