Division Div 5 - Carbon Credits (Carbon Farming Initiative—Estimation of Soil Organic Carbon Sequestration Using Measurement and Models) Methodology Determination 2021 - sets out that change in soil organic carbon in a CEA for a reporting period must be worked out between the first estimation event in the CEA and the last estimation event in the reporting period for a CEA. The difference is conservatively estimated by applying a specified probability of exceedance estimation based on the difference between the mean of the soil organic carbon stock at the first estimation event and the mean of the soil organic carbon stock at the last estimation event in the reporting period. The probability of exceedance approach uses the variance of each estimate and its degrees of freedom (based on the number of samples taken), and a statistical confidence level set out in the Supplement (alpha value for the students t-test) to ensure the estimate of the change that has occurred in the CEA is conservative.

Division 5 sets out that change in soil organic carbon in a CEA for a reporting period must be worked out between the first estimation event in the CEA and the last estimation event in the reporting period for a CEA. The difference is conservatively estimated by applying a specified probability of exceedance estimation based on the difference between the mean of the soil organic carbon stock at the first estimation event and the mean of the soil organic carbon stock at the last estimation event in the reporting period. The probability of exceedance approach uses the variance of each estimate and its degrees of freedom (based on the number of samples taken), and a statistical confidence level set out in the Supplement (alpha value for the students t-test) to ensure the estimate of the change that has occurred in the CEA is conservative.

If a project proponent uses model-only or model-assisted estimates to calculate the change in soil organic carbon stock for a CEA for a reporting period, then Schedule 1 cannot be used to calculate that amount for the CEA for any subsequent reporting period.

In this Schedule:

0–30 cm layer of soil means the soil layer measured from the soil surface to a soil depth of 30 centimetres.

0–x cm layer of soil means the soil layer measured from the soil surface to a soil depth greater than 30 centimetres referred to as x.

30–x cm layer, of soil, means the soil layer measured from the lower end of the 0-30 cm layer of the soil to the lower end of the 0-x cm layer of the soil.

calibration sample—see section 3(4) of this Schedule.

composite sample—see section 3 of this Schedule.

ESM—see section 13 of this Schedule.

estimation event is a point in time for which carbon stocks are estimated in a CEA in accordance with section 5 of this Schedule.

first estimation event, is the first estimation event for a CEA that occurred in accordance with paragraph 5(2)(a) of this Schedule.

fine earth means soil material having a particle size ≤ 2 mm.

gravel means soil material having a particle size > 2 mm.

last estimation event, for a CEA, is the last estimation event for the CEA in a reporting period which is covered in the offsets report for that reporting period.

layer means a 0-30 cm layer, 30-x cm layer or a 0-x cm layer.

modelled carbon stock estimate is:

(a) a model-only estimate of carbon stocks for a CEA for a time that corresponds, as closely as required by the Supplement, with an estimation event; and

(b) in the form of a geospatial file for the CEA (or multiple applicable CEAs) that meets the requirements of the Supplement; and

(c) provides at least three geospatially distinct estimates of carbon stocks (in tonnes of soil organic carbon per hectare) within each stratum in the CEA for as many layers (or sublayers) as nominated, or required, under section 10 of this Schedule, and a specification of the oven dry whole soil mass for each carbon stock, to enable validation of the model and estimation of variance in accordance with Division 4 of this Schedule.

model-validation sample—see section 3 of this Schedule.

sample—see section 3 of this Schedule.

sampling round—see section 7 of this Schedule.

sub-layer means a depth of soil within a layer that is less than the layer.

Note: The 0-30 cm layer and 30-x cm layers of a sample will be sub-layers of the 0-x cm layer of the sample.

SOCCEA—see section 11 of this Schedule.

validated model carbon stock estimate is a modelled carbon stock estimate that meets the validation requirements set out in the Supplement and based on which of the following variables have been calculated:

(a) extrapolated bias of the model given by the Supplement, in tonnes of soil organic carbon per hectare;

(b) fraction of variance given by the Supplement, in tonnes of soil organic carbon per hectare;

View image in the official source—see section 12 of this Schedule.

whole soil means all material contained within a soil layer including both gravel and fine earth.

(1) In this Schedule a sample may be:

(a) an individual sample taken from a particular location; or

(b) a composite sample (composite sample) which combines samples taken from a number of locations into a single sample consistent with any requirements in the Supplement.

(2) A sample must be obtained and analysed consistent with the requirements in Division 2 of this Schedule.

(3) In this Schedule a model-validation sample is a sample that is:

(a) an individual sample taken from a particular location; and

(b) not a composite sample; and

(c) collected after a modelled carbon stock estimate is provided to the Regulator for an estimation event in the relevant CEA consistent with any requirements in the Supplement.

