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Methodologies
Technical specifications and calculation frameworks for evaluating avoided emissions through wood product substitution.
Technical specifications and calculation frameworks for evaluating avoided emissions through wood product substitution.
Forest Stand Carbon
Harvested Wood Product
The Landscape Tool enables users to evaluate forest carbon dynamics and harvesting activity across user-defined geographic areas within the United States. Using data from the USDA Forest Service Forest Inventory and Analysis (FIA) program, the tool provides consistent, population-representative estimates of forest carbon stocks, stock changes, and associated forest product removals.
The Landscape Tool computes a suite of complementary landscape-level metrics that provide broader context for interpreting forest carbon conditions and trends. These include net annual carbon stock change, carbon change per unit area, carbon change per unit of harvested wood, growth-to-removals ratios, annual harvest levels and harvest intensity, and mortality rates expressed both per unit area and as a percentage of standing carbon stocks (See Box 1). Together, these metrics provide a more complete characterization of forest carbon dynamics, allowing users to assess not only whether carbon stocks are increasing or decreasing, but also how those changes relate to forest growth, mortality, and harvesting activity.
To accomplish this, the Landscape Tool uses pre-processed FIA plot data that include both current and previous measurements for each plot. Carbon stocks are estimated across multiple ecosystem pools, and stock changes are annualized based on plot-specific remeasurement periods. These estimates are then combined with delivered wood volumes to derive associated metrics.
Importantly, the tool is intended to provide landscape-level, population-representative estimates rather than stand-level or project-specific carbon accounting. Results reflect averages across large areas and should be interpreted accordingly, particularly when applied to decision-making or comparisons across regions.
AGLIVE = Aboveground live tree carbon
AGDEADAboveground dead tree carbon
BGLIVE = Belowground live tree carbon
BGDEAD = Belowground dead tree carbon
CDD = Carbon in down dead wood
CL = Carbon in litter (forest floor organic material)
CSO = Carbon in soil organic matter
CU = Carbon in understory vegetation
TOTC = Total ecosystem carbon; sum of all carbon pools
CURR_* = Prefix indicating carbon stock estimates for the most recent measurement
PREV_* = Prefix indicating carbon stock estimates for the previous measurement
CHNG_* = Change in carbon stock between current and previous measurements
ANN_CHNG_* = Annualized carbon stock change (CHNG divided by REMPER)
REMPER = Remeasurement period (decimal years between successive plot measurements)
DELIVGRNWT = Delivered green weight of harvested wood (short tons); harvested biomass delivered to mills after accounting for logging residues
HARVC = Annual carbon removed through harvest
GROWC = Annual carbon increment from tree growth
MORTC = Annual carbon loss due to mortality
LCAF = Land Carbon Accounting Factor, Ratio of annual carbon stock change in live trees to annual delivered wood (MT CO₂e per short ton delivered)
Net Carbon Change = Sum of annualized carbon stock change in the live tree pool across plots within a defined geographic area (MT CO₂e yr⁻¹)
Net Change per Acre = Annual live tree stock change by land area (MT CO₂e ac⁻¹ yr⁻¹)
Net Change per Harvest = Annual live tree stock change by delivered wood volume (MT CO₂e per short ton)
Growth-to-Removals Ratio = Ratio of annual growth to annual harvest removals (unitless)
Annual Harvest = Total delivered wood volume per year (MT CO₂e yr⁻¹)
Harvest per Acre = Carbon in harvested wood, normalized by land area (short tons ac⁻¹ yr⁻¹)
Mortality per Acre = Annual mortality normalized by land area (MT CO₂e ac⁻¹ yr⁻¹)
Mortality as Percent of Stock = Annual mortality expressed as a percentage of previous live carbon stocks
STATECD = State code
UNITCD = FIA survey unit code
COUNTYCD = County code (FIPS)
LAT, LON = Approximate latitude and longitude coordinates of plot locations
CHNG_ACRES = Area represented by a plot for change calculations
CURR_OWNGRPCD = Ownership group classification (e.g., National Forest, private)
RESERVCD = Indicator of reserved forest land (0 = unreserved; 1 = reserved)
CO₂e = Carbon dioxide equivalent
MT CO₂e = Metric tonnes of carbon dioxide equivalent
Short ton (st) = Unit of weight equal to 2,000 pounds
FIA = USDA Forest Service Forest Inventory and Analysis (FIA) program
Evaluation Group (EVAL_GRP) = A complete set of FIA plot measurements for a state, typically collected over a 5–10 year period
The Landscape Tool relies on user-defined geographic selection and filtering options to subset pre-processed forest inventory data and generate landscape-scale estimates of forest carbon dynamics and harvesting activity.
