Quantifying Greenhouse Gas Emissions from Managed and Natural Soils

Quantifying Greenhouse Gas Emissions from Managed and Natural Soils

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  INSTITUTE OF METEOROLOGYAND CLIMATE RESEARCH, ATMOSPHERIC ENVIRONMENTAL RESEARCH, IMK-IFU DIVISION/Working Group… (change in master view) Quantifying Greenhouse Gas Emissions from Managed and Natural Soils Klaus Butterbach-Bahl1,2, Björn Ole Sander3, David Pelster2, Eugenio Díaz-Pinés1 1: Karlsruhe Institute of Technology, Institute of Meteorology and Climate Research, Atmospheric Environmental Research (IMK-IFU) 2: International Livestock Research Institute (ILRI) , Nairobi , Kenya 3: International Rice Research Institute (IRRI) , Los Baños, Philippines
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  2 Motivation Worldwide, agriculture isresponsible for 47 and 84 % of anthropogenic CH4 and N2O emissions, respectively (Smith et al 2007, IPCC WG III) Smallholder farms are crucial in e.g. Sub-Saharan Africa 75 % of both agricultural and job production (Africa Development Bank 2010) 80 % of farms in SSA are smaller than 2 ha (FAO 2010) Yields are low (ca. 1 Mg ha-1) Evidence-based data of GHG emissions in smallholder farms is scarce Source: Rosenstock et al. 2016. D.O.I. 10.1007/978-3-319-29794-1_1
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  3 Chamber methods formeasuring GHG fluxes in terrestrial ecosystems Pros + Simple, no in-situ analyzers needed + Allow for treatment-plots experiments + Existence of protocols Cons - Change in the soil environmental conditions - Spatial and temporal variability of fluxes - Accuracy and reliability of measurements
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  4 Chamber Placement Terrain Soil Vegetation Management Logistics •Depressions/ ridges/ slope (deposition/erosion, depth to groundwater) / aspect •Paths (bulk density) •Stones/ terraces (management) •Color (SOC/ flooding) •Texture (water/ nutrient availab.) •Compaction/Plough pan (bulk density) •Natural (vegetation layers/ patchiness, species, coarse woody materialnutrient/ water availability) •Row crops (row/ interrownutrient/ water availability) •Intercropping (nutrient/ water availability) •Irrigation/ flood water inlet/outlet (soil processes) •Fertilization (water/ nutrient availab.) •Compaction/Plough pan (bulk density) •Accessibility •Change of soil properties along access paths •Interference with management
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  5 Gas sampling Monitor Timing & interval Vials Sampling Storage •Crop performancein/ outside chamber • Animal activity (e.g. ants, termites, earthworms) •Chamber seals/ maintainance •Approx. at average daily soil-T (e.g. morning 9-11) •Minimize closure time (determine minimum detectable flux) to minimize chamber effects on soil environmental conditions •Flushing (min. 2x volume) or use pre-evacuated vials •Overpressurize •Logical numbering •Minimize disturbance at the plot (plant cover/ soil compaction) •Flush syringe •Ensure headspace mixing •Check seal tightness •Determine max. storage time •Use standards for comparison •Store vials in boxes
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  6 Gas analysis and data processing Responsibility Measurement instrument Flux calculation Maintenance Reporting •Hierarchyof responsibility (instrument maintenance/ analysis/ data storage/ reporting) •Understand principles •Optimize sensitivity in terms of accuracy & precision •Coefficient of variation for repeated concentration measurements (e.g. N =5) <1% •Check relationship between instrument signal and concentration •Linear or non-linear (understand advantages and disadvantages of both) •Calculate detection limits •If slope of regression = 0 (check p- value of slope)  flux = 0 •Stock spare parts •Check & service instrument regularly •Clean environment •Do flux calculations immediately •Report back problems to sampling team (e.g. numbering/ unusual noise in concentration changes across sampling interval •Check logic of fluxes with observations of auxilliary measurements
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  7 Auxilliary Measurements & Reporting Socio- economy Meteorology Soil properties Soil hydrology Crop/plant performance •Precipitation •Air temperature •Photosynthetic active radiation •Wind speed/ direction •Relative humidity •Evapotranspiration rates •Soil-temperature/ moisture (different layers down to 1m if possible) Multi-layer (0-10, 10-20, 20-50, 50- 100 cm) •Texture/ SOC/ total N / inorganic N/ bulk density/ pH •Water saturated conductivity •Microbial biomass C and N •Litter type / depth / C and N content (if applicable) •Water infiltration / hydraulic conductivity / water holding capacity •Distance to groundwater •Floodwater depth (e.g. rice paddies) •Depth of drainage tiles •Biomass development (monthly) •Pests/ diseases/ weeds •Development stages (e.g. tillering/ flowering) •LAI •Harvest index •Yield / N content Management •Field operations (e.g. ploughing, seeding, weeding, fertilization, irrigation, harvesting, pesticide applic.) •Fertilizer types & amounts •Crop type / rotation, variety and planting density •Residue management
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  8 Spatial and temporalvariability of soil GHG fluxes Source: Barton et al. 2015, Scientific Reports, D.O.I. 10.1038/srep15912 Source: Cowan et al. 2015, Biogeosciences, D.O.I. 10.5194/bg-12-1585-2015
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  9 Chamber 1 The gaspooling technique Arias-Navarro et al. 2013, Soil Biol Biochem, D.O.I. 10.1016/j.soilbio.2013.08.011 Close Mixing of the gas sample Pressurize/ Expand T0 Inject, flush & overpressurize glass vial T0 T0 T1T2T3 T2 T1T3 Gas Chromatograph
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  10 Chamber-based methods arerecommended in complex landscapes such as smallholder agriculture. Spatial and temporal variability remains a huge challenge  adequate design and sampling frequency are crucial. QA/QC is essential at all steps. Chamber design and positioning Gas sampling and analysis Calculations and reporting Conclusions Voice: David Pelster, Klaus Butterbach-Bahl & Allison Kolar