(4) In this Schedule a calibration sample is a sample that is collected before a modelled carbon stock estimate is provided to the Regulator for the relevant CEA consistent with any requirements in the Supplement.

Note: This definition is not intended to limit the data collected for the purposes of calibrating models but only what data can also feed into calculating abatement.

Division 2—Operation of a soil carbon project under this Schedule

Subdivision 1—Operation of Division

4 Operation of a soil carbon project

Where this Schedule has been applied to a CEA that is part of an eligible offsets project for an estimation event, the project must be operated in accordance with this Schedule for the relevant CEA for the duration of the project’s crediting period.

Note: This Schedule allows measurement-based, model-only and model-assisted estimation of soil organic carbon stocks.

Subdivision 2—Project accounting

5 Steps involved in accounting for a soil carbon project

(1) For each area of land included as part of a project area for a soil carbon project, the land must be mapped according to section 6 of this Schedule.

(2) The following must occur, for each CEA:

(a) a first estimation event, involving:

(i) a sampling round (the baseline sampling round) in the CEA; and

(ii) for the CEA, an estimate of soil organic carbon stock under either Subdivision 1 of Division 4 of this Schedule as required by subsection 14(3) of this Schedule or Subdivision 4 of Division 4 of this Schedule as required by subsection 14(5) of this Schedule,

that must occur:

(iii) if the CEA is part of the project area of the project when the section 27 declaration for the project is made—before the end of the first reporting period for the project; or

(iv) if the CEA or any land in it is included in the project area as the result of a section 29 application—before the end of the first reporting period for the project during which the land is included in the project area; and

(b) for the duration of the crediting period for the project, at least one subsequent estimation event, involving:

(i) a sampling round in the CEA; and

(ii) for the CEA, an estimate of soil organic carbon stock under either Subdivision 1 of Division 4 of this Schedule as required by subsection 14(3) of this Schedule or Subdivisions 1 and 3 of Division 4 of this Schedule as required by subsection 14(5) of this Schedule,

that must occur not later than every 10 years after the previous estimation event for the CEA that meets the requirements of this subsection; and

(c) for the duration of the crediting period for the project, at least one subsequent estimation event, involving for the CEA, an estimate of soil organic carbon under Subdivisions 1, 2 or 3 of Division 4 of this Schedule as required, respectively, by subsections 14(3), 14(4) or 14(5) of this Schedule, that must occur not less than 1 year and not later than every 5 years after the previous estimation event for the CEA.

Note 1: The application of subsection 14(3) of this Schedule results in measurement-based estimates. The application of subsection 14(4) results in model-only estimates and subsection 14(5) results in model-assisted estimates (models with sampling).

Note 2: Sampling is not conducted on exclusion areas or emissions accounting areas.

(3) Unless the Regulator agrees in writing that exceptional circumstances exist, an estimation event must meet any timing requirements specified in the Supplement.

Note: Exceptional circumstances may include poor weather conditions that inhibit site access or where the soil moisture is unsuitable for sampling at the planned time.

(4) For each reporting period for the project, all CEAs for which an estimation event (other than the first estimation event) has been completed to determine an estimate of soil organic carbon in those CEAs under Subdivisions 1, 2 or 3 of Division 4 of this Schedule as required, respectively, by subsections 14(3), 14(4) or 14(5) of this Schedule, must be included in the net abatement calculations.

(5) For each estimation event conducted for a CEA, the CEA must be divided into strata consistent with any requirements in the Supplement.

6 Carbon estimation areas (CEAs), exclusion areas and emissions accounting areas

(1) The project proponent must map land within a project area for the project into one or more carbon estimation areas (CEAs) such that:

(a) all the land in each CEA:

(i) is eligible land; and

(ii) is subject to the carrying out or maintenance of at least one eligible management activity until the end of the permanence obligation period for the project; and

(iii) is within a single State or Territory; and

(iv) has identical responsible landholders; and

(b) if the project was declared as an eligible offsets project after 1 September 2020—the mapping is completed, and provided to the Regulator as required by the Supplement, prior to each first estimation event for each CEA.

(2) The project proponent may map non-contiguous parts of a project area as a single CEA, where the furthest boundaries of non-contiguous areas do not exceed 10 kilometres in distance from each other within a singular CEA.

(3) The boundaries of a CEA may be revised only to merge and split existing CEAs in accordance with requirements in the Supplement.

Note: If the boundaries of a CEA are revised, baseline emissions and baseline soil organic carbon stocks may need to be recalculated.

(4) The project must not remove project areas which would remove part of a CEA rather than the entire CEA unless such a removal is provided for in, and meets the requirements of the Supplement.

