Alterniflora In China Research Articles

Invasion of Spartina alterniflora in China is greatly facilitated by increased growth and clonality: a comparative study of native and introduced populations

Different mechanisms have been proposed to explain invasion success of alien species, among which genetic differentiation and phenotypic plasticity are extensively studied. In order to explore whether the invasion of Spartina alterniflora is facilitated by enhanced phenotypes or trait plasticity, we conducted a common garden experiment on this clonal invasive plant, in which three native populations (from the US) and eight introduced populations (from China) were included and grown at two water levels. We measured their plant traits related to growth, reproductive phenology, reproductive output, and their plasticity in response to water availability. No difference in plant height was observed between native and introduced populations of S. alterniflora, but introduced populations had greater total biomass than the native ones at high water level. Reproductive performances facilitating invasion success were also found for introduced populations, indicated by the advanced initiation of phenological events, greater total number of ramets, and more investment of total biomass in rhizomes versus stalk and leaf in both water treatments. Finally, a non-significant difference in inflorescence biomass for flowering individuals and phenotypic plasticity of most measured traits was observed between native and introduced populations. In conclusion, enhanced growth and asexual reproduction make greater contributions to the invasion success of S. alterniflora in China.

Genetic Diversity, Ecotype Hybrid, and Mixture of Invasive Spartina alterniflora Loisel in Coastal China

Spartina alterniflora, a native species at the east coast of North America, is currently the focus of increasing management concern due to its rapid expansion in coastal China. To better understand the plant traits associated with the success of invasion, we examined the genetic variation and the possible existence and distribution of ecotype hybrids and ecotype mixtures of the species in China. We collected and analyzed 144 samples from seven populations throughout coastal China (21.6°–38.6°N; 109.7°–121.8°E) using amplified fragment length polymorphisms markers. The results indicated that the genetic diversity of S. alterniflora in China was low, with a percentage of polymorphic bands (PPB) = 23.24%, heterozygosity (HE) = 0.2979 and the average diversity within populations = 0.4427 at the population level, as well as PPB = 28.07%, HE = 0.3743 and the total diversity of the species = 0.5520 at the species level. The majority of the variation was found within rather than among populations, as estimated by Nei's genetic diversity (20.39%), Shannon's index (19.80%) and analysis of molecular variance (23.56%). Results of assignment show that both ecotype hybrids and ecotype mixtures exist in coastal China, especially in southern populations. Therefore, the species’ success in coastal China may be attributable largely to the coexistence of various ecotype hybrids and ecotype mixtures resulting from three independent introductions of the species’ three ecotypes from their native ranges coupled with increasing human disturbances in the region.

Nitrogen‐Enriched Eutrophication Promotes the Invasion of Spartina alterniflora in Coastal China

AbstractPollution‐driven eutrophication is a significant by‐product of rapid economic growth in China. Such environmental changes have huge consequences on local biodiversity and ecosystem functions through the spread of invasive introduced species. Spartina alterniflora has been spreading quickly and extensively throughout China since the mid 1980s, soon after its intentional introduction from the eastern United States. The range expansion of S. alterniflora coincides with a significant increase in the per unit standing biomass of the species in the Chinese coastal wetlands from the 1980s to 2000s. Here we showed that the long term per m2 biomass of S. alternifolia changes are significantly correlated with human‐induced increases of the inorganic nitrogen level in the Chinese coastal water. We established this causal relationship by showing that reproduction, growth, and biomass of individual S. alterniflora, grown in experimental tanks, increased with higher levels of soil inorganic nitrogen. Competition experiments indicated that S. alterniflora out competed Phragmites australis at both low and high soil nitrogen levels. These field and experimental based results support the hypothesis that nitrogen‐enriched eutrophication contributed significantly to the successful invasion of S. alterniflora in China.

