These references would be really suitable to you

Article Post-fire soil respiration in relation to burnt wood managem...

What do you mean by burning biomass? Aboveground biomass? The simplest way would be to measure the total soil C and organic C before and after burning to determine organic carbon loss (or comparing burned and unburned plots). For measuring CO2 emission into the atmosphere, I don't have any specific protocols but this has been a major topic in Global Change research and you could look at the IPCC reports and global change literature for suggestions.

Dr sara marañón-jiménez , thank you for this reference. Pls can you send me your own copy, because the link in self archiving restriction.

All references (Spain worked at lot on this topic: CARBALLAS, ALMENDROS; VALLEJO, etc.) said that the usual forest fires DO NOT influence too much on the quality & quantity of the SOM, because they affect only the first -2 cm soil depth.

Only extreme, static fires can affect the soil if remain too much time in the site burning big amounts of biomass, but this is not usual situation.

Forest fires burn usually very quickly dry stand litter and leaves or needles in the canopy, reamining trunks and soil slighty affected. Only some special, intense fires can burn trunks and in this situation we can loss a significant part of SOM, in special if they is scarcely humified; this is the case of mars and peats.

Then, kind of fires detemines the influence of forest fires on soil & then SOM.

Dennis, you need to know the difference in the amount of carbon in the soil ie C sequestered . before and after the burning. Directly to your query. To convert C to CO2. From IPCC (2007)

CO2 = amount of Carbon sequestered X 3.75 divide by 1000.

Reference

IPCC (2007) Fourth assessment report, climate change synthesis report. Cambridge University Press. UK.

Thank you Oku. Please can you explain 3.75 and 1000 used in that equation

This is the formula given by IPCC (2007) 3.75 is a factor and expressed per thousand

3.75 equals molecular weight of CO2 divided by atomic weight of carbon. IPCC does not use 44 and 12, respectively, but the weighted average of molecules containing the several carbon isotopes found in the atmosphere, mainly 12C and 13C.

I do not know where the 1000 presented by Oku comes from: you are converting grams (or Mg...) of C to grams etc of CO2, not to express anything per thousand.

CO2/C ratio is 3,67, then, the amount of isotopes considered seems to be significant. Obviously, the factor 1000 could be a question of units. It seems to refer to a conversion, probably from g C m-2 to Mg C ha-1 (in this case a '0' is lacking) or similar transformation.

Dear Dennis,

Which approach to chose is quite dependant on what type of ecosystem you're interested in. Measuring soil respiration rates before and after a fire would be one way to go but that is of course only possible in the case where you're planning a burning and not really for natural fires.Eddy covariance (EC) measurements would integrate CO2 fluxes over larger areas and does not require a lot of manual work. If you're ecosystem is a dense forest, understory EC measurements would be difficult while it would be an excellent choice for shublands, grasslands etc. Chamber measurements of soil respiration is probably a better choice in most cases but it is labor intensive and you'll face problems of scaling up your results to the ecosystem level.

One thing to keep in mind is that if all or a major part of the aboveground vegetation disappears in the fire, the belowground autotrophic respiration (root excudates etc) will stop/decrease and cause a change in total soil respiration rates, which might make it difficult to interpret what happened to the heterothrophic soil respiration rates.

Combining soil respiration measurements with measurements of soil organic carbon before and after a fire is recommended but not straightforward, I think. SOC might increase after the fire as a consequence of a lot of dead organic material being deposited on the soil surface during the fire. You'll also need a lof of samples for scaling up and that is labor intensive and expensive.

I've attached two references for you. I also think there has been some work on carbon fluxes in relation to fires at the Hyytiälä site in Finland. You should be able to find some references from those experiments.

Ma et al (2004) - Short-Term Effects of Experimental Burning and Thinning on Soil Respiration in an Old-Growth, Mixed-Conifer Forest

Ryu et al (2009) - Prescribed burning and mechanical thinning effects on belowground conditions and soil respiration in a mixed-conifer forest, California

Thank you all for your useful contributions

In Many European Countries, they do not allow the burning of bio mass at all

due to the release of CO2.

An alternative is grinding and terrating, or grinding and composting.

The concept is to dramatically increase the surface area of the bio mass,

and place it into a warm moist environment that promotes growth of

bio mass eating micro organisms.

To improve soil you need to put as many nutrients back into the soil as possible.

Grinding and terrating improves the soil, but it takes far longer to break down the

material into plant useful nutrients.

Composting is better, but it requires keeping it warm and moist, and occasionally

you need to turn the piles and mix them up ( oxygenation ).

To break down woody substances, you need Fungi ( Mushrooms , etc. ).

During the Carboniferous period, there were no Mushrooms, so the carbon

just sat in the swamps and was compressed to create lignite ( coal ).

When Fungi learned to process Lignin, the materials changed from coal to

peat ( the undigested cell walls of wood ). Thus grinding is used to

promote access of Fungi to the material inside the cells of the wood.

During the Carboniferous ( 359 MYA to 299 MYA ) the CO2 concentration

dropped from 2,000 ppm to 400 ppm over the 60 million year period.

At the same time the O2 increased from 20 % to 30%.

Even during the Permian ( 299 MYA to 251 MYA ) the CO2 continued to

drop from 400 ppm to 300 ppm.

At the end of the Permian the CO2 suddenly increased from 300 ppm

to 2500 ppm and the temperature increased from 13 C to 22 C.

The increase in CO2 by burning, any burning, including bio mass

burning is a proven global warming process.

The question becomes, which process produces less CO2 ?

Grinding, Composting, and Terrating biomass, or burning, and tilling.

Both processes require machinery that requires petroleum products for combustion

but Geologic History indicates that burying biomass produces less CO2

than burning. It may also mean that buried biomass promotes more tree

growth that pulls more CO2 from the atmosphere.

The lesson here is to limit the area of disturbance required for agriculture,

promote tree growth in unused areas to pull CO2 from the atmosphere,

and when you cut down, or harvest, return the rest back to the soil to

improve both the soil and the atmosphere.

Having reread the question, the simple answer is that the combustion of

organic materials produces Carbon dioxide and water, and smoke that enters the atmosphere.

The burning of biomass does not really benefit the soil, nor does it benefit the

atmosphere.

Most soils are benefited by grinding up the biomass and terrating it back into the

soil where it benefits bacteria, mushrooms, and new growth, and helps with reduction

in the erosion of disturbed soils.

My question in return is why would you want to assess doing something that

has such deleterious effects on the soil and the atmosphere, when grinding

and terrating biomass has such important benefits for the soil quality?

Poor countries seem to still be clearing forests with slash and burn techniques

without the understanding of the long term deleterious effects of clearing

the forests, and then burning the cleared materials that are lost to the atmosphere.

I suppose that assessing the productivity of the soil by the three methods,

slash and burn, grinding and terrating, and composting and tilling the soil

would be most instructive by a simple method of side by side comparison

of three plots of soil that are repeatedly processed by the same three

methods year after year.

Am I missing something about the question, or addressing far more than what was asked.