Calcareous fens provide habitat for a disproportionate number of rare and specialist plant species, yet little is known about the conditions that allow fens to support these species. We compared the importance of geography, land-use legacies, current hydrologic disturbance, and stressors in predicting rare and specialist species occurrence and richness in calcareous fens throughout their Wisconsin range. On each fen, we measured the occurrence and richness rare and specialist species, as well as potential predictors including stress variables (root-zone saturation and nutrient availability), land-use-legacies (history of plowing or abandoned drainage projects), current groundwater extraction (high-capacity-well pumping), and geographic variables (UTM coordinates). We used Partial Least Squares Regression models to assess the predictive power of each of these factors. We found that stressor models best predicted occurrence and richness of most species. Groundwater saturation was the best single predictor of high species occurrence and richness, while historic plowing and drainage, high-capacity-wells, and high nitrogen availability were the best predictors of species absence and low richness. Our results suggest that high saturation and low nutrient availability are likely drivers of rare and specialist species occurrence and richness in calcareous fens, while anthropogenic activities that alter stressors contribute to the continued imperilment of these species.

钙质沼泽为数量不成比例的稀有和特殊植物物种提供栖息地，但人们对沼泽能够支持这些物种的条件知之甚少。我们比较了地理、土地利用遗产、当前水文干扰和压力因素在预测威斯康星州范围内钙质沼泽中稀有和专业物种的出现和丰富度方面的重要性。我们测量了每一块土地上稀有和特殊物种的出现和丰富度，以及潜在的预测因素，包括压力变量（根区饱和度和养分可用性）、土地利用遗产（耕作或废弃排水项目的历史）、当前地下水提取（大容量井抽水）和地理变量（UTM 坐标）。我们使用偏最小二乘回归模型来评估这些因素中的每一个的预测能力。我们发现压力源模型最能预测大多数物种的发生和丰富度。地下水饱和度是物种出现率高和丰富度高的最佳单一预测因子​​，而历史耕作和排水、高容量井和高氮可用性是物种缺失和低丰富度的最佳预测因子。我们的研究结果表明，高饱和度和低营养可用性可能是稀有和特殊物种出现和钙质沼泽丰富的驱动因素，而改变压力源的人为活动则导致这些物种的持续危害。地下水饱和度是物种出现率高和丰富度高的最佳单一预测因子​​，而历史耕作和排水、高容量井和高氮可用性是物种缺失和低丰富度的最佳预测因子。我们的研究结果表明，高饱和度和低营养可用性可能是稀有和特殊物种出现和钙质沼泽丰富的驱动因素，而改变压力源的人为活动则导致这些物种的持续危害。地下水饱和度是物种出现和丰富度高的最佳单一预测因子​​，而历史耕作和排水、高容量井和高氮可用性是物种缺失和低丰富度的最佳预测因子。我们的研究结果表明，高饱和度和低营养可用性可能是稀有和特殊物种出现和钙质沼泽丰富的驱动因素，而改变压力源的人为活动则导致这些物种的持续危害。