PCS TA 008 Deadwood & Litter Tool_v1.0

Document Control

Document identification

• Document code: PCS-TA-008

• Title: Deadwood & Litter Carbon Stock Tool

• Scope: Quantification tool defining measurement, sampling, calculation, scaling, uncertainty and QA/QC procedures for estimating deadwood and litter biomass and carbon stocks within PCS project boundaries (where included carbon pools).

• Application: Used whenever an applicable PCS methodology requires deadwood and/or litter pools to be included in baseline and/or monitoring carbon accounting.

Version history and change log

Table DC-1. Revision history

Version	Date	Status	Summary of changes	Prepared by	Approved by
v1.0	TBD	Draft	Release for public consultation	PCS	TBD

Superseded versions

No superseded versions for v1.0.

Governance note on versioning and archiving

Only the latest approved version of this tool shall be used for new project registrations and for quantification/verification of monitoring periods unless PCS specifies otherwise. Superseded versions shall be archived and retained for traceability and audit purposes, including for projects assessed under earlier versions where applicable, consistent with PCS governance rules.

Chapter 1 - Introduction and Purpose

1

Overview

The Dead Wood and Litter Carbon Stock Estimation Tool establishes standardized procedures for quantifying carbon stored in dead wood and litter within PCS Nature-Based Solutions project boundaries. These pools represent important components of ecosystem carbon storage, especially in forests and wooded landscapes where natural mortality, disturbance, and accumulation processes contribute significantly to overall carbon dynamics.

2

Purpose

The purpose of this tool is to ensure that estimates of carbon stocks and stock changes in dead wood and litter are produced using consistent scientific methods. The tool provides measurement rules, calculation procedures, and parameter values for both pools. It supports the quantification of baseline carbon stocks as well as changes resulting from project activities, natural processes, or disturbances. Dead wood includes standing and downed dead trees, coarse woody debris, and large woody fragments, whereas litter comprises fine organic material such as leaves, twigs, small branches, and decomposing surface matter.

3

Application requirements

This tool must be applied whenever the applicable PCS methodology includes dead wood or litter as accounted carbon pools. It is designed for use in a wide range of ecosystems, including tropical and temperate forests, mangroves, dryland woodlands, shrublands, and regenerating landscapes. The tool accommodates both direct measurement approaches and the use of default values where allowed.

4

Intended outcomes

By providing a standardized calculation framework, this tool ensures that estimates of dead wood and litter carbon are transparent, verifiable, and consistent across monitoring periods. It supports high-integrity carbon accounting, facilitates validation and verification, and ensures alignment with PCS methodological requirements.

Chapter 2 - Scope and Applicability

1

This tool applies to the quantification of carbon stocks and carbon stock changes in dead wood and litter pools within PCS Nature-Based Solutions projects. It must be used whenever these pools are included in the accounting framework of the applicable PCS methodology, either as required pools or optional pools selected by the project developer.

2

Dead wood includes standing dead trees, fallen logs, coarse woody debris, and large woody fragments meeting specified size thresholds. Litter includes small organic materials such as leaves, flowers, fruits, bark fragments, twigs, and decomposing plant matter that accumulate on the soil surface. If a methodology requires the inclusion of one or both pools, this tool provides the measurement and calculation procedures that must be followed.

3

The tool is applicable to a wide range of ecosystems, including forests, woodlands, mangrove systems, shrublands, and mixed vegetation landscapes. It applies under baseline and monitoring conditions and is suitable for projects involving reforestation, afforestation, forest rehabilitation, reduced-impact logging, avoided degradation, and natural regeneration. The tool accommodates both field-based sampling methods and the use of default carbon density values where allowed and justified.

4

The tool does not apply to below-ground dead roots, soil organic matter, or peat deposits, which are addressed under separate PCS tools. It is also not intended for estimating carbon in harvested wood products or non-woody debris. Any excluded pools must be justified in accordance with the methodology requirements.

5

Sampling and plot layout must be consistent with the procedures described in the tree and shrub biomass tool unless the methodology specifies alternative approaches for dead wood and litter. All results generated using this tool must be integrated with other biomass pools at the stratification and project levels following PCS aggregation rules.

