Heathland Climate Change Experiment at Clocaenog

Automated facility for field-based climate change experiments

The Heathland Climate Change Experiment at Clocaenog is used to test how drought or warming impact upland ecosystems, which can be an important source or sink for greenhouse gases. This experimental site has run for more than 25 years and provides important data on wet, carbon-rich soil for UK, EU and global networks. Above and belowground sensors allow for continuous measurements of environmental variables.

To date, research from the site contributed to 69 scientific publications of local, European, and global nature, and produced 19 datasets. The site is also part of the Ecological Continuity Trust, a UK network of long-term experiments.

The Clocaenog site with nine experimental plots

The Clocaenog site featuring a total of nine experimental plots, of which six are exposed to climate treatments and three plots remain untreated.

A warming “roof” moving over the vegetation, reflecting heat back to the vegetation and soil, and creating a treatment of artificial (indirect) warming.

A warming “roof” moving over the vegetation, reflecting heat back to the vegetation and soil, and creating a treatment of artificial warming.

Scientific importance

Uplands have traditionally been used for livestock grazing and timber production. They are also of high conservation and amenity value, and important for water resources and carbon storage. Often, uplands are vulnerable to changes in land-use and climate and require monitoring.

Our long-term climate change manipulation site is an upland heath. We study the effects of climate change within this typical upland ecosystem. Scientists can explore the links between above and below-ground diversity, and the resistance of communities to climate change. The site is also ideal for researchers investigating soil carbon dynamics, soil hydraulics and the impact of microbial communities on these processes.

Scientific objectives

Our aim is to understand the effects of climate change on ecosystem services. We are specifically interested in ecosystem carbon storage, water storage and diversity.

Objective 1: We determine how climate change alters soil carbon storage and ecosystem carbon fluxes.
Objective 2: We model how climate change influences soil hydraulic properties, and the feedbacks to the soil microbial community and carbon fluxes.
Objective 3: We investigate the response of plant and soil microbial communities to climate change.

Our questions were guided by the wet nature of the site, being seasonally water-logged at the beginning of the experiment in 1998. Thus, specific interest was paid to soil microbes, soil respiration, and soil structural adaptation. Long-term data from the UK site were also part of major global meta-analyses on climate change effects on soil respiration and soil carbon stocks.

Data of the site are openly available as part of the Clocaenog data series on the Environmental Information Data Centre (EIDC).

How it started

The experiment started in 1998 as part of a European climate gradient consisting of five, later seven, locations featuring heathland vegetation across Europe. Across all sites, climate change treatments and controls were initiated in 1999. The UK site was equipped with above and belowground sensors in 2005. Data from an on-site automated weather station and plot-level temperature and moisture data are telemetered to UKCEH servers daily. The UK site provides the wet and cold endmember of the European climate gradient on a shallow organo-mineral soil.

Across the European sites, major measurement campaigns were coordinated to answer overarching questions related to ecosystem responses to climate change. These included, but are not limited to, plant responses, soil respiration, soil microbes and soil fauna, and ecosystem responses and services.

Site treatments and characteristics

Clocaenog is an upland heathland dominated by heather (Calluna vulgaris) and has a rich moss and lichen understory. The site receives high rainfall, on average 1550 mm each year and is the wettest site of the European rainfall gradient. The drought treatment operated between May and September until 2018, reducing summer rainfall on average by 60%.

The average air temperature is about 7°C. The warming treatment increases air temperature on average by 0.2°C. Although this is a subtle increase, the number of growing degree days in the warming plots increased by over 100%.

The ecosystem holds large pools of carbon. The top 0-10 cm of the soil is organic material and is made from 100% carbon. Below the organic layer is a mineral soil layer (10-20 cm), containing up to 40% carbon. Data from the experiment have been used in several modelling exercises and cross ecosystem syntheses.

Routine measurements

Soil meaurements being taken with a tape measure — Soil depth measurements being taken at the site

The following data is collected routinely at the site, and in most cases, historic data is available for climate data, soil water quality measurements, soil gas flux measurements, soil nitrogen transformation measurements, litter decomposition, vegetation production, nutrient status and plant and microbial composition changes. Available datasets can be requested from the EIDC.

As part of the site, we can also measure the following:

Plants

Aboveground plant biomass can be measured in permanently installed quadrats (50 cm x 50 cm) using the pin-point method.
Plant greenness measurements can be carried out using spectral reflectance measurements.
Equipment to measure leaf-level photosynthesis (Licor) is available in the project.

