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| Titel |
Sugars in soil: Review of sources, contents, fate and functions |
| VerfasserIn |
Anna Gunina, Yakov Kuzyakov |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250102033
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| Publikation (Nr.) |
 EGU/EGU2015-1311.pdf |
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| Zusammenfassung |
| Sugars are the most abundant organic compounds in the biosphere because they are
monomers of all polysaccharides. We summarized the results of the last 40 years on sources,
content and fate of sugars in soil and discussed their main functions in soil. We especially
focused on uptake and utilization of sugars by microorganisms as this is by far the
dominating process of sugars transformation in soil.
Two databases have been created and analyzed. The 1st database was focused on the
contents of cellulose, non-cellulose, hot water and cold water extractable sugars in soils
(348 data from 32 studies). This database was also used to determine the primary
(plant derived) and secondary (microbially and soil organic matter (SOM) derived)
sources of carbohydrates in soil. The galactose+mannose/arabinose+xylose (GM/AX)
ratio was calculated to analyze the origin of sugars in soil. The 2nd database was
focused on the fate of sugar C in soil (734 data pairs from 32 studies), and only the
papers used 13C or 14C labelled sugars were included. All data to the fate were
analyzed and presented in dynamics. This allowed to calculate: 1) maximal rate of
glucose-C decomposition, 2) mean residence time (MRT) of C of the initially applied
sugars, 3) MRT of glucose-C incorporated into microbial biomass (MB) and SOM
pools.
Content of hexoses was 3-4 times higher than that of pentoses for both cellulose and
non-cellulose sugars, because hexoses have two sources in soil: plants and microorganisms.
The GM/AX ratio revealed higher contribution of hexoses in forest (ratio was 1.5) than in
cropland and grassland soils (ratio was 0.7-1), reflecting high input of hexoses with forest
litter.
The MRT of sugars in soil solution was much less than 30 minutes. Based on the
experiments with 13C or 14C labelled glucose, the maximal rate of glucose C decomposition
in microbial biomass was ≈ 1min-1. Considering this rate, the glucose input
from plants and content of sugar C in soil, we estimated that only about 20soil originate from
the primary source – decomposition of plant biomass and root exudation. The remaining
80from microbial recycling.
Estimated MRT of sugar C in MB was about 230 days, showing intense and
efficient recycling of sugars in microorganisms. In contrast, MRT of sugar C in
SOM was about 360 days, reflecting essential accumulation of sugar C in dead
MB.
Thus, very fast uptake of sugars by microorganisms as well as intensive microbial
recycling clearly shows the importance of sugars for microbes in soil. Based on the assessed
MRT we conclude that real contribution of sugar C (not only whole sugar molecules,
which are usually determined) in SOM is much higher than commonly measured
10-15 |
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