Foliar Nutrients Reflect Variation in Floristic Quality and Hydrology of Calcareous Fens

Calcareous fens are a rare type of groundwater dependent wetland with plant communities adapted to environmental stressors that include low nutrient availability, low oxygen availability, and various chemical toxicities. The conservation status/integrity of these plant communities is often quantified through floristic quality metrics that depend on intensive floristic inventories. Here we examine relationships between floristic quality, foliar chemistry, hydrology, and soil chemistry descriptors of six calcareous fens in southern Wisconsin in various states of degradation. Through examination of site descriptor correlations, Partial Least Squares Regression (PLSR), variation partitioning, and predictor variable stability analysis, we found foliar nutrient levels (e.g., foliar nitrogen and phosphorus) to be the strongest and most consistent predictors of floristic quality in these fens. Relationships between foliar nutrient levels, hydrology, and soil chemistry suggest water saturation is strongly linked to foliar nitrogen, phosphorus, and manganese. Since foliar nutrients are readily measurable both remotely and in-situ, our finding that foliar nutrients are strong predictors of floristic quality could have implications regarding monitoring the ecological integrity of these imperiled ecosystems.