Phenotypic plasticity of Spartina alterniflora and Phragmites australis in response to nitrogen addition and intraspecific competition

Abstract

Phenotypic plasticity of the two salt marsh grasses Spartina alterniflora and Phragmites australis in salt marshes is crucial to their invasive ability, but the importance of phenotypic plasticity, nitrogen levels, and intraspecific competition to the success of the two species is unclear at present. Spartina alterniflora Loisel. is an extensively invasive species that has increased dramatically in distribution and abundance on the Chinese and European coasts, and has had considerable ecological impacts in the regions where it has established. Meanwhile, Phragmites australis Cav., a native salt marsh species on the east coast of China, has replaced the native S. alterniflora in many marshes along the Atlantic Coast of the US. This study determined the effects of nitrogen availability and culm density on the morphology, growth, and biomass allocation traits of Spartina alterniflora and Phragmites australis. A large number of morphological, growth, and biomass parameters were measured, and various derived values (culm: root ratio, specific leaf area, etc.) were calculated, along with an index of phenotypic plasticity. Nitrogen addition significantly affected growth performance and biomass allocation traits of Spartina alterniflora, and culm density significantly affected morphological characteristics in a negative way, especially for Spartina alterniflora. However, there were no significant interactions between nitrogen levels and culm density on the morphological parameters, growth performances parameters, and biomass allocation parameters of the two species. Spartina alterniflora appears to respond more strongly to nitrogen than to culm density and this pattern of phenotypic plasticity appears to offer an expedition for successful invasion and displacement of Phramites australias in China. The implication of this study is that, in response to the environmental changes that are increasing nitrogen levels, the range of Spartina alterniflora is expected to continue to expand on the east coast of China.

Cordgrass Biomass in Salt Marshes

“…Some studies have concluded that the observed variability in growth forms among Spartina populations may be the result of genetic differentiation (Gallagher et al, 1988;Sanchez et al, 1997;Proffitt et al, 2003), identifying ecotypes with different canopy heights and biomass accumulation (Lessmann et al, 1997;Daehler, 1999;Otero et al, 2000;Seliskar et al, 2002;Proffitt et al, 2005). In contrast, other studies have attributed different growth forms to phenotypic plasticity in response to differences in environmental factors (Anderson & Treshow, 1980), such as the availability of nutrients (Dai & Wiegert, 1997;Wigand et al, 2003;Zhao et al, 2010), salinity (Phelger et al, 1971;Trnka & Zedler, 2000) or sediment anoxia (Castillo et al, 2005a). The consequence of this is that the different growth forms are ecophenes.…”

Phenotypic plasticity of Chenopodium murale across contrasting habitat conditions in peri-urban areas in Indian dry tropics: Is it indicative of its invasiveness?

“…This strategy of plant biomass allocation is suggested to vary constantly with environmental changes (Berendse and Möller 2009;Bloom et al 1985;Hermans et al 2006;Zhao et al 2010). As there is an intimate relationship between the phenotypic changes and resource acquisition, such changes facilitate stress tolerance and invasiveness of a species (Tyler et al 2007), particularly in open areas in and around the urbanizing landscapes that witness variety of land-use changes and disturbance regimes.…”

Plant invasions in China: an emerging hot topic in invasion science

“…Correspondingly, the top 13 plant invaders in China (based on the number of published papers) are clonally growing perennials (Huang et al 2009). Greenhouse experiments in Alternanthera philoxeroides and Spartina alterniflora supported the idea that clonal integration and phenotypic plasticity of clonal plants have enhanced their invasion success (e.g., Geng et al 2006, Yu et al 2009, Zhao et al 2010. By using genetic techniques, Dong et al (2006) found that sexual reproduction facilitated the initial establishment of Solidago canadensis populations, while clonal growth led to a subsequent expansion of established populations.…”