The definition you are using for POM corresponds with what I would call the fermentation (F) layer of the forest floor. In temperate deciduous forests, this layer lies below the fresh litter on top (L) and grades into the humus (H) layer below. One can strip off the fresh litter and remove the L layer to be weighed and dried. If the L to H transition is not abrupt, one can define an arbitrary boundary (e.g., 10 cm depth) and consider anything below that to be humus. Such definitions are always an approximation, but at least they are consistent.

Outside of a deciduous forest the matter becomes more difficult because the forest floor layers may be intermixed (coniferous forest) or barely discernible (grassland). An alternative is to measure annual litterfall (litter traps) and use litter bags to measure mass loss over the period during which fresh litter becomes what you would call POM. If fresh litter loses 25% of its mass to become POM, then the total POM in an area would be total litterfall x 0.75.

I hope that helps, and (as usual) that I haven't misunderstood the question.

Dear Barry Taylor

I have 80 soil sample from 0-20 cm depth that sampling in arid and temperate rangeland in two management regime (40 sample in each climate). because of POM-N and POM-C are very sensitive to management, I want to see effect of different management regime on both POM-N and POM-C, and Is different this respond to management regime in different climate?

a method for measure of POM is in " Cambardella and Elliott. 1992" (attached), But this method is very old and we have not shaker set that can 15 hour work!!!

Now I am researching for new and simple method for measure of this soil organic matter.

tank you for your comment and your help.

Good Luck

Hello,

I don't know any method that doesn´t use the shaker. But take a look at this article, maybe it can help you.

http://www.planta.cn/forum/files_planta/soil_organic_matter_fractions_and_their_relevance_to_soil_function_380.pdf

Dear Alejandro Becerra

Hello, I hope you are good.

my means was that we have shaker set , But according " Cambaerdella and Elliot, 1992 " for measure of POM we must sake the soil sample 15 hour, and its may blemish the shaker set.

As well as, in this paper the describe measure of POM is not clear, so I need to help for find a new, simple and exactly method.

your chapter book is great help for me.very tanks

Good Luck.

Do you want to determine total POM (which consists of free POM and POM occluded into aggregates) or only free POM? We are using density fractionation (in sodium polytungstate solution) combined with ultrasonic dispersion to gain both POM fraction in seperate steps. Ultrasonic dispersion is in my opinion the prefered method for disaggregation because it is more or less the only one which allows to quantify the applied energy (compared to with sieving procedures or shaking with glass balls). If you are interestes in free POM electrostatic seperation of POM and mineral soil constituents might be interesting for you. You can find a description here:

Kaiser, M.; Ellerbrock, R. H. & Sommer, M. Separation of Coarse Organic Particles from Bulk Surface Soil Samples by Electrostatic Attraction All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Permission for printing and for reprinting the material contained herein has been obtained by the publisher.

Soil Sci. Soc. Am. J., 2009, 73, 2118-2130

It has still some drawbacks but it likely to be the easiest and cheapest method to seperate free POM from other soil constituents. If you are more interested density fractionation feel free to contact me for further details.

Hi Dear Markus

I really tank you for your help. its was great help for me.

Best regards.

Hi Dear Felix

I really tank you for your help. its good reference and was great help for me.

I Hope after this I'll use your view.

best regards