In The Field: Exploring Big Lagoon Fen
Welcome to In the Field, a new CNPS blog feature in which we’ll be sharing periodic highlights of staff and volunteers working to document California’s rare plants, vegetation, and sensitive natural communities.
Surveying Sensitive Natural Communities with the CNPS North Coast Chapter
By Sara Bandali and Claudia Voigt
In 2022, CNPS’s Vegetation field data specialist Claudia Voigt and Barbara Rice Intern Sara Bandali conducted a vegetation sampling day at Big Lagoon Fen with CNPS North Coast Chapter volunteers Dana York, Gordon Leppig, Kale McNeill, Laurel Goldsmith, Peter Warner, Renee Pasquinelli, Tony LaBanca, and Andrea Pickart. More than 103 plant species have been recorded in this unique North Coast peatland fen, including 11 rare species.
Big Lagoon Fen is a Sensitive Natural Community, which is a way to characterize groupings — or assemblages — of plants that are uncommon, locally or statewide, and may contain special plants or conditions that make them necessary to protect. Approximately 60% of California’s described vegetation is considered sensitive and includes habitat like coast redwood stands, riparian woodlands, and valley oak savannas.
Volunteers enjoyed seeing Alpine marsh violet (Viola palustris, Rank 2B.2), Round-leaved sundew (Drosera rotundifolia), and Buxbaum’s sedge (Carex buxbaumii, Rank 4.2). The most exciting finding of the day was a small population of Bog club-moss (Lycopodiella inundata, Rank 2B.2) which has been barely persisting for decades and is one of only two populations in California. Other rare plants include the marsh pea (Lathyrus palustris, Rank 2B.2), and the green yellow sedge (C. viridula, Rank 2B.3). The bristle-stalked sedge (Carex leptalea, Rank 2B.2), one of California’s rarest sedges, also occurs here.
Fens like this one are known to harbor a high diversity of special-status botanical species which are particularly important to sample because these plant communities are at risk due to new threats, both natural and human-caused. While the introduction of invasive plants like Mountain heath grass (Danthonia decumbens) has posed a threat to the biological diversity of Big Lagoon Fen, the biggest threat to these kinds of peatland fens is encroachment by woody vegetation. Fire exclusion, changes in grazing patterns, and reductions in fire return intervals can make way for woody vegetation encroachment, resulting in the loss of wetland habitat. This kind of encroachment and the associated transition towards drier soils is occurring in many wetland habitats, resulting in a marked decline in herbaceous species richness and cover. Many rare herbaceous wetland species are dependent on early successional conditions, and as such, are increasingly at risk of extirpation (being wiped out).
Survey data from of this sensitive fen habitat will provide state and local land managers with floristic and environmental information on this complex wetland, and the delicate balance that disturbance plays in supporting and affecting herbaceous plant richness (including special status species) towards maintaining a healthy ecosystem. Plus, we’re documenting a new vegetation plant assemblage that hasn’t yet been documented in our Manual of California Vegetation!