Unlike tools that require user-supplied inventory data, the Landscape Tool uses a pre-calculated dataset derived from the USDA Forest Service Forest Inventory and Analysis (FIA) program. These data include both current and previous measurements for each inventory plot, along with pre-computed carbon stocks, stock changes, and harvested wood estimates.
As a result, user inputs are limited to defining the geographic domain and selecting from a set of optional filters that determine how results are summarized.
Users first define an area of interest using predefined administrative boundaries (e.g., states, counties, or regions) or custom spatial inputs (e.g., shapefiles or user-defined coordinates). The tool then subsets FIA plots that fall within the selected domain and aggregates plot-level estimates to produce population-representative summaries of carbon stocks, carbon stock change, and harvesting activity.
In addition to geographic selection, users may refine their analysis by selecting ownership categories and specifying whether to include only measured carbon pools or all available carbon pools (measured and modeled). These selections influence both the scope of the data included in the analysis and the interpretation of results, particularly with respect to uncertainty.
Once inputs are defined, the tool processes the selected data to compute a suite of landscape-level metrics, including total carbon stocks, annualized carbon stock change, harvested wood volumes, and the Land Carbon Accounting Factor. Because the tool is based on FIA sampling data, all outputs represent statistically derived estimates for the selected population of forest land rather than exact measurements for specific locations.
To use the Landscape Tool, the user must first define the geographic area for which carbon stocks, stock changes, harvest estimates, and associated landscape metrics will be summarized. The forest land within this selected area becomes the analysis domain for the tool.
The Landscape Tool uses a pre-calculated dataset derived from FIA plots across the conterminous United States (CONUS). Forest carbon estimates for the Landscape Tool, as well as other tools in the FACT platform, are drawn from FIA plots that match the FIA’s “unreserved forest” definition, which represents forest land not withdrawn from management for production of wood products through statute or administrative designation.
Once a user specifies an area of interest, the tool subsets the available FIA plot records to include only those plots that fall within the selected domain. Current and previous plot measurements associated with that domain are then used to compute the reported metrics. Depending on the selections, the tool identifies plots either by matching geographic codes (such as state or county identifiers) or by performing a spatial intersection between the user-defined area and FIA plot locations.
Because FIA plot data underpin all Landscape Tool analyses, the tool enforces a minimum plot threshold to ensure sufficient sample size and reduce sampling uncertainty in the results. It therefore requires that any selected analysis domain include a minimum of 150 FIA plots. Selections below this threshold are flagged as insufficient for reliable results, and users are prompted to expand the analysis area.
The tool provides the following options for defining the area of interest:
Note that because the tool uses the publicly-available version of the FIA database, the latitude/longitude coordinates of plots are “fuzzed”, or randomly adjusted to protect landowner confidentiality. Therefore when the geographic selection depends on geographic overlay (National Forest, circular area, or shapefile) some plots may be erroneously included or excluded due to the fuzzed location. This is likely to have a very minimal effect on results, especially for larger spatial domains.
After the geographic area is defined, the user initiates data retrieval within the tool. The tool then subsets the plot-level dataset for the specified domain and prepares the records needed for summary calculations.
