Relationships between vegetation type, peat hydraulic conductivity, and water table dynamics in mountain fens

Abstract

The ecohydrologic function of fens is characterized by feedbacks between biological and hydrologic processes. Vegetation composition is one important factor that is both responsive to the site hydrologic regime and, by providing the organic material that determines peat hydrophysical properties, influences hydrologic conditions. In this study, we investigated the relationship between vegetation type and peat soil hydraulic conductivity in fen wetlands within the Rocky Mountain National Park, Colorado. We used ponded infiltration tests to estimate the saturated hydraulic conductivity of near-surface peat in mountain fens with differing vegetation, including large-sedge fens dominated by Carex aquatilis and Carex utriculata, small-sedge fens dominated by Eleocharis quinqueflora, and fens with an abundance of woody plants and mosses. Estimated hydraulic conductivities were lowest at the fens dominated by E. quinqueflora, with a median value of 1·3 × 10 À3 cm s À1 compared with 1·3 × 10 À2 and 9·6 × 10 À3 cm s À1, respectively, at the large-sedge and woody fens. These data help explain historical water table observations at each fen. The E. quinqueflora-dominated fens in our study area maintain a high water table with saturated conditions throughout the summer growing season. Other fens with higher-conductivity peat show a more dynamic water table that is below ground surface by late summer.

Numerical Assessment of Morphological and Hydraulic Properties of Moss, Lichen and Peat from a Permafrost Peatland

“…Mean hydraulic conductivity decreases when the computed region size becomes smaller, for each direction and each sample (Supplementary section B2). In-situ measurements, conducted by infiltration (Table 2), give an average of 10 -5 m.s -1 , which is in the same order of magnitude as previously published field measurements (Crockett et al, 2016) and computed values (McCarter & Price, 2012). Analogous values for vertical hydraulic conductivity have been found in the literature at kzz ≈10 -2 m.s -1 (Päivänen, 1973;Crockett et al, 2016;Golubev et al, 2021).…”

“…In-situ measurements, conducted by infiltration (Table 2), give an average of 10 -5 m.s -1 , which is in the same order of magnitude as previously published field measurements (Crockett et al, 2016) and computed values (McCarter & Price, 2012). Analogous values for vertical hydraulic conductivity have been found in the literature at kzz ≈10 -2 m.s -1 (Päivänen, 1973;Crockett et al, 2016;Golubev et al, 2021). However, other studies showed results of a different order of magnitude for Sphagnum samples, with values under 10 -4 m.s -1 (Hamamoto et al, 2015).…”

“…Hence, quantitative assessments of some key hydrological properties of ground vegetation layers are needed, such as total, open and enclosed porosity, hydraulic conductivity and specific surface area. In terms of hydraulic properties, hydraulic conductivity has been assessed in the laboratory using constant or falling-head permeameters (Quinton et al, 2000;Price et al, 2008;Hamamoto et al, 2015;Weber et al, 2017) or via field measurements (Päivänen, 1973;Crockett et al, 2016;this study). The results are presented in Table 2, with some peat results for comparison.…”

Hydrological Function of a Mountain Fen at Low Elevation Under Dry Conditions

“…Fens are a common wetland type in mountain regions (Bao, Wang, Pratte, Mackenzie, & Klamt, ; Chagué‐Goff, Mark, & Dickinson, ; Cooper, Chimner, & Merritt, ), occurring in topographies where groundwater flow is slowed or where there is convergence of surface and subsurface flow paths that maintain saturated soils throughout the growing season (Morrison, Westbrook, & Bedard‐Haughn, ; Winter, ; Wolf & Cooper, ). Hydrological behaviour is thus a critical control on mountain fen ecological and biogeochemical function, including water and carbon storage (Crockett, Ronayne, & Cooper, ; Harbert & Cooper, ; Millar, Cooper, Dwire, Hubbard, & von Fischer, ). Mountain fens are expected to be highly sensitive to changing climate as what are thought to be their primary water supplies (precipitation, snowpack) are directly influenced by climate (Lee et al, ).…”

“…Some fens have water tables that remain near the surface throughout the summer while others experience strong water table declines. Dynamic water tables occur in part because the current and historic fen vegetation composition, which varies widely, influences peat hydraulic parameters (Crockett et al, 2016). Although, a number of intra-fen feedbacks, such as declining hydraulic conductivity with depth (Kvaerner & Kløve, 2008), act to ensure fens do not experience runaway drying during droughts (Waddington et al, 2015).…”