The SEREN Project

Carbon Soil Sequestration

The Aberystwyth and Bangor University collaboration focuses on the potential for the sequestration and retention of carbon in Welsh soils under a range of different scenarios.

Aberystwyth will concentrate on the impacts to soil carbon of restoration strategies on degraded land, novel crop varieties and the growth of bioenergy crops.

How carbon is sequestered in soils and why it is important?

Soils are a sink in the global carbon cycle that contains more than twice the amount of carbon than the atmosphere. This highlights the importance of maintaining and increasing the stocks of soil carbon as part of a wider greenhouse gas emission strategy. Carbon primarily enters the soil through the fixation of atmospheric CO2 by plant photosynthesis.summary diagram

Some of this carbon finds a way directly into the soil as root systems that senesce over time and through root exudates. The above ground biomass (stems, shoots and leaves) also senesce and are either broken down through microbial activity on the surface or are incorporated into the soil via the activity of the soil macro-fauna.    

Carbon in soils is returned to the atmosphere as the carbon substrates are oxidised for energy by the soil fauna. Organic matter that is harder to break down forms long-term soil carbon.

The amount of carbon in a soil therefore depends on the productivity of the above ground biomass and also the efficiency of the soil micro-organisms in breaking down plant material.

In soils such as peats the turnover of plant biomass is very slow as water-logging reduces the availability of oxygen, essential for efficient decomposition, and hence carbon accumulates steadily over time. In other soils the turnover is much more rapid and the carbon content is consequently lower.

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