(5) The project proponent may map other land within the project area for the project into one or more exclusion areas such that:

(a) no land management or agricultural activities are to be conducted in the area; and

(b) none of the land is included in a CEA.

Note: Exclusion areas would generally be dwellings, roads, dams or other infrastructure.

(6) Any part of the project area which is neither a CEA nor an exclusion area is an emissions accounting area.

Note: The soil organic carbon stock change of an emissions accounting area is not included in the net abatement amount, but emissions from these areas are included in the net abatement amount calculations. Emissions accounting areas are likely to include agricultural land which is not suitable or conducive to sampling (such as rocky outcrops) and densely forested land where land management activities are not applied.

(7) Subsections (8), (9) and (10) apply to a CEA that:

(b) includes land that is not eligible, or has ceased to be eligible, because it does not satisfy paragraph 9(1)(b) of this determination (dwelling or structures); and

(8) Despite subparagraph (1)(a)(i), ineligible land may remain in a CEA if:

(a) less than the smaller of 1% or 5 hectares of the area of the CEA is covered by dwellings or other structures; or

(b) the Regulator determines, in accordance with subsection (10), that the land can continue to remain in the CEA.

Note: CEAs must not contain dwelling or structures at the time of stratification, however land may remain in the CEA if dwellings or other structures are constructed on it after stratification in accordance with subsection (8).

(9) If subsection (8) does not apply, land in CEAs that is ineligible land must be removed from the project area.

(10) The Regulator may determine that land can continue to be mapped as a CEA if:

(a) the Regulator has consulted with the project proponent about making such a determination; and

(b) the continued mapping of the CEA is unlikely to result in the crediting of non-genuine carbon abatement; and

(c) the Regulator considers that the continued mapping of the CEA is appropriate, having regard to all the circumstances.

(11) Subsection (12) applies to a CEA that:

(b) includes land that is not eligible, or has ceased to be eligible, because it does not satisfy paragraph 9(2)(a) of this determination.

(12) The project proponent must remove the CEA from the project area.

(13) The mapping of each CEA, exclusion area or emissions accounting area must be done in accordance with the Supplement.

7 Sampling design

(1) Each estimation event must involve, consistent with any requirements in the Supplement:

(a) the division of each CEA into at least three strata; and

(b) taking at least three samples in each stratum where a sampling round is required under subsection 5(2).

(2) The sampling design must meet any requirements included in the Supplement.

(3) For each sampling round, the project proponent must submit to the Regulator, prior to undertaking any sampling, a sampling plan, meeting any requirements included in the Supplement.

8 Sampling

(1) The nominated soil depth for the baseline sampling round in a CEA:

(a) must be 30 centimetres; and

(b) must be greater than 30 centimetres where required by section 10(2)(b) of this Schedule, or the Supplement; and

(d) must be consistent across the CEA.

(2) The sampling undertaken must:

(a) aim to achieve:

(i) for an estimation event after the first estimation event—the equivalent soil mass for the CEA as used for the previous estimation event; and

(ii) the depth of soil disturbed by management activities (consistent with section 10(2)(b)(ii) of this Schedule) plus 10 centimetres; and

(iii) depths consistent with any requirements in the Supplement; and

Note: Bedrock or impenetrable layers may prevent a sample from achieving its nominated soil depth.

(b) if the sampling undertaken achieves a depth greater than 30 centimetres—obtain and analyse separate information for the 0-30 cm layer of the soil and the soil at depth greater than 30 centimetres (which may include sub-layer analysis); and

(i) has experience in the collection of soil samples; and

(ii) has a good understanding of the sampling requirements of this determination and the Supplement; and

(iii) has no financial interest in the soil carbon project; and

(iv) did not prepare or review the land management strategy for the project; and

(v) meets any requirements included in the Supplement; and

Note : Being paid to undertake the sampling would not involve a breach of subparagraph (iii).

(d) take into account any recommendations in the Supplement; and

(e) meet any requirements included in the Supplement.

9 Sample analysis

(1) The preparation of a soil sample and analysis of the soil sample must:

(a) meet any requirements included in the Supplement; and

(b) take into account any recommendations in the Supplement.

(2) The preparation of a soil sample must be undertaken by a person who meets the requirements set out in subparagraphs 8(2)(c)(ii) to (iv) of this Schedule.

Note: Being paid to undertake sampling preparation would not involve a breach of subsection (2).

10 Working out the change in soil organic carbon stock for a CEA

(1) If, pursuant to section 15 of this determination, the change in soil organic carbon stock for a reporting period for a CEA with a specified probability of exceedance is worked out using Schedule 2, then that change must be worked out using equation 116.

