joseph c. blankinship , emma p. mccorkle, matthew w. meadows, ryan g. lucas, and stephen c. hart
DESCRIPTION
AGU 2012 Fall Meeting B21I. When Winter Changes: Hydrological, Ecological, and Biogeochemical Responses I. Consequences of warming and altered snowmelt timing on soil CO 2 , CH 4 , and N 2 O fluxes in the Sierra Nevada rain-snow transition zone. - PowerPoint PPT PresentationTRANSCRIPT
Consequences of warming and altered snowmelt timing on soil CO2, CH4, and N2O fluxes in the
Sierra Nevada rain-snow transition zone
Joseph C. Blankinship, Emma P. McCorkle, Matthew W. Meadows, Ryan G. Lucas, and Stephen C. Hart
AGU 2012 Fall MeetingB21I. When Winter Changes: Hydrological, Ecological, and Biogeochemical Responses I
Kearney Foundation of Soil Science 2006-
2011 Mission
Western North America is facing major climatic and hydrological changes
Stewart et al. 2005, Journal of Climate
more rain
Bales et al. 2006, Water Resources Research
II. Snowmelt Timing
I. Precipitation Type
Due to 3ºC warmingno changeWhat do these changes mean for soil microbial activities and
greenhouse gas (GHG) emissions during the warm season?
Connecting precipitation type & snowmelt timing to soil GHG fluxes
Warming in Seasonally Snow-Covered Ecosystems
More Rain Earlier Snowmelt
Timing of Soil Water Availability
Timing/Extent of Resources
Longer “Microbial Growing Season”?
↑ Microbial Stress?
↑ Soil GHG Emission? ↓ Soil GHG Emission?
FALL, WINTER, SPRING
SUMMER
Realistic simulation is difficult
Most studies confounded by summer precip and altered water input
Soil and plant heterogeneity
Research Questions
1. Will winter and spring warming exacerbate summer microbial stress in the rain-snow transition zone, thus reducing GHG emissions?
2. If water input stays the same, does snowmelt timing impact soil GHG fluxes for days, weeks, or months?
Warm & Rainy
Cold & Snowy
Image from The Mighty Sierra: Portrait of a Mountain World (1972) by Paul Webster and Francis Farquhar
Sierra Nevada climatic gradient
“Rain-snow transition zone”
Water Year 2011: 2nd wettest on record(~170% normal runoff; ~3.5 m max. snow depth)
Water Year 2012: 4th driest on record(~50% normal runoff; ~1.5 m max. snow depth)
Grant Grove, CA; Western Regional Climate Center
Little precip after snowmelt
Ideal, extreme seasonal and interannual variation in precipitation
Low elevation site (1,816 m ASL)MAT = 8.2 °C; MAP = ~1000 mm; 40-65% rain
To simulate warming, we moved forest soils across the rain-snow transition zone, twice
Downward Transfer
High elevation site (2,365 m ASL)MAT = 6.8 °C; MAP = ~1000 mm; 75-90% snow
* No difference in mean soil temperature during summer
Soil GHG fluxes:
Carbon Dioxide (CO2)
Methane (CH4)
Nitrous Oxide (N2O)
• Measured weekly or biweekly after snowmelt, and then monthly
• Not measured when snow depth > 5 cm
Winter warming accelerated summer GHG fluxes
CO2 emission CH4 uptake N2O emission
“Early Snowmelt”
n = 12
“Late Snowmelt”
3.1 m
3.1 m
n = 12
Snowmelt was manipulated by 2 to 3 weeks
Earlier snowmelt reduced CO2 emission and increased CH4 uptake
CO2
CH4
Wet Year Dry Year
Complete Snowmelt
Research Questions
1. Will winter and spring warming exacerbate summer microbial stress in the rain-snow transition zone, thus reducing GHG emissions? No , warming increased net GHG emission and seemed to relieve stress
2. If water input stays the same, does snowmelt timing impact soil GHG fluxes for days, weeks, or months?
CH4: WeeksCO2 (and N2O): Months
The warming effect…
Warming in Seasonally Snow-Covered Ecosystems
More Rain (Less Extreme Winter)
More Resources for Microbial Growth?
↑ Soil GHG Emission
…is likely constrained by earlier snowmelt.
Warming in Seasonally Snow-Covered Ecosystems
Earlier Snowmelt
↓ Soil Resources During Summer
↑ Microbial Stress?
↓ Soil GHG Emission
Questions?
EXTRA SLIDES FOLLOW:
* indicates significant elevation difference (P < 0.05 in one-way ANOVA); # indicates significant effect of snowmelt timing
Soil Temperature
Soil water content outside of experimental cores
n.s.
n.s.
CO2 fluxes
0
20
40
60
80
100
120
140So
il Ca
rbon
Dio
xide
Em
issio
n (m
g CO
2-C
m-2
h-1) Low Elevation
High Elevation
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