In 2008 a calcareous mound fen not listed in the state Natural Heritage Inventory was discovered in south-central Wisconsin. Air photo interpretations and interviews with land users indicated two distinct major historical alterations to this fen: (1) drainage tiling without widespread soil disturbance and (2) plowing with or without direct drainage. Nonmetric multidimensional scaling ordination of survey plots revealed that an assemblage of calciphiles, fen indicators, and wetland generalists persisted in the mound's center, while invasive herbaceous and woody vegetation reached highest cover along the disturbed flanks. Cluster analyses revealed three distinct communities: (1) a fen meadow in the center of the fen, (2) invading shrub-carr in tiled areas, and (3) a weedy/invasive herbaceous community where soil disturbance was widespread. This study lends support to past assertions that drainage can lead to shrub-carr invasion and suggests that widespread soil disturbance can lead to domination by herbaceous invasive plants on fen flanks.