Cropland

3.3

CROPLANDThis section provides Good Practice Guidance on inventorying and reporting greenhouse gas emissions andremovals in ‘cropland remaining cropland (CC)’ and ‘land converted to cropland’ (LC). Cropland includes allannual and perennial crops as well as temporary fallow land (i.e., land set at rest for one or several years before
being cultivated again). Annual crops may include cereals, oils seeds, vegetables, root crops and forages.
Perennial crops can include trees and shrubs, in combination with herbaceous crops (e.g. agroforestry) or as
orchards, vineyards and plantations such as cocoa, coffee, tea, oil palm, coconut, rubber trees, and bananas,
except where these lands meet the criteria for categorisation as forest land.1 Arable land which is normally used
for cultivation of annual crops but which is temporarily used for forage crops or grazing as part of an annual
crop-pasture rotation is included under cropland.
The amount of carbon stored in and emitted or removed from permanent cropland depends on crop type,management practices, and soil and climate variables. For example, annual crops (e.g. cereals, vegetables) are
harvested each year, so there is no long-term storage of carbon in biomass. However, perennial woody
vegetation in orchards, vineyards, and agroforestry systems can store significant carbon in long-lived biomass,
the amount depending on species type, density, growth rates, and harvesting and pruning practices. Carbon
stocks in soils can be significant and changes in stocks can occur in conjunction with most management practices,
including crop type and rotation, tillage, drainage, residue management and organic amendments.
The conversion of other land uses into cropland can affect carbon stocks and other greenhouse gases in a variety
of ways. Land-use conversions to cropland from forest land, grassland and wetlands usually result in a net loss ofcarbon from biomass and soils to the atmosphere. However, cropland established on previously sparsely
vegetated or highly disturbed lands (e.g. mined lands) can result in a net gain in both biomass and soil carbon.
The term land-use conversion refers only to lands coming from one type of use into another. In cases where
existing perennial cropland is replanted to the same or different crops, the land use remains cropland; therefore,
the carbon stock changes should be estimated using the methods for cropland remaining cropland, as describedin Section 3.3.1 below.
For cropland remaining cropland, emissions of methane (CH4) and nitrous oxide (N2O) from the management of
permanent agricultural lands are covered in Chapter 4 of the IPCC report on Good Practice Guidance andUncertainty Management in National Greenhouse Gas Inventories (GPG2000). This report provides guidanceon inventorying and reporting of N2O emissions from land-use conversions to cropland as a result of soiloxidation.
In this section, guidance on the use of basic and advanced methodologies for inventorying and reporting
emissions and removals for cropland remaining cropland and land converted to cropland is provided for biomass
and soil carbon pools. Methodologies follow a hierarchical tier structure where Tier 1 methods use default values,
typically with limited disaggregation of area data. Tier 2 corresponds to use of country-specific coefficients andtypically finer scale area disaggregation, which will reduce uncertainty in emission/removal estimates. Tier 3
methods refer to the use of country-specific approaches, which may include process models and detailed
inventory measurements. Where possible, default values from the IPCC Guidelines are updated and new default
values are provided based on the most up-to-date research findings.

3.3.1

Cropland Remaining Cropland

Emissions and removals from cropland remaining cropland can include two subcategories of CO2
emissions/removals. Equation 3.3.1 summarises net emissions or removals of carbon from cropland remaining
cropland for these subcategories: changes in carbon stocks in living biomass (Section 3.3.1.1) and changes incarbon stocks in soils (3.3.1.2). As noted above, emissions of CH4 and N2O are estimated as part of theAgriculture Chapter in the IPCC Guidelines and GPG2000. Table 3.3.1 summarises the methodological tiers foreach of the two subcategories covered below.

1

As described in Chapter 2, Section 2.2 (Land categories), the IPCC does not provide a single definition for forest or otherland uses. Rather, countries should determine their own definition for the purposes of inventory reporting. It is goodpractice to use clear definitions in the inventory report (include threshold values, e.g. for tree cover, land area, and treeheight) and to ensure that the categorisation is consistent across inventory reports and with other land use definitions.

