Showing papers by "Chris Soulsby published in 2006"

The dispersal characteristics of the invasive plant Mimulus guttatus and the ecological significance of increased occurrence of high-flow events

Abstract: 1 Increased occurrence of high-flow events as a result of climate change may affect the dispersal success of an invasive plant species Mimulus guttatus and may result in range expansion. Predicted changes in climate point to a continuation of the recent observed trends in increased precipitation and high-flow events in Northern Europe. 2 The study focused on the dispersal characteristics of M. guttatus, and especially the roles of vegetative fragmentation with increasing water velocities, subsequent fragment survival, regeneration and colonization, as well as the buoyancy, survival and germination success of seeds. 3 M. guttatus was found to fragment readily under velocities typical of high flow conditions and even small fragments had high survival, regeneration and colonization capacity. 4 Large numbers of small (< 0.02 mg) seeds are produced; however, seeds have a short buoyancy period so the timing and magnitude of high-flow events is crucial in determining potential dispersal distances. Seeds germinate readily both in water and on sand with an average 33% germination within 9 days. 5 The dual strategy of dispersal by vegetative fragments and seeds, together with the opportunity of dispersing the two types of propagules during different periods of the year, facilitates local dominance by M. guttatus as well as long-distance colonization. As a result, the rate of spread of M. guttatus into inundation communities along rivers is likely to increase with more frequent high-flow events, especially if these coincide with the growing season. Thus, predicting the response of riparian invasive species to environmental change requires not only an understanding of the role of climate in plant demography but also the impact of changes in hydrology on rates of spread.

Scaling up and out in runoff process understanding: insights from nested experimental catchment studies

Abstract: Received 30 March 2006 Accepted 25 April 2006 Background International research initiatives such as Hydrology, Environment, Life and Policy (HELP) and Prediction in Ungauged Basins (PUB) have underlined the need for hydrologists to upscale process understanding gleaned in small experimental catchment studies to aid management decisions at larger spatial scales (Sivapalan et al., 2003; Bonell et al., 2006). Arguments as to why this has proved difficult are well rehearsed, and calls for experimentalists to work more closely with modellers to aid this task are widespread (e.g. McDonnell, 2003). One constraint on hydrologists meeting such challenges is that the research infrastructure required to reveal hydrological functioning at nested and larger spatial scales is lacking. Another is the risk in losing information moving from detailed process-based work to more generalized approaches at larger scales (Sidle, 2006). Here, we share experiences and insights from an upscaling initiative in the Feshie catchment in the Cairngorm Mountains of Scotland; this combines consideration of the dangers inherent in extrapolating from small-scale experimental catchments with discussion of the benefits offered through integrated use of environmental tracers and a geographical information system (GIS) to gain insight into the hydrological behaviour of larger catchments. The potential in using readily available spatial data (in conjunction with the insights from targeted field investigations) in deriving regionally based predictions of catchment function is also examined.

High‐frequency logging technologies reveal state‐dependent hyporheic process dynamics: implications for hydroecological studies

Abstract: This paper presents a novel method for assessing hyporheic water quality dynamics using advances in sensor technology. High-resolution (15 min) dissolved oxygen (DO) and hydraulic head data were combined to assess groundwater–surface water (GW–SW) interactions in the hyporheic zone. DO concentrations varied at fine temporal and spatial scales, depending on the relative contributions of GW and SW. The effect of sample frequency on observed patterns of variability was assessed with reference to studies of the ecology of salmon spawning habitat. Conventional approaches fail to capture the full range of temporal variability in hyporheic water quality and demonstrate the need to reassess the interpretations of previous studies of the hyporheic zone. © Crown Copyright 2006. Reproduced with the permission of Her Majesty's Stationery Office. Published by John Wiley & Sons, Ltd.

Water source dynamics in a glacierized alpine river basin (Taillon‐Gabiétous, French Pyrénées)

Abstract: [1] Currently, there is minimal information relating to temporal variability of water source contributions in alpine glacierized basins or the influence of glacier meltwater in a basin-wide context. This study adopts an end-member mixing approach to understand basin-scale water source dynamics in a French Pyrenean, alpine glacierized river system (Taillon-Gabietous). Major ion and Si data were collected for snow, groundwater tributaries, and four mainstream sites during the 2002/2003 melt seasons. Three conceptual water sources were identified: "quick flow" (dilute, rapidly routed meltwater), "distributed" (SO 2- 4 enriched, slow routed subglacial waters), and "groundwater" (Si-enriched groundwater). Water source contributions at nested spatial and temporal scales were determined using end-member mixing and uncertainty analysis. Changes in stream hydrochemistry indicated marked meltwater-groundwater mixing. Quick flow contributions typically decreased over the melt season; groundwater contributions were highest at the beginning of the melt seasons following recharge by snowmelt but also later in the 2002 melt season following prolonged precipitation. Overall, the results suggest an alternative alpine basin melt season hydrological progression compared with previous models (i.e., simple snowmelt to glacier melt to groundwater domination) and emphasize the need to understand water source dynamics to inform related water resource availability, water quality, and stream ecology studies within alpine basins.

Discharge and hydraulic interactions in contrasting channel morphologies and their influence on site utilization by spawning Atlantic salmon (Salmo salar)

Abstract: Six study sites were selected to represent the range of channel morphologies, extending from dynamic pool–riffle to transitional step–pool/plane bed reach types, used by spawning Atlantic salmon (S...

Using factor analysis and end-member mixing techniques to infer sources of runoff generation

Abstract: Factor analysis and (two-component) end member mixing analysis (EMMA) were applied to high resolution stream chemistry data from three catchments to infer sources of iron- and manganese-rich runoff in the catchment area and to evaluate their temporal and spatial influence on the stream water quality. Two Fe and Mn sources were identified: (a) an organic soilwater source, associated with Fe and Mn accumulation in the organic-rich upper soil horizons and (b) a deep soilwater/groundwater source arising from reduced metal mobilisation in the deeper soils. While (a) provides the dominant Fe and Mn inputs during storm events, (b) becomes important just before peak flow when riparian groundwater is displaced into the stream, giving rise to high Fe and Mn concentrations. The timing of such high Fe and Mn loadings in the stream runoff has important implications for the water supply management of the catchment.