Transcript Vegetation Structure Influence on Soil Respiration

The Influence of Vegetation Type on
Winter Soil Respiration Rates
Scott Clingan
Winter Ecology Spring 2014
Terrestrial Carbon Cycle
• Soil respiration estimated to
account for 20-38% of annual
biogenic CO2 emissions (Scott 2002)
• Increased Respiration from
global warming = lower carbon
sequestration (positive
feedback?)
How does vegetation type
influence soil respiration?
• Snow depths<1m, vegetation type exerts a signifant
influence on landscape level CO2 respiration (Grogan 2012)
• Vegetation influences abiotic and biotic factors of
respiration
• Soil moisture, soil temp, litter quantity/quality, litter
depth (Fu 2013)
• AET (Actual Evapotranspiration) good predictor of soil
respiration
• High levels of spatial heterogeneity
Questions
• Q1: Does vegetation type influence winter soil
respiration?
– Hypotheses:
• H1:Vegetation type influences the amount of winter soil
respiration
• H0: Winter respiration rates do not differ across vegetation thypes
• Q2: Does soil moisture impact soil respiration rates
– Hypotheses:
• H1: High soil moisture content will inhibit soil respiration rates in
the winter
• H0: Soil Moisture does not effect soil respiration rates
Methods
• PP Systems SRC-1 Soil CO2 Flux System
– Measured soil CO2 emissions over 120 seconds
• 3 Vegetation Types (~100cm snow depth)
– Aspen (Populus tremuloides)
– Lodgepole Pine (Pinus contorta)
– Mixed Grass Meadow (various species)
• 2 Replicates of each type
– 3 Subsamples per replicate
• Supplemental Data1
– Soil Moisture (0-4)
– Amount of Organic Matter (0-5)
• Analyzed with “R” statistical software
1Collaboration with
Coin Pettinati
Site
Characterization
•
•
•
•
•
Elevation ~9,500 ft.
Mean Annual Precipitation: 20 to 40 inches
Mean Annual Air Temp 36-39 degrees F
Frost-Free Period: 30 to 50 days
Soils1
• Aspen: Slight/moderate decomposition to sandy loam
• Lodgepole: Cobbly silt loam to Very Cobbly Silt Loam
• Meadow- Organic Layer Cobbly to gravely sandy loam
• Glacial till and/or alluvium derived from igneous and
metamorphic rock
1Retrieved from: www.websoilsurvey.nrcs.usda.gov 3/6/2014
Replicate Results
Mean Respiration per Replicate
CO2 (ppm)
850
800
Aspen 1
y = 0.2603x + 528.75
R² = 0.9826
750
Aspen 2
700
y = 0.2413x + 451.81
R² = 0.8988
650
Lodgepole 1
y = 1.4924x + 484.75
R² = 0.9975
600
Lodgepole 2
y = 1.7984x + 591.39
R² = 0.9979
550
Mixed Grass Meadow
y = 0.1993x + 459.88
R² = 0.9955
500
Mixed Grass Meadow 2
450
y = 0.4733x + 470.21
R² = 0.9288
400
0
20
40
60
80
Time (Seconds)
100
120
140
Comparison of Respiration Rates
2.0
Vegetation Type CO2 Respiration
1.0
(f-value 119.7)
0.5
CO2 Respiration (ppm/sec)
1.5
Significance
• Lodgepole-Aspen: p<.001
• Lodgepole-Meadow: p<.001
• Aspen-Meadow: p=0.5264186
Aspen
Lodgepole
Site
Meadow
Is soil moisture a good predictor of soil
respiration rates?
Moisture Values
• Low: 1&2
• Moderate: 3
• High:
Significance
• Low-High: p=0.5264186
• Moderate-High: p<0.001
• Moderate-Low: p<0.001
(fvalue= 119.7)
Does Litter Amount influence Soil
Respiration Rates?
Significance
• Medium-High: p<0.001
• Medium/High-High: p<0.001
• Medium/High-Medium: p<0.5265186
(f value 119.7)
Summary
• Vegetation Type does influence soil respiration
rates….however
– Aspen respiration is lower that other studies
• Limiting Factor?
• Litter amount directly influences rates
– What about quality?
• Research litter C:N ratios
• Problems
– High levels of spatial heterogeneity
– Highly variable (diurnal, seasonal, interannual time scales)
Questions?
Special thanks to the following people who
contributed to this project:
• Tim Kittel, Kelly Matheson, Derek Sweeney,
Colin Pettinati, Angel Bigas, Evan Esfahani
References
• Fu, Xiaoli, et al. "Soil Respiration as Affected by Vegetation Types in a
Semiarid Region of China." Soil Science and Plant Nutrition 59.5 (2013):
715-26. Print.
• Grogan, Paul. "Cold Season Respiration Across a Low Arctic Landscape: The
Influence of Vegetation Type, Snow Depth, and Interannual Climatic
Variation." Arctic Antarctic and Alpine Research 44.4 (2012): 446-56. Print.
• Merbold, Lutz, Nele Rogiers, and Werner Eugster. "Winter CO2 Fluxes in a
Sub-Alpine Grassland in Relation to Snow Cover, Radiation and
Temperature." Biogeochemistry 111.1-3 (2012): 287-302. Print.
• Morgner, Elke, et al. "The Importance of Winter in Annual Ecosystem
Respiration in the High Arctic: Effects of Snow Depth in Two Vegetation
Types." Polar Research 29.1 (2010): 58-74. Print.
• Scott-Denton, Laura E., Kimberlee L. Sparks, and Russell K. Monson.
"Spatial and Temporal Controls of Soil Respiration Rate in a High-Elevation,
Subalpine Forest." Soil Biology and Biochemistry 35.4 (2003): 525-34.
Print.