Investigating relationships between land-use legacies and current vegetation in Southern WI fens

Background/Question/Methods

Little is known about the relationships among past land-use, edaphic conditions, and current vegetation in calcareous fens. Here we present results of a study describing associations among these factors in southern Wisconsin fens. The ultimate goal is to use this information to provide practical management strategies for fen restoration. Species cover and composition for herbaceous species were recorded from 20 plots within 11 fens (220 plots total). We measured depth to water table, vertical hydrological gradient, and soil volumetric water content. Root-zone N and P availability were also determined for each plot. Site histories were reconstructed using air photos, management records, and oral histories. The land-use variable most focused on was whether a plot was ever plowed. Associations among predictor variables and current vegetation cover were determined using bi-plot overlays on Non-Metric Multidimensional Scaling ordination. Root-zone moisture and nutrient availability explained most of the variation in community composition among and within fens.

Results/Conclusions

Plowed plots were generally drier and more nutrient rich than never-plowed plots, and had higher relative cover of weedy-mesic and invasive species. The fact that a history of plowing predicts dry and nutrient-rich plots as well as increased invasive-species composition suggests the possibility that biotic or abiotic legacies of plowing continue to influence species composition. However, whether these associations are causal cannot be addressed by this study. This study also suggests that saturated, nutrient-poor root zones predict desirable assemblages of wetland generalists and fen specialists. These results suggest that maintaining strong ground-water influence and low nutrients are essential goals in managing and restoring fens.