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EQUATION 3.3.1
ANNUAL CHANGE IN CARBON STOCKS IN CROPLAND REMAINING CROPLAND∆CCC = ∆CCCLB + ∆CCCSoils
Where:∆CCC = annual change in carbon stocks in cropland remaining cropland, tonnes C yr-1
∆CCCLB= annual change in carbon stocks in living biomass, tonnes C yr-1

∆CCCSoils = annual change in carbon stocks in soils, tonnes C yr-1
To convert tonnes C to Gg CO2, multiply the value by 44/12 and 10-3. For the convention (signs), refer to Section
3.1.7 or Annex 3A.2 (Reporting Tables and Worksheets).
TABLE 3.3.1
TIER DESCRIPTIONS FOR SUBCATEGORIES UNDER CROPLAND REMAINING CROPLAND
Tier

Tier 1

Tier 2Tier 3Use default coefficients forcarbon accumulation and loss
rates. The average area of
perennial woody crops isestimated by climate region.

Use at least some country-specificvalues for carbon accumulation andloss rates. Use detailed annual or
periodic surveys to estimate the areaof land in perennial woody crops,
disaggregated to scales that matchthe country-specific rates. Consider
including belowground biomass inestimate, if data are available. May
rely on alternate approach of
measuring or estimating carbon
stocks at two points in time, in lieu
of developing rates of change incarbon stocks.

Use highly disaggregated area
estimates for detailed
categories of perennial woody
crops (e.g., coffee, orchards,
intercropping systems).

For both mineral and organic soils
use some combination of default
and/or country-specific coefficientsand area estimates of increasingly
finer spatial resolution. For
emissions from liming, use emission
factors differentiated by forms oflime.

Use country-specific approachat fine spatial scale (e.g.,modeling, measurement)

Subcategories
Living Biomass(for perennial
woody crops)

Applies country-specific rates
or estimates of carbon stockchanges in the specificperennial woody crop systems.
May use a country-specificapproach at fine spatial scale(e.g., modeling, measurement)
provided it yields a moreaccurate estimate of carbon
stock changes.

Soils

For changes in soil carbon
from mineral soils use default
coefficients. Areas should be
stratified by climate and soil
type. For changes in soil
carbon from organic soils use
default coefficients andstratify the areas by climatic
region. For emissions fromliming, use default emission
factors as given in IPCC
Guidelines.

3.3.1.1

C HANGE IN CARB ON STOCKS IN LIVING BIOMASS

Carbon can be stored in the biomass of croplands that contain perennial woody vegetation, including, but notlimited to, monocultures such as coffee, oil palm, coconut, and rubber plantations, and fruit and nut orchards,
and polycultures such as agroforestry systems. The basic methodology for estimating changes in woody biomass
is provided in the IPCC Guidelines Section 5.2.2 (Changes in Forest and Other Woody Biomass Stocks) and in
Section 3.2.1.1 (Changes in Carbon Stocks in Living Biomass) under Section 3.2.1 (Forest land Remaining
Forest land) of this report. This section elaborates these methodologies with respect to estimating changes incarbon stocks in living biomass in cropland remaining cropland.

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Cropland

3.3.1.1.1 METHODOLOGICAL ISSUES
The change in biomass is only estimated for perennial woody crops. For annual crops, increase in biomass stocks
in a single year is assumed equal to biomass losses from harvest and mortality in that same year - thus there is no
net accumulation of biomass carbon stocks.
The principal equation for total change in carbon stocks of living biomass in perennial woody crops on cropland(∆CCCLB) is the same as Equation 3.2.2 in Section 3.2.1 (Forest land Remaining Forest land), with the only
difference being that estimates of carbon stock changes apply to aboveground biomass only because limited data
are available on belowground biomass. Default growth and loss rates are given in Table 3.3.2.
TABLE 3.3.2
DEFAULT COEFFICIENTS FOR ABOVEGROUND WOODY BIOMASS AND HARVEST CYCLES IN CROPPING SYSTEMS CONTAINING
PERENNIAL SPECIESClimate region

Abovegroundbiomass carbon
stock at harvest-1

Harvest/Maturity
cycle

Biomass
accumulation rate(G)
-1

Biomass carbon loss
(L)

-1

Error range1(tonnes C ha-1)(tonnes C ha )(yr)(tonnes C ha yr )Temperate (allmoisture regimes)

63

30

2.1

63

+ 75%

Tropical, dry

9

5

1.8

9

+ 75%

Tropical, moist

21

8

2.6

21

+ 75%

Tropical, wet

50

5

10.0

50

+ 75%

Note: Values are derived from the literature survey and synthesis published by Schroeder (1994).
1

Represents a nominal estimate of error, equivalent to two times standard deviation, as a percentage of the mean.

