Fens as whole-ecosystem gauges of groundwater recharge under climate change

Spatial patterns of meadow sensitivities to interannual climate variability in the Sierra Nevada

“…Conversely, meadows with low sensitivity in September may lack significant annual snow cover (i.e., are at low elevations) or may have groundwater inputs that vary on longer than interannual timescales, resulting in end‐of‐season vegetation vigour that is less sensitive to interannual variations in snowpack. Indeed, many of the meadows exhibiting low September sensitivity to snowpack were located at lower elevations and in the northern portion of the study region (Figure ), where precipitation occurs more commonly as rain, rather than snow, and where groundwater is influential over slower (i.e., decadal) varying timescales (Drexler et al, ), suggesting that multiyear lag effects may be more important than same‐year precipitation or snowpack. Variations in sensitivity could also be due to a number of other factors, including human modifications or unmeasured landscape changes at the meadow or watershed scales that occurred over the course of the study.…”

“…Climate influences meadows directly through the timing and amount of precipitation and evapotranspiration (ET), which modifies the position of the water table, and indirectly through changes in vegetation, which can alter meadow hydrology based on differential patterns of water use among species (Darrouzet‐Nardi, D'Antonio, & Dawson, ). Due to the relatively shallow groundwater systems that support many meadows in the Sierra Nevada, decreases in spring snowpack and an earlier snowmelt may limit the availability of late‐season water, resulting in a loss of meadow area and a shift to upland/xeric dominated ecosystems (Drexler, Knifong, Tuil, Flint, & Flint, ). Meadows may also experience declines in surface and shallow groundwater availability over longer time periods as warmer temperatures and longer growing seasons lead to increased ET rates (Goulden & Bales, ).…”

“…At the local scale, geology can influence the relative timing and amount of groundwater and surface water inputs into montane wetlands (Kitlasten & Fogg, ; Onda, Komatsu, Tsujimura, & Fujihara, ). For example, permeable fractured volcanic and/or metamorphic rocks (typical of the Cascades) can transmit and store more water than impermeable crystalline intrusive rocks (typical of the Sierra Nevada), resulting in differential long‐term responses to climate change (Drexler et al, ). Meadow site characteristics such as soil hydraulic properties, local climate, surface water availability from direct snowmelt or streamflow, and hillslope factors that influence lateral groundwater flow further influence meadow hydrology and vegetation characteristics (Loheide et al, ; Lowry, Deems, Loheide, & Lundquist, ).…”

Understanding fen hydrology across multiple scales

“…Even though protecting Skiff Lake would protect MacCready fen, managing the entire master recharge area (critical node) would be more efficient, because its impact would be felt over the entire system. It is important to note that because fens occur at the critical interface between groundwater and surface water, and because of their sensitivity to changes in water level and water chemistry, they can be used as a barometer for the health of the overall system (Drexler et al, 2013). For instance, if regional groundwater recharge rates are lowered in the future, the fens will be among the first to disappear from the landscape.…”

“…Fens also play a critical role in maintaining stream water quality and buffering surface water temperatures as they are generally located near the headwaters of major streams (Bedford and Godwin, 2003). Given their location near headwaters, fens have sometimes been used as 'whole-ecosystem gauges' of groundwater recharge under climate change (Drexler et al, 2013).…”