Chapter 3 - Key Concepts and Definitions

3.1 Dead Wood

Dead wood refers to non-living woody biomass within the project area that remains onsite and continues to store carbon. It includes standing dead trees (snags), downed dead wood, coarse woody debris, stumps, and large woody fragments. Dead wood may result from natural mortality, past disturbance, harvesting residues, or project activities.

3.2 Standing Dead Trees

Standing dead trees, often called snags, are upright dead stems that have retained some vertical structure. Their biomass depends on diameter, height (or remaining height), and decay class. Standing dead trees may lose branches, bark, or upper stem sections over time, influencing biomass estimates.

3.3 Downed Dead Wood

Downed dead wood includes fallen stems, logs, large branches, and other woody material resting on or near the ground surface. Measurement typically involves length, diameter, or cross-sectional attributes. Decay class plays a significant role in determining density and biomass retention.

3.4 Decay Class

Decay class represents the degree of decomposition of dead wood. Classes range from recently dead (with structural integrity and bark present) to highly decomposed material that is soft, fragmented, and partially integrated into the forest floor. Each class is associated with specific density reduction factors.

3.5 Coarse Woody Debris (CWD)

Coarse woody debris refers to woody material above a defined minimum diameter, typically 7–10 cm, depending on methodology or national inventory standards. CWD plays a significant ecological role and stores substantial carbon.

3.6 Fine Litter

Fine litter consists of small organic materials such as leaves, twigs, and fragments typically below 2–5 cm in diameter. It forms the uppermost layer of decomposing organic material on the forest floor. Litter accumulates continuously and decomposes rapidly, causing carbon turnover within short timescales.

3.7 Litter Depth and Bulk Density

Litter depth is the vertical thickness of the litter layer. Bulk density represents the dry mass per unit volume and is necessary for converting litter volume to biomass. Depth and density vary with vegetation type, climate, and decomposition stage.

3.8 Expansion Factors for Dead Wood

Expansion factors convert field measurements such as log diameter and length into volume, and subsequently to dry biomass. These factors incorporate shape assumptions and density values based on decay class.

3.9 Carbon Fraction of Dead Wood and Litter

Dead wood and litter contain a proportion of carbon relative to their dry biomass. Typical carbon fractions range from 0.47 to 0.50 for woody material and may vary for litter depending on composition and decomposition level. These must be applied consistently when converting biomass to carbon stock.

3.10 Sampling Plot for Dead Wood and Litter

Sampling plots used for dead wood and litter follow similar placement principles as live tree plots but may differ in measurement subplots or transect orientation. Transect-based methods are commonly used for downed dead wood; small quadrats may be used for litter sampling.

3.11 Dead Wood Biomass Models

Dead wood biomass models use taper equations, volume formulas, and density adjustments to estimate the dry mass of logs, snags, and debris. Decay class determines the density reduction applied to initial biomass volume estimates.

3.12 Litter Biomass Models

Litter biomass is estimated through direct collection of samples within defined subplots, followed by drying and weighing. If direct sampling is not feasible, default litter biomass values or bulk density factors may be used with justification.

Chapter 4 - Parameters and Symbols

This chapter defines the parameters and symbols used throughout the dead wood and litter carbon estimation procedures. These parameters must be applied consistently and documented clearly in the Monitoring Report. Where project-specific measurements are not available, conservative default values must be used as allowed by the methodology.

Table 1. Parameters and Symbols Used in Dead Wood and Litter Estimation

Symbol	Description	Units	Notes
DBH_dead	Diameter at breast height of standing dead tree	cm	Used when allometric or snag equations require DBH
H_dead	Height of standing dead tree	m	Remaining height for snags
D_log	Diameter of downed log	cm	May include multiple diameter measurements along log
L_log	Length of downed log	m	Used for volume estimation
V_dead	Volume of dead wood	m³	Derived from diameter and length
ρ_dead	Bulk density of dead wood	g/cm³	Adjusted by decay class
DC	Decay class	—	Used to apply density reduction factors
BD_litter	Bulk density of litter	g/cm³	Used with litter depth to estimate biomass
Depth_litter	Litter layer depth	cm	Sampled within litter quadrats
Biomass_dead	Dead wood biomass	t/ha	Sum of all dead wood components
Biomass_litter	Litter biomass	t/ha	Derived from ground samples
CF_dead	Carbon fraction of dead wood	—	Default = 0.50 unless otherwise justified
CF_litter	Carbon fraction of litter	—	Typically 0.47–0.50
Plot_area	Plot size used for dead wood sampling	m²	May differ from live tree plots
PEF	Plot expansion factor	—	Converts plot values to per-hectare
Carbon_dead	Carbon stock in dead wood	tC/ha	Biomass_dead × CF_dead
Carbon_litter	Carbon stock in litter	tC/ha	Biomass_litter × CF_litter

