The Rich Sloping Fens at Baltimore Woods

Figure 1. Baltimore Woods Fens: #2 at right, #3 at center, and #4 at left. General surface water flow is from upper left (northwest) to lower right (southeast). Photographed Jan. 6, 2019 from 113 meters above the south end of fen #2. Download original.

Baltimore Woods Nature Center has a number of small wetlands that have been categorized as rich sloping fens, one of many classifications given to ecological communities by the New York Natural Heritage Program (NYNHP).

Figure 2. Baltimore Woods Fen #4, looking downstream (toward the southeast). Parts of fens #3 and #2 can be seen at the top of the image. Photographed from above the south end of the wet meadow from an altitude of 56 meters above the center of fen #4 on Dec. 27, 2018. Download original.

Rich sloping fens are ranked as critically imperiled (S1) or imperiled (S2) within the state. NYNHP states that here are fewer than 100 documented occurrences of these communities in New York, and while some are in good condition and well-protected, many are small and suffer various levels of disturbance. Threats to these fens include changes to the hydrology, encroaching development, invasive plants, and herbivores. For the Baltimore Woods fens, now that they have been identified, invasive plants, and herbivores are likely to be the main threats to these fens.

Figure 3. Baltimore Woods Fen #1. General surface water flow is from the left (west) to the lower right (southeast). Photographed Dec. 30, 2018 from 82 meters above the south side of the stream. Download original.

Rich sloping fens are fed by groundwater seepage or small springs as can be seen uphill from the primary stream in these aerial images of the Baltimore Woods fens. Rich fens in general, are named as such for being rich in minerals, as they are fed by ground water that has dissolved minerals from the substrate that it has flowed through. The mineral-rich water reduces the acidity inherent in the decomposing plant material (peat) that has accumulated in the fen. This results in a higher-pH growing medium for plants and often produces a fen that is relatively rich in species diversity as well as mineral content. In the case of rich sloping fens, the substrate consists primarily of calcareous glacial deposits.

Figure 4. Fen #1 from about 6 meters up. Upload original.

Upstream from fen #4 is a wet meadow, shown in figure 5.

Figure 5. The wet meadow upstream from Fen #4. General surface water flow is from the upper right (north) to the lower left (south). Download original.