nabs 2005 – teaching session: my favorite ecology …...anderson, j. p. e. 1982. soil respiration....
TRANSCRIPT
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How Ecosystems Breathe: How Ecosystems Breathe: Measuring Respiration of Measuring Respiration of
SoilSoil
Matthew E. McTammany
NABS 2005 – Teaching session: my favorite ecology lab exercise
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Typical Ecology LabsTypical Ecology Labs
• Computer simulations• Field observations• Semester-long field projects• Non-experimental but data-rich labs• Focus on ecophysiology, population
interactions• Ecosystem processes largely ignored• Most observational, not experimental
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What Is Soil R?What Is Soil R?• Production of CO2 or consumption of O2
by organisms living on or in soils• Players: bacteria, protozoans, soil fauna
(nematodes, worms, snails, arthropods), fungi
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Why Measure Soil R?Why Measure Soil R?• Reinforce concepts about
metabolism of individual organisms
• Promote appreciation for microbes and invertebrates
• Can perform experiments virtually anywhere
• Show big picture of ecosystem processes (C flux, energy flow, mineralization rates)
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Lab Lab RespirometerRespirometerBI-2000® Laboratory RespirometerBioscience Environmental Products and Services
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ManometricManometric TechniquesTechniques
Time
KOH wick
Soil sample
CO2
Absorbed by KOHCO2 + KOH K2CO3
Pressure in chamber decreases
Kerosene
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Field Field RespirometerRespirometer
CFX-2 Soil CO2 Flux SystemPP Systems
LI-8100 Automated Soil CO2 Flux System
LI-COR Biosciences
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+ =Chamber COChamber CO22 TitrationTitration
1N KOHCup
Stand
Chamber
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Example ExperimentExample Experiment
Chillisquaque Creek Natural Area, central PA• Vegetation and slope affect soil conditions
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Natural Area SitesNatural Area SitesOld field
Mature bottomland forest
Young red maple forest
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Field Methods (Week 1)Field Methods (Week 1)
• 20 mL 1N KOH• Treatments &
controls• Seal chamber• 24-hour
incubation
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Lab Methods (Week 2)Lab Methods (Week 2)• 10 mL sample to centrifuge tube• 5 mL 3N BaCl2, BaCO3 precipitate• Centrifuge (~1000 RPM, 3 min.)• 5 mL supernatant, 3 drops
phenolphthalein• Titrate w/ 1N HCl to clear
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CalculationsCalculations
mg CO2 = (C – T) N E
Rate = mg CO2 / soil area / incubation time
Compare sites... STATS!!!
mL HCl Control – Treatment
Normality of acid Equivalent weight (22)
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Results: 11 April 2005Results: 11 April 2005
Results similar day-to-dayGood for lab reports (unlike many eco labs)
0
50
100
150
Field Young forest Old forest
R (m
g C
O2/m
2 /h) A
B
C
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Possible ExperimentsPossible Experiments• Compare R with other ecosystems• Nutrient enrichment• Organic matter quality manipulation• Pesticide/herbicide application• On-campus habitats (mulched flower bed
vs. grass vs. exposed dirt on foot path)• Opaque vs. transparent containers• Many possible ancillary measurements
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Cost ComparisonCost Comparison• Lab respirometers $20,000-100,000• Gilson respirometer $2000-10,000• Field respirometer $2000-15,000• Chamber titration (50 samples)
– $225 for buckets, cups, and stands (one-time cost)
– $37.50 for reagents (yearly)– Assuming labs have pipets, centrifuge tubes,
centrifuge, 25-mL beakers, burets, and stands
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ReferencesReferencesAnderson, J. P. E. 1982. Soil respiration. Pages 831-871
in Methods of soil analysis, Part 2, chemical and microbiological properties. Agronomy Monographs #9. ASA-SSSA, Madison, Wisconsin.
Rochette, P., E. G. Gregorich, and R. L. Desjardins. 1992. Comparison of static and dynamic closed chambers for measurement of soil respiration under field conditions. Canadian Journal of Soil Science 72:605-609.
Witkamp, M. 1966. Rates of carbon dioxide evolution from the forest floor. Ecology 47:492-494.
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AcknowledgmentsAcknowledgments• Jack Webster, Biology,
Virginia Tech• Biology Department
and Environmental Studies Program, Bucknell University
• Co-instructors, TAs, and students of BIOL 208, 2004 & 2005
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Anderson, J. P. E. 1982. Soil respiration. Pages 831-871 in Methods of soil analysis, Part 2, chemical and microbiological properties. Agronomy Monographs #9. ASA-SSSA, Madison, Wisconsin.
Rochette, P., E. G. Gregorich, and R. L. Desjardins. 1992. Comparison of static and dynamic closed chambers for measurement of soil respiration under field conditions. Canadian Journal of Soil Science 72:605-609.
Witkamp, M. 1966. Rates of carbon dioxide evolution from the forest floor. Ecology 47:492-494.
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