(2) In working out the change in soil organic carbon stock for a reporting period for a CEA with a specified probability of exceedance:

(a) for the 0-30 cm layer of the CEA, Division 4 of this Schedule must be applied to the first estimation event in the CEA and the last estimation event (that is not the first estimation event) in the reporting period, with Division 5 of this Schedule used to calculate the difference between the two estimation events; and

(b) for the 0-30 cm layers and 0-x cm layers of the CEA, Division 4 of this Schedule must be applied to the first estimation event in the CEA and the last estimation event (that is not the first estimation event) in the reporting period, with Division 5 of this Schedule used to calculate the difference between the two estimation events:

(i) if the project proponent elects to account for soil organic carbon changes for the 0-x cm layer of the estimation for the CEA; or

(ii) if land management activities disturb the soil deeper than 20 centimetres (where x must equal or exceed the depth of disturbance plus 10 centimetres); or

(iii) if an estimate under equation 116 were to be applied to the 0-x cm layer, and the corresponding change in soil organic carbon stock in the 30-x cm layer in the CEA calculated is negative as determined by subsection (3); and

Note: This subsection allows participants to elect to estimate and account for changes in the 30-x cm layer – unless they are required to account for it under the circumstances listed in paragraph (2)(b). Accounting for the 30-x cm layer can make it more difficult to detect changes in the 0-30 cm layer due to potentially slower rates of change in the deeper layer and the effect of baseline soil organic carbon stocks on the standard error terms in equation 116. The purpose of this subsection is to allow the 30-x cm layer to be monitored for soil organic carbon increases but accounting to occur just for the 0-30 cm layer, unless negative changes occur in the 30-x cm layer which then requires the 30-x cm layer to be included in accounting to prevent over crediting.

(c) if Divisions 4 and 5 of this Schedule are applied to the 0-x cm layer of the estimation for the CEA—the change in organic in soil organic carbon stock for a CEA for equation 116 is deemed to be the value for the 0-x cm layer, not the 0-30 cm layer.

Note: Crediting is based on the whole soil profile (0-x cm layer). However, crediting can be based on only the 0-30 cm layer if permitted by this section. Results of the 30-x cm layer contribute to crediting once changes are observed in the layer. Reporting of results in the 0-30 cm layer is required, even if it does not impact crediting, to inform the national inventory.

(3) For the purposes of subparagraph (2)(b)(iii), the change in soil organic carbon stock in the 30-x cm layer for a reporting period is taken to be negative if the change in that layer View image in the official source worked out in accordance with the following equation has a value less than 0:

| View image in the official source | equation 70 |

View image in the official source is the change in soil organic carbon stock for the CEA for the reporting period between the first estimation event t0 for the CEA and the last estimation event tx for the CEA in the reporting period, for the 0-x cm layer, worked out using equation 113.

View image in the official source is the standard error of the mean difference (the View image in the official source) between total soil organic carbon stock for the CEA between the first estimation event t0 for the CEA and the last estimation event tx for the CEA in the reporting period, in tonnes of soil organic carbon, for the 0-x cm layer, worked out using equation 114.

View image in the official source is the value of the quantile function (inverse distribution function) for the t-distribution with the value for alpha (View image in the official source) set out in the Supplement and the value for the degrees of freedom, View image in the official source for the 0-x cm layer worked out using equation 115.

Note: The value should be negative.

(4) The change in soil organic carbon stock with a specified probability of exceedance for a reporting period for a CEA which has not undergone an estimation event (or has only undertaken the first estimation event) in the reporting period is zero.

Subdivision 1—Area, soil mass and estimation approaches for the calculation of soil organic carbon stock and sampling variance for a CEA

11 Working out the soil organic carbon stock for a CEA

The total estimated soil organic carbon stock for a CEA (the SOCCEA), in tonnes of soil organic carbon, is worked out using the following equation:

| View image in the official source | equation 71 |

View image in the official source is the mean soil organic carbon stock for the CEA, in tonnes of carbon per hectare, given by section 14 of this Schedule.

12 Working out the sampling variance of soil organic carbon stock for a CEA

The sampling variance of soil organic carbon stock for a CEA (the View image in the official source), in (tonnes of soil organic carbon)2, is worked out using the following equation:

| View image in the official source | equation 72 |

View image in the official source is the sampling variance of the mean soil organic carbon stock for the CEA, in (tonnes of soil organic carbon per hectare)2, given by section 14 of this Schedule.

13 Determining Equivalent Soil Mass (ESM) from the sampled soil masses derived during the baseline sampling round

(1) The equivalent soil mass (the ESM), in tonnes of oven dry whole soil per hectare, for a CEA must be worked out in accordance with this section and the Supplement based on any samples collected from the CEA for the purposes of paragraph 5(2)(a) of this Schedule for the first estimation event.

