Major research issues/sites:

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.

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.

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.

Short technical description:

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.

Specific features/uniqueness:

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.