Indicators of regional high capacity well impacts predicts fen floristic quality and composition in Wisconsin calcareous fens

High-capacity wells (HCWs) are known to reduce groundwater discharge to fens and impact their floristic quality, but whether HCW impacts have become predictive of fen floristic quality across large areas has not been studied. Here we used Thiem-equation-estimated drawdown as an indicator of regional HCW impacts to predict floristic quality, floral richness, and community composition in fens throughout their Wisconsin (USA) range. This indicator of HCW influence (HCWinfluence) was associated with a strong decline in floristic quality measures and native-species richness, while non-native-species richness increased sharply. Fuzzy Set Ordination of community data suggested estimated drawdown was associated with the loss of high coefficient-of-conservatism graminoids and forbs, specialist species, and state-listed rare species. The abundance of non-native species and weedy natives increased with increasing HCW impact. The fact that our indicator of HCW influence has become predictive of fen quality and community composition statewide suggests that HCWs are a driver of floristic quality across large areas, and that possible declines in fen quality due to cumulative impacts should be addressed before siting wells.

Automated summary

High-capacity wells have a significant impact on the floristic quality of fens, leading to a decline in native species and an increase in non-native species. This study found that the impact of high-capacity wells can predict the floristic quality of fens across a large area, highlighting the importance of addressing potential declines in fen quality due to cumulative impacts before siting wells.