The Sonoma County carbon inventories methodology is based on the Resilient Counties Guide, which provides the most up-to-date county-level natural and working lands analysis in line with State’s 2018 natural and working lands inventory. The first step includes estimating carbon stocks by land cover class (i.e., forest, grassland, and shrub) using the 2013 and 2022 datasets described in the Data Sources section and Literature and Data Evaluation review provided to the County in July of 2023. The second step involves calculating carbon stored in different carbon pools (i.e., above- and below-ground live biomass, litter, and soil) based on existing vegetation type, cover, and height. The sections below describe the methodology and findings of the two carbon inventories. The inventory of carbon stocks for natural and working lands in Sonoma County will cover 1,016,469 acres, which includes all natural, agricultural, and urban areas countywide. The best available data were used in this analysis to allow for progress on estimating carbon stock stability and developing strategies for optimizing carbon sequestration in Sonoma in a timely manner. Some changes in land cover and carbon stock between the two years may be data artifacts. Future updates to the Sonoma Veg Map data will allow for more accurate carbon stock and trends analysis.

Carbon stock estimates are based on the sum of carbon stored in different carbon pools. Carbon stock analysis includes carbon stored in the following carbon pools:

• Above- and below-ground live biomass

• Above- and below-ground biomass associated with dead standing trees

• Lying dead wood (e.g., branches, logs, etc., lying on the ground surface)

• Litter (e.g., freshly fallen or slightly decomposed leaves, bark, twigs, flowers, fruits, and other vegetable matter)

• Soil

Carbon stored in all above- and below-ground biomass (including live, dead, and litter), is calculated using volumetric estimates of carbon mass (metric tons per hectare) provided by the California Air Resources Board (CARB). These estimates will be provided for every combination of Existing Vegetation Type, Height, and Cover and assigned to each 30 by 30-meter cell in the county. The carbon values are then summed within each land cover class.

Soil carbon values are obtained using the combined The National Cooperative Soil Survey (NCSS) Characterization Database, the National Soil Information System (NASIS), and the Rapid Carbon Assessment (RaCA) datasets. The soil carbon inventory estimates are determined by using the values provided for soil organic carbon and soil bulk density at a depth of 0-30 centimeters. The soil organic carbon estimates are calculated as described in Quantification Guidance for Use with Forest Carbon Projects report from the CAR FPP Quantification Guidance Version 4.0 (the Conversion of Organic Matter to Carbon step was skipped as the input data was provided as Soil Organic Carbon, Climate Action Reserve, 2017).

To view the tables and for more info, please download the Report.

The Sonoma County carbon inventories methodology is based on the Resilient Counties Guide, which provides the most up-to-date county-level natural and working lands analysis in line with State’s 2018 natural and working lands inventory. The first step includes estimating carbon stocks by land cover class (i.e., forest, grassland, and shrub) using the 2013 and 2022 datasets described in the Data Sources section and Literature and Data Evaluation review provided to the County in July of 2023. The second step involves calculating carbon stored in different carbon pools (i.e., above- and below-ground live biomass, litter, and soil) based on existing vegetation type, cover, and height. The sections below describe the methodology and findings of the two carbon inventories. The inventory of carbon stocks for natural and working lands in Sonoma County will cover 1,016,469 acres, which includes all natural, agricultural, and urban areas countywide. The best available data were used in this analysis to allow for progress on estimating carbon stock stability and developing strategies for optimizing carbon sequestration in Sonoma in a timely manner. Some changes in land cover and carbon stock between the two years may be data artifacts. Future updates to the Sonoma Veg Map data will allow for more accurate carbon stock and trends analysis.

Carbon stock estimates are based on the sum of carbon stored in different carbon pools. Carbon stock analysis includes carbon stored in the following carbon pools:

• Above- and below-ground live biomass

• Above- and below-ground biomass associated with dead standing trees

• Lying dead wood (e.g., branches, logs, etc., lying on the ground surface)

• Litter (e.g., freshly fallen or slightly decomposed leaves, bark, twigs, flowers, fruits, and other vegetable matter)

• Soil

Carbon stored in all above- and below-ground biomass (including live, dead, and litter), is calculated using volumetric estimates of carbon mass (metric tons per hectare) provided by the California Air Resources Board (CARB). These estimates will be provided for every combination of Existing Vegetation Type, Height, and Cover and assigned to each 30 by 30-meter cell in the county. The carbon values are then summed within each land cover class.

Soil carbon values are obtained using the combined The National Cooperative Soil Survey (NCSS) Characterization Database, the National Soil Information System (NASIS), and the Rapid Carbon Assessment (RaCA) datasets. The soil carbon inventory estimates are determined by using the values provided for soil organic carbon and soil bulk density at a depth of 0-30 centimeters. The soil organic carbon estimates are calculated as described in Quantification Guidance for Use with Forest Carbon Projects report from the CAR FPP Quantification Guidance Version 4.0 (the Conversion of Organic Matter to Carbon step was skipped as the input data was provided as Soil Organic Carbon, Climate Action Reserve, 2017).

To view the tables and for more info, please download the Report.