The Legacy of Winter Climate Change on Summer Soil Biogeochemical Fluxes Joey Blankinship, Emma McCorkle, Matt Meadows, Ryan Lucas, and Steve Hart University of California, Merced SSCZO 2012 Annual Meeting – 21 August 2012

Low Elevation Site 1816 m; MAT = ~8.2 °C; MAP = 1512 mm ( ); 40-65% Rain To simulate climate change, we moved forest soils within the rain-snow transition zone (field incubation experiment) Downward Transfer Upward Transfer High Elevation Site 2365 m; MAT = ~6.8 °C; MAP = 1517 mm ( ); 75-90% Snow n = 12 for both soils (n = 8 for gas flux measurements) Meteorological data are from Hunsaker et al. (2012) J. American Water Resources Assoc.

Another goal was to isolate effects of snowmelt timing at the high-elevation site

Early Snowmelt

n = 12

Late Snowmelt 3.1 m n = 12

Soil Temperature

 Our snowmelt treatments worked!  Good luck to simulate climate change in contrasting Water Years

 Providence soil warmer than Bull, except during summer and when snow covered  Response of soil temperature to winter drought varied with elevation * indicates significant elevation difference (P < 0.05 in one-way ANOVA); # indicates significant effect of snowmelt timing

Soil Volumetric Water Content 0-12 cm deep inside soil cores 0-15, 15-30, and cm deep outside cores

 Snowmelt timing influenced shallow (0-30 cm) but not “deep” soil moisture (30-60 cm) during the subsequent summer Blankinship et al., Water Resources Research, in review

Soil Greenhouse Gas Fluxes Carbon Dioxide (CO 2 ) Methane (CH 4 ) Nitrous Oxide (N 2 O)

 Soil CO 2 flux tracks moisture during spring and summer, but temperature during fall and winter  Low Elevation: Warmer winter = Less spring CO 2 emission

 Warming increased high-elevation soil CO 2 emission by 32%

 2- to 3-week advancement of snowmelt reduced summer CO 2 emission by 10-35%

 Warming increased high-elevation soil CH 4 uptake by 48%

 And for N 2 O too, the high elevation soil responded more strongly to warming than low elevation soil

 Our results suggest that climatic warming in snow-dominated ecosystems of the Sierra will increase net greenhouse gas emission from the soil to the atmosphere in the short-term.  However, continued advancement of the snowmelt date, without a simultaneous increase in precipitation, will likely constrain the extent of the temperature-induced increase in greenhouse gas fluxes. Other Directions:  Rates and ‘leakiness’ of nitrogen cycling  Microbial population sizes (e.g., total biomass, methane oxidizers, nitrifiers, denitrifiers)  Mechanisms for C release with warming and C sequestration with drying  Scale up snowmelt treatments to larger areas to include plant responses and plant-soil interactions  What exactly is going on during winter? Conclusions

The End