Parameter Notes:

• Standing dead trees often lose structural components as they decompose, such as bark or crowns. When equations require DBH but the stem has lost integrity at breast height, alternative diameter measurement rules must be applied using lower measurement points or stump diameter measurements.

• Bulk density of dead wood must reflect the decay class. Advanced decay results in lower density, which must be applied through density reduction factors. Litter bulk density is highly variable and must be determined through field sampling when required by the methodology.

• Plot expansion factors must be calculated based on the area of each dead wood or litter sampling unit. Carbon fractions for dead wood and litter must be applied consistently and based on defensible scientific values.

Chapter 5 - Dead Wood Biomass Estimation Procedures

Dead wood biomass consists of standing dead trees and downed dead wood. Each component requires specific measurement procedures and calculation methods to ensure accurate biomass and carbon estimation. This chapter describes the procedures for quantifying dead wood biomass within sample plots using standardized field measurements, decay class adjustments, and volume-to-mass conversions.

5.1 Classification of Dead Wood for Measurement

1

Standing dead trees (snags)

Trees that remain upright but no longer exhibit signs of living tissue. Biomass depends on remaining height, DBH, and decay class.

2

Downed dead wood

Woody debris lying on the ground, including logs, fallen stems, and large branches. Biomass is derived from diameter, length, and decay-adjusted density.

Classification ensures that the appropriate measurement and calculation methods are applied.

5.2 Standing Dead Trees (Snags)

Standing dead trees must be measured using modified versions of live-tree approaches. Required measurements typically include DBH_sd (diameter at breast height) and remaining height (H_sd).

5.2.1 Estimating Volume of Standing Dead Trees

The volume of a standing dead tree may be estimated using taper-based formulas or by applying simplified geometric approximations. Commonly applied parameters include diameter at breast height, remaining height, and a form factor accounting for trunk taper (typically 0.5–0.7).

5.2.2 Adjusting Density by Decay Class

Standing dead wood density decreases with decomposition. The density value must be adjusted using decay class factors from Annex B:

• Apply species-level or generic live-wood density multiplied by the decay class density factor.

5.2.3 Estimating Biomass of Standing Dead Trees

Convert decay-adjusted volume to dry mass using the adjusted density and appropriate unit conversions to obtain dry mass in tonnes.

5.3 Downed Dead Wood

Downed dead wood includes logs and large woody fragments lying on the ground surface. Measurement procedures depend on plot design and must follow consistent protocols.

5.3.1 Volume of Downed Dead Wood

For cylindrical approximations, use midpoint diameter and length to compute log volume. When logs taper significantly, measure diameters at both ends and apply appropriate geometric formulas.

5.3.2 Adjusting Density for Decay

Assess decay class visually or with standard forestry classifications and apply the corresponding density reduction factors.

5.3.3 Biomass of Downed Dead Wood

Convert volume to dry mass using decay-adjusted density to obtain dry biomass within the plot.

5.4 Summation of Dead Wood Biomass Within the Plot

Total plot biomass for dead wood is the sum of standing dead biomass and downed dead biomass. This value must then be scaled to per-hectare values using the plot expansion factor.

5.5 Per-Hectare Biomass for Dead Wood

Apply the plot expansion factor (based on plot or transect area) to convert plot biomass to t/ha.

5.6 Conversion to Carbon Stock

Carbon stock for dead wood is obtained by multiplying biomass_dead by CF_dead (typically 0.50 unless species-specific values are used).

5.7 Documentation Requirements

The Monitoring Report must:

• Provide decay class definitions used;

• Present diameter, length, and height measurements;

• Identify density values and sources;

• Show all intermediate steps in biomass calculations;

• Present per-plot and per-stratum results clearly.

