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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 Presentation
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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
How do ecosystems respond to changes in precipitation patterns?
Photo Credit: Greg Greene
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!
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).
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.
Licor-7500 sensor head
Flags outline measured area
Fan
Tripod to mount sensor head
Apply chamber
Water increases as plants transpire
Remove Chamber
Example of How Water Bends
Water increases as plants transpire
Water flux is the slope of this line!
Example of How Water Bends
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
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
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)
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
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
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
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