Increased invasive potential of non‐native Phragmites australis: elevated CO₂ and temperature alleviate salinity effects on photosynthesis and growth

Abstract

The prospective rise in atmospheric CO2 and temperature may change the distribution and invasive potential of a species; and intraspecific invasive lineages may respond differently to climate change. In this study, we simulated a future climate scenario with simultaneously elevated atmospheric CO2 and temperature, and investigated its interaction with soil salinity, to assess the effects of global change on the ecophysiology of two competing haplotypes of the wetland grass Phragmites australis, that are invasive in the coastal marshes of North America. The two haplotypes with the phenotypes ‘EU-type’ (Eurasian haplotype) and ‘Delta-type’ (Mediterranean haplotype), were grown at 0‰ and 20‰ soil salinity, and at ambient or elevated climatic conditions (700 ppm CO2, +5 °C) in a phytotron system. The aboveground growth of both phenotypes was highest at the elevated climatic conditions. Growth at 20‰ salinity resulted in declined aboveground growth, lower transpiration rates (E), stomata conductance (gs), specific leaf area, photosynthetic pigment concentrations, and a reduced photosynthetic performance. The negative effects of salinity were, however, significantly less severe at elevated CO2 and temperature than at the ambient climatic conditions. The Delta-type P. australis had higher shoot elongation rates than the EU-type P. australis, particularly at high salinity. The Delta-type also had higher maximum light-saturated rates of photosynthesis (Asat), maximum carboxylation rates of Rubisco (Vcmax), maximum electron transport rates (Jmax), triose phosphate utilization rates (Tp), stomata conductance (gs), as well as higher Rubisco carboxylation-limited, RuBP regeneration-limited and Tp-regeneration limited CO2 assimilation rates than the EU-type under all growth conditions. Our results suggest that the EU-type will not become dominant over the Delta-type, since the Delta-type has superior ecophysiological traits. However, the projected rise in atmospheric CO2 and temperature will alleviate the effects of salinity on both phenotypes and facilitate their expansion into more saline areas.

Belowground advantages in construction cost facilitate a cryptic plant invasion

“…In contrast to our expectations, and unlike most performance metrics measured in introduced Phragmites under global change conditions (Holdredge et al 2010; Mozdzer and Megonigal 2012; Eller et al 2014), our plant-scale data suggest that advantages due to CC will diminish with rising atmospheric CO 2 and nutrient proliferation. If efficient tissue construction and short payback time are particularly strong components of introduced Phragmites invasiveness, as global change intensifies, the competitive dynamics of these lineages may shift such that introduced Phragmites is less able to dominate ecosystems.…”

Complementary responses of morphology and physiology enhance the stand‐scale production of a model invasive species under elevated CO2 and nitrogen

“…We found contrasting results between morphological traits and leaf‐level physiological traits in response to interacting global change factors. As expected, P. australis displayed strong trait responses to both eCO 2 and N in our field experiment, some of which have been observed previously in containerized settings (Caplan et al., ; Eller et al., ; Mozdzer et al., 2012). However, because this study was based on mature clones grown in a field setting, it provides a more realistic assessment of the magnitude of morphological and physiological responses to these interacting global change factors.…”

“…As a C 3 facultative halophyte, it invades freshwater, brackish and saline wetlands, but its distribution is thought to be limited by high salinity (Chambers, Osgood, Bart, & Montalto, ; Mozdzer, Brisson, & Hazelton, ). Because it has responded strongly to eCO 2 and N in containerized experimental conditions (Caplan et al., ; Eller, Lambertini, Nguyen, & Brix, ; Mozdzer & Megonigal ) and is among the most well‐studied organisms globally (Meyerson et al., ), it is an appropriate species for investigating C 3 plant responses to the interactive effects of eCO 2 and N on plant functional traits.…”

Threats to Marsh Resources and Mitigation

“…More recently, a European M haplotype of P. australis has increased in abundance and expanded its coverage into higher salinity areas of salt marshes (Bertness et al, 2002;Saltonstall, 2002;Michinton and Bertness, 2003;Vasquez et al, 2005). Increases in atmospheric carbon dioxide (CO 2 ) and temperature because of climate change may reduce the sensitivity of P. australis to higher salinities, allowing it to expand further into salt marshes (Eller et al, 2014). Increases in atmospheric carbon dioxide (CO 2 ) and temperature because of climate change may reduce the sensitivity of P. australis to higher salinities, allowing it to expand further into salt marshes (Eller et al, 2014).…”