Investigation of carbon cycling in Sierra Nevada meadow ecosystems

Authors: Andrew Oliphant*, San Francisco State University, Department of Geography & Environment, Darren Blackburn, San Francisco State University, Department of Geography & Environment, Suzanne Maher, San Francisco State University, Department of Geography & Environment, Shamim Mousavi, San Francisco State University, Department of Geography & Environment
Topics: Climatology and Meteorology, Biogeography, Mountain Environments
Keywords: Mountain meadow, carbon cycle, ecosystem CO2 exchange, micrometeorology
Session Type: Paper
Day: 4/13/2018
Start / End Time: 3:20 PM / 5:00 PM
Room: Astor Ballroom I, Astor, 2nd Floor
Presentation File: No File Uploaded

Montane and alpine meadows are common features of the Sierra Nevada (SN) landscape and play critical roles in regulating seasonal flows, reducing sediment transport and producing vibrant, biodiverse ecosystems in a Mediterranean climate. Dominant plant communities include sedges, grasses and herbs, which vary spatially by soil moisture. These communities show strong annual growth and tend to produce organic soils. Here we consider the carbon cycle of meadow ecosystems and their diurnal and seasonal characteristics. We present results from direct observations of CO2 exchanges as well as phenological image time-series analysis and field observations over two meadows; Knuthson and Loney, located just east and west of the SN crest at 1450m and 1850m respectively, and following particularly dry and average-precipitation winters respectively. The wetter Loney Meadow sequestered 18.51 gCm-2d-1 during the peak of the growing season in early summer, which is extremely large by global ecosystem standards. This steadily diminished as soil moisture declined during the remainder of the summer and the ecosystem switched from a sink to a source of CO2 on a daily basis by mid-August. In Knuthson Meadow, following the dry winter, the peak sink of CO2 was much smaller (-7.2 gCm-2d-1) and switched from sink to source of daily CO2 about five weeks earlier. Estimates of the annual CO2 budget for this meadow was -222 gCm-2a-1, representing a significant carbon sink by global standards. Compared with observations in related ecosystems, this is equivalent to a productive grassland or a weakly productive wetland.

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