Description

Total carbon removed or stored.

Accounting for C stored in soil and vegetation in an urban area can indicate the condition of natural green spaces, total free surface area and total quantity of vegetation in the area examined. Measures of C storage and sequestration also provide a tangible connection to climate change mitigation, and the impacts of local land use, planning and management decision-making. It is important to note the substantial variation in C sequestration and storage capacity of different types of NBS

Scale as linked to D2.2 framework

• Project area

Data source [ link to data framework]

• CORINE landcover information or similar local dataset (2.2.4) 
• Data need to be collected manually by the project personnel.

Data needs

In DivAirCity the CO2 absorption is associated to the NBS intervention involving increasing urban vegetation. This can be either trees, bushes planted in specific area of the city or also as green roofs.

The CO2 absorption capacity of a plant depends on the biomass increase in a certain temporal range. The increase in plant biomass depends on intrinsic characteristics of the plants that determine the specific growth rate, such us the photosynthesis rate and the plant form and architecture. The CO2 absorbed by a plant is calculated starting from the plant fresh weight taking into consideration the percentage of water, the proportion between above and below ground biomass and the Carbon content of plants. To allow these evaluations, the following data are needed:

• For trees, at least trunk diameter at breast height and tree height
• For bushes and other type of vegetation, the canopy volume
• Expected CO2 sequestration potential of each new species planted at maturity
• Expected time taken for each new species to reach maturity 

When the Carbon absorbed value is obtained for one plant, to upscale to the whole NBS intervention area, data about the total amount of plants should be considered. This can be evaluated according to the type of interventions as:

• New green space (m²) after interventions
• Tree cover after interventions
• Ratio evergreen to deciduous of trees used for the interventions
• Total area of green roofs after the intervention including:

• area of intensive green roofs
• area of semi-intensive green roofs
• area of extensive green roofs

To be able to measure the difference in CO2 absorbed by vegetation following the NBS intervention, the CO2 absorbed by the vegetation before and after the intervention is needed.

• Pre-existing area of greenspace enhanced by the DivAirCity intervention
• Ratio of evergreen to deciduous new trees before intervention
• Ratio of evergreen to deciduous new trees after intervention
• Mean canopy cover percentage for all forested pixels in the region
• Mean canopy cover percentage for all non-forest pixels in region
• Area sum of all non-forest pixels in region

The potential CO2 sequestration depends on the maturity time of the vegetation used in the intervention. When the future Carbon sequestration is envisaged, the use of models to forecast the growth rate (also in association to forecasted future climate change). For tree species, models such as Yield-safe, can be used to perform this kind of projections. 

Expected Outputs

• Measured as per unit area per unit time 
• tonnes/ha/y or similar unit
• Annual data collection or before (baseline) and after the intervention 

Calculation methods

To evaluate C removal or storage per unit area per unit time:

• Determine C storage in vegetation or soil as described in Carbon storage and sequestration in vegetation or Carbon storage and sequestration in soil indicators, respectively, for the same area at two different points in time
• Divide each C storage value obtained by the area assessed to determine C storage per unit area
• Subtract the earlier value obtained for C storage and sequestration/unit area from the more recent value, then divide by the length of time between measures to obtain an estimate of C removal or storage per unit area per unit time.

The growth rate of a forest has significant impact on its C storage potential. Forest C sequestration (FCS) is usually estimated as a function of forest area, forest type, and forest age:

Links and references

• Smith, J.E., Heath, L.S., Skog, K.E., & Birdsey, R.A. (2006). Methods for Calculating Forest Ecosystem and Harvested Carbon with Standard Estimates for Forest Types of the United States. USDA Forest Service Report GTR-NE-343. Newtown Square, PA: Northeastern Research Station, United States Department of Agriculture, Forest Service.
• Zheng, D., Ducey, M.J. & Heath, L.S. (2013). Assessing net carbon sequestration on urban and community forests of northern New England, USA. Urban Forestry & Urban Greening, 12, 61- 68.
• Zheng, D., Heath, L.S., Ducey, M.J. & Smith, J.E. (2011). Carbon changes in conterminous US forests associated with growth and major disturbances: 1992–2001. Environmental Research Letters, 6, 014012.