Chapter 6 - Litter Biomass Estimation Procedures

Litter biomass represents the fine organic material that accumulates on the forest floor, including leaves, twigs, small branches, fruiting bodies, and partially decomposed organic fragments. Unlike dead wood, litter has rapid turnover and requires direct sampling to obtain accurate biomass estimates. This chapter describes the standardized procedures for sampling, measuring, and calculating litter biomass within PCS project areas.

6.1 Litter as a Carbon Pool

Litter forms a dynamic carbon pool with relatively high variability across seasons and ecosystem types. It must be measured where required by the applicable PCS methodology. Because litter decomposes rapidly, sampling must be performed consistently within the monitoring period to ensure comparability.

Litter estimation relies on direct collection from defined subplots, bulk density determination, and area-based expansion to derive per-hectare biomass.

6.2 Litter Sampling Subplots

Litter biomass must be measured within dedicated subplots placed systematically or randomly within each sample plot. Subplot size may vary depending on vegetation density and methodology requirements, but common dimensions include:

• 0.5 m × 0.5 m

• 1 m × 1 m

Subplots must be located so that they represent average forest floor conditions. Placement must avoid anomalies such as decomposing logs, termite mounds, or unusually bare soil unless these features characteristically occur within the stratum.

6.3 Litter Depth Measurement

Litter depth must be measured at one or more points within each subplot using a ruler or calibrated probe. Depth measurements must represent the vertical thickness of the litter layer from the top surface to the mineral soil interface. If depth varies significantly within the subplot, multiple measurements must be taken and averaged.

Depth measurements help determine litter density and confirm consistency across sites but are not a substitute for direct biomass measurement.

6.4 Collection and Drying of Litter Samples

All litter material within the subplot must be collected carefully, ensuring that mineral soil is excluded. Samples must be placed in labeled containers or bags and transported to a drying facility. Drying must occur at a controlled temperature—typically 65–70°C—until constant mass is achieved.

The dry mass of each sample must be recorded. This value forms the basis for biomass per unit area and is the most accurate method for estimating litter biomass.

6.5 Litter Bulk Density (BD_l)

Bulk density is calculated as:

BD_l = Dry mass / Subplot volume

Where subplot volume = subplot area × mean litter depth.

Bulk density values may vary widely between ecosystems and must be determined through direct measurement unless a methodology explicitly permits default values.

6.6 Litter Biomass per Hectare

Biomass per unit area is calculated using:

Biomass (t/ha) = (Dry mass / Subplot area) × 10,000 m²/ha

When multiple subplots exist within a plot or stratum, the mean value must be used. Variance must be recorded for uncertainty analysis.

6.7 Carbon Stock in Litter

To convert litter biomass to carbon:

Carbon_litter = Biomass_litter × CF_litter

Where the default carbon fraction for litter (CF_litter) is 0.47 unless species- or stratum-specific values are available.

6.8 Treatment of Exceptional Conditions

Litter biomass may be influenced by seasonal patterns, recent disturbances, or extreme weather events. When such conditions affect measurement, the Monitoring Report must describe the circumstances and explain how sampling remains representative.

If litter accumulation is extremely uneven, additional subplots may be required to ensure accurate estimates of stratum-level biomass.

6.9 Documentation Requirements

The Monitoring Report must include:

• Subplot dimensions and placement rules

• Depth measurements

• Dry mass values for each litter sample

• Calculated bulk density and biomass per hectare

• Carbon fraction values used

• Intermediate and final calculation tables

All raw data must be archived for verification.

Chapter 7 - Scaling Litter and Dead Wood Carbon Stocks to Stratum and Project Levels

Scaling ensures that biomass and carbon estimates derived from sample plots accurately represent the conditions across entire strata and the full project boundary. This chapter describes how to aggregate plot-level results for dead wood and litter; how to derive stratum-level means; and how to integrate carbon stocks across strata into project-level totals.

7.1 Stratum-Level Biomass Estimates

Dead wood and litter biomass must be calculated separately for each stratum. Plot-level per-hectare values obtained through the procedures described in previous chapters must be averaged within each stratum. This mean biomass per hectare forms the basis for estimating total stratum-level biomass.

