|
Title
|
|
|
|
Sensitivity of soil carbon fractions and their specific stabilization mechanisms to extreme soil warming in a subarctic grassland
|
|
|
Author
|
|
|
|
|
|
|
Abstract
|
|
|
|
| Terrestrial carbon cycle feedbacks to global warming are major uncertainties in climate models. For in-depth understanding of changes in soil organic carbon (SOC) after soil warming, long-term responses of SOC stabilization mechanisms such as aggregation, organo-mineral interactions and chemical recalcitrance need to be addressed. This study investigated the effect of 6 years of geothermal soil warming on different SOC fractions in an unmanaged grassland in Iceland. Along an extreme warming gradient of +0 to ~+40 °C, we isolated five fractions of SOC that varied conceptually in turnover rate from active to passive in the following order: particulate organic matter (POM), dissolved organic carbon (DOC), SOC in sand and stable aggregates (SA), SOC in silt and clay (SC-rSOC) and resistant SOC (rSOC). Soil warming of 0.6 °C increased bulk SOC by 22 ± 43% (010 cm soil layer) and 27 ± 54% (2030 cm), while further warming led to exponential SOC depletion of up to 79 ± 14% (010 cm) and 74 ± 8% (2030) in the most warmed plots (~+40 °C). Only the SA fraction was more sensitive than the bulk soil, with 93 ± 6% (010 cm) and 86 ± 13% (2030 cm) SOC losses and the highest relative enrichment in 13C as an indicator for the degree of decomposition (+1.6 ± 1.5 in 010 cm and +1.3 ± 0.8 in 2030 cm). The SA fraction mass also declined along the warming gradient, while the SC fraction mass increased. This was explained by deactivation of aggregate-binding mechanisms. There was no difference between the responses of SC-rSOC (slow-cycling) and rSOC (passive) to warming, and 13C enrichment in rSOC was equal to that in bulk soil. We concluded that the sensitivity of SOC to warming was not a function of age or chemical recalcitrance, but triggered by changes in biophysical stabilization mechanisms, such as aggregation. |
|
|
|
Language
|
|
|
|
English
|
|
|
Source (journal)
|
|
|
|
Global change biology. - Oxford, 1995, currens
|
|
|
Publication
|
|
|
|
Oxford
:
Blackwell
,
2017
|
|
|
ISSN
|
|
|
|
1354-1013
[print]
1365-2486
[online]
|
|
|
DOI
|
|
|
|
10.1111/GCB.13491
|
|
|
Volume/pages
|
|
|
|
23
:3
(2017)
, p. 1316-1327
|
|
|
ISI
|
|
|
|
000396829300028
|
|
|
Pubmed ID
|
|
|
|
27591579
|
|
|
Full text (Publisher's DOI)
|
|
|
|
|
|
|
Full text (open access)
|
|
|
|
|
|
|
Full text (publisher's version - intranet only)
|
|
|
|
|
|