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| Titel |
Vegetation change in dryland environments: understanding changes in fluvial fluxes via changes in hydrological connectivity |
| 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 |
250063730
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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.
The 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. Functional change is characterised by 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.
Connectivity is a key concept in understanding the hydrological response to this
vegetation change, with reduced vegetation coverage in woody environments being
associated with longer and more connected overland flow pathways. This increase in
hydrological connectivity results in an accentuated rainfall-runoff response and
increased fluvial fluxes of eroded sediment and associated soil organic carbon and other
nutrients.
This project uses an ecohydrological approach, characterising ecological structure
and monitoring natural rainfall-runoff events over bounded plots with different
vegetation covering the transitions from C4 pure-grass (Bouteloua eriopoda) to C3
creosote (Larrea tridentate) shrubland and C3 piñon-juniper (Pinus edulis-Juniperus
monosperma) mixed stand woodland. Data collected quantifies 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). Structural characterisation data along with
results collected during the 2010 and 2011 monsoon seasons will be presented;
illustrating the usefulness of viewing environmental structure via the concept of
connectivity when trying to understand fluxes of water, sediment and associated
nutrients.
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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