Stratum-level biomass values must reflect all valid plots measured within the stratum. If outlier plots are excluded due to clearly documented measurement errors or disturbances outside the scope of the methodology, such exclusions must be justified.

7.2 Scaling Biomass to Stratum Area

Total biomass in a stratum is calculated as:

Total biomass = mean biomass per ha × stratum area (ha)

If a methodology requires reporting dead wood and litter separately, each pool must be scaled independently.

7.3 Carbon Stock per Stratum

Once total biomass in a stratum has been determined, carbon stock is derived using the appropriate carbon fraction:

Carbon_stratum = Total biomass × CF_pool

Where CF_pool may differ between dead wood (typically 0.50) and litter (typically 0.47). Each pool must use its corresponding carbon fraction.

7.4 Aggregation of Carbon Pools to Project Level

Project-level carbon stock is the sum of carbon stocks from all strata and all included pools:

Project carbon = Σ Carbon_stratum,pool

If the methodology includes additional pools (e.g., live biomass, soil carbon), results from this tool must be integrated with estimates from other PCS tools to generate a complete project-level carbon assessment.

7.5 Tracking Carbon Stock Changes Over Time

Carbon stock change is determined by comparing baseline values with monitoring-period values for each stratum. Dead wood and litter may experience increases or decreases due to natural mortality, restoration activities, decomposition, disturbances, or improved forest management. These changes must be captured consistently across monitoring periods.

Project-level carbon stock change is the sum of all stratum-level changes across included pools.

7.6 Addressing Disturbances and Transfers Between Pools

Dead wood and litter pools may increase or decrease due to disturbances such as storms, pests, fire, or harvesting. When such events occur, biomass transfers between pools must be documented clearly.

Examples include:

• A fallen live tree becomes downed dead wood.

• Decomposing dead wood contributes to litter and eventually soil carbon.

Only the pools included under the methodology must be quantified; transfers to excluded pools need to be described but not quantified.

All disturbances must be described in the Monitoring Report, including their impact on carbon stocks.

7.7 Reporting Requirements for Scaling

The Monitoring Report must include:

• Mean biomass per hectare per stratum for both dead wood and litter

• Total stratum biomass and carbon for each pool

• Project-level totals

• Carbon stock changes since baseline

• Maps or spatial files showing stratum boundaries

• Documentation of disturbances or unusual conditions that influenced stock changes

All calculations must be transparent and replicable.

Chapter 8 - Uncertainty and Conservativeness

Uncertainty arises naturally in the quantification of dead wood and litter due to spatial variability, decomposition stages, measurement limitations, and parameter selection. This chapter outlines the procedures for identifying, quantifying, and managing uncertainty in biomass and carbon estimates for these pools. Conservativeness must be applied wherever uncertainty creates a risk of overestimation.

8.1 Sources of Uncertainty

Uncertainty in dead wood and litter biomass estimation arises primarily from:

• Sampling variability, due to uneven spatial distribution of debris and litter accumulation.

• Measurement error, including diameter, length, height, and depth measurements for dead wood and litter.

• Decay class assignment, which introduces subjectivity and affects density values.

• Density values, which vary by species, decay state, and environmental conditions.

• Carbon fraction values, which may differ between woody and non-woody materials.

Each source must be addressed within the uncertainty analysis to ensure that reported carbon stocks reflect realistic ranges.

8.2 Sampling Uncertainty

Sampling uncertainty is derived from the variability of plot-level biomass measurements. The standard error and confidence interval must be calculated for each stratum. If the sampling uncertainty exceeds the threshold established by the applicable PCS methodology, additional plots may be required or conservativeness must be applied.

Strata with highly variable biomass distributions—such as post-disturbance forests or mangroves with dense woody debris—may require greater sampling intensity.

8.3 Measurement Uncertainty

Measurement uncertainty may occur due to inconsistent field techniques or difficult site conditions. To reduce this uncertainty:

• Diameter and length must be measured using calibrated equipment.

• Decay class must be assessed using clear classification criteria.

• Litter depth and mass must be recorded carefully, avoiding inclusion of mineral soil.

The Monitoring Report must document field conditions that may have influenced measurements and describe steps taken to ensure measurement accuracy.

