COS 148-6 - Restoring function: The impact of hydrologic restoration on soil C sequestration, nutrient cycling, and primary production in Sierra Nevada meadows

Thursday, August 10, 2017: 3:20 PM
B117, Oregon Convention Center
Cody C. Reed, Natural Resources and Environmental Science, University of Nevada Reno, Reno, NV and Benjamin W. Sullivan, Natural Resources and Environmental Science, University of Nevada, Reno

High-elevation meadows are biological hotspots that contribute disproportionately to ecosystem services including nutrient cycling, water storage and purification, habitat, and carbon (C) sequestration. However, 60-70% of meadows in the Sierra Nevada of California have been degraded as a result of anthropogenic disturbance – resulting in lowered water tables, decreased primary productivity, and aerobic soil conditions that have altered ecosystem function. Though meadow restoration efforts have occurred for several decades, recent California C mitigation legislation has spurred interest in the potential of restoration to increase soil C sequestration. The C sequestration potential of restored meadows should stem from higher groundwater levels and associated higher primary productivity and anaerobic soil conditions. As a result, we expected to observe increased primary productivity and soil C and nitrogen (N) stocks over time following restoration of floodplain hydrology. To test this, we sampled soil C and N stocks and above- and belowground primary productivity in a chronosequence of 4 meadows restored between 2001 and 2010 in the same region of northern California. Each restored meadow was paired with an unrestored control meadow within the same watershed, allowing us to observe the relative effects of restoration through time.


In the three older sets of meadows, soil C and N stocks increased significantly as a result of restoration relative to the paired control meadow – in the youngest meadow, the increase was not significant. However, the increase in soil C and N stocks was not steadily positive as we expected. In 3 out of 4 meadow pairs, increases in N stocks (19-186%) were greater than C stocks (4-60%), highlighting the potential role of restored meadows in regional N cycles. Both above- and belowground biomass increased significantly in all meadows following restoration (vegetation: 185-1515% increase, roots: 42-261% increase). Increases in meadow C stocks were only significantly related to increases in belowground biomass (p = 0.001, r2 = 0.997), elucidating the importance of conditions favoring root growth in promoting soil C sequestration. These findings demonstrate that, in addition to increasing primary productivity, restoration of floodplain hydrology increases the net C sequestration potential of meadows. Extrapolated across degraded meadows in the Sierra Nevada, restoration could sequester 2.5 Tg of C in the first 15 years after restoration. The effects on soil N stocks may be even greater though, with implications for the productivity, water quality, and biogeochemical cycles of these ecosystems.