Fractionation Classification Updates

[coreylawrence]

See also #110

I've spent some time working through a new framework for classifying fractionation methods, which I think will be more straightforward and accurate. I know this is a major change but I think this is something we need to do sooner than later.

Please have a look at THIS google drive file to see a comparison of the old vs. proposed new approach and add any suggestions you have as a comment

The new approach would require entries for frc_scheme, frc_approach, and frc_property to better capture the range of methods and to, hopefully, make it easier to standardize the categorization. The various combinations of approach and property choices are organized around the more general scheme selection.

After addressing any additional feedback on this, I will work on applying these changes to the database. My plan is to clone the repository, make the changes to the template, TIF, and existing data entries. Once it is working, we can merge the updates back with the main branch. However, if there is a better way, please let me know.

[olgavinduskova]

Hi Corey, I had a look and I like it. I checked your new framework against the template of Harden_1987 that I filled in a while ago and is now held back from being ingested because of the issues around fractions and I think with your changes it is very close to being ingestable! My first suggestions is to add "pipette method" into the frc_agent for Particle_Size fractionation scheme. Secondly, will lower and upper cutoff will still be a required field? I like how you splitted up the cases for the different schemes so I guess it would be nice to add also examples of some of the less intuitive cutoffs there, what do you think? The one that comes to my mind is what cutoffs to use for ABA extractable or residual fraction when units are presence/absence. As indicated by Alison here> #20 the cutoffs should always be 0 and 1 although I can't really wrap my head around this (the cutoffs seem unnecessary to me in cases of presence/absence units).

[olgavinduskova]

Dealing with fractionation in Doetterl et al. 2018, I am thinking how to classify their coarse POM (cPOM) which was separated after Six et al. 2002 by disrupting macroaggregate fraction (previously obtained by wet sieving >250 µm) in a microaggregate isolator (shaking with glass beads and wet sieving to get the >250 µm fraction). After disruption of maccroagregates, both cPOM and sand is captured on the 250 µm sieve, but sand content is then subtracted and C concentrations corrected so the data that I am entering describe cPOM only.

What description should I use? In the new version of fraction vocab proposed by Corey, there seems to be no suitable combination of descriptors.

I am considering frc_input macroaggregates, frc_scheme Aggregate (or Particle size?), frc_agent wet sieve and frc_property occluded-light, frc_lower 250 and frc_upper 2000. However, I am not sure about the occluded-light descriptor because technically the macroaggregate fraction can contain both occluded and free light fraction. Do we need a new "light" only or "POM" descriptor and add it to the Particle size or Aggregate frc_scheme?

[Kate-Heckman]

How do I enter water extractable carbon (the soluble fraction you can pull off in the lab - not DOC from the field)? It doesn't work in the interstitial tab. I can put it in the fraction tab, which makes more sense, but there don't seem to be any good options for "f_property", "f_scheme_units", "frc_lower", or "frc_upper". Guidance?

[jb388]

@Kate-Heckman I'd put it in the fraction tab, too. It's hard to fit this procedure into our current scheme--there's no corresponding frc_property. However, my understanding is that the typical approach for chemical extractions is to use "presence/absence" for frc_scheme_units, and 0 and Inf as the upper and lower limits. Since frc_property isn't required, I guess I'd leave it blank, and put a note in the frc_note column that the water-extractable-fraction/residue was measured.

[Kate-Heckman]

Thanks, Jeff!

From: Jeff B [mailto:notifications@github.com] Sent: Monday, March 25, 2019 3:12 PM To: International-Soil-Radiocarbon-Database/ISRaD ISRaD@noreply.github.com Cc: Heckman, Katherine A -FS kaheckman@fs.fed.us; Mention mention@noreply.github.com Subject: Re: [International-Soil-Radiocarbon-Database/ISRaD] Fractionation Classification Updates (#147)

@Kate-Heckmanhttps://github.com/Kate-Heckman I'd put it in the fraction tab, too. It's hard to fit this procedure into our current scheme--there's no corresponding frc_property. However, my understanding is that the typical approach for chemical extractions is to use "presence/absence" for frc_scheme_units, and 0 and Inf as the upper and lower limits. Since frc_property isn't required, I guess I'd leave it blank, and put a note in the frc_note column that the water-extractable-fraction/residue was measured.

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[jb388]

Closing as fraction overhaul is complete