Because all subsequent calculations are based on the selected geographic domain, the area selection step is one of the most important user inputs in the LandscapeTool. Smaller or highly customized areas may better reflect a user’s area of interest, but they may also reduce the number of FIA plots available for estimation. Larger areas generally provide more stable estimates because they include more plots and therefore more information from the underlying FIA sample.
In addition to defining a geographic area of interest, users may optionally filter results by ownership group. Ownership classifications are based on categories provided in the FIA program dataset and represent broad groupings of forest land ownership across the United States. The available ownership categories include:
These categories correspond to the ownership group codes included in the underlying dataset and are applied to the current plot measurement.
When an ownership filter is applied, the tool subsets the selected geographic domain to include only FIA plots that currently match the specified ownership category or categories. All subsequent calculations, including carbon stocks, stock changes, harvest estimates, and derived landscape metrics, are then computed using only the filtered subset of plots. If no ownership selection is made, all ownership groups are included by default. This results in estimates that represent the full population of unreserved forest land within the selected geographic area.
Ownership selection can have a meaningful influence on results, as forest structure, management intensity, and harvesting patterns often differ across ownership types. For example, privately owned forests may exhibit different growth, harvest, and mortality dynamics compared to federally managed lands. As a result, filtering by ownership allows users to isolate and evaluate carbon dynamics within specific management or ownership contexts.
Because ownership filtering reduces the number of FIA plots included in the analysis, it may also affect the statistical robustness of estimates, particularly when combined with smaller geographic selections. Users should consider the tradeoff between specificity and sample size when applying ownership filters. Where ownership filtering results in fewer than 150 representative FIA plots, users will be directed to adjust selections to meet the minimum threshold.
The Landscape Tool allows users to control which forest carbon pools are included in the analysis. This selection determines how total carbon stocks, carbon stock change, and all derived landscape metrics are calculated and interpreted. Users may choose to include only measured carbon pools or to include all carbon pools. The measured carbon pool option includes those components of forest carbon that are either directly measured in the FIA program or estimated using well-established allometric relationships applied to measured tree attributes. These pools consist of aboveground live tree carbon, belowground live tree carbon, aboveground dead tree carbon, and belowground dead tree carbon. Because these estimates are closely tied to field measurements and widely accepted estimation approaches, they are generally considered to have lower uncertainty.
The all carbon pools option includes the above-mentioned measured pools as well as additional ecosystem components that are not directly measured at the same level of detail in FIA and are therefore estimated using modeling approaches. These additional pools include carbon in down dead wood, litter, understory vegetation, and soil organic matter. Inclusion of these pools provides a more complete accounting of total ecosystem carbon by capturing carbon stored outside of tree biomass, but these estimates may carry greater uncertainty due to the assumptions and models used in their derivation.
The selected carbon pool option directly affects all reported outputs. Total carbon stocks are calculated as the sum of the included pools, and carbon stock change is computed using those same pools across current and previous measurements. Because derived metrics such as net carbon change, carbon change per unit area, and the Land Carbon Accounting Factor are based on these totals, their values will differ depending on whether measured-only or all pools are included.
To support interpretation, the tool maintains a distinction between measured and modeled components in its outputs. In some cases, results may be presented separately or visually differentiated to highlight the contribution of modeled pools and to provide transparency regarding the sources and relative certainty of estimates.
Users should consider the intended application of results when selecting carbon pools. Analyses focused on comparability, reporting consistency, or lower-uncertainty estimates may benefit from using measured carbon pools only. In contrast, analyses seeking a more complete representation of ecosystem carbon should include all carbon pools, recognizing the additional uncertainty associated with modeled components.
After defining the geographic area of interest and selecting optional filters, the LCAF Tool generates a set of outputs describing forest carbon stocks, carbon stock change, forest growth, mortality, and harvesting activity for the selected domain.
All outputs are derived from aggregated FIA plot-level data and represent population-level estimates for the selected geographic area. Carbon stocks are summarized for both the current and previous measurement periods, and carbon stock change is annualized using the remeasurement period associated with each plot.
