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| Titel |
Vertical δ13C and δ15N changes during pedogenesis |
| VerfasserIn |
Melanie Brunn, Sandra Spielvogel, Andrew Wells, Leo Condron, Yvonne Oelmann |
| 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 |
250107388
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| Publikation (Nr.) |
 EGU/EGU2015-7086.pdf |
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| Zusammenfassung |
| The natural abundance of soil organic matter (SOM) stable C and N isotope ratios are
subjected to vertical changes throughout the soil profile. This vertical distribution is a widely
reported phenomenon across varieties of ecosystems and constitutes important insights of soil
carbon cycling. In most ecosystems, SOM becomes enriched in heavy isotopes by several per
mill in the first few centimeters of the topsoil. The enrichment of 13C in SOM with soil depth
is attributed to biological and physical-chemical processes in soil e.g., plant physiological
impacts, microbial decomposition, sorption and transport processes. Such vertical trends
in 13C and 15N abundance have rarely been related to SOM composition during
pedogenesis. The aims of our study were to investigate short and long-term δ13C and δ15N
depth changes and their interrelations under progressing pedogenesis and ecosystem
development.
We sampled soils across the well studied fordune progradation Haast-chronosequence, a dune
ridge system under super-humid climate at the West Coast of New Zealand’s South Island
(43° 53’ S, 169° 3’ E). Soils from 11 sites with five replicates each covered a time span of
around 2870 yr of soil development (from Arenosol to Podzol). Vertical changes of δ13C and
δ15N values of SOM were investigated in the organic layers and in 1-cm depth intervals of
the upper 10 cm of the mineral soil.
With increasing soil depth SOM became enriched in δ13C by 1.9 ± SE 0.1 ‰ and in
δ15N by 6.0 ± 0.4 oËL itter δ13C values slightly decreased with increasing soil
age (r = -0.61; p = 0.00) likely due to less efficient assimilation linked to nutrient
limitations. Fractionation processes during mycorrhizal transfer appeared to affect δ15N
values in the litter. We found a strong decrease of δ15N in the early succession
stages ≈¤ 300 yr B.P. (r = -0.95; p = 0.00). Positive relations of vertical 13C and 15N
enrichment with soil age might be related to decomposition and appeared to be
affected by a change of hydrology, nutrient limitations, secondary minerals and root
impacts.
The investigation of vertical changes of soil organic matter (SOM) stable isotope
ratios provides the opportunity to detect combined processes that enhance our
understanding of terrestrial ecosystem functioning and pedogenetic processes leading to
stabilization/destabilization in soil and therefore addressing the soil’s sink/source
function. |
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