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Soil is an important component of the forest ecosystem. it is a complex and variable medium comprising mineral particles, organic matter, water, air and living organisms. the characteristics of soil largely determine the nature of the flora and fauna that sustains the world’s terrestrial biodiversity and its productive potential. it is a vital resource that must be used in a sustainable way to ensure it can continue to perform its many functions.

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About the Dyfi Catchment


The Dyfi Catchment is located in west Wales, in Gwynedd. The town of Machynlleth lies in the centre of the catchment.

Dyfi_satellite_map.pdf (PDF-390K)

Situation, relief and drainage

The Dyfi Catchment and Woodland Research Platform is situated in the Dyfi catchment, with an altitudinal range from 905 m at Aran Fawddwy in south Snowdonia to sea level at the Estuary at Aberdovey. On the eastern slopes of Aran Fawddwy is the small lake named Creiglyn Dyfi, the source of the River Dyfi. The Catchment area extends into the estuary in order to encourage research that encompasses both terrestrial and marine science, and the links between them. The Catchment drainage is dominated by the Dyfi, but there are many tributaries. The Dyfi floodplain is approximately one third km wide at the junction with the Afan Cerist 40 km upstream from Aberdovey and widens considerably as the estuary is approached. Above the floodplain, the relief is characterised by steep hills and mountains between a fluvially incised landscape.


Western Wales is amongst the sunniest and mildest parts of Britain, but the coastal regions are very exposed to westerly winds. Rainfall in the Dyfi catchment is comparatively high, from c. 1000 mm at the coast to over 2000 mm at the fringes of the catchment. The coast benefits from an early rise in spring temperatures, but summer temperatures are comparatively low. Accumulated temperate decreases with altitude and distance from the coast.

Geology and soils


The geological succession in the Dyfi Catchment spans the mid-Ordovician (Caradoc Series) to mid-Silurian (Wenlock Series) Periods. The oldest Ordovician rocks occur in the northern part of the area where the Aran Fawddwy Formation comprises 350-400 m of acid ash-flow tuffs. In the south, late Ordovician (Ashgill Series) argillaceous sedimentary rocks crop out in the core of the Machynlleth Inlier and in periclinal folds along the western margin of the Plynlimon Inlier. The Ordovician sequence is conformably overlain by Silurian sedimentary rocks dominated by a thick succession of turbiditic mudstones.

Soil types

The main soils of the Dyfi valley are podzolic soils, ground water gleys and peat soils. Podzolic soils have a peaty surface layer and humus and/or iron enriched subsoils. Ground water gleys occur along the River Dyfi and are permeable, seasonally waterlogged and affected by the groundwater table. Peat soils are classified as having more than 40 cm of organic material that has a well drained surface layer. Soils of the alluvial flats and terraces are gleyed and peaty. Saltmarsh soils, located along the estuary, are naturally wet, have a loamy texture and are lime-rich, but saline. Loamy and clayey floodplain soils and soils of the coastal flats have a natural high groundwater with moderate fertility.

Woodland and forest

Native woodland which developed over much of the area in postglacial times was greatly reduced from Neolithic times onward. Remnants of native woodland survive in the valleys and on the lower hillsides. There are 1,325 hectares of Ancient Semi Natural Woodland and 1,359 hectares of Plantations on Ancient Woodland Sites (PAWS), giving a total land cover of 3.5% for ancient woodland in the catchment.

Large areas were acquired by the Forestry Commission in the 1930s and many upland sheep walks planted with conifer species. During the 1960s to the 1980s, private conifer forests were also established. Currently 14 % of the catchment is conifer woodland.

Further information

Further information on the geography of the Dyfi catchment (PDF-572K)

Organisations collaborating on the Dyfi Catchment and Woodland Research Platform

We welcome collaboration to extend the existing research and monitoring input in the Dyfi Catchment area. Please get in touch if you would like to work with us on this multi-disciplinary research initiative.

Forest Research


The creation of the Dyfi Research Platform givesour scientists a valuable opportunity to consolidate scientific understanding and develop new knowledge in a well-characterised wooded catchment in Wales.

Through its Aberystwyth Unit, led by Tom Jenkins,, we look forward to working with scientists from other research providers and the university sector in collaborative and, increasingly, multi-disciplinary projects of direct relevance to policy makers, planners and land managers.

The Dyfi Platform supports a variety of current research programmes, including work on:

Institute of Geography and Earth Sciences (IGES), Aberystwyth University


Aberystwyth University’s Institute of Geography and Earth Sciences (IGES) has a long history of research in the Dyfi catchment (funded by the Welsh Government, CCW, Environment Agency Wales, Higher Education Funding Council for Wales (HEFCW), local authorities and industry).

This continues under existing NERC-funded research programmes (led by Professor Mark Macklin and Dr Paul Brewer) investigating tidally-influenced rivers and developing a virtual observatory as part of NERC’s Environmental Virtual Observatory research programme.

Professor Chris Thomas (IBERS) and Professor Macklin are currently leading NERC-funded research integrating ecology and hydrology in Africa, a model they intend to apply to the Dyfi area, along with further initiatives using Earth Observation technology provided by Professor Richard Lucas.

Natural ResourcesWales

Woodlands managed byNatural Resources Wales on behalf of the Welsh Government represent an important component of the project area, extending to 6000 ha out of a total area of 24000 ha in the Dyfi catchment.

Through participation in the Dyfi research platform, Natural Resources Wales will work towards evaluating the long-term influences of woodlands in the landscape and how forest operations and changing management practices affect a range of social, environmental and economic outcomes. The findings will be applicable across Wales in public and privately owned woodlands.

Much of the forest planning and subsequent operations carried out by Natural Resources Wales are the result of forest managers building on accurate and applied research. Integration with research in the Dyfi will help Forestry Commission Wales, and the wider forestry sector, to make operational choices that consider natural resources in a manner that delivers maximum benefits to people without compromising future choices and natural systems within and beyond the forest boundary.

Institute of Biological Environmental and Rural Sciences (IBERS), Aberystwyth University


Aberystwyth University’s Institute of Biological Environmental and Rural Sciences (IBERS) has a strong interest in the Dyfi area.

Recent research by Dr Mike Christie has demonstrated the economic and social values of ecosystem services delivered by habitats protected by the UK Biodiversity Action Plans and Sites of Special Scientific Interest. The Dyfi catchment provides a unique opportunity to extend this work by exploring:

  • How the mosaic of habitats within the Dyfi catchment combines to contribute to the delivery of important services; and
  • How policy might be applied at a landscape scale to maximise ecosystem service delivery and benefits.

Current research undertaken in the Dyfi Research Platform is linked to a number of national, European and global research networks. These links provide a strong science network and facilitate knowledge sharing with the wider research community, including:

Further information

Related pages

Publications catalogue

Research into soil

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