Hydrogeochemical and Vegetation Characterization of Sphagnum-dominated Peatlands in the Puget Lowlands of Washington State, USA.

Sphagnum-dominated peatlands in the Puget lowlands of western Washington provide important biodiversity, ecological functions, and cultural resources. Historical and ongoing land uses have resulted in regional loss and degradation of these ecosystems. Effective conservation and management of peatland biodiversity and other ecological values requires an understanding of a peatland's landscape setting, hydrological processes, water chemistry, biotic patterns, and response to human stressors. This research identified the climate, watershed size, hydrologic regime, and land use characteristics influencing these peatlands. Shallow groundwater, vertical and lateral water movement, pore water chemistry, and vegetation composition were measured in two locations within each of the 17 study sites: the peatland center and lagg. Study sites had some ecological characteristics similar to ombrotrophic bogs in the Northern Hemisphere, but many sites lacked strong hydrological evidence of being solely rain-fed. Climate, watershed size, and adjacent land use were correlated with hydrological, chemical, and vegetation variability across study sites. Land use correlations with ecological changes were most prominent in laggs but some effects were observed in peatland centers. Preventing anthropogenically derived surface or groundwater inputs from entering the peatland basin is essential for protecting peatland biodiversity and ecological functions. This can be accomplished by establishing natural vegetated buffers around contributing water features, removing stormwater inputs, and maintaining peatland watersheds with as much natural land cover as possible.

Supplementary information: The online version contains supplementary material available at 10.1007/s13157-025-01927-7.