soil co 2 efflux from a subalpine catchment
DESCRIPTION
Soil CO 2 Efflux from a Subalpine Catchment Diego A. Riveros-Iregui 1 , Brian L. McGlynn 1 , Vincent J. Pacific 1 , Howard E. Epstein 2 , Daniel L. Welsch, Kelsey Jencso 1 - PowerPoint PPT PresentationTRANSCRIPT
Soil CO2 Efflux from a Subalpine CatchmentDiego A. Riveros-Iregui1, Brian L. McGlynn1, Vincent J. Pacific1, Howard E. Epstein2, Daniel L. Welsch, Kelsey Jencso1
[email protected]; Watershed Hydrology Lab, Department of Land Resources and Environmental Sciences, Montana State University, Bozeman, MT 597172.Department of Environmental Sciences, University of Virginia, Charlottesville, VA 22904. 3. Department of Geography, Frostburg State University, Frostburg, MD 21532
• Soil CO2 efflux is the single largest respiratory flux from forested
ecosystems. Understanding its spatial and temporal dynamics will
provide insight into C exchange at the ecosystem level.
• Evaluating and predicting soil respiration response to changing
hydrologic and biophysical conditions is currently constrained by
understanding of first-order controls and the methods used to
measure, model, and interpret soil respiration.
• We measured soil CO2 concentration, soil CO2 flux, soil moisture,
soil temperature, groundwater dynamics, and precipitation at 20-
minute intervals throughout two growing seasons at 4 sites and at
sub-weekly intervals at 62 sites covering the range of topographic
position, slope, aspect, and land cover.
• Our goal is to quantify watershed-scale heterogeneity in soil CO2
concentrations and surface efflux and gain understanding of the
relative contribution of biophysical controls on soil respiration.
Acknowledgments: This work is supported by the NSF Integrated Carbon Cycle Research Program, a Student Research Grant from the Montana Water Center and a MSU College of Graduate Studies Fellowship. We appreciate extensive logistic collaboration from the U.S. Forest Service.
Figure 2: Two growing season averages of soil respiration and soil water content at 34 of 62 total sites. These comparisons highlight the relative controls of water content on controlling soil respiration across the watershed. For example, note the high variability of water content in riparian areas, whereas high uplands remain dry during most of growing season. Note how increasing upslope contributing area (i.e., moving in the downhill direction) controls total soil respiration in high, dry uplands. Error bars are one S.D. Refer to colors in Figure 1 for location.
Figure 1. (A) Current instrumentation at the TCEF includes five real-time monitoring stations for soil moisture and temperature, >60 groundwater wells and piezometers, two eddy covariance towers, and >120 gas wells. We seek to understand the effect of watershed-scale heterogeneity on CO2 distribution and flux across
environmental gradients.
• Long-term monitoring of soil respiration, soil moisture, and soil temperature at 62 sites across the watershed.
• Continuous measurements of soil respiration in riparian and upland settings.
• Land cover analysis from Airborne Laser Swath Mapping (ALSM) sub-meter topographic and vegetation data.
• These methods are targeted to investigate the effect of heterogeneity of biophysical controls on soil CO2 efflux at the
watershed scale.
INTRODUCTION
METHODS
SITE
1. Understanding linkages between the biophysical controls
of soil respiration and hydrology from the point, to the plot,
to the watershed scale is critical to understanding
dynamics of net ecosystem CO2 exchange.
2. High elevation mountain landscapes play an important role
in the North American carbon cycle, yet the number of
studies of coupled C and water cycles in the Northern
Rocky Mountains is limited.
3. The relative sensitivity of soil respiration to biophysical
variables is poorly understood. However, catchment level
studies allow comparison of magnitude and variability of
biophysical controls across environmental gradients.
SIGNIFICANCE
Sites
T1
W4
T1
W3
T1
W2
T1
W1
T1
E1
T1
E2
T1
E3
T1
E4
T2
W4
T2
W3
T2
W2
T2
W1
T2
E1
T2
E2
T2
E3
T2
E4
SW
1S
W2
SW
3S
W4
SW
5S
W6
NW
Co
n6
NW
Co
n5
NW
Co
n4
NW
Co
n3
NW
Co
n2
NW
Co
n1
NW
Di6
NW
Di5
NW
Di3
NW
Di2
NW
Di1C
O2
Eff
lux
(g m
-2h
r-1)
0.0
0.5
1.0
1.5
2.0
Wa
ter
Co
nte
nt
(m3 m
-3)
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
Transect 1 Transect 2
Increase in upslope contributing area, (downhill)
A Stringer Creek(550 ha)
2090 m
2425 mElevation
LEGEND
Soil moisture & temperature
Biometry plots
Gas wells and respiration plots
Eddy covariance systems
Flume
SOIL RESPIRATION AND SOIL MOISTURE
MODELING SOIL CO2
Tenderfoot CreekExperimental Forest(TCEF)
SEASONALITY IN THE SOIL [CO2]- SOIL TEMP RELATIONSHIP
,,COCO 22
SHA TkPARkz
nDzt
Figure 3. (A) Relationship of soil [CO2] and soil temperature at 20-min
intervals at a riparian site with pronounced summer dry-down. (B) Highlighted evolution of hysteresis throughout the summer. Soil water content values are given in parentheses for each highlighted day. (From Riveros-Iregui et al. in review)
SOIL MOISTUREtop_ind
Value
High : 21.715910
Low : 1.928115
Figure 4: Triangle Topographic Index for Stringer Creek Watershed (Seibert and McGlynn, WRR 2007) based on a 3-m DEM. This is an estimate of soil wetness potential across the catchment.
tan
a ln.. IT
angle slope local :
area contr. upslope :a
SPATIAL AND TEMPORAL HETEROGENEITY
Contours are every 10 m
Stringer Creek Watershed(550 ha)