Abstract
Increased resource availability can promote invasion by exotic plants, raising concerns over the potential effects of global increases in the deposition of nitrogen (N). It is poorly understood why increased N favors exotics over natives. Fast growth may be a general trait of good invaders and these species may have exceptional abilities to increase growth rates in response to N deposition. Additionally, invaders commonly displace locals, and thus may have inherently greater competitive abilities. The mean growth response of Centaurea stoebe to two N levels was significantly greater than that of North American (NA) species. Growth responses to N did not vary among C. stoebe populations or NA species. Without supplemental N, NA species were better competitors than C. stoebe, and C. stoebe populations varied in competitive effects. The competitive effects of C. stoebe populations increased with N whereas the competitive effects of NA species decreased, eliminating the overall competitive advantage demonstrated by NA species in soil without N added. These results suggest that simulated N deposition may enhance C. stoebe invasion through increasing its growth and relative competitive advantage, and also indicate the possibility of local adaptation in competitive effects across the introduced range of an invader.
Highlights
Soil nitrogen (N) is the most limiting factor for plant growth in most terrestrial ecosystems [1,2] and human activity is increasing rates of N deposition [3]
Nitrogen addition enhanced the mean growth of North American (NA) species, from 56% under the low N deposition to 122% under the high N deposition (F = 25.51, df = 1,63, P = 0.013); there were no differences in this response among NA species (F = 4.19, df = 3,61, P = 0.135) (Fig. 2)
The mean relative interaction intensity (RII) for five C. stoebe populations on NA species differed among species (F = 29.85, df = 3,316, P,0.001) and among N levels (F = 13.01, df = 2,317, P = 0.001) (Fig. 3)
Summary
Soil nitrogen (N) is the most limiting factor for plant growth in most terrestrial ecosystems [1,2] and human activity is increasing rates of N deposition [3]. Why should exotic invaders benefit more from higher N supply than natives? Good invaders tend to be fast growing species and fast growing species tend to be N-efficient, achieving relatively high carbon gain per unit of N [11]. A key physiological mechanism in converting N into plant growth, has been reported to be higher in comparisons of groups of invasive species to native species [12]. Exotic invaders are often good competitors, as indicated by very high relative abundances and community-scale decreases in native diversity and abundance [16,17,18,19,20,21,22]. In addition to disproportional effects on growth, increased N may alter competition among native and exotic plant species. N-efficient species usually outcompete high N-requiring species [23,24]; invaders, which appear to be strong competitors in general, tend to be high N-requiring species, often with higher leaf
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
