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Scientific importance

Uplands have traditionally been exploited for livestock grazing and timber production. Uplands 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 need 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 link 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.

We are currently developing the streaming of real-time soil moisture from the climate change manipulation plots. Soil moisture is the amount of water in the soil. It provides the biological moisture pool for plants and soil organisms. Our climate change manipulations change the soil moisture.

Climate change experiments at the Clocaenog field site

Experimental plots at Clocaenog. Photo: Rachel Harvey

About the site

The Clocaenog monitoring site is one of the longest running climate change experiments in the UK. Research at the site has resulted in more than 60 publications to date. Our site is part of a European climate change manipulation network (INCREASE).

Sites in the network span a European rainfall (West to East) and temperature (North to South) gradient. Automated retractable curtains exclude rainfall from plots to impose extended summer droughts. A similar set of curtains cover the vegetation during night-time resulting in artificial warming.

The network offers unique facilities for scientists to study effects of climate change on shrublands.

Clocaenog is an upland heathland dominated by heather (Calluna vulgaris), and has a rich moss and lichen understory. The site has very high rainfall, on average 1550 mm each year. The average air temperature is about 7°C. The Clocaenog site is the wettest site of the European rainfall gradient.

The ecosystem holds large pools of carbon. The top 0-10 cm of the soil are organic material and are made out of 100 % carbon. Below the organic layer is a mineral soil layer (10-20 cm), containing ~ 40 % carbon.

Data from the experiment have been used in several modelling exercises and cross ecosystem syntheses.

See below: Soil layers at the Clocaenog field site; Map showing European climate change manipulation network.

Measuring soil layers
Map showing European climate change manipulation network

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 test 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.

Facilities and equipment

Climate change manipulations at Clocaenog comprise three untreated control plots, three drought and three warming plots. The warming treatment increases air temperature by ~0.2 °C. Although this is a subtle increase, the number of growing degree days in the warming plots is increased by 111 %. The drought treatment operates May-September, reducing summer rainfall by about 60 %.

Plants: Aboveground plant biomass can be measured in permanently installed quadrats (50 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 CEH, 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 plots 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 but cannot be used at the site due to shrub height.

See below: A curtain (roof) which covers the plot during rain. Photo: Rachel Harvey; Heather - the dominant plant species at the Clocaenog field site.

Curtain (roof) which covers the plot during rain. Photo: Rachel Harvey
Heather (Calluna vulgaris)

Routine measurements

The following data is collected routinely at the site, and in most cases we also have a ten-year back-catalogue available: climate data, soil water quality measurements, soil gaseous flux measurements, soil nitrogen transformation measurements, litter decomposition, vegetation production, nutrient status and plant and microbial composition changes.

Available datasets can be requested here.

A weather station and a rain water collector

A weather station and a rain water collector.


The focus of our research is to understand ecosystem responses to climate change. The Clocaenog field site is a platform to test hypotheses related to responses of organo-mineral soils to climate change. The Clocaenog site also represents an extreme ecosystem within the European gradient, and data are valuable in synthesis and meta-analysis studies.

The following news and blog posts give more details on the site and some of our research:

Selected publications

  • Quantifying global soil carbon losses in response to warming. Nature (2016), doi: 10.1038/nature20150
  • Temperature response of soil respiration largely unaltered with experimental warming. PNAS (2016), doi: 10.1073/pnas.1605365113
  • Experimental evidence for drought induced alternative stable states of soil moisture. Scientific Reports (2016), doi: 10.1038/srep20018
  • Increased sensitivity to climate change in disturbed ecosystems. Nature Communications (2015), doi: 10.1038/ncomms7682
  • Contrasting effects of repeated summer drought on soil carbon efflux in hydric and mesic heathland soils. Global Change Biology (2008), doi: 10.1111/j.1365-2486.2008.01643.x

Work with us

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