Note 1: The Supplement may include provision for sub-layer analysis (analysing carbon stocks at more discrete intervals than 0-30 cm, 0-x cm) which allows for the mass of each sample to be adjusted by removing sub-layers from carbon stock estimates to keep masses between sample rounds comparable. Restrictions on removal of sub-layers will be subject to requirements such as to continue to account for the soil mass to the depth of any disturbance as per paragraph 8(2)(a) of this Schedule and the Supplement.

Note 2: The samples for which the ESM is worked out can include calibration samples and model-validation samples.

(2) Rank from smallest to largest for the CEA the mass of oven dry whole soil in the 0-30 cm or 0-x cm layer for the sample (View image in the official source) collected for the first estimation event, worked out in accordance with any requirements in the Supplement, in tonnes of oven dry whole soil per hectare.

(3) With the ranked samples from subsection (2), assign a sequential rank k from 1 for the smallest through to N for the largest, where N is the total number of samples collected for a CEA for the first estimation event.

(4) A percentile P must be worked out for each sample k using the following equation:

| View image in the official source | equation 73 |

View image in the official source is the value of the sequential rank assigned to a sample from the first estimation event under subsection (3).

View image in the official source is the total number of samples collected from the CEA for the first estimation event.

(5) If one of the percentiles worked out in equation 73 for a sample is equal to PSupp—the ESM for the CEA is the mass of the sample (View image in the official source) given by subsection (3) for the relevant rank of k, where PSupp is the percentile value to which ESM is set, specified in the Supplement.

(6) If subsection (5) does not apply—the ESM for a CEA is given by the following equation:

| View image in the official source | equation 74 |

MLB is the mass of oven dry whole soil associated with the sample having the value of P given by equation 73 closest to and lower than PSupp, in tonnes of oven dry whole soil per hectare.

MUB is the mass of oven dry whole soil associated with the sample, having the value of P given by equation 73 closest to and higher than PSupp , in tonnes of oven dry whole soil per hectare.

PSupp is the percentile value to which the ESM is set, specified in the Supplement

PLB is the percentile P associated with the sample used for MLB, as a percentile.

PUB is the percentile P associated with the sample used for MUB, as a percentile.

Note: The sample used for MLB is the lower bound LB and the sample used for MUB is the upper bound UB.

The equivalent soil mass:

acts as a cap to the mass of soil for which carbon stocks are worked out (both in the first and subsequent estimation event). Samples for subsequent estimation events should target the equivalent soil mass set for the first estimation event.
is intended to be set to the nth percentile sample weight (set in the Supplement), rather than average sample weight, to ensure that the mass is set at a rate that can be expected to be achieved around 90% of the time (everything else being held equal) in subsequent samples. This avoids underestimating carbon stock changes as a result of collecting a mass less than the equivalent soil mass in subsequent sample rounds.

- may need to be recalculated for each layer (0-30 cm, 0-x cm) if sub-layers are excluded from calculations (for the purposes of equalising soil masses between estimation events).

is defined for each 0-30 cm layer and 0-x cm layer within each CEA in a project.

14 Approaches for estimating mean soil organic carbon stock and its sampling variance and degrees of freedom in a CEA

(1) The mean soil organic carbon stock for a CEA (View image in the official source), in tonnes of soil organic carbon per hectare, and its sampling varianceView image in the official source, in (tonnes of soil organic carbon per hectare)2, and degrees of freedom (View image in the official source must be worked out for the estimation event in accordance with the following subsections.

(2) If more than one of the following subsections could apply to the CEA for a reporting period, the subsection that results in the lowest value of View image in the official source for the CEA for the reporting period is taken to apply.

(3) If sampling has occurred in accordance with the Supplement for an estimation event, then Subdivision 2 of this Division must be applied to any samples collected for the estimation event, and, for the CEA for the reporting period:

(a) View image in the official sourceis worked out using equation 78; and

(b) View image in the official source is worked out using equation 80; and

Note: This applies a measurement-based approach to soil organic carbon stock estimation. It applies to samples collected for a measurement-based approach, or for the purposes of calibration and validation of a model. Subsections (3) and (4) will also need to be applied if validated model carbon stock estimates or modelled carbon stock estimates are available, with the resulting estimates being compared under subsection (2).

(4) If validated model carbon stock estimates are available for an estimation event for a reporting period for the CEA, and model-validation sampling has not occurred in accordance with the Supplement for the estimation event, then Subdivision 3 of this Division must be applied, and, for the CEA for the reporting period:

(a) View image in the official sourceis the View image in the official sourcefor the CEA, worked out using equation 86; and

(b) View image in the official source is the View image in the official sourcefor the CEA, worked out using equation 87; and

Note: This applies a model-only approach to soil organic carbon stock estimation. The validation approach and model requirements are set out in the Supplement. Subsections (2) and (3) will also apply if model calibration samples were collected from the CEA, with the resulting estimates being compared under subsection (2).

