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CO 2 fluxes following simulated monsoon rain events - PowerPoint PPT Presentation


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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.

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slide1

CO2fluxes following simulated monsoon rain events

Rene Aguilera

Mentor: Shirley Kurc, University of Arizona

August 16th, 2007

Sevilleta LTER - REU Symposium

Photo Credit: Doug Moore

slide3

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!

slide5

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).

slide6

How do I measure CO2 flux?

Whole plant chamber

Licor-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.

slide7

Flags outline measured area

Licor-7500 sensor head

Fan

Tripod to mount sensor head

slide9

Example of How Water Bends

Apply chamber

Remove Chamber

Water increases as plants transpire

slide10

Example of How Water Bends

Water flux is the slope of this line!

Water increases as plants transpire

slide12

7 hours following 1st stimulated rainstorm on July 12

Large has largest response!

Rainfall applied:

0 mm control

5 mm small

10 mm large

Control has smallest response!

slide13

7 hours following 1st stimulated rainstorm on July 12

Net Ecosystem Exchange of CO2

Rainfall applied:

0 mm control

5 mm small

10 mm large

Lagged ‘respiration’ after small storm?

(+) Respiration

NEE (umol/m2/s)

( - ) Uptake

Uptake in all 3 cases

Continued uptake after large storm?

slide14

One week after July 12

Natural Rain Event

slide16

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
slide17

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