Soil carbon dynamics in montane meadows of the Sierra Nevada and southern Cascade mountain ranges

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Authors

Reed, Cody C.

Issue Date

2020

Type

Dissertation

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carbon loss , carbon sequestration , montane , peatland , subalpine , wetland

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Soils are important drivers of the terrestrial carbon cycle and may present greater opportunities for C sequestration than aboveground ecosystem components. Anthropogenic disturbance and restoration can impact the direction and magnitude of net ecosystem C fluxes, potentially mitigating or amplifying rates of climate change. Changes in ecosystems with large soil C stocks, including montane meadows, may have outsized impacts on terrestrial C cycles. My dissertation quantifies rates and patterns of soil C flux in pristine, degraded, and restored montane meadows throughout the Sierra Nevada and southern Cascade mountain ranges. My results suggest that montane meadows can be large net C sinks (577.6 ± 250.5 g C m-2 y-1), sequestering as much C as evergreen tropical forests per unit land area, or sources of C to the atmosphere (-391.6 ± 154.2 g Cm-2 y-1). The direction and magnitude of the net C flux in meadows appears to be driven by belowground C inputs rather than outputs and associated with levels of disturbance. Modeled rates of net ecosystem C flux based on high resolution field measurements and remote sensing data revealed that, region-wide, meadows were a net source of 408 Gg C between August 2015 and July 2016. However, restoration of meadow floodplain hydrology appears to stem the loss of C from degraded meadows and increase rates of soil C sequestration. Across a 22-y meadow restoration chronosequence, soil C stocks increased at a rate of 256 g C m-2 y-1 and soil C concentration increased by 0.3% per year. My dissertation provides estimates of previously unquantified ecosystem-level C fluxes in montane meadows and underscores that, in their current condition, many meadows throughout the region may be large net sources of C to the atmosphere. However, I also demonstrate the potential of relatively undisturbed or restored montane meadows to sequester and store large amounts of C. My results suggest that effective C management in meadows will involve identifying and conserving meadows that are net C sinks along with efforts designed to restore floodplain hydrology in degraded meadows.

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