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Hedges and Carbon


Catherine Keena, Countryside Management Specialist and Lilian O’Sullivan, Research Officer, Environment Soils and Land Use, Teagasc, discuss the role of hedgerows in relation to carbon storage and sequestration. They also have information on the Teagasc Farm Carbon research project.

Role of hedgerows in relation to carbon

Hedgerows are a prevalent feature in the Irish landscape and best practice management is important to maximise the delivery of important ecosystem services such as biodiversity and carbon. Up to now most research on hedgerows has focused on the role of hedgerows in terms of biodiversity and how they function as landscape features in terms of biodiversity provision. There is less research on the role of hedgerows in relation to carbon storage and sequestration. Research is needed on carbon stocks and the impact of management on biomass accumulation in hedgerows but also how carbon and biodiversity are related. Very often the indicators or attributes that are good for biodiversity are also important for carbon. For example the structure, in particular width, density and connectivity of hedges are attributes that are important for biodiversity, but also important for the carbon profile.

Biomass

Biomass is an important part of the global carbon cycle because dried wood biomass weight is estimated to contain about fifty percent carbon (Houghton et al., 2009). Biomass density which refers to the amount of biomass in a unit area is a good indicator of carbon. Hedgerows can contain a relatively high biomass per unit area and so they potentially represent a considerable carbon stock. Research in the UK indicates that species like whitethorn (hawthorn) and blackthorn, which are common in Irish hedges contain about 48.3% carbon on average (Axe, 2015). While we have good estimates on the extent of hedgerows in Ireland, there is a need to take direct biomass measurements to estimate carbon stocks.

To estimate the carbon contained in hedges different carbon pools must be considered. Carbon that is contained in the biomass includes above ground biomass which is visible along with below ground biomass. Consideration must be given to different organic matter returns into the system so if there is deadwood or if leaf litter is being lost seasonally – how much is going back into the system and cycled into the carbon pool. Regarding soil organic matter, consideration must be given to the amount of carbon that is being contained in the soil under hedgerows relative to adjacent land use. Also there is a need to understand how management impacts biomass accumulation and the sequestration difference between managed and unmanaged hedgerows.

Farm Carbon Project

Teagasc are currently leading Farm Carbon, a research project co-funded by the Environment Protection Agency and DAFM. The aim is to quantify the carbon stock of selected hedgerows by measuring the different carbon pools. A biomass function will be based on volume measurement captured using remote technologies, through the development of a 3D digital surface model. An integrated scorecard for hedgerow assessment will be developed along with a best practice management advice for the delivery of ecosystem services such as carbon and biodiversity.

Follow the Farm Carbon project on twitter at @farm_carbon

References:

Axe, M., (2015), Carbon measurement, prediction and enhancement of the agricultural hedgerow ecotone, PhD Thesis, Coventry University in association with the Royal Agricultural University, Cirencester.

Houghton, R.A., Hall, F., Goetz, S.J., (2009), Importance of biomass in the global carbon cycle, Journal of Geophysical Research, vol. 114, G00E03, doi:10.1029/2009JG000935

To see all of the activity of Hedgerow Week follow this link https://www.teagasc.ie/environment/biodiversity--countryside/farmland-habitats/hedgerows/