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Stream temperature under contrasting riparian forest cover: Understanding thermal dynamics and heat exchange processes

Dugdale, Stephen J.; Malcolm, Iain A.; Kantola, Kaisa; Hannah, David M.

Authors

Iain A. Malcolm

Kaisa Kantola

David M. Hannah



Abstract

Climate change is likely to increase summer temperatures in many river environments, raising concerns that this will reduce their thermal suitability for a range of freshwater fish species. As a result, river managers have pursued riparian tree planting due to its ability to moderate stream temperatures by providing shading. However, little is known about the relative ability of different riparian forest types to moderate stream temperatures. Further research is therefore necessary to inform best-practise riparian tree planting strategies. This article contrasts stream temperature and energy fluxes under three riparian vegetation types common to Europe: open grassland terrain (OS), semi-natural deciduous woodland (SNS), and commercial conifer plantation (CS). Data was recorded over the course of a year by weather stations installed in each of the vegetation types. Mean daily stream temperature was generally warmest at OS and coolest at CS. Energy gains at all sites were dominated by shortwave radiation, whereas losses where principally due to longwave and latent heat flux. The magnitude of shortwave radiation received at the water surface was strongly dependent upon vegetation type, with OS and SNS woodland sites receiving approximately 6 × and 4 × (respectively) the incoming solar radiation of CS. Although CS lost less energy through longwave or latent fluxes than the other sites, net surface heat flux was ordered OS > SNS > CS, mirroring the stream temperature results. These findings demonstrate that energy fluxes at the air-water interface vary substantially between different riparian forest types and that stream temperature response to bankside vegetation depends upon the type of vegetation present. These results present new insights into the conditions under which riparian vegetation shading is optimal for the reduction of surface heat fluxes and have important implications for the development of ‘best-practice’ tree planting strategies to moderate summer temperature extremes in rivers.

Citation

Dugdale, S. J., Malcolm, I. A., Kantola, K., & Hannah, D. M. (2018). Stream temperature under contrasting riparian forest cover: Understanding thermal dynamics and heat exchange processes. Science of the Total Environment, 610-611, 1375-1389. https://doi.org/10.1016/j.scitotenv.2017.08.198

Journal Article Type Article
Acceptance Date Aug 18, 2017
Online Publication Date Aug 30, 2017
Publication Date Jan 1, 2018
Deposit Date Nov 23, 2018
Publicly Available Date Nov 29, 2018
Journal Science of the Total Environment
Print ISSN 0048-9697
Electronic ISSN 1879-1026
Publisher Elsevier
Peer Reviewed Peer Reviewed
Volume 610-611
Pages 1375-1389
DOI https://doi.org/10.1016/j.scitotenv.2017.08.198
Public URL https://nottingham-repository.worktribe.com/output/1302534
Publisher URL https://www.sciencedirect.com/science/article/pii/S0048969717321952?via%3Dihub

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