co 2 fluxes following simulated monsoon rain events
DESCRIPTION
CO 2 fluxes following simulated monsoon rain events. Rene Aguilera Mentor: Shirley Kurc, University of Arizona August 16 th , 2007 Sevilleta LTER - REU Symposium. Photo Credit: Doug Moore. How do ecosystems respond to changes in precipitation patterns?. Photo Credit: Greg Greene. - PowerPoint PPT PresentationTRANSCRIPT
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CO2 fluxes following simulated monsoon rain events
Rene AguileraMentor: Shirley Kurc, University of Arizona
August 16th, 2007Sevilleta LTER - REU Symposium
Photo Credit: Doug Moore
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How do ecosystems respond to changes in precipitation patterns?
Photo Credit: Greg Greene
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Monsoon Rainfall Manipulation Experiment (MRME):
Water addition alters size and frequency of rainstorms during the summer monsoon (July – Sept) at the black grama grassland.
Treatment 1: Ambient rainfall only Control
Treatment 2: One 5 mm storm each week Small
Treatment 3: One 20 mm storm each month Large
Same amount of water addition, different timing!
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Hypothesis 1: In the first day or two following all rainfall events, CO2 will be released, followed by a period of lagged CO2 uptake (Potts et al. 2006, Huxman et al. 2004)
Hypothesis 2: Over the course of the monsoon season, there will be less CO2 response following the treatment of more frequent small storms than infrequent large storms. (Spoonseller 2007).
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How do I measure CO2 flux?
Whole plant chamberLicor-7500
~ 380 ppm
Either soil is releasing carbon (respiration) or plants are taking up carbon (sequestration), so that concentration in chamber will become higher or lower than ambient.
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Licor-7500 sensor head
Flags outline measured area
Fan
Tripod to mount sensor head
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Apply chamber
Water increases as plants transpire
Remove Chamber
Example of How Water Bends
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Water increases as plants transpire
Water flux is the slope of this line!
Example of How Water Bends
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12000
12200
12400
12600
12800
13000
13200
13400
13600
13800
14000
0 20 40 60 80 100 120 140 160 180 200
sec
CO
2 u
mo
l/m3
Example of How Carbon Dioxide Bends
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Rainfall applied:0 mm control5 mm small10 mm large
Control has smallest response!
Large has largest response!
7 hours following 1st stimulated rainstorm on July 12
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Rainfall applied:0 mm control5 mm small10 mm large
7 hours following 1st stimulated rainstorm on July 12
(+) Respiration
( - ) Uptake
Uptake in all 3 cases
Lagged ‘respiration’ after small storm?
Continued uptake after large storm?
Net Ecosystem Exchange of CO2
NE
E (
um
ol/
m2
/s)
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Water Fluxes
-6
-4
-2
0
2
4
6
0 1 2 3 4 5 6 7 8 9
Days
ET
(m
mo
l/m2/
s)
Control
Small
Large
Natural Rain Event
One week after July 12
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Net Ecosystem Exchange of CO2
-6
-4
-2
0
2
4
6
0 1 2 3 4 5 6 7 8 9
Days
NE
E (
um
ol/m
2s)
Control
Small
Large
One week after July 12
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More measurements to come, including a diurnal measurement in September.
Results thus far:
•Large less frequent storms trigger grasses to sequester more C, which alters carbon storage.
•H2O availability drives carbon storage
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Acknowledgments
• Jennifer Johnson• Shirley Kurc• Scott Collins• Chris Chen• Ben Gutzler• Tori, Ash, Jarrod, Enrico, Kate, Alexandra & Judd• Kathy McQueen• Mom & Dad
Photo Credit: Doug Moore