Soil

We have the equipment to measure soil physical properties such as soil water release curves and hydraulic conductivity.
Within UKCEH, we have the facilities to measure phospholipid fatty acids and the microbial community composition.

Ecosystem

Soil respiration and ecosystem respiration can be measured in pre-installed collars in each of the climatic treatments.
Soil respiration can also be measured using automated chambers obtaining high-resolution flux measurements (Licor flux chambers).
Ecosystem respiration chambers are also available

Work with us

To discuss opportunities to collaborate with UKCEH and use our facilities at the long-term climate manipulation experiment, contact: Dr Sabine Reinsch.

Publications

Methodology
Beier, C. et al. 2004. Novel Approaches to Study Climate Change Effects on Terrestrial Ecosystems in the Field: Drought and Passive Nighttime Warming. Ecosystems. DOI: 10.1007/s10021-004-0178-8

Plants
Peñuelas, J. et al. 2004. Nonintrusive Field Experiments Show Different Plant Responses to Warming and Drought Among Sites, Seasons, and Species in a North–South European Gradient. Ecosystems. DOI: 10.1007/s10021-004-0179-7
Kröel-Dulay, G. et al. 2015. Increased sensitivity to climate change in disturbed ecosystems. Nat Commun. DOI: 10.1038/ncomms7682
Estiarte, M. et al. 2016. Few multiyear precipitation–reduction experiments find a shift in the productivity–precipitation relationship. Glob Chang Biol. DOI: 10.1111/gcb.13269

Respiration
Emmett, B. A. et al. 2004. The Response of Soil Processes to Climate Change: Results from Manipulation Studies of Shrublands Across an Environmental Gradient. Ecosystems. DOI: 10.1007/s10021-004-0220-x
Sowerby, A., Emmett, B., Tietema, A. & Beier, C. 2008. Contrasting effects of repeated summer drought on soil carbon efflux in hydric and mesic heathland soils. Glob Chang Biol. DOI: 10.1111/j.1365-2486.2008.01643.x

Soil microbes
Rousk, J., Smith, A. R. & Jones, D. L. 2013. Investigating the long-term legacy of drought and warming on the soil microbial community across five European shrubland ecosystems. Glob Chang Biol. DOI: 10.1111/gcb.12338
Toberman, H. et al. 2008. Summer drought effects upon soil and litter extracellular phenol oxidase activity and soluble carbon release in an upland Calluna heathland. Soil Biol Biochem. DOI: 10.1016/j.soilbio.2008.01.004
Seaton, F. M. et al. 2022. Long-Term Drought and Warming Alter Soil Bacterial and Fungal Communities in an Upland Heathland. Ecosystems. DOI: 10.1007/s10021-021-00715-8

Soil fauna
Holmstrup, M. et al. 2012. Increased frequency of drought reduces species richness of enchytraeid communities in both wet and dry heathland soils. Soil Biol Biochem. DOI: 10.1016/j.soilbio.2012.05.001

Ecosystem responses
Reinsch, S. et al. 2017. Shrubland primary production and soil respiration diverge along European climate gradient. Sci Rep. DOI: 10.1038/srep43952
Li, Q. et al. 2023. Higher sensitivity of gross primary productivity than ecosystem respiration to experimental drought and warming across six European shrubland ecosystems. Science of The Total Environment. DOI: 10.1016/j.scitotenv.2023.165627
Domínguez, M. T. et al. 2015. Sustained impact of drought on wet shrublands mediated by soil physical changes. Biogeochemistry. DOI: 10.1007/s10533-014-0059-y
Robinson, David. A. et al. 2016. Experimental evidence for drought induced alternative stable states of soil moisture. Sci Rep. DOI: 10.1038/srep20018

Data contributions to major meta-analyses
Crowther, T. W. et al. 2016. Quantifying global soil carbon losses in response to warming. Nature. DOI: 10.1038/nature20150
Carey, J. C. et al. 2016. Temperature response of soil respiration largely unaltered with experimental warming. Proceedings of the National Academy of Sciences. DOI: 10.1073/pnas.1605365113
Robinson, D. A. et al. 2019. Global environmental changes impact soil hydraulic functions through biophysical feedbacks. Glob Chang Biol 25. DOI: 10.1111/gcb.14626