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| Titel |
Developing an Understanding of Vegetation Change and Fluvial Carbon Fluxes in Semi-Arid Environments |
| VerfasserIn |
A. Puttock, R. E. Brazier, J. A. J. Dungait, R. Bol, C. J. A. Macleod |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250058599
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| Zusammenfassung |
| Dryland environments are estimated to cover around 40% of the global land surface (Okin et
al, 2009) and are home to approximately 2.5 billion people (Reynolds et al. 2007). Many of
these areas have recently experienced extensive land degradation. One such area and the
focus of this project is the semi-arid US Southwest, where degradation over the
past 150 years has been characterised by the invasion of woody vegetation into
grasslands.
Transition from grass to woody vegetation results in a change in ecosystem structure and
function (Turnbull et al, 2008). Structural change is typically characterised by an increased
heterogeneity of soil and vegetation resources, associated with reduced vegetation coverage
and an increased vulnerability to soil erosion and the potential loss of key nutrients
to adjacent fluvial systems. Such loss of resources may impact heavily upon the
amount of carbon that is sequestered by these environments and the amount of carbon
that is lost as the land becomes more degraded. Therefore, understanding these
vegetation transitions is significant for sustainable land use and global biogeochemical
cycling.
This project uses an ecohydrological approach, monitoring natural rainfall-runoff events
over six bounded plots with different vegetation coverage. The experiment takes
advantage of a natural abundance stable 13C isotope shift from C3 piñon-juniper (Pinus
edulis-Juniperus monosperma) mixed stand through a C4 pure-grass (Bouteloua
eriopoda) to C3 shrub (Larrea tridentata). Data collected quantify fluvial fluxes of
sediment and associated soil organic matter and carbon that is lost from across the
grass-to-shrub and grass-to-woodland transition (where change in space is taken to
indicate a similar change through time). Results collected during the 2010 and 2011
monsoon seasons will be presented, illustrating that soil and carbon losses are greater
as the ecosystem becomes more dominated by woody plants. Additionally this
project utilises novel biogeochemical techniques, using stable 13C isotope and lipid
biomarker analyses, to trace and partition fluvial soil organic matter and carbon
fluxes during these events. Results show that biomarkers specific to individual plant
species can be used to define the provenance of carbon, quantifying whether more
piñon or juniper derived carbon is mobilised from the upland plots, or whether more
Larrea tridentata carbon is lost when compared to Bouteloa eripoda losses in the
lowlands.
The combined approach of monitoring carbon fluxes and tracing types of carbon shows
great promise for improved understanding of carbon dynamics in areas subject to rapid
vegetation change.
References
Okin, G. S., A. J. Parsons, J. Wainwright, J. E. Herrick, B. Bestelmeyer, T., D. C. Peters,
and E. L. Fredrickson. 2009. Do Changes in Connectivity Explain Desertification?
Bioscience 59:237-244.
Reynolds JF, et al. 2007. Global desertification: Building a science for dryland
development. Science 316: 847–851.
Turnbull, L., J. Wainwright, and R. E. Brazier. 2008. A conceptual framework for
understanding semi-arid land degradation: ecohydrological interactions across multiple-space
and time scales. Ecohydrology 1:23-34. |
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