(5) If model carbon stock estimates or validated model carbon stock estimates are available for an estimation event for a reporting period for the CEA and model-validation sampling has occurred in accordance with the Supplement for the estimation event, then Subdivision 4 of this Division must be applied to the model-validation samples, and, for the CEA for the reporting period:

(a) View image in the official sourceis the RegView image in the official source for the CEA, worked out using equation 104;

(b) View image in the official source is the View image in the official source for the CEA, worked out using equation 108; and

Note: This applies a model-assisted approach to soil organic carbon stock estimation which uses samples in conjunction with modelled estimates to provide an estimate with potentially lower sampling variance than using samples alone. The approach is also used to calculate statistics that may be relevant to other CEAs using a model-only approach under subsection (4). The model requirements are set out in the Supplement. If model calibration samples were also collected from the CEA, subsection (2) will also apply, with the resulting estimates being compared under subsection (2).

Subdivision 2—Measurement-based soil organic carbon stock estimation and its sampling variance for the CEA for each estimation event

15 Working out the soil organic carbon stock of each sample in each layer

(1) The soil organic carbon stock (View image in the official source for each soil sample i, for the 0-30 cm and 0-x cm layers, in tonnes of soil organic carbon per hectare, must be worked out under subsection (2) or (3) based on the relationship between:

(a) the mass of oven dry whole soil collected (View image in the official source) for the sample layer (0-30 cm and 0-x cm) worked out in accordance with any requirements in the Supplement, in tonnes of oven dry whole soil per hectare; and

(b) the equivalent soil mass (the ESM) defined for the CEA, given by section 13 of this Schedule, in tonnes of oven dry whole soil per hectare.

(2) IfView image in the official source, View image in the official source is worked out using the following equation:

| View image in the official source | equation 75 |

View image in the official source is the number of sub-layers in the 0-30 cm or 0-x cm layers and used to derive View image in the official source (in accordance with any requirements in the Supplement).

Note: The value of n increases with increasing depth such that sub-layer 1 denotes the soil sub-layer including the soil surface and sub-layer n denotes the deepest sub-layer that contributes to equation 75 as required by the Supplement.

View image in the official source is the soil organic carbon stock in a soil sub-layer determined in accordance with any requirements in the Supplement, in tonnes of soil organic carbon per hectare.

(3) If View image in the official source, View image in the official source is given by the following equation:

| View image in the official source | equation 76 |

View image in the official source is the number of sub-layers progressing incrementally down from the soil surface required to produce a value for View image in the official source that is equal to or exceeds the ESM, given by section 13 of this Schedule, in tonnes of oven dry whole soil per hectare.

Note: The value of n increases with increasing depth such that sub-layer 1 denotes the soil sub-layer including the soil surface and sub-layer View image in the official source denotes the sub-layer View image in the official source.

View image in the official source is the soil organic carbon stock in a soil sub-layer determined in accordance with any requirements in the Supplement, in tonnes of soil organic carbon per hectare.

View image in the official source is the sum of soil organic carbon stocks in all sub-layers excluding sub-layer n, in tonnes of soil organic carbon per hectare.

View image in the official source is the soil organic carbon stock in the sub-layer n, in tonnes of soil organic carbon per hectare, determined in accordance with any requirements in the Supplement.

ESM is the equivalent soil mass for the CEA where the soil samples were collected given by section 13 of this Schedule, in tonnes of oven dry whole soil per hectare.

View image in the official source is the oven dry mass of whole soil within a sub-layer, in tonnes of oven dry whole soil per hectare, determined in accordance with any requirements in the Supplement.

View image in the official source is the sum of the mass of oven dry whole soil in all sub-layers excluding sub-layer n, in tonnes of oven dry soil per hectare.

View image in the official source is the mass of oven dry whole soil contained in the soil sub-layer n, in tonnes of oven dry soil per hectare, determined in accordance with any requirements in the Supplement.

Note: The number of samples collected may inform for the calculation of statistics in the Supplement for the purposes of model-only estimates in other CEAs under Subdivision 2 of this Division. The number of samples may vary depending on the application of this subdivision. In some circumstances it is equivalent to only the number of model-validation samples (when this Subdivision is applied under subsection 14(5) or the number of validation and calibration samples (when this Subdivision is applied under subsection 14(3)).

16 Mean soil organic carbon stock in a stratum

Work out the mean soil organic carbon stock for each stratum h (the View image in the official source) in the CEA, in tonnes of soil organic carbon per hectare, using the following equation:

| View image in the official source | equation 77 |

View image in the official source is an identifier for each soil sample collected from the stratum View image in the official source.

