Biotic constraints on the invasion of diffuse knapweed (Centaurea diffusa) in North American grasslands |
| |
Authors: | T R Seastedt K N Suding |
| |
Institution: | (1) Institute of Arctic and Alpine Research, Department of Ecology and Evolutionary Biology, University of Colorado, Boulder, CO 80309-0450, USA;(2) Present address: Ecology and Evolutionary Biology, University of California, Irvine, CA 92697-2525, USA |
| |
Abstract: | Knapweeds (Centaurea spp.) are among the most invasive of non-indigenous plant species that have colonized western North America over the last
century. We conducted a 4-year experiment in a reconstructed grassland to test hypotheses related to the ability of grasslands
to resist the invasion of diffuse knapweed (C. diffusa). We experimentally invaded C. diffusa and three native species into areas where we manipulated soil nitrogen (N) and phosphorus (P) availability and removed extant
grasses to reduce competition. We evaluated the growth response of these species to these resources and competitive manipulations.
Of the native species that were experimentally added, only one species, Ratibida pinnata (prairie coneflower), established in any numbers. Establishment values in intact vegetation were low for both species, but
establishment by C. diffusa (0.02%) clearly outperformed that of R. pinnata (0.001%). Under reduced grass competition, establishment was enhanced, but the values for C. diffusa (0.68%) were not statistically different from those of R. pinnata (0.57%). Neither species performed better under higher soil nutrients in the presence of competing grasses. In plots with
both species, biomass of the two planted species was positively correlated, but the biomass of both species was negatively
correlated with non-added weedy species. Subsequent harvests of C. diffusa indicated that establishment was enhanced in treatments with higher soil nutrients but that the biomass of these plants could
only be enhanced when plant competition was also reduced. These results indicate that C. diffusa can establish in intact grasslands at rates higher than natives, but opportunism rather than competitive ability best describes
the invasiveness of C. diffusa. Thus, the mechanisms contributing to the establishment of this knapweed species are different from factors identified as
contributing to the dominance of this invader. |
| |
Keywords: | Competition Fertilization Nutrient limitation Seedling establishment Ratibida |
本文献已被 PubMed SpringerLink 等数据库收录! |
|