Ragweed models and Bird Island measurements - CEH paperblog 6

In our latest paperblog, we first highlight two new papers resulting from a European Commission-funded project to assess and control the spread and effects of Common ragweed in Europe. Accurate models are needed to forecast the progress and impact of alien invasive species. For Common ragweed Ambrosia artemisiifolia such forecasts are extremely important as the species is a serious crop weed and its airborne pollen is a major cause of allergy and asthma in humans.

Newly published in Global Change Biology, Dan Chapman leads the paper, "Phenology predicts the native and invasive range limits of common ragweed", collaborating with CEH colleague Prof James Bullock and researchers from the UK, Austria and South Africa. Their study shows that phenology can be a key determinant of species' range margins, and thus integrating phenology into species distribution models can offer great potential for the mechanistic modelling of range dynamics.

Dan and James are co-authors of a second paper entitled "An operational model for forecasting ragweed pollen release and dispersion in Europe", published in Agricultural and Forest Meteorology and led by the Finnish Meteorological Institute. This study produces the first European-scale simulation of ragweed pollen concentrations. The modelling illustrates the potential for a relatively localized invasive species to produce impacts on human health at a continental scale.

The remote Bird Island in the south Atlantic is home to large seabird and seal colonies, including Macaroni and Gentoo penguins, and Antarctic fur seals. Our NERC colleagues British Antarctic Survey have a research station there. A new open access paper in Atmospheric Chemistry and Physics involving the Max Planck Institute for Chemistry, CEH, BAS and Kings College looks at how Bird Island's fauna are influencing the composition and characteristics of remote marine aerosol measured on the island. Many aspects of marine aerosol systems are not yet fully understood, but a detailed understanding is essential to quantify more fully the role of marine aerosol in the functioning of the Earth system.

The study, which saw the first stationary deployment of an aerosol mass spectrometer to a field site in the sub-Antarctic, generally found the aerosol to be less acidic than in other marine environments due to the high availability of ammonia from local fauna emissions.

Finally, we highlight a paper by Professor Colin Neal who recently retired from the Centre for Ecology & Hydrology but who remains a research fellow of the organisation. Colin's invited commentary in Hydrological Processes discusses "Catchment water quality: the inconvenient but necessary truth of fractal functioning", drawing on his long-term research, particularly at the Plynlimon catchments in Wales (data freely available from the CEH Information Gateway).

Paulette Burns, Media Coordinator

Additional information

If you'd like a fuller picture of new papers from CEH, just follow the CEH Paper Alerts Twitter feed, which lists CEH peer-reviewed papers newly published online. Full details of Centre for Ecology & Hydrology science publications, including those published in peer-reviewed science journals, are eventually catalogued on the NERC Open Research Archive (NORA).

Those of you who follow the scientific literature will know some journal websites require registration and some are subscription-only. CEH, as part of NERC, is working with publishers and funders to make more of our output open access, and we have indicated above where this is the case.

We also publish lots of our other outputs including biological records atlases and project reports. More details can be found in the publications section of the CEH website.

The Plynlimon catchments - an open air laboratory

The Plynlimon catchments in central Wales are the most important intensively studied long-term research basins in the UK. Managed by the Centre for Ecology & Hydrology (CEH), Plynlimon is among the key European and world sites in terms of catchment science - not just for the length of the records gathered (40 years and counting) but crucially because of the breadth of measurements, spanning hydrology and including water chemistry, groundwater studies, geomorphology, ecology and atmospheric science.

With the study now in its fifth decade, and inspired by a new paper* by Dr Mark Robinson, working with former colleagues John Rodda and John Sutcliffe, who played key roles in establishing Plynlimon, we take a look at the history behind the establishment of one of CEH's most significant scientific experiments, a long-term environmental monitoring project which has evolved and adapted to stay relevant to current problems and scientific needs.

Landscape view over the Plynlimon catchments in central Wales (photo: Simon Grant / CEH)

In the mid-20th century, against a backdrop of population growth, rising living standards and post-war industrial recovery, there was growing concern in the UK about increased demand for water and possible future water shortages. A severe drought in summer 1959 and dry winters in 1962/3 and 1963/4 underlined the belief in government circles that a national plan for water use was needed, as it seemed likely that demand would soon outstrip available resources.

There were concerns too about other factors potentially affecting water availability, not least the government's policy of encouraging widescale tree planting on reservoir catchments. The rapid growth characteristics of the conifer and the cheapness of the land resulted in conifer plantations on many upland regions of Britain throughout the first half of the 20th century. However, there were conflicting scientific views on the hydrological impact of forests, with some catchment studies, particularly in the USA, indicating that tree cover could reduce water yield relative to short vegetation.

Research in the late 1950s by Frank Law Senior, a water engineer in north-west England, tried to find out more about the water balance of woodlands under British conditions. His conclusions were controversial: that afforestation of the Stocks reservoir catchment area was substantially reducing runoff, with the additional evaporation representing a reduction in reservoir yield of over one third. At a time of anticipated increasing domestic and industrial water demands, the debate about water versus forestry was set for the decades ahead.