Genotypic diversity enhances invasive ability of Spartina alterniflora

Although genetic diversity is very important for alien species, which have to cope with new environments, little is known about the role that genetic diversity plays in their invasive success. In this study, we set up a manipulation experiment including three levels of genotypic diversity to test whether genotypic diversity can enhance the invasive ability of alien species, in our case the invasive Spartina alterniflora in China, and to infer the underlying mechanisms. There was no significant relationship between genotypic diversity and parameters of performance in the first year; however, from the summer of the second year onwards, genotypic diversity enhanced four of the six parameters of performance. After two growing seasons, there were significant positive relationships between genotypic diversity and maximum spread distance, patch size, shoot number per patch, and aboveground biomass. Moreover, abundance of the native dominant species Scirpus mariqueter was marginally significantly decreased with genotypic diversity of S.alterniflora, suggesting that enhanced invasive ability of S.alterniflora may have depressed the growth of the native species. There was no significant difference in most measures of performance among six genotypes, but we observed a transgressive over performance in four measures in multiple-genotype patches. At the end of the experiment, there were significant nonadditive effects of genotypic diversity according to Monte Carlo permutations, in six-genotype, but not three-genotype plots. Our results indicated that both additive and nonadditive effects played roles in the positive relationship between genetic diversity and invasion success, and nonadditive effects were stronger as duration increased.

The positive and negative effects of exotic Spartina alterniflora in China

Spartina alterniflora is a perennial salt marsh grass native to the Atlantic and Gulf Coasts of North America. Recognized for its effects of diminishing strong tide even storms and accelerating sediment deposition, S. alterniflora was introduced into China in 1979. Now the artificial vegetation of Spartina has expanded to around 50 000 h m 2 along the east coast of China due to its strong capability of propagating by seeds and rhizome fragments. Although it was listed among 16 harmful exotic species in China 3 years ago, we need to evaluate its positive and negative effects in the coastal region of China objectively. This paper reviews some major positive effects of S. alterniflora in China, e.g. being a dominant primary producer, buffering against tides, accelerating accretion and reclamation, absorbing nutrients and digesting pollutants, as well as some major negative effects, e.g. occupying the niche of local species, altering the mudflat habitat, changing and even diminishing biodiversity, and damaging the aquiculture in the tidal land. In addition, its biomaterial uses and biological substitution as a means of ecological regulation is also discussed.

Sediment burial stimulates the growth and propagule production of Spartina alterniflora Loisel.

Spartina alterniflora Loisel., an extensively invasive species on the Chinese coast, is a focus of increasing management concern due to its high expansion rate in estuaries and tidal zone, and the significant damage it causes to native ecosystems. In order to understand the processes and mechanisms of invasion of S. alterniflora in China, the impact of three sediment types (sand, sand–loam mixture and loam) and five buried patterns (unburied, 50% burial of initial plant height, 75% burial of initial plant height, complete burial and repeated burial) on the growth of seedlings or ramets was investigated. Results showed that each of the three factors (sediment types, burial pattern and plant materials) and interactions between/among them, significantly affected height and clonal growth, and biomass accumulation and allocation. Plant height, total biomass and number of new vegetative propagules significantly increased with progressive burial treatments. However, the complete burial treatment resulted in the death of all plant materials, and the maximum values of three parameters were found in the 50% burial or repeated burial treatments. Plant responses were determined by the instantaneous thickness of sediment of each time burial rather than by the total quantity of repeated burial. The growth of S. alterniflora was not shown to be dependent on specific types of sediment in sedimentation environment. In contrast to the unburied control, the proportion of primary tillers produced directly from initial individuals and the ratio between the aboveground and belowground biomass were greater under burial treatments. Seedlings produced more new vegetative propagules than vegetative offspring in all experimental treatments, and the former were apt to produce ramets from rhizomes rather than primary tillers. It is concluded that under various sedimentation environments, the clonal spread efficiency of seedlings was higher than that of vegetative offspring, and there is a positive feedback relationship between sedimentation and the growth of S. alterniflora. Thus, moderate sedimentation may stimulate the invasion of exotic species, S. alterniflora in coastal China.