View image in the official source is the number of relevant samples collected from the stratum h.

SOCi is the soil organic carbon stock for each sample i collected from stratum h , worked out using equation 75 or 76, in tonnes of soil organic carbon per hectare.

17 Area-weighted mean soil organic carbon stock in a CEA

Work out the area-weighted mean soil organic carbon stock in the CEA (the View image in the official source), in tonnes of soil organic carbon per hectare, using the following equation:

| View image in the official source | equation 78 |

View image in the official source is the relative area of the CEA covered by stratum h in the CEA, expressed as a proportion of the total CEA area.

View image in the official source is the mean soil organic carbon stock in the stratum h, in tonnes of soil organic carbon per hectare, worked out using equation 77.

18 Sampling variance of the mean soil organic carbon stock within a stratum

Work out the sampling variance of the mean soil organic carbon stock for each stratum h in the CEA (the View image in the official source, in (tonnes of soil organic carbon per hectare)2, using the following equation:

| View image in the official source | equation 79 |

View image in the official source is an identifier for each sample collected from the stratum View image in the official source

View image in the official source is the number of relevant samples collected from the stratum h.

SOCi is the soil organic carbon stock for each sample i from stratum h, in tonnes of soil organic carbon per hectare, worked out using equation 75 or 76.

View image in the official source is the mean soil organic carbon stock in the stratum h, in tonnes of soil organic carbon per hectare, worked out using equation 77.

19 Sampling variance of the mean soil organic carbon stock within a CEA

Work out the sampling variance of the mean soil organic carbon for the CEA (the View image in the official source, in (tonnes of soil organic carbon per hectare)2, using the following equation:

| View image in the official source | equation 80 |

View image in the official source is the relative area of the CEA covered by stratum h in the CEA, expressed as a proportion of the total CEA.

View image in the official source is the sampling variance of the mean soil organic carbon for stratum h, in (tonnes of soil organic carbon per hectare)2, worked out using equation 79.

20 Degrees of freedom for the sampling variance of the mean soil organic carbon stock within a CEA

(1) Where individual or within-strata composite samples were used for the estimation event, work out the degrees of freedom (View image in the official source to use in equation 115 for a given estimation event, using the following equation:

| View image in the official source | equation 81 |

View image in the official source is the relative area of the CEA covered by stratum h in the CEA, expressed as a proportion of the total CEA area.

View image in the official source is the sampling variance of the mean soil organic carbon for each stratum h in the CEA in (tonnes of soil organic carbon per hectare)2, worked out using equation 79.

View image in the official source is the number of relevant samples collected from the stratum h (either within-strata composites samples or individual samples as appropriate).

Note 1: Equation 81 is a simplified equation using the condition that View image in the official source The original version of the equation is: View image in the official source

Note 2: Where a CEA contains three strata, equation 81 written in its expanded form, where the subscripts 1, 2, and 3 are used to denote values for stratum 1, stratum 2, and stratum 3, respectively takes the following form:

(2) Where across-strata composite samples were collected across equal area strata, work out the degrees of freedom (View image in the official source to use in equation 115 for a given estimation event, using the following equation:

| View image in the official source | equation 82 |

View image in the official source is the number of relevant across-strata composite samples collected from CEA.

Subdivision 3—Model-only soil organic carbon stock estimation and its sampling variance for the CEA for each estimation event

21 Working out the modelled soil organic carbon stock in each layer of each stratum

(1) The modelled soil organic carbon stock (View image in the official source) for each stratum h in the CEA, for the 0-30 cm and 0-x cm layers, in tonnes of organic carbon per hectare, must be worked out under subsection (2) or (3) based on the relationship between:

(a) the mass of oven dry whole soil in the stratum estimated by a validated model carbon stock estimate for the estimation event in accordance with any requirements in the Supplement (View image in the official source) for the layer (0-30 cm or 0-x cm), in tonnes of oven dry whole soil per hectare; and

(b) the equivalent soil mass (the ESM) defined for the CEA in the first estimation event given by section 13 of this Schedule, in tonnes of oven dry whole soil per hectare.

(2) If View image in the official source, ModView image in the official source is worked out using the following equation:

| View image in the official source | equation 83 |

View image in the official source is the number of sub-layers in the 0-30 cm or 0-x cm layers and used to derive View image in the official source(in accordance with the requirements in the Supplement).

View image in the official source is the mean modelled soil organic carbon stock in a soil sub-layer, for stratum h, determined by a validated model carbon stock estimate for the estimation event in accordance with the requirements in the Supplement, in tonnes of soil organic carbon per hectare.

