Wendy's Page

I am a finishing graduate student at the University of California – Berkeley
in the Department of Environmental Science, Policy and Management. My
major professor is Whendee Silver.

The project has three major areas. The theme linking all three
is the relationship between climate and the emissions of greenhouse
gases that enhance warming of the atmosphere.

(I) Response of grassland respiration to increased rainfall
Motivation: I am interested in whether a feedback loop exists
between increased rainfall and increased production of carbon dioxide.

Activities: I’m monitoring changes in the amount of carbon dioxide
emitted by California grassland soils. Carbon dioxide is an important
greenhouse gas, and the reservoir of carbon stored naturally in soil
is greater than the amount stored in vegetation or in the atmosphere.
These changes in soil respiration (another term for the emitted carbon
dioxide) I'm seeing are occurring under simulated climate change—an
increased amount of rainfall that I accomplish via sprinklers. Because the
climate in N. California is so seasonal, we decided to look at the role of
both the amount and timing of water added. Thus, we are adding water during
the normal wet season. Second, because the grasslands experience a strong
summer drought (May - September), we are relieving this by adding a water
pulse in spring and fall, which represent transition times between the wet
and dry periods.

Setting: The research takes place at the Sierra Foothill Research and
Extension Center, in the northern part of the state, east of the great
Central Valley. The site is approximately 50 miles northeast of
Sacramento, the state capital.

(II) Contribution of spring-fed wetlands to greenhouse gas emissions from
the grassland landscape
Motivation: increased soil moisture in wetland soils permits the production
and release of significant amounts of methane and nitrous oxide, gases which
are more powerful warming agents than carbon dioxide on a per-molecule basis.

Activities: I measured trace gas fluxes monthly in wetlands and drew correlations
between trace gas fluxes and climate and biotic variables. Seasonally, the fluxes
from wetlands and grassland differed, with summer fluxes of methane and nitrous
oxide playing an important role in wetlands. I also estimated the state-wide
emission of methane and nitrous oxide from emergent wetlands based on estimated
land areas of wetlands and grasslands.

(III) Laboratory experiment: combining rainfall and temperature treatments
Motivation: Given that multiple global changes are expected to operate on
terrestrial ecosystems, how do temperature and water interact to affect trace
gas fluxes, from grasslands, especially nitrous oxide and carbon dioxide?

Preliminary results:

In April 2007 I gave a presentation on my work at the Sierra Foothills Research
and Extension Center Field Day in Browns Valley, CA. This presentation
summarizes the last three years of experimental data on Project I above.
You can view the slideshow--unfortunately, without any supplementary
notes for the moment--if you have Adobe reader, here
(right-click to save the file). You might notice that for reasons of
space and time, the slideshow addresses only carbon.

If you have Quicktime or some other video player, click here to see a brief
video about my study on carbon cycling in California grasslands.
(Works best if you save the file, it is 14 MB)