Results are presented through a combination of summary metric panels, tabular outputs, and visualizations. Together, these outputs provide a comprehensive view of forest carbon dynamics and the relationship between carbon change and forest product removals.
The Landscape Tool results page first presents a geographic representation of the selected analysis area, along with a summary of the underlying data used in the calculations. The map displays the user-defined area of interest and the spatial distribution of FIA plots included in the analysis. Plot locations are shown within the selected boundary, providing a visual indication of the sample used to generate estimates. The density and distribution of plots can vary depending on the size and location of the selected area.
Accompanying the map is a summary description of the analysis domain. This includes the number of FIA plots used in the calculations and the total acreage of unreserved forest land represented by those plots. These values provide important context for interpreting results, as they reflect the sample size and spatial extent underlying all reported metrics.
Ownership information may also be displayed alongside the map, showing the distribution of plots across ownership categories within the selected area. This helps users understand how different ownership groups contribute to the overall analysis.
Because all subsequent outputs are derived from the subset of plots shown in the map, this section provides a critical link between user inputs and reported results. Users should consider both the number of plots and their spatial distribution when evaluating the reliability and representativeness of the outputs.
The primary outputs of the tool are displayed as summary panels that highlight key landscape metrics. These metrics are derived by aggregating plot-level values across the selected geographic domain and are intended to provide interpretable indicators of forest condition and carbon dynamics.
Net carbon change represents the total annual change in aboveground live tree carbon across the selected area (MT CO₂e yr⁻¹). This value indicates whether the live tree component of the forested landscape is acting as a net carbon sink (positive values) or a net carbon source (negative values). This metric is calculated as the sum of annualized carbon stock change in the aboveground live tree pool across all plots.
Carbon change per acre expresses this same quantity on a per-area basis (MT CO₂e ac⁻¹ yr⁻¹), allowing for comparison across regions of different sizes. This metric is calculated by dividing net carbon change by the total acreage represented by the selected plots.
Carbon change per harvest unit (Land Carbon Accounting Factor) represents the ratio of annual carbon stock change in the aboveground live tree pool to the amount of harvested wood delivered to mills (MT CO₂e yr⁻¹ per short ton). This metric links forest carbon dynamics directly to wood utilization and provides a measure of how tree carbon stocks are changing relative to harvest intensity.
Growth-to-removals ratio (Growth/Drain) compares annual forest growth to annual harvest removals. Values greater than 1 indicate that forests are accumulating biomass (growth exceeds removals), while values less than 1 indicate that removals exceed growth. This is a commonly used indicator of forest sustainability and wood supply balance.
Annual harvest represents the total amount of harvested wood delivered to mills (short tons per year). This reflects the level of harvesting activity within the selected region after accounting for logging residues.
Annual harvest per acre expresses harvest intensity on a per-area basis (MT CO₂e ac⁻¹ yr⁻¹), providing a measure of how intensively forest resources are being utilized across the landscape. Note that this harvest metric is expressed in carbon units, and is not adjusted for harvest residues as the annual harvest number is. In this way, it is directly comparable to mortality per acre.
Mortality per acre represents the annual carbon transferred from live trees to the dead tree pool due to mortality (MT CO₂e ac⁻¹ yr⁻¹). This metric provides an indicator of forest health and disturbance.
Mortality as percent of stock expresses annual mortality as a proportion of live tree carbon at the previous measurement; it represents the percentage of carbon at the previous measurement that transferred to the dead tree pool. This is relevant when comparing regions with dramatically different levels of tree carbon stocks (such as the Pacific Northwest versus the US South). Higher values may indicate aging forests or increased disturbance from factors such as insects, disease, or weather events.
In addition to summary metrics, the LCAF Tool provides graphical and tabular outputs that allow users to explore carbon stocks and carbon dynamics in greater detail.
A primary component of these outputs is the carbon pool table, which summarizes carbon stocks for both the previous and current measurement periods, along with the associated annualized change for each carbon pool. Carbon pools are categorized as measured or modeled, allowing users to distinguish between components derived more directly from field measurements and those estimated using modeling approaches. Totals across all pools are also provided to support evaluation of overall ecosystem carbon dynamics.
