Dominant environmental factors in wetland plant communities invaded by Phragmites australis in East Harbor, Ohio, USA

Abstract

Elevation, standing crop, disturbance and soil fertility often emerge from studies of freshwater plant communities as the dominant environmental factors determining both species richness and species composition. Few studies in North America have investigated the relationship between these factors and species abundance (standing crop) and species composition in the context of invasion by Phragmites australis. This study explores the influence of key abiotic and biotic variables on species abundance and composition across three Lake Erie wetlands differing in hydrology and Phragmites abundance in East Harbor, Ohio, USA. Standing crop for 92 species was related to standard sediment analyses, wave exposure, distance to shoreline, elevation, light interference, species density, and Phragmites standing crop in each of 95 1 Â 1 m quadrats by using canonical correspondence analysis (CCA). Elevation (Axis I) and Phragmites standing crop-soil fertility (Axis II) explained 35.7 and 26.2%, respectively, of the variation in the speciesenvironment relationships. Wave exposure was not a primary component of the first four canonical axes. Axis I was instrumental in describing species composition, separating wet meadow species from marsh species. Axis II was inversely related to species density for both wet meadow and marsh species. These findings generally support prevailing models describing the distribution of wetland plants along environmental gradients. Two discrepancies were noted, however: (1) species density was highest in the most sheltered sites and (2) wave exposure was directly associated with Phragmites standing crop-soil fertility gradient. The structural integrity of Phragmites stems, topographic heterogeneity and differential responses to anthropogenic disturbance may contribute to departure from prevailing multivariate models. This information has direct implications for local and regional wetland managers.

Promoting Species Establishment in aPhragmites-Dominated Great Lakes Coastal Wetland

“…very little Phragmites prior to treatments, and Phragmites is less successful at establishing under sustained flooding conditions (Armstrong et al 1999;Amsberry et al 2000;Welch et al 2006). However, once established in shallow areas, rhizomes can spread to deeper zones (Cross and Fleming 1989;Amsberry et al 2000), which can explain the presence of Phragmites in deep areas of this study.…”

“…Despite this, promoting native species establishment and richness, through management, is achievable. Welch et al (2006) observed increased diversity with both reduced and increased Phragmites abundance, suggesting that greater species richness can be achieved despite the level of Phragmites dominance, provided that Phragmites does not limit light availability (Haslam 1972;Güsewell and Edwards 1999) or ecologically engineer the site (Minchinton et al 2006). If the goal is to maintain diversity rather than eradicate Phragmites, cutting or cutting and litter removal may be sufficient for a few years following aerial spray and initial CRS treatment.…”

Interspecific Interactions between Phragmites australis and Spartina alterniflora along a Tidal Gradient in the Dongtan Wetland, Eastern China

“…ex Steud. (common reed) and Spartina alterniflora Loisel (smooth cordgrass) are two well-known invasive salt marsh species [13], [14] in different regions. Phragmites australis , a salt marsh species native to the east coast of China, is aggressively invading salt marshes along the Atlantic coast of North America [15], [16].…”

Assessing invasive plant infestation and disturbance gradients in a freshwater wetland using a GIScience approach

“…Chambers et al (1999) detail the spread of Phragmites into tidal wetlands across North America and summarize that disturbance of hydrologic cycles can often promote invasion and reduce biodiversity. Welch et al (2006) found hydrology and topographic factors were driving Phragmites trends in sampled Great Lakes coastal wetlands. In this study, the hydrologic disturbance measure was linked to the magnitude of Phragmites infestation.…”