Changes between Version 122 and Version 123 of Documentation/TrunkFunctionality4

Timestamp:

2022-10-07T17:04:02+02:00 (19 months ago)

Author:

mmcgrath

Comment:

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Documentation/TrunkFunctionality4

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+The following summarizes the soil dynamics of nitrogen in both ORC3 and TAG4.1 (r7761), in part based on https://doi.org/10.5194/gmd-12-4751-2019 and in part based on the source code.  Both nitrification (conversion of NH4+ to NO3-) and denitrification (conversion of N03- to N2) are present.  Only four species are considered: nitrate (NO3-), nitrogen oxides (NOx), nitrous oxide (N2O), and nitrogen gas (N2).  The pathways are impacted by pH, temperature, soil moisture, and soil carbon (which dictates denitrifier bacteria biomass).  N2O is produced during both processes, although it is also consumed during denitrification.  If oxygen availability is high, the  fraction of anaerobic microsites is low and nitrification is reduced; oxygen availability is limited by oxygen diffusion from the atmosphere as well as oxygen lost to respiration of soil carbon.  Oxygen does not appear to impact denitrification.
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+In TAG4.1, ammonium in the soil can be lost through leaching and adsorption onto clays, while nitrate can be lost through leaching.  Leaching is mentioned as an output of nitrogen in https://doi.org/10.5194/gmd-12-4751-2019, but not which species.  Clays are not mentioned, though both loss mechanisms are present in r7104 of ORC3.
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 === Nitrogen reserve pools ===
 Describes r6904. As for carbon, the model simulates two non-structural nitrogen pools: labile and reserve. Nitrogen uptake is stored in the labile pool, and after the growth, nitrogen in excess of the calculated target labile pool is moved to reserve nitrogen. Before r6825, nitrogen limitation during plant growth was rather common but was solely based on the labile nitrogen pool. It was rather common that the labile pool was empty but that at the same time the reserve pool was very well filled. Plant growth experienced n-stress despite having a good amount of N in the reserves. To deal with this issue, r6825 also considers the reserve nitrogen for estimating nitrogen limitation. The parameter '''use_reserve_n''' controls the functionality along with nitrogen uptake feedback which was added r6869 (See [wiki:TrunkFunctionality4#Rootnitrogenuptake Root nitrogen uptake]).