The tool also presents graphical visualizations of carbon by pool, showing carbon stocks for each pool across the two measurement periods. These visualizations allow users to quickly assess which pools contribute most to total carbon storage and how those contributions change over time. Measured and modeled pools are visually distinguished to support interpretation.
In addition, the tool provides ownership-based visualizations, where carbon stocks within each pool are partitioned among ownership groups. These graphics illustrate how carbon is distributed across ownership categories within the selected region and help identify which ownership types contribute most to total carbon stocks and carbon stock changes.
Together, these graphical and tabular outputs complement the summary metrics by providing additional detail on the composition and distribution of forest carbon. They allow users to move beyond aggregate values and better understand the underlying structure of carbon stocks and changes across pools and ownerships.
The Landscape Carbon Accounting Factor (LCAF) Tool is built on a pre-processed dataset derived from the USDA Forest Service Forest Inventory and Analysis (FIA) program. The FIA program provides a nationally consistent, plot-based inventory of forest conditions, including tree measurements, land use, ownership, and associated carbon estimates. These data are collected on a rotating basis across the United States, with individual plots remeasured at intervals that typically range from approximately five to ten years.
Rather than querying the FIA database directly, the LCAF Tool relies on a single, integrated dataset (to be updated at least annually) that combines current and previous plot measurements, carbon pool estimates, and forest change variables. Each record in this dataset represents a plot/condition combination, where a condition corresponds to a distinct forested portion of a plot. Because a single FIA plot may contain multiple forest conditions, multiple records may share the same plot identifier but differ in condition identifier and proportional area. The proportion of each plot represented by a given condition is explicitly tracked and used in all subsequent aggregation steps.
The dataset includes only unreserved forest land, meaning forest areas that are not legally restricted from timber harvest. This ensures that estimates of carbon change and harvested wood are aligned with actively managed forest systems and avoids inclusion of lands where harvest is not permitted.
The workflow underlying the dataset can be summarized as:
All outputs in the tool are derived from these plot-level quantities.
FIA plots may contain multiple forest conditions (e.g., different forest types or ownerships). Therefore, the fundamental unit of analysis is the plot-condition, not the plot itself. Each plot-condition represents only a fraction of the total plot area. To convert this into a population estimate, FIA provides expansion factors that scale each plot-condition to represent a known number of acres. The area represented by each record is calculated as:
where:
Aj = area represented by record j (acres)
EXPCHNGj = FIA expansion factor for change estimate
CONDPROPj = proportion of the plot in that condition
ADJj = subplot or macroplot adjustment factor
This step is critical because all subsequent carbon estimates are interpreted as totals over the landscape. Without this expansion, values would only represent measurements at individual plots.
Carbon stocks and carbon stock change in the LCAF Tool are calculated at the plot-condition level using a combination of FIA tree-level and condition-level data. The workflow follows a structured sequence: (1) estimation of carbon stocks for current and previous measurements, (2) expansion of those values to represent landscape area, and (3) calculation and annualization of carbon stock change.
Carbon stock estimation by pool
Carbon is estimated for eight ecosystem pools. These are derived using two distinct approaches depending on how the data are represented in FIA. For tree-based pools (aboveground and belowground live and dead carbon), values are calculated from individual tree records. FIA provides tree-level carbon estimates, which are expanded to the plot-condition level using trees-per-acre values, plot-size adjustment factors, and the FIA expansion factor. For a given plot-condition j, tree carbon is calculated as:
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In addition to carbon stocks and carbon stock change, the LCAF dataset includes estimates of growth, mortality, harvest removals, and delivered wood. These variables describe the processes driving changes in forest carbon over time and are derived from FIA growth, removals, and mortality (GRM) data. All values are calculated at the plot-condition level and expressed on an annual basis.
