Significance of macroscale peat flux for carbon export in upland fluvial systems

点击翻译按钮获取中文摘要

Peatlands contain up to 30% of global terrestrial carbon. However, many of these sensitive environments are seriously threatened by changing climate and human-induced degradation. Upland peatlands form a significant part of this resource in the UK and scientists have developed carbon budget models to describe these systems. Although such models are becoming increasingly sophisticated, the export of large (c.100-1000 mm length scale) peat blocks and debris has never been included. However, peat block transport is an important component of the total organic sediment flux in upland fluvial systems and must be included in carbon budget estimates. Understanding the nature of this unique process and the potential magnitude of this flux is essential because fluvial components are the second most important component in the upland terrestrial carbon budget and carbon budget studies are now being used by upland managers to implement strategies on carbon stewardship. Our aim is to determine, for the first time, the significance of large peat block transport (> 100 mm) in the carbon budget of an upland catchment. We will test three main hypotheses: 1. The initiation of peat block transport (by flotation) is a function of block dimensions and the local hydraulics of the flowing river. Such a process has NEVER been fully documented. 2. The total peat block flux is a significant component of the total fluvial carbon flux and, in some high flow events may exceed the particulate organic flux. There is currently NO quantitative data to test this. 3. Where active in-channel peat block transport occurs, the river reaches downstream will show elevated values of particulate organic carbon due to rapid abrasion and breakdown of peat blocks. These three hypotheses will be tested at a range of scales: micro (individual peat block scale); meso (peat blocks store at the river bar scale), macro (peat block river reach sediment budget) and catchment scale. These experiments will be carried out at the Moor House and Upper Teesdale National Nature Reserve in the North Pennines. Monitoring is nested at these four scales and involves a novel, integrated system of data loggers, environmental sensors and three remote digital cameras.