How will increased levels of CO2 affect forest ecosystems?
Birmingham Institute of Forest Research launches carbon enrichment facility to find out
April 19th 2017
Scientists at Birmingham University’s Institute of Forest Research are carrying out a ground-breaking research project that will investigate the impact of climate change on our woodlands. The project will help us to understand how our forests and woodlands will respond to future increases in atmospheric carbon dioxide, including the effects on tree growth and their resilience to agricultural pests and diseases.
The Birmingham Institute of Forest Research (BIFoR) was established some years ago thanks to a £15m. donation from a former professor, and the Institute is supported by the Forestry Commission, Natural England, the Woodland Trust, and a number of other organisations.  The project is being carried out in woodlands in Staffordshire and involves “treating 30-metre plots of semi-natural oak woodland to the concentrations of carbon dioxide expected to prevail in 2050. Autonomous sensors and instrumented trees will allow scientists to take measurements continuously and remotely, over timescales ranging from seconds to decades, and to follow the carbon as it is taken up by the plants and moved through the woodland ecosystem.” 
The Free-Air Carbon Dioxide Enrichment Facility (FACE)
The apparatus for the field experiment is called a Free-Air Carbon Dioxide Enrichment (FACE) facility and the experiment, the first of its kind in Europe, is one of four similar research projects in other countries with different climates.  When combined, BIFoR says this will form the largest machine ever built to study how landscapes will respond to our changing climate. Planning permission for constructing the facility was awarded by Staffordshire County Council in December 2014. Work has been progressing since late spring 2015 on protecting the ecology of the woodland, building the apparatus, and spending a year taking vital baseline measurements before subjecting three of six plots in the woodland to elevated levels of CO2, which started a couple of weeks ago.
BIFoR says that the basic element of the FACE facility is a cylindrical ring structure, supporting pipes that deliver CO2 in such a way that the woodland inside the ring is immersed in elevated CO2 while the rest of the woodland remains largely unaffected. Winds disperse the CO2 continuously so it must be replenished using substantial gas-handling facilities; otherwise, the CO2 would be vented directly to the atmosphere. Six completely open cylindrical rings, 30m wide and as high as the tree canopy, are served by these gas-handling facilities, which store 100 tonnes of liquid CO2 and vaporise and deliver up to 15 tonnes of CO2 per day to 3 of the 6 rings via 25m masts. 
The scientists say that a FACE experiment requires bespoke control engineering which responds rapidly to changes in wind speed and direction “so that CO2 is introduced into the ring always on the upwind side and in just sufficient quantity to maintain the target concentration. A successful experiment will expect to provide CO2 within 10% of the target concentration at least 98% of the time when operating for the entire duration of the CO2 application. In order to detect a signal, and to eliminate effects of the FACE installation itself, control rings must be built in which ambient air is used instead of CO2-enriched air.”
BIFoR describes forest FACE experiments as “big science” and liken the BIFoR programme to a terrestrial ecology version of a space programme, large physics experiments, or advanced manufacturing centres in terms of the requirements for sustained and stringent quality assurance and quality control: “Only in this way, can we ‘follow the carbon’ to establish the true contribution of mature forests to the removal of CO2 from the air.”
The experiment will continue to 2026 at least, and the scientists will be measuring a number of aspects over the next decade, including tree growth and interactions with surrounding ecosystems such as leaf litter, soil and insects. BIFoR’s Director, Professor of Atmospheric Science Rob MacKenzie, said the findings will provide evidence on which to base strategies for the protection of iconic landscape features, such as oak woodlands, into the future.
“The entire experiment depends on changing the woodland as little as possible”
There have been a number of experiments across the globe using FACE facilities, including a project in Australia called AGFACE (the Australian Grains Free Air CO2 Enrichment facility), which “enables the exposure of field-grown crops to elevated CO2 levels under dry-land field conditions.”  However, BIFoR chose the woodland at Mill Haft because similar experiments in woodlands have only been carried out on young trees in plantations, whereas Mill Haft Wood is an unmanaged woodland of mature trees. In a paper delivered to the 2016 General Assembly of the European Geosciences Union, the scientists describe the woodland as a “mature oak and hazel coppice-with-standards woodland,” with the oaks estimated to be 150 years old.  Reporting on this month’s launch of the experiment, the BBC’s environment correspondent Roger Harrabin says the woodland is part of the former hunting ground of the Earl of Lichfield: “It covers 25 hectares and is thought to have been under continuous tree cover for more than than 300 years.” 
In the planning and design stage of the experiment, a major challenge for the scientists was how to build the facility without damaging the delicate natural ecosystem as “the entire experiment depends on changing the woodland as little as possible.” No concrete foundations were used and major elements of the infrastructure were put in place by helicopter. The scientists “nestled all of the experimental equipment into the woodland by hand” while the ancillary buildings were designed to blend in with the woodland. The lighting is low-level and non-intrusive to minimise interference with wildlife and to ensure that the facility sits unobtrusively in its location. The whole site is surrounded by a 3m fence.
On the amount of CO2 that will be used in the course of the experiment, BIFoR says: “Our monthly usage is equivalent to one return transatlantic flight so, although not carbon neutral, our experiment is not as profligate as it sounds and is of course directed at understanding the implications of climate change on our fragile ecosystem.”
Looking after our forests: The need for research
Trees soak up carbon dioxide in the atmosphere via the process known as photosynthesis, releasing oxygen and storing carbon. As humans need oxygen, our relationship with trees is a mutually beneficial one in which trees are fed by CO2 which would otherwise remain in the atmosphere and contribute to global warming, while we are fed by the oxygen. However, estimates of how much of the carbon produced by burning fossil fuels is currently stored by trees varies from 25% to 60%. 
