Reporting the effect of Grassland
Management on carbon storage in soils
and biomass
Janet Moxley, and Heath Malcolm, CEH, Bush Estate, Penicuik Midlothian, EH26 0QB [email protected]
Grassland Management affects the amount of carbon stored in soils and biomass. We can estimate carbon storage in
Grassland biomass, but more field data is needed to allow estimation of how Grassland Management affects soils.
Grassland in the UK LULUCF inventory
Key Management Practices for UK Grassland
The UK has chosen to use a wide definition of Grassland in its
Land Use, Land Use Change and Forestry (LULUCF) inventory.
This includes improved and semi-natural Grassland and other
habitats which may not have grassy vegetation including
dwarf shrub heath, bracken, montane habitats, fens, marsh,
swamp, and bog.
Soil
• Improvement including manure and fertiliser
application, drainage of mineral soils, reseeding, and
liming.
• Stocking levels
Internationally agreed methodology for estimating carbon
stock changes from Grassland Management was published in
2006 (IPCC 2006). Methodology for estimating emissions and
removals of greenhouse gases as a result of Wetland
Drainage and Rewetting (WDR) activities was published in
2013 (IPCC 2013).
• Drainage of organic soils
Biomass
• Grassland type “Shrubby Grassland (dwarf shrub
heath, bracken, montane) vs “Non Shrubby Grassland”
(improved and semi-natural grass including fens,
marsh, swamp and bog).
The UK has elected to include reporting of carbon stock
changes resulting from Grassland Management WDR
activities in its LULUCF inventory by the end of the second
Kyoto Protocol (KP) commitment period in 2020.
Soil
A lack of field data on the response of Grassland soils to
management activities means that it is not currently possible to
include estimates of the effect of Grassland Management on soils in
the LULUCF inventory
• IPCC default emission factors may not be appropriate for UK soils,
particularly organo-mineral soils where there is a risk that
intensification could promote oxidation of soil carbon.
• Literature suggests that intensification may increase soil carbon
stocks on organo-mineral soils, but there are few data on the
effects of intensification on high carbon organo-mineral soils.
• A separate project will implement reporting WDR activity on
Grassland.
Biomass
• Biomass carbon stocks of different Grassland types were assessed
from UK and international literature.
•
Areas under different Grassland types assessed using data on the
Countryside Survey Broad Habitats which is collected
approximately decadally. Change was assumed to follow a linear
trajectory between surveys.
• Carbon stock change assumed to happen with the year of land
use change.
Issues for future improvement
Field data are needed to improve understanding how the carbon
stocks of organo-mineral soils currently under semi-natural
grassland respond to improvement.
Identify sources of more frequent data on land use change including
hedge length.
Use spatially explicit data to improve tracking of land use change.
Implement the IPCC Wetland Supplement Guidance om WDR
Carbon stocks of main Grassland land covers
Crop Type
Total biomass Carbon Stock
t C/ha
Uncertainty
t C/ha
Root:Shoot ratio
Pasture and Semi-natural
Grassland
Shrubby Grassland.
Hedges
2.8
1.5
4.0
10
546
3.6
148
0.53
2.8
45,000,000
Biomass Carbon Stocks of Scottish Grassland
40,000,000
Carbon stock (tC)
Approaches used:
• Hedge creation and removal.
35,000,000
30,000,000
25,000,000
20,000,000
15,000,000
10,000,000
5,000,000
0
1990
1995
Non-shrubby Grassland
2000
Hedges
2005
Total biomass
2010
Shrubby Grassland
Conclusions
• It is not possible to estimate how Grassland Management affects soil carbon stocks at present
because there are insufficient field data to develop emission factors for organo-mineral soils.
• Increasing Grassland area is the main driver of increasing Grassland biomass carbon stocks.
• Hedge removal and creation has more impact on biomass carbon stocks than conversions
between shrubby and non-shrubby Grassland. Although the area change involving hedges is
small, carbon stock per unit area is high.
• The frequency of Countryside Surveys means that it leads to step changes in the data and is
slow to pick up changes. Using data which is produced more frequently would improve the
time-series, especially for Grassland types with high carbon stocks e.g hedges.
• Hedge creation/restoration could contribute to carbon storage.
References IPCC (2006). 2006 IPCC Guidelines for National Greenhouse Gas Inventories. Eggleston H.S. et al. (eds.) IPCC National Greenhouse Gas Inventories Programme Technical Support Unit.
Volume 4: Agriculture, Forestry and Other Land Use.
IPCC (2013) Supplement to the 2006 Guidelines for National Greenhouse Gas Inventories: Wetlands (Wetlands Supplement).
Moxley, J et al.(2014a) Capturing Cropland and Grassland Management Impacts on Soil Carbon in the UK LULUCF Inventory Contract Report prepared for the Department for Environment, Food and
Rural Affairs Project SP1113.
Moxley, J et al Capturing the effect of Cropland and Grassland Management on biomass carbon stocks in the UK LULUCF inventory. Unpublished report by CEH for Department of Energy and Climate
Change contract TRN265/09/2011 (2014b)
Funding from Defra (SP1113) and DECC (TRN265/09/2011) is gratefully acknowledged.
WHY SHOULD WE TRY TO INCREASE CARBON
STORAGE IN GRASSLAND?
BECAUSE IT HELPS TO TACKLE CLIMATE CHANGE
AND CAN ALSO INCREASE SOIL FUNCTION,
PRODUCTIVITY AND BIODIVERSITY.