Growth, mortality, and harvest represent distinct components of forest carbon dynamics. Growth (more precisely, net growth; equal to gross growth minus mortality) reflects the net accumulation of carbon in live trees between measurements, including both survivor growth and ingrowth. Mortality represents carbon transferred from live trees to dead pools due to natural or anthropogenic causes. Harvest removals represent carbon removed from the forest through management activities. These quantities are estimated using FIA GRM components, which track changes in tree biomass between successive measurements. For each plot-condition, these components are calculated using tree-level information and then aggregated to the plot-condition level, consistent with the carbon stock calculations described in Section 5.3.
Harvest removals are further processed to estimate delivered wood, which represents the portion of harvested biomass that is transported to mills. This calculation involves converting harvested dry biomass to green weight using species-specific conversion factors and then adjusting for logging residues using region-specific residue factors. The resulting variable represents delivered wood in green tons per year at the plot-condition level.
These variables provide the basis for several key metrics reported by the Landscape Tool. Growth and harvest are used to calculate the growth-to-removals ratio, which indicates whether forests are accumulating or losing biomass relative to removals. Delivered wood is used in the calculation of the Land Carbon Accounting Factor (LCAF), linking forest carbon change to wood utilization. Mortality is used to quantify carbon losses due to primarily natural processes and is reported both as a per-acre value and relative to carbon stock. Because all variables are calculated at the plot-condition level and expressed on an annual basis, they can be aggregated consistently across user-defined geographic areas.
All variables described in Sections 5.1 through 5.4 are calculated at the plot-condition level and represent expanded, population-level estimates. When a user defines a geographic area, the LCAF Tool identifies all plot-conditions within that area and aggregates their values to produce landscape-level estimates.
Carbon stocks, carbon stock change, growth, mortality, harvest, and delivered wood are calculated as the sum of plot-condition values within the selected region. Because carbon stock change and GRM variables are expressed on an annual basis, aggregated results represent average annual rates of change. Per-acre metrics are derived by dividing aggregated totals by the total area represented, and ratio-based metrics are calculated using the corresponding aggregated components (e.g., growth divided by harvest).
This aggregation approach ensures that all reported outputs are consistent with FIA’s design-based sampling framework while allowing users to evaluate carbon dynamics across flexible, user-defined geographic areas.
Aboveground live tree carbon pool: Carbon stored in the aboveground portion of living trees, including stems, branches, and foliage, typically expressed per unit area. Estimates are derived from tree measurements using established allometric relationships and conversion models applied within the USDA Forest Service.
Administrative unit: A user-defined analysis boundary based on political or jurisdictional divisions (e.g., states or counties) used to group FIA plots.
Belowground live tree carbon pool: Carbon stored in the living root biomass of trees, including coarse and fine roots, typically expressed per unit area. Estimates are derived from tree measurements using established allometric relationships and conversion models applied within the USDA Forest Service.
Biomass: The mass of organic material in trees, typically expressed as oven-dry or green weight, including stems, bark, and branches. Biomass may refer to live or dead components and can be converted to carbon using standard conversion factors.
Dead wood carbon pool: Carbon stored in non-living woody biomass, including both standing and downed material, typically comprising standing dead trees (snags), down dead wood, and associated coarse woody debris within a defined area.
Forest type group: A classification used by FIA program that aggregates individual forest types into broader categories based on dominant tree species and ecological similarity, enabling consistent summarization and reporting of forest attributes across regions. In the conterminous United States (CONUS), FIA defines 28 forest type groups (USDA Forest Service, FIA; see Forest Type Group metadata: https://data.fs.usda.gov/geodata/rastergateway/forest_type
Litter carbon pool: Carbon stored in non-living organic material on the forest floor, including leaves, needles, twigs, bark fragments, and other fine debris that have not yet decomposed into soil organic matter, typically expressed per unit area.
Merchantability specification: A set of criteria defining which portion of a tree is considered usable or “merchantable” for wood products, based on attributes such as minimum diameter, top diameter, stem form, and usable length, used to determine merchantable volume within the USDA Forest Service.
