Competitive interactions between native and invasive exotic plant species are altered under elevated carbon dioxide

Abstract

We hypothesized that the greater competitive ability of invasive exotic plants relative to native plants would increase under elevated CO(2) because they typically have traits that confer the ability for fast growth when resources are not limiting and thus are likely to be more responsive to elevated CO(2). A series of competition experiments under ambient and elevated CO(2) glasshouse conditions were conducted to determine an index of relative competition intensity for 14 native-invasive exotic species-pairs. Traits including specific leaf area, leaf mass ratio, leaf area ratio, relative growth rate, net assimilation rate and root weight ratio were measured. Competitive rankings within species-pairs were not affected by CO(2) concentration: invasive exotic species were more competitive in 9 of the 14 species-pairs and native species were more competitive in the remaining 5 species-pairs, regardless of CO(2) concentration. However, there was a significant interaction between plant type and CO(2) treatment due to reduced competitive response of native species under elevated compared with ambient CO(2) conditions. Native species had significantly lower specific leaf area and leaf area ratio under elevated compared with ambient CO(2). We also compared traits of more-competitive with less-competitive species, regardless of plant type, under both CO(2) treatments. More-competitive species had smaller leaf weight ratio and leaf area ratio, and larger relative growth rate and net assimilation rate under both ambient and elevated CO(2) conditions. These results suggest that growth and allocation traits can be useful predictors of the outcome of competitive interactions under both ambient and elevated CO(2) conditions. Under predicted future atmospheric CO(2) conditions, competitive rankings among species may not change substantially, but the relative success of invasive exotic species may be increased. Thus, under future atmospheric CO(2) conditions, the ecological and economic impact of some invasive exotic plants may be even greater than under current conditions.

Competitive interactions between established grasses and woody plant seedlings under elevated CO2 levels are mediated by soil water availability

“…We suggest that any increase in the 'escapability' of woody plant seedlings due to elevated CO 2 levels will depend on resource availability, with soil water being of particular importance. Interestingly, we found no significant differences in CO 2 responsiveness between native and invasive exotic woody species, or between N 2 -fixing and non-N 2 -fixing plants (see Weltzin et al 2003;De Graaff et al 2006;Manea and Leishman 2011).…”

Nonindigenous Plant Advantage in Native and Exotic Australian Grasses under Experimental Drought, Warming, and Atmospheric CO2 Enrichment

“…For example, many invasive NIPS have broad geographic ranges or environmental niches [1,7], display high levels of phenotypic plasticity [8,9,10], and have short generation times or morphological features that facilitate dispersal [1,11]. Many also exhibit ecologically important traits that increase fitness relative to native species [12,13], and often, but not always, respond more strongly to atmospheric CO 2 enrichment [14,15,16]. NIPS also frequently undergo rapid adaptive evolution for fitness-enhancing traits [17,18], even following population bottlenecks [19], and clinal variation in climate-related traits has been widely observed among invasive plant species (e.g., [20,21,22,23,24]).…”

Responses of two endemic species of Hippophae at the Qinghai-Tibet Plateau to elevated CO₂ concentration

“…But the growth responses between the two species were different, with HG accumulating more biomass (DM) under EC than HRY, in accordance with its higher photosynthesis and water-use efficiency. The interspecific variation in growth response to EC is likely to have important consequences on competitive relationships between species (Baxter et al 1994, Dixon et al 1995, Curtis et al 1996, Ward and Strain 1997, Dawes et al 2011, Ziska et al 2003, Song et al 2009, Manea and Leishman 2011. Plants with fast growth are considered to be favored under high [CO2] (Smith et al 2000, Manea andLeishman 2011).…”

“…However, the effects of EC on these physiological traits vary greatly with species and such differences may have important consequences on future competitive relationships between species (Curtis et al 1996, Smith et al 2000, Körner et al 2005, Dawes et al 2011, Bezemer and Jones 2012, Chaturvedi et al 2013. If a plant grows fast and possesses traits that contribute to fast growth, it is expected to be favored by the increasing [CO2] (Smith et al 2000, Manea andLeishman 2011).…”