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Global change impacts on organic matter dynamics in stream ecosystems

Pye, Marian C. 2017. Global change impacts on organic matter dynamics in stream ecosystems. PhD Thesis, Cardiff University.
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1. With freshwater ecosystems worldwide at significant risk from global change, there is an urgent need to understand the processes involved and to develop adaptive responses. Riparian management might offer a means of increasing resilience to global change in headwaters, but evidence is scarce. This thesis investigates the potential effects of riparian management on the storage, processing and downstream export of resource subsidies – dominantly as terrestrial litter – that enter streams from the riparian zone. 2. In a large scale field study over four years, natural and experimental systems were used to test the hypothesis that riparian woodlands enhance stream ecosystem resilience to climatically mediated changes in flow regimes. Specific work included assessments of benthic organic matter stocks and export in contrasting catchments (broadleaf woodland, conifer plantations or sheep-grazed moorland), flow manipulations in mesocosms, and a large-scale field experiment simulating riparian broadleaved tree planting. 3. Standing stocks of particulate organic matter (POM) were influenced by flow regime, and declined following larger and longer flow-events, but event frequency had no apparent impact. Experimental data showed also that coarse fractions of POM in transport were significantly elevated in the early stages of simulated floods. 4. Despite flow effects on POM dynamics, streams bordered by broadleaves maintained consistently higher standing stocks of POM than conifer or moorland streams. Broadleaved streams also transported the highest concentrations of carbon in the form of high-quality FPOM. Leaf litter additions of stream channels did not reproduce these effects, possibly because the scale was insufficient to mimic real riparian woodlands. 5. While predicted flow changes under a warmer climate might affect the storage and flux of organic matter, riparian broadleaves are likely to mitigate these effects in stream ecosystems. This project illustrates the value of blending catchment-scale studies with field-based mesocosms to understanding complex global change processes.

Item Type: Thesis (PhD)
Status: Unpublished
Schools: Biosciences
Subjects: Q Science > QH Natural history > QH301 Biology
Uncontrolled Keywords: climate change; land use; riparian; streams; rivers; catchment; organic matter; detritus; ecosystem services
Funders: NERC
Date of First Compliant Deposit: 9 March 2017
Date of Acceptance: 9 March 2017
Last Modified: 12 Jun 2019 02:50

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