(3) If View image in the official source, View image in the official source is worked out using the following equation:

| View image in the official source | equation 84 |

View image in the official source is the number of sub-layers progressing incrementally down from the soil surface required to produce a value for View image in the official source that is equal to or exceeds the ESM for the CEA given by section 13 of this Schedule, in tonnes of oven dry whole soil per hectare.

View image in the official source is the modelled soil organic carbon stock in a soil sub-layer, for stratum h, determined by a validated model carbon stock estimate for the estimation event in accordance with the requirements in the Supplement, in tonnes of soil organic carbon per hectare.

View image in the official source is the sum of modelled soil organic carbon stocks in all sub-layers excluding sub-layer n, for stratum h, determined by a validated model carbon stock estimate for the estimation event in accordance with any requirements in the Supplement, in tonnes of soil organic carbon per hectare.

View image in the official source is the modelled soil organic carbon stock in the soil sub-layer n, for stratum h, determined by a validated model carbon stock estimate for the estimation event in accordance with any requirements in the Supplement, in tonnes of soil organic carbon per hectare.

ESM is the equivalent soil mass for the CEA given by section 13 of this Schedule, in tonnes of oven dry whole soil per hectare.

View image in the official source is the modelled oven dry mass of whole soil within a sub-layer, for stratum h, determined by a validated model carbon stock estimate for the estimation event in accordance with any requirements in the Supplement, in tonnes of oven dry whole soil per hectare.

View image in the official source is the sum of the mass of oven dry whole soil in all sub-layers excluding sub-layer n, for stratum h, estimated by a validated model carbon stock estimate for the estimation event in accordance with the requirements in the Supplement, in tonnes of oven dry soil per hectare.

View image in the official source is the modelled mass of oven dry whole soil contained in the soil sub-layer n, for stratum h, estimated by a validated model carbon stock estimate for the estimation event in accordance with the requirements in the Supplement, in tonnes of oven dry soil per hectare.

22 Mean modelled soil organic carbon stock in a CEA

Work out the mean modelled soil organic carbon stock in the CEA (the ModView image in the official source), in tonnes of soil organic carbon per hectare, using the following equation:

| View image in the official source | equation 85 |

View image in the official source is the relative area of the CEA covered by stratum h in the CEA, expressed as a proportion of the total CEA.

View image in the official source is the mean soil organic carbon stock in the stratum h, in tonnes of soil organic carbon per hectare, worked out using section 21 of this Schedule.

23 Extrapolated bias-adjustment of the modelled soil organic carbon stock within a CEA

Work out the mean bias-adjusted modelled soil organic carbon stock for the CEA (BiasAdjModView image in the official source), in tonnes of soil organic carbon per hectare, using the following equation:

| View image in the official source | equation 86 |

View image in the official source is the mean modelled soil organic carbon stock for the CEA, worked out using equation 85 of this Schedule, in tonnes of soil organic carbon per hectare.

View image in the official source is the extrapolated bias of the model given by the Supplement for the validated model carbon stock estimates for the estimation event, in tonnes of soil organic carbon per hectare.

Note: The Supplement allows the bias of the model to be given from other CEAs where model-validation sampling occurred for the estimation event.

24 Extrapolated estimate of the sampling variance of mean carbon stocks in the CEA

Work out the extrapolated estimate of the sampling variance of mean carbon stocks in the CEA (the View image in the official source, in (tonnes of soil organic carbon per hectare)2, using the following equation:

| View image in the official source | equation 87 |

View image in the official source is the mean bias-adjusted modelled soil organic carbon stock for the CEA, worked out using equation 86, in tonnes of soil organic carbon per hectare.

View image in the official source is the fraction of sampling variance given by the Supplement for validated model carbon stock estimate for the estimation event, in tonnes of soil organic carbon per hectare.

View image in the official source is the discount factor for sampling variance given by the Supplement for the validated model carbon stock estimate for the estimation event.

View image in the official source is the correlation coefficient given by the Supplement for the validated model carbon stock estimate for the estimation event.

Note: The fraction of sampling variance and the correlation coefficient are not sourced from the following Subdivision but rather from other CEAs (where model-validation sampling has occurred) in accordance with the Supplement

The discount factor for sampling variance provides an estimate of model variance for a CEA where model-validation sampling has not occurred based on the variance of the model for the CEA which was model-validation sampled for the estimation event. This ensures the calculation of the creditable change in soil organic carbon stock for a CEA where model-validation sampling has not occurred under Division 5 is conservative. The impact of the discount reduces to 0 as the coefficient of determination increases towards one.

25 Degrees of freedom for the sampling variance of the mean soil organic carbon stock within a CEA

The degrees of freedom (View image in the official source to use in equation 115 for a given estimation event, is given by the Supplement for the validated model carbon stock estimate for the estimation event.

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