Using hydrological connectivity to develop understanding of water, soil and carbon losses across drylands undergoing vegetation change

Geophysical Research AbstractsVol. 16, EGU2014-16477, 2014EGU General Assembly 2014© Author(s) 2014. CC Attribution 3.0 License.Using hydrological connectivity to develop understanding of water, soiland carbon losses across drylands undergoing vegetation changeAlan Puttock (1), Jennifer Dungait (2), Kit MacLeod (3), and Roland Bol (4)(1) Geography, College of Life and Environmental Sciences, University of Exeter, Exeter, Devon, EX4 4RJ, UK, (2) TheJames Hutton Institute, Craigiebuckler, Aberdeen, Scotland, AB15 8QH, UK. , (3) The James Hutton Institute, Craigiebuckler,Aberdeen, Scotland, AB15 8QH, UK. , (4) Institute of Bio- and Geosciences, Agrosphere (IBG-3), Forschungszentrum JülichGmbH, 52425 Jülich, Germany.Connectivity has emerged as a key concept for understanding the hydrological response to vegetation change indrylands, providing an explanatory link between abiotic and biotic, structure and function. Reduced vegetationcover following woody encroachment, generally promotes longer, more connected overland flow pathways, whichhas the potential to result in an accentuated rainfall-runoff response and fluxes of both soil erosion and carbon.Changing hydrological connectivity was investigated as an emergent property of changing ecosystem structureover two contrasting semi-arid grass to woody vegetation transitions in New Mexico, USA. Vegetationstructure was quantified to evaluate if it can be used to explain observed variations in water, sediment and carbonfluxes. Hydrological connectivity was quantified using a flow length metric (mean flowpath length), combiningtopographic and vegetation cover data.Results at the large plot scale (300 m2) demonstrated that the two woody-dominated sites had significantlylonger mean flowpath lengths (4.3 m), than the grass-dominated sites (2.4 m). Mean flowpath lengths illustrateda significant positive relationship with the functional response. The woody-dominated sites lost more water, soiland carbon than their grassland counterparts. Woody sites eroded more, with mean event-based sediment yieldsof 1203 g, compared to 295 g from grasslands. In addition, the woody sites lost more organic carbon, with meanevent yields of 39 g compared to 5 g from grassland sites (Puttock et al, 2013).Hydrological connectivity will be discussed as a meaningful measure of the interaction between structure andfunction and how this manifests under the extreme rainfall events that occur in drylands. Further work is requiredto assess how flow length varies across spatial scales and evolves across temporal scales. However, it is argued thatflow path length metrics provide a valuable tool by which to classify hydrological connectivity at the catchmentscale and to quantify the relationship between structure, function and resultant fluvial fluxes in dryland landscapesundergoing vegetation change.ReferencePuttock, A., Macleod, C. J.A., Bol, R., Sessford, P., Dungait, J. and Brazier, R. E. (2013), Changes in ecosystemstructure, function and hydrological connectivity control water, soil and carbon losses in semi-arid grass to woodyvegetation transitions. Earth Surf. Process. Landforms, 38: 1602–1611. doi: 10.1002/esp.345