8.4 Parameter Uncertainty

Dead wood density and carbon fraction values vary with decay class and environmental conditions. When species- or decay-class-specific density values are unavailable, default values must be applied conservatively. For highly decomposed material, lower density values should be applied to avoid overestimation of biomass.

Litter bulk density varies significantly between strata; using default values without justification can introduce substantial error. Direct measurements should be used whenever feasible.

8.5 Combined Uncertainty Assessment

The uncertainty of dead wood and litter pools may be assessed independently from live biomass pools or integrated with overall project uncertainty, depending on methodology requirements. Combined uncertainty must consider:

• Variance within each pool

• Number of plots sampled

• Parameter uncertainty

• Confidence intervals

If uncertainties across multiple pools are consolidated, the calculation method must be transparent and documented.

8.6 Application of Conservativeness

Conservativeness must be applied when uncertainty is high or measurement conditions result in potential overestimation. This may involve:

• Using lower-bound density values for higher decay classes

• Applying reduced carbon fractions where decomposition is advanced

• Selecting the lower range of plausible biomass values when decay class is ambiguous

• Applying deductions at the stratum level when sampling uncertainty exceeds the acceptable threshold

Conservativeness ensures environmental integrity while allowing projects to account for these pools responsibly.

8.7 Reporting of Uncertainty

The Monitoring Report must present:

• Standard deviation, standard error, and confidence interval for each stratum

• Decay class distribution of measured dead wood

• Density values used and their sources

• Bulk density and depth measurements for litter

• Any deductions applied due to uncertainty

• A clear explanation of how conservativeness was implemented

The report must allow a VVB to replicate all uncertainty calculations fully.

Chapter 9 - Reporting Requirements

Accurate reporting of dead wood and litter biomass is essential to ensure transparency, traceability, and reproducibility of carbon stock estimates. The Monitoring Report must present all measurement procedures, parameter values, and calculation steps used to derive biomass and carbon stock estimates for each pool. This chapter outlines the minimum reporting elements required for validation and verification.

9.1 Description of Strata and Sampling Design

The Monitoring Report must describe each stratum where dead wood and litter measurements were conducted. This includes ecological characteristics, sampling justification, and any changes in stratum boundaries since the previous period. The sampling design must be documented, including subplot size, plot layout, number of samples, and the rationale for sampling intensity. Maps or geospatial files must be provided to show the spatial distribution of sample plots.

9.2 Dead Wood Measurements

The report must present all measurements used to quantify standing dead wood and downed dead wood. Required information includes:

• DBH and remaining height for standing dead trees

• Diameters and lengths of downed wood pieces

• Decay class assignment for each item measured

• Field conditions that may have influenced measurements

Tables summarizing measured values must accompany the report. Any assumptions, estimation procedures for incomplete logs, or adjustments for missing data must be documented clearly.

9.3 Litter Measurements

The Monitoring Report must include subplot dimensions, depth measurements, and dry mass results for litter samples. The number of subplots per stratum and the representativeness of their placement must be documented. If litter samples were collected under unusual environmental conditions (e.g., heavy rainfall, recent leaf fall), the report must describe these conditions and their potential impact on results.

Dry mass data, moisture adjustments, and calculation steps must be provided either within the report or in an appendix.

9.4 Parameter Values and Sources

All parameter values used in calculations must be reported, including:

• Dead wood density values by decay class

• Carbon fraction values for dead wood and litter

• Bulk density values for litter

• Volume formulas and form factors

Sources for each parameter must be cited. If project-specific measurements replace default parameter values, full documentation of laboratory methods or field procedures must be included.

9.5 Plot-Level and Stratum-Level Biomass Calculations

The report must provide plot-level biomass results for dead wood and litter, including:

• Standing dead biomass per plot

• Downed dead biomass per plot

• Litter biomass per subplot or plot

• Biomass per hectare after applying expansion factors

Stratum-level values must show means, sample size, variance, and confidence intervals. If strata were combined or subdivided for improved accuracy, the rationale must be stated clearly.

9.6 Aggregation to Project-Level Carbon Stocks

The Monitoring Report must present:

• Total carbon stock for each stratum

• Combined carbon stock for dead wood and litter pools across the project

• Changes in carbon stock since baseline or previous monitoring period

All aggregation steps must be shown explicitly.