British hydrology and water industry were still rather fragmented in the decade after the Second World War, but these national pressures meant that more rational management of water resources was required. The particular need to understand the role of vegetation in the hydrological cycle led to the creation by the Department of Scientific and Industrial Research (DSIR) of a Committee on Hydrological Research in 1961. This committee soon proposed the establishment of a specialist unit to be responsible for applied research into surface water hydrology, including studies of the water balance of catchment areas in relation to land use.

The new Hydrological Research Unit was set up in the following year and attached to the existing Hydraulics Research Station at Wallingford in Oxfordshire. A steering group was appointed to guide its studies, with a range of potentially competing stakeholder representatives from the Forestry Commission, Nature Conservancy, Water Research Association, Met Office and Agricultural Research Council.

The Unit was asked to conduct a hydrological study of catchments with contrasting land cover, preferably grassland and coniferous forest, since that was seen as the land use distinction most likely to reveal differences in behaviour and was the most common source of land use concern.  The catchments would need to be on watertight geology, and it was felt that the difference in water used by the two vegetation types would be most clearly apparent in relatively dry climate.

Where exactly to base the experiment was not a straightforward decision. It proved difficult to identify pairs of almost identical catchments that differed only in their vegetation and had landowner agreement for access. Plynlimon was not even on the original eight potentially suitable paired catchments identified. The climate criterion was later relaxed to include ‘wet’ sites, and the adjoining headwater catchments of the Severn and the Wye rivers draining the slopes of Pumlumon Fawr, i.e. Plynlimon, were added to the list, and later judged to be the most promising of the possible sites. The headwaters of each catchment provide a land use contrast between the two major upland land uses: moorland (Wye) and plantation forest (Severn).

In addition to the ongoing scientific debate concerning forest evaporation, the organisational framework for UK environmental research was undergoing major change as part of a wider government reorganisation. In 1965 the HRU was transferred to the newly formed Natural Environment Research Council (NERC). The Unit’s remit was then expanded to encompass all aspects of the hydrological cycle including physical and applied studies, instrumentation and mathematical modelling.

The Plynlimon study officially started on 1 January 1967, with the NERC Annual Report foreseeing it as being an “outdoor laboratory of immense value to all sciences”. The delays in establishing a field site actually afforded the opportunity to develop expertise in cutting edge instruments and new technologies. There was pioneering work (widely adopted elsewhere) on neutron probes for soil water content measurement, as well as automatic weather stations capable of operating at remote locations, and new raingauge designs for windy sites.

Cefn Brywn crump weir on the River Wye, late 1960s

In recognition of the growing importance of hydrological research in Britain, NERC designated the HRU as a full component institute: on 1 April 1968 it became the Institute of Hydrology, which later became part of the Centre for Ecology & Hydrology. The Plynlimon study played a crucial role in proving beyond doubt the potentially serious reduction in water flows resulting from afforestation, leading to major changes in the management of water and land use by resource managers and policy makers.

Work continues at the Plynlimon catchments to this day. CEH conducts long-term measurements of weather, streamflow and chemical fluxes. We use this information to look for time trends, understand the processes operating, and investigate the impacts of land use on water resources, floods, drought flows, stream sediment and dissolved chemicals and acidification. 

Other Plynlimon research highlights

·        The original aim of the Plynlimon catchment experiment was to make measurements which could resolve the uncertainties concerning the water use of conifer forests. It not only helped to answer this question but subsequently developed into a long-term multi-disciplinary project.

·        Building upon the established catchment infrastructure, hydrochemical measurements commenced and now more than almost 30 years are available, together with the longer record of hydrological data.

·        The Plynlimon catchments have been one of the more successful catchment studies, advancing science and its findings have directly altered UK forestry environmental policy and informed UK government policy.

·        The Plynlimon study provided a considerable stimulus to the development of the science of hydrology in Britain. The research findings have been reported in more than 500 papers in refereed journals, and much of the Plynlimon record has been freely available to the international research community for decades, and is also accessible via the internet from the CEH Information Gateway.

  

Summarising the importance of the Plynlimon catchments, Dr Mark Robinson told us, “We owe a great debt to the farsightedness of the stakeholders and academics who recognised the need for, and supported the establishment of, the research catchments at Plynlimon. The catchments provided an important focus in British hydrology, promoting excellence in experimental hydrology and advancing our understanding of the physical processes controlling the hydrological cycle.”

Additional information

* The full paper reference is: Robinson, M., Rodda, J.C., and Sutcliffe, J.V. (2012), Long-term environmental monitoring in the UK: origins and achievements of the Plynlimon catchment study. Transactions of the Institute of British Geographers. doi: 10.1111/j.1475-5661.2012.00534.x 

View archive photos from Plynlimon on Flickr

CEH: Why monitor upland catchments? [PDF, 4.95mb]