Dynamic Connectivity in the Landscape
Chair: Adam Ward (Indiana University)
Connectivity between different locations on the landscape is defined by the movement of water, solutes, energy, and organisms. The magnitude and persistence of connections is critical to prediction of ecological functions, many of which are mediated by hydrological stores and fluxes. In this session we consider connectivity as a spatially and temporally variable process in catchments and river systems.

"Ecohydrological connectivity between landscapes and riverscapes"
Speaker: Doerthe Tetzlaff (University of Aberdeen)

It is increasingly recognised that the processes and connections in our landscapes are influencing the functioning of aquatic ecosystems. Fundamental scientific understanding of the functioning of both aquatic and terrestrial ecosystems is required for an integrated and sustainable management of landscapes and riverscapes to maintain their ecosystem services and biological integrity at multiple scales. This talk will show how the connectivity in ecohydrological systems can be quantitatively assessed through a number of novel, integrated approaches. Importantly, this talk will discuss the need to understand the role of vegetation in regulating the connectivity between terrestrial and aquatic ecosystems. Environmental tracers are valuable tools to understand the functioning of ecohydrological systems at the landscape scale in terms of understand flow paths, sources of water and associated biogeochemical interactions. Extensive empirical studies were conducted at the plot and hillslope scale to understand ecohydrological systems, and in particular, soil-vegetation-water connections. This empirically based understanding was then integrated into spatially distributed, tracer-aided models to understand mixing of water, flows to the stream and water age distribution at the catchment scale. We use the physically-based, distributed tracer-aided ecohydrologic model (EcH2O-ISO) which we have extended to track 2H and 18O (including fractionation processes) and water age. EcH2O-ISO combines a hydrologic scheme with an explicit representation of plant growth and phenology while resolving the energy balance across the soil-vegetation-atmosphere continuum. We also implemented isotope routing, mixing and fractionation (and used flux tracking for mean water age calculation). This tracer-aided modelling allows us to simulate stream and soil isotope responses very well and at some sites can account for the composition of xylem water. Our simulations showed contrasting time-variant age distributions of water exiting catchments as evapotranspiration and stream flow; these differences are strongly influenced by vegetation cover and other landscape controls (topography, soils, geology).