Merchantable volume: The volume of wood within a tree that meets specified merchantability criteria, typically referring to the usable portion of the stem between a defined minimum diameter and a specified top diameter, expressed in cubic units
Product class: A categorical classification of harvested wood based on its intended use and physical characteristics, such as sawtimber, pulpwood, or other wood products, used to differentiate how timber is processed and valued within the USDA Forest Service.
Region: A spatial unit defined by administrative or analytical boundaries that groups multiple geographic areas for the purpose of summarizing and comparing forest attributes. Within the FACT Platform regions may be defined in multiple ways to enhance analytical flexibility, including U.S. Forest Service administrative regions, RPA regions, or aggregations of states.
Sapling: A live tree of small diameter, typically defined as having a diameter at breast height (dbh) between 1.0 and 4.9 inches (2.5–12.7 cm), within the USDA Forest Service classification system.
Soil carbon pool: The carbon stored in soil organic matter within a defined depth (commonly up to 1 meter), including decomposed organic material and fine roots, but excluding coarse root biomass accounted for in belowground biomass pools, typically expressed per unit area.
Species group (SPGRPCD): A classification used by the Forest Inventory and Analysis program that aggregates individual tree species into broader groups based on taxonomic and ecological similarity for consistent summarization and analysis of forest attributes.
Stand: A community of trees on a minimum of 1 acre (0.4 ha) that can be distinguished from adjacent communities due to similarities and uniformity in tree and site characteristics, such as age-class distribution, species composition, spatial arrangement, structure, etc.
Stand age: A stand descriptor that indicates the average age of the live dominant and codominant trees in the predominant stand-size class of a condition.
Stand key: A unique identifier used to distinguish and track a specific forest stand or condition within a dataset, enabling linkage of plot-level observations and attributes across measurements.
Stand Origin (STDORGCD): A classification used by the Forest Inventory and Analysis program that indicates the regeneration origin of a forest stand, distinguishing between stands established through natural regeneration and those established through artificial means (e.g., planting or seeding).
Carbon Stock Change: The net change in the mass of carbon within a defined carbon pool over a specified period, typically expressed as mass per unit time (e.g., Mt CO2·yr⁻¹). It reflects the balance between carbon gains (e.g., growth, inputs) and losses (e.g., harvest, decomposition, disturbance). A positive value indicates a net increase in stored carbon, while a negative value indicates a net decrease.
Note: In some reporting frameworks, decreases in carbon stocks may be reported as positive emissions rather than negative stock changes. Carbon stock change is equal in magnitude and opposite in sign to net greenhouse gas flux.
Carbon Flux: he rate of transfer of greenhouse gases between a defined system and the atmosphere over a specified time interval, typically expressed as mass per unit time (e.g., tCO₂e·yr⁻¹). Positive values indicate emissions to the atmosphere, while negative values indicate removals (sequestration).
Note: Net flux is equal in magnitude and opposite in sign to carbon stock change within the system, although sign conventions differ between stock-based and flux-based reporting frameworks.
Stratum: A relatively homogeneous subset of a population, defined by selected attributes, within which sampling and estimation are conducted to reduce variance and improve the precision of statistical estimates.
Survey unit: A sub-state geographic division used by the USDA Forest Service to organize and report forest inventory data, typically grouping counties with similar forest characteristics for sampling and estimation purposes.
Tops: The portion of a tree above the defined merchantable limit (e.g., minimum top diameter), consisting of smaller stem sections and branches that are not considered merchantable under specified utilization standards but contribute to total tree biomass and carbon.
Understory carbon pool: Carbon stored in non-tree vegetation beneath the forest canopy, including woody shrubs and tree seedlings or saplings below 1 inch (2.5 cm) dbh, as well as herbaceous plants, typically expressed per unit area.
Unreserved Forest Land: Forest land not withdrawn from management by statute or administrative designation, and therefore generally available for multiple uses, including timber production.