- Metric Name:  Total Carbon (F3)

- Data Vintage:  2021

- Unit Of Measure: Mg C/ha

Identifying ecosystem carbon is essential to land managers and the Total Carbon (F3) metric provides an estimate of the amount of existing carbon and its location on California’s landscape. The metric also provides context for the other metrics used to quantify carbon sequestration. For example, instability or lack of forest resilience, if there wasn’t much carbon in the first places, would be of lesser concern than if there were a lot of carbon, all other things being equal.- Creation Method:  The F3 model generated multiple raster surfaces from the Fire and Fuels Extension of the FVS Carbon Report. These raster surfaces estimated the total aboveground live trees, including stems, branches and foliage (not including roots) to provide the Tons C per acre (Abovegroun); the belowground live tree roots (Belowgroun) and belowground roots of dead and cut trees (Belowgro_1); standing dead trees for all size classes including stems, branches, and foliage still present but not including roots (Standing_D); forest down dead wood, regardless of size (Forest_Dow); forest floor litter and duff (Forest_Flo); and the herbs and shrubs (Forest_Shr). Conversion from short tons per acre (the default F3 output units) to Mg/ha requires multiplication by 2.2417023114334.

2019 to 2021 Update:  Values for 2021 were adjusted using the Ecosystem Disturbance and Recovery Tracker (eDaRT), described in the Introduction. All eDaRT events beginning August 1, 2019 through November 30, 2021 were identified, and the corresponding Mortality Magnitude Index (MMI) values for these events was summed, giving the estimated fractional canopy cover loss per 30m pixel over that time period. Values for the total aboveground live tree carbon raster (Abovegroun) and for the belowground live tree roots carbon raster (Belowgroun) were adjusted for 2021 following the same procedure using eDaRT MMI. MMI values for canopy cover loss were used as a direct proxy to estimate Carbon loss, following the formula:

2021 Abovegroun = 2019 Abovegroun – (2019 Abovegroun * MMI/100)

The assumption of direct correlation between canopy cover and Carbon should be viewed with caution.

The 2021 values for the standing dead trees raster (Standing_D) and for the belowground roots of dead and cut trees raster (Belowgro_1) were adjusted in a similar procedure:

--	Standing_D: The difference between 2019 and 2021 live volume (as estimated using eDaRT MMI) was converted to short tons/acre using a conversion factor of 32.1 cubic feet/ton and the result was summed with 2019 standing dead.

--	Belowgro_1: The difference between 2019 and 2021 belowground live tree roots (as estimated using eDaRT MMI) was summed with 2019 belowground roots of dead and cut trees.

No adjustments were made for 2021 (Forest_Dow, Forest_Flo, Forest_Shr) due to uncertainties in conversions based on the limits with which change detection information can quantify the individual components of this metric. For areas with disturbance 2019-2021 (defined as eDaRT MMI greater than or equal to 10% canopy cover loss), raster values are not represented for 2021 (i.e., NULL). For areas undisturbed 2019-2021, it is a reasonable assumption that raster values did not change significantly over the course of two years.

This layer for the Total Carbon metric is derived from F3 layers (2021) using the following formula:

[sum(Abovegroun, Belowgroun, Belowgro_1, Standing_D, Forest_Dow, Forest_Flo, Forest_Shr)]*2.2417023114334

In cases where any individual input to the formula is NULL, the resulting sum cannot be computed and is therefore also NULL.

- Credits:  F3 data outputs, Region 5, MARS Team
USDA Forest Service - Region 5 - Pacific Southwest Region