Holocene Climate dynamic with appropriate modifications of vegetation leaves the certain marks in soil. Is it possible in this case to distinguish their own natural dynamics of macroelements?
After processing the soil samples (air drying, followed by grinding), soil may be extracted with 2M KCl, 0.5 M K2SO4 or 0.01 M CaCl2. After extractation, the filterate can be analyzed for the ammonium, nitrite and nitrate-N fractions. These fractions are considered as the readily available pool of N.
Potentially available mineralizable N can be determined that correlates best with crop uptake. Read article of D. S. Jenkinson (1968)
http://onlinelibrary.wiley.com/doi/10.1002/jsfa.2740190310/abstract
The other fractions of N are bound and are available slowly on mineralization. Bulk of this N is in the organic form. This is the form that is closely linked to the soil C. So you may need to look at this fractionsince you are interested in the N linked to C.
Some references that would help you are given below:
Batjes (1996) Total carbon and nitrogen in the soils of the world. European Journal of Soil Science, June 1996, 47, 15 1 - 163 .
Read this Book which has separate chapters on inorganic-N, total N and also the organic N analytical methods. It gives a detailed list of analytical options to choose from.
Page (1982) Methods of soil analysis. Part 2. Chemical and microbiological properties. ASA, Wisconsin.
Total N can be determined by the kjeldahl method. Difference of the total N and the mineralizable N would give you the organic N. This is a rather crude estimate, assuming that all other fractions are organically bound and not readily available to the plant.
The Kjeldahl procedure is based on acid digestion followed by steam distillation of ammonia formed after addition of alkali (Bremner, 1965).
Dr.Blaise, good comments .Small correction. Organic N is equivalent to totaN-mineral N,not mineralizable N.Mineralizable N includes mineral N and easily oxidizable organicN.Along with nitrate, nitrite and ammonium N,one can estimate the fixed N as component of mineral N.
The comments deal effectively with measuring ammonium, nitrate and 'total' organic-N, but I'm not sure if they answer your question about 'signatures' of the Holocene climate. Were you seeking information about isotopic differences? (Not my field.)
As a form of indigenous knowledge one might look at the types of "weeds" that are growing in the soil (or not growing) as an indicator of the lack of or abundance of Nitrogen in the soil. The plants will tell us a lot if we only take the time to listen to them. This is not chemical analysis of course, but indigenous peoples have used non-chemical methods successfully in the past and still do so. For instance, where I live, I have seen that certain plants do not grow well together, and others do. Hardwood trees do not like acidic soils and will not take root under pine trees or where ash has been placed on the ground. Bloodroot grows near beech and poplar trees. Sassafras trees grow near pine. Nitrogen fixing "weeds" such as clover tend to grow in abundance where the soil is disturbed and needs more nitrogen. Plants with a taproot grow where the soil is compacted, such as in clay soils, and needs to be broken to allow better aeration for other plants. If you are looking for low-tech but high-results soil solutions, the indigenous knowledge is often very reliable, depending on the wisdom of the people in question, and their tendency to be close to and sensitive to the needs of the land. After using these indicators, then other analysis can be used to back up the assumption if needed. One might look at the variety of plants that grew at a given time to determine soil acidity.
Nice explanation, Karolina! I just read part of the article on Beech and Spruce forests in Norway and found the article to be fascinating, truly founding some of my non-chemical observations. This is just the kind of information that would help conservationists in my own country to be able to manage forests more effectively. I would like to share your article if I may.
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