As CO2 acts as a plant fertiliser, scientists believe that trees will be able to absorb more CO2 as levels increase, storing carbon in their trunks, roots and organic matter in the soil. On the other hand, however, they also believe that the ability to absorb increased levels of CO2 will be mitigated over time by factors such as rising temperatures, a lack of water and a lack of nutrients, which will counterbalance the fertilizing effect. The question is, how long will trees continue to absorb CO2 as levels increase before these mitigating effects come into play? How will our woodlands respond to future increases in atmospheric CO2, and what will the impact be on tree growth and a plant’s resilience to pests and diseases? 
Those are the questions that BIFoR’s research is aiming to answer. Talking to BBC News, BIFoR’s Director Rob MacKenzie said: “The impact of changing CO2 should show up in the leaf chemistry of exposed trees within days, and in the soil within weeks. Within three years stem growth, canopy structure, and a host of other structural forest elements should be different in the patches exposed to elevated CO2. Continuing out to 2026, the ‘push’ provided by the elevated CO2 will pass through all the checks and balances of a mature forest ecosystem, allowing, as each year passes, increasingly better estimates to be made of the extent and capacity of the land carbon sink in 2050 and beyond.” The experiment may also reveal other intriguing effects, he said. For instance, trees in a mature forest, in which the intake and the release of CO2 are in balance, might adapt to high CO2 levels by reducing their pores, which in turn would make them more tolerant to drought.
In the UK, our woodlands face a whole raft of problems specific to the region, such as inadequacies in forestry management and a variety of tree diseases, all of which provide further reasons why this research is vital, as BIFoR explains: 
“Forests are critical components of global carbon, nutrient and water cycles, influencing the thermal balance of the planet directly and indirectly, and are home to more than half of all known species. As human populations have expanded, increasing pressures have been placed on forests, with the 20th century witnessing the steepest rise in rates of deforestation. The UK has the lowest woodland cover of any large European country, and what remains is under serious threat from climate change and imported tree diseases such as ash dieback, responsible for the loss of 60-90% of ash trees in Denmark and now identified at 600 sites in the UK. Our forest industries struggle to compete effectively with imports, which now constitute 70-80% of our timber use, and our level of skills in forest management is on the decline just when a leap to sustainable stewardship of our landscape is urgently required. FACE experiments study to what extent these environmental benefits will persist into the future.”
 In an article for BBC News, Roger Harrabin said the experimental site in Staffordshire has been funded by a Birmingham alumnus and philanthropist, Professor Joe Bradwell, who made money selling diagnostic medical kits developed at the university, mainly in the USA. BIFoR’s Director Rob Mackenzie said Professor Bradwell calculated that to offset his carbon footprint he needed to plant 300,000 trees, and the research project was part of his commitment. See “Sci-fi forest tracks carbon impact,” BBC News, April 3rd 2017, at http://www.bbc.co.uk/news/science-environment-39472425.
 “Unique forest experiment given the green light,” Birmingham University news, 18th December 2014, at http://www.birmingham.ac.uk/news/latest/2014/12/Unique-forest-experiment-given-the-green-light.aspx.
 One such research project is focused on an old-growth forest in the Amazon basin near Manaus, Brazil. See “Amazon FACE” at https://amazonface.org/about/.
 “The Birmingham Institute of Forest Research (BIFoR),” Birmingham University website at http://www.birmingham.ac.uk/university/building/bifor.aspx and “The BIFoR Vision,” Birmingham University website at http://www.birmingham.ac.uk/research/activity/bifor/about/bifor-vision.aspx#visionimpact.
 “AGFACE (Australian Grains Free Air CO2 Enrichment),” Primary Industries Climate Challenges Centre. The researchers say: “To successfully adapt crop production practices and agro-ecosystem management in the face of increasing CO2, plant production must be studied in a range of environments under field conditions… The FACE (Free Air CO2 Enrichment) technique is used internationally at more than 30 sites, investigating a multitude of ecosystems including cropping systems, pastures, and forests.” See http://www.piccc.org.au/research/project/252.
 The abstract is available as a PDF from the Copernicus website at http://meetingorganizer.copernicus.org/EGU2016/EGU2016-4919.pdf.
 See .
 “Forests and Climate Change,” Food and Agriculture Organization (FAO) of the United Nations, at http://www.fao.org/docrep/005/ac836e/AC836E03.htm. The FAO says: “The increase of CO2 in the atmosphere has a ‘fertilizing effect’ on photosynthesis and thus plant growth. There are varying estimates of this effect: + 33%, + 25%, and + 60% for trees, and + 14% for pastures and crops.” The figures are taken from Climate Change 2001 – IPCC Third Assessment, published by the IPCC (Intergovernmental Panel on Climate Change).
 See our article “Conifers and Climate Change” for news of research on the impact of climate change on conifers. Two research projects have produced results that appear to be contradictory.
 “About BIFoR,” Birmingham University website at http://www.birmingham.ac.uk/research/activity/bifor/about/index.aspx.
Photograph: The view towards Mill Haft Wood from the tunnel underneath the Shropshire Union Canal, near Norbury Junction, Staffordshire © Copyright Roger Kidd and licensed for reuse under this Creative Commons Licence. The caption to the photograph says the mile-long embankment supporting the Shropshire Union Canal here was the cause of years of delay to its final opening in 1835: “its height here is about 14m and the distance through the tunnel is about 60m.” Scientists from the Birmingham Institute of Forest Research have created a “living laboratory” at Mill Haft Wood to investigate the impact of increased levels of CO2 on our woodlands.