9.7 Treatment of Disturbance, Decomposition, and Transfers Between Pools

The report must describe any disturbances—natural or anthropogenic—that affected dead wood or litter during the period. This includes storms, fires, disease outbreaks, harvesting, or site preparation activities. Transitions from live biomass to dead wood, or from dead wood to litter, must be explained where relevant.

Any decomposition adjustments applied must be documented.

9.8 Uncertainty and Conservativeness

Uncertainty values and calculations must be reported, including:

• Standard deviation, standard error, and confidence intervals

• Parameter uncertainty considerations

• Decay class variability

• Litter mass variability

If conservativeness was applied, the method, magnitude, and rationale must be clearly documented.

9.9 Supporting Documentation and Archiving

Supporting materials must be retained and made available for verification. These include:

• Field sheets and raw measurements

• Photographic evidence of decay classes or complex dead wood structures

• Laboratory drying records for litter samples

• GIS data showing plot and subplot locations

• Calculation spreadsheets

Evidence must be organized so that a VVB can replicate all estimates.

Chapter 10 - Quality Assurance and Quality Control (QA/QC)

Quality assurance and quality control ensure that measurements, calculations, and reporting for dead wood and litter biomass are accurate, replicable, and consistent with PCS requirements. This chapter establishes the procedures that must be followed to reduce measurement error, verify data integrity, and maintain transparent documentation throughout the carbon accounting process.

10.1 QA/QC for Sampling Design

The sampling design must undergo review before field work begins to confirm that the number of sampling plots and subplots satisfies methodological requirements. This review must evaluate whether the sampling strategy adequately reflects site variability, especially in ecosystems with uneven distribution of woody debris or litter. Adjustments to sampling intensity or stratification must be justified and documented.

10.2 Field Measurement QA/QC

Field teams must apply consistent measurement procedures across all sample plots. Instruments used to measure diameter, length, height, and depth must be calibrated prior to field deployment. Detailed instructions must be provided to testers to ensure uniform decay class assessment, proper handling of litter samples, and avoidance of contamination with mineral soil.

Supervisors must periodically observe field crews to verify measurement accuracy and adherence to protocols. When discrepancies are found, field corrections must be made and documented.

10.3 Litter Sampling QA/QC

Litter sampling requires particular consistency due to its rapid turnover and sensitivity to disturbance. Subplots must be established according to defined placement rules, and all organic material within the subplot must be collected without loss. Samples must be labeled clearly, stored appropriately, and dried under controlled laboratory conditions.

When moisture content is high, drying must continue until a stable mass is achieved. Laboratory balances must be calibrated and records maintained. Any anomalies in mass or decomposition state must be recorded before final biomass is calculated.

10.4 Dead Wood Measurement QA/QC

Measurements of standing dead trees and downed dead wood must be verified to ensure correct application of diameter and length measurement techniques. Decay class classification must follow the definitions in this tool. If different field teams work across plots, cross-checking between teams must be performed to maintain consistency.

In cases where dead wood is fragmented or partially buried, the portion included in biomass calculations must be documented, and assumptions clearly stated.

10.5 Data Entry and Verification

All field data must be entered into electronic formats using controlled procedures. Quality checks must be implemented to identify missing values, extreme outliers, or inconsistent decay class assignments. When using spreadsheets or data collection applications, automated validation rules should be applied to prevent input errors.

Corrections must be traceable, with justification recorded for each adjustment. Raw field notes must be retained for cross-referencing.

10.6 Verification of Parameter Values

Default values for density, decay class factors, carbon fractions, and bulk density must be reviewed before use to confirm their relevance and consistency with the project area. When project-specific measurements are used, the laboratory or field procedures must be documented. Any update to parameter values between monitoring periods must be accompanied by justification.

Where decay class-specific densities are uncertain, conservative values must be applied to prevent overestimation of carbon stocks.

10.7 Calculation QA/QC

All biomass and carbon calculations must undergo internal review. This review must confirm that plot expansion factors were applied correctly, that units were converted properly, and that biomass-to-carbon conversions followed the required procedures. If automated spreadsheets or models are used, formulas must be checked to ensure they reflect the methodological requirements accurately.

Independent recalculation of a subset of plots is recommended as part of QA/QC. Any discrepancies must be investigated, corrected, and recorded.

