Spatiotemporal ecohydrological patterns and processes in temperate uplands: linking field observations and model results
Abstract
There are obvious surface expressions - in terms of vegetation patterning - of ecohydrological feedbacks on dryland and peatland hillslopes. Much less is known about subsurface ecohydrological patterns, and whether or not they 'map onto' surface patterns. Likewise, few attempts have been made to investigate how such ecohydrological patterns affect whole-hillslope hydrological behaviour or how widespread they are in non-dryland and non-peatland hillslopes. In this study we investigate surface and near- surface patterning in temperate hillslopes, which to date have been the focus of much hydrological work but little ecohydrological work. In particular, we consider the extent to which the direct and the indirect effects of past and present plant assemblages on local and whole-hillslope soil moisture conditions may contribute to patterning. We have conducted a field study of two temperate upland hillslopes in Northern Scotland, UK, on one of which human intervention plays a major part in shaping the landscape. Repeat measurements have been made of near- surface soil-moisture content, taken at lag distances of 0.25 m to 20 m, under different antecedent hydrological conditions together with characterisation of plant assemblages at the same points through both ground-based vegetation surveys of 1 m × 1 m plots and kite aerial photography (KAP) of > 20 m2 plots. Results from this have indicated that changes in ecohydrological patterns can occur over small spatial scales (< 1 m2) and short time scales (< 1 day). Comparison of values of near-surface soil moisture content with topographic wetness indices, calculated using 1 -m resolution topographic data collected in the field, has highlighted that topography does not explain all of the spatial variation in soil moisture content at this scale. KAP images allowed detection of vegetation patterns not obvious from the ground. Comparison of KAP images and historic aerial photographs has highlighted the persistence of vegetation patterns over time at both sites, and that the current structure of the landscape is clearly related to current and past vegetation management practices. Evidence of sustained patterning under relatively steady environmental conditions has prompted us to consider how internal system dynamics such as competition and facilitation between different plant assemblages, and persistence of ecological memory at a range of timescales may lead to a range of ecohydrological behaviours at the scale of whole hillslopes. To help conceptualize ways in which patterning may arise, we have built a two-dimensional cellular automata-type model in which local interactions between biotic and abiotic components have the potential to lead to emergence of larger-scale patterns within the model landscape. Results from the field study have been used to gauge how well temperate hillslope ecohydrological dynamics are represented in our model, and to check that local neighbourhood patterns in the model outputs resemble real-world patterning. Key words: temperate upland ecohydrology, plant assemblage dynamics, ecological memory, kite aerial photography, cellular automata.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2011
- Bibcode:
- 2011AGUFM.H14D..07D
- Keywords:
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- 0515 COMPUTATIONAL GEOPHYSICS / Cellular automata;
- 1813 HYDROLOGY / Eco-hydrology