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| Titel |
How land degradation affects the carbon balance and its component processes: case of study in SE Spain |
| VerfasserIn |
Ana López Ballesteros, Cecilio Oyonarte, Andrew S. Kowalski, Penelope Serrano-Ortíz, Enrique P. Sánchez-Cañete, M. Rosario Moya, Francisco Domingo |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250143802
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| Publikation (Nr.) |
 EGU/EGU2017-7556.pdf |
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| Zusammenfassung |
| The concept of land degradation stems from the loss of an ecosystem’s biological
productivity, which in turn relies on several degradation processes such as long-term loss of
natural vegetation, depletion of soil nutrients, soil compaction or water and wind erosion. In
this context, desertification means land degradation in arid, semi-arid and dry sub-humid
areas due to climatic and/or human factors. Currently, drylands occupy more than one third of
the global terrestrial surface and will probably expand under future climate change scenarios.
Drylands′ key role in the global C balance has been demonstrated, but the effects of
desertification and/or climate change on C sequestration by these ecosystems needs further
research.
In the present study, we compare net carbon exchange between two experimental sites
representing a “degraded” and “non-degraded” grazed semiarid grasslands, separated by ∼15
km in SE Spain, via eddy covariance measurements over 6 years, with high variability in
precipitation magnitude and distribution. Results show a striking difference in the annual C
balances with average emissions of 196 ± 40 and -23 ± 20 g C m−2 yr−1 for the “degraded”
and “non-degraded” sites, respectively. At the seasonal scale, differing patterns in net CO2
fluxes were detected over both growing and dry seasons. As expected, larger net C
uptake over longer periods was observed in the “non-degraded” site, however, much
greater net C release was measured in the “degraded” site over drought period. We
tested differences in all monitored meteorological, ambient and subsoil variables
and found most relevant that CO2 at 1.50 m belowground was around 1000 ppm
higher in the “degraded” site. Thus, we believe that subterranean ventilation of
this vadose zone CO2, observed at both sites, largely drives the differences in C
dynamics between them. Overall, the 12 site-years of data allow direct exploration
of the roles of climate and land degradation in the biological and non-biological
processes that ultimately control the C sequestration capacity of semiarid ecosystems. |
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