10.8 Documentation and Record Management

All QA/QC procedures must be documented fully in the Monitoring Report or in a dedicated annex. Documentation must include:

• Calibration records for measurement tools

• Field verification logbooks

• Data entry quality checks

• Laboratory drying records for litter samples

• Calculation audits

• Notes on any deviations from standard procedures

Records must be stored securely and retained throughout the project’s crediting period.

10.9 Continuous Improvement

Projects must periodically review and refine QA/QC procedures to incorporate updated scientific knowledge, improved measurement techniques, or lessons learned from verification feedback. Any modifications to QA/QC procedures must be applied consistently across subsequent monitoring periods to maintain comparability.

Annex A - Decay Class Definitions and Density Reduction Factors

Decay class assignment is essential for adjusting wood density as dead material decomposes. The following standardized decay class system must be used for PCS projects.

A.1 Decay Class Definitions

Decay Class	Description	Physical Characteristics
Class 1	Recently dead	Bark intact, branches present, wood hard, little discoloration
Class 2	Early decomposition	Bark partly missing, slight softening, limited fungal activity
Class 3	Moderate decomposition	Bark mostly absent, wood soft in outer layers, visible decay
Class 4	Advanced decomposition	Wood easily broken by hand, deep softness, significant fragmentation
Class 5	Highly decomposed	No structural integrity, wood crumbles easily, partially integrated into forest floor

These definitions must be applied consistently across all sampling periods.

A.2 Density Reduction Factors

Density decreases with decomposition. The following density factors adjust live-wood density to obtain dead-wood density:

Decay Class	Density Factor (DF)	Notes
Class 1	0.90	Minimal decomposition
Class 2	0.75	Minor density loss
Class 3	0.55	Moderate density loss
Class 4	0.35	Significant density loss
Class 5	0.20	Advanced decay, highly conservative

These factors must be applied to species- or genus-level live wood density values when estimating dead wood biomass.

Annex B - Default Density and Carbon Fraction Tables

Default density values may be used when species-specific or region-specific data are unavailable. The Monitoring Report must justify the use of defaults.

B.1 Default Wood Density for Common Vegetation Types

Vegetation Type	Live Wood Density (g/cm³)
Tropical hardwoods	0.60
Mangroves (Rhizophora)	0.83
Mangroves (Avicennia)	0.65
Temperate hardwoods	0.55
Softwoods / Conifers	0.42
Dryland species (general)	0.50

After applying decay class reduction factors, these values produce decay-adjusted density.

B.2 Carbon Fraction Values

Material Type	Carbon Fraction
Dead wood	0.50
Litter (fine organic matter)	0.47
Mixed woody and non-woody litter	0.48

Carbon fractions may be replaced with laboratory-derived values if available.

Annex C - Litter Sampling Templates

These templates standardize field sampling and ensure reproducibility in reporting.

C.1 Litter Sampling Field Form

Subplot ID	Plot ID	Coordinates	Subplot Area (m²)	Litter Depth (cm)	Fresh Mass (g)	Dry Mass (g)	Notes

All fresh and dry mass measurements must use calibrated scales.

C.2 Litter Bulk Density Calculation Template

Subplot ID	Dry Mass (g)	Volume (cm³)	Bulk Density (g/cm³)	Biomass (t/ha)

Volume = Subplot Area × Litter Depth Biomass = (Dry Mass / Subplot Area) × 10,000

Annex D - Dead Wood Field Measurement Templates

Field forms must capture all attributes needed for accurate biomass estimation.

D.1 Standing Dead Tree Measurement Template

Tree ID	Plot ID	Species (if known)	DBH_sd (cm)	Height_sd (m)	Decay Class	Density Factor	Notes

D.2 Downed Dead Wood Measurement Template

Piece ID	Plot ID	Diameter D (cm)	Length L (m)	Decay Class	Density Factor	Volume (m³)	Biomass (kg or t)	Notes

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If you want, I can:

• Convert other numbered sub-sections into steppers as well,

• Add code-block examples for the key calculation formulas (volume → biomass → carbon) using the GitBook code block pattern, or

• Provide ready-to-use calculation spreadsheet templates in CSV/Markdown table format.