All scales | Within marsh | Regional | Continental | |

R^{2} = 0.46 b | R^{2} = 0.27 b | R^{2} = 0.61 b | R^{2} = 0.17 b | |

Ln (geographic distance) | 0.40^{***} | 0.47^{***} | ||

Ln (plant similarity + 0.005) | ||||

Ln (100 – % sediment moisture) | 0.17^{**} | 0.63^{**} | 0.19^{*} | 0.14 |

Ln (ammonium +1) | ||||

Ln (nitrate +1) | 0.10 | 0.17^{*} | ||

Ln (phosphate +1) | 0.11 | |||

pH | ||||

% plant cover | 0.13^{*} | 0.34^{***} | n.s. | |

Salinity | 0.10 | 0.16 | ||

Water temperature | 0.09 | na | 0.45^{***} | |

Air temperature | 0.14^{**} | na | 0.24^{*} | 0.16^{*} |

↵The variation (

*R*^{2}) of ln community distance (distance = 1 – similarity) that is explained by the remaining variables and the partial regression coefficients (*b*) of the final model is reported (all values are significant at*P*≤ 0.0001,*n*= 62). If a partial regression coefficient is reported, its significance level (one-way tests) is < 0.0500. **P*≤ 0.0100, ***P*≤ 0.0010, and ****P*≤ 0.0001. Water and air temperature were measured for each marsh, and therefore are not included in the within-marsh models.