Currently, there is not sufficient information to provide a basic approach with default parameters to estimate
carbon stock changes in dead organic matter pools in cropland remaining cropland.

3.3.1.1.1.1 Choice of Method
To estimate change in carbon in cropland biomass (∆CCCLB), there are two alternative approaches: (a) estimate
annual rates of growth and loss (Equation 3.2.2 in Forest land section) or (b) estimate carbon stocks at two points
in time (Equation 3.2.3 also in Forest land section). The first approach is developed below as the basic Tier 1
method; it can also serve as a Tier 2 or 3 method with refinements described below. The second approach isdeveloped as either a Tier 2 or Tier 3 method.
As described in more detail below, Tier 1 is based on highly aggregated area estimates for generic perennial
woody crops using default carbon accumulation rates and carbon losses. A Tier 2 estimate, in contrast, will
generally develop estimates for the major woody crop types by climate zones, using country-specific carbon
accumulation rates and stock losses where possible or country-specific estimates of carbon stocks at two points
in time. A Tier 3 estimate will use a highly disaggregated Tier 2 approach or a country-specific method
involving process modeling and/or detailed measurement. All countries should strive for improving inventory
and reporting approaches by advancing to the highest tier possible given national circumstances. It is goodpractice for countries to use a Tier 2 or Tier 3 approach if carbon emissions and removals in cropland remaining
cropland is a key category and if the subcategory of living biomass is considered significant based on principles
outlined in Chapter 5. Countries should use the decision tree in Figure 3.1.1 to help with the choice of method.
Tier 1: The basic method is to multiply the area of perennial woody cropland by a net estimate of biomass
accumulation from growth and subtract losses associated with harvest or other removals (according to Equation
3.2.2. in the Forest land section). Losses are estimated by multiplying a carbon stock value by the area ofcropland on which perennial woody crops are harvested or removed.
Default Tier 1 assumptions are: all carbon in perennial woody biomass removed (e.g., biomass cleared andreplanted with a different crop) is emitted in the year of removal; and perennial woody crops accumulate carbon
for an amount of time equal to a nominal harvest/maturity cycle. The latter assumption implies that perennial
woody crops accumulate biomass for a finite period until they are removed through harvest or reach a steadystate where there is no net accumulation of carbon in biomass because growth rates have slowed and incremental
gains from growth are offset by losses from natural mortality, pruning or other losses.
At Tier 1, default factors, which are discussed in more detail in Section 3.3.1.1.1.2 and Table 3.3.2., are applied
to nationally derived estimates of land areas (A in Equation 3.2.4. in Forest land section).

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Example 1: In the inventory year, 90,000 hectares of perennial woody crops are cultivated in a
tropical moist environment, while 10,000 ha are removed. The immature perennial woody
cropland area accumulates carbon at a rate of approximately 2.6 tonnes of C ha-1 yr-1. The area
harvested loses all carbon in biomass stocks in the year of removal. Default carbon stock losses fora tropical moist perennial woody cropland are 21 tonnes C ha-1 yr-1. Using equation 3.2.2, anestimated 234,000 tonnes C accumulates per year and 210,000 tonnes C are lost. The net change incarbon stocks in the tropical moist environment are 24,000 tonnes C yr-1.
Tier 2: One of two alternative approaches can be used at Tier 2. In principle, either approach should yield thesame answer.
The approaches include:•

Extending Tier 1 by matching more disaggregated area estimates (e.g., by specific perennial woody crop
types and detailed climate regions) with at least some country-specific carbon accumulation and harvest dataapplicable at the same scale. Countries should prioritize development of country-specific parameters byfocusing on either the most common perennial woody crops or the systems with relatively high levels of
perennial woody biomass per unit of land (i.e., high carbon stocks). Guidance on developing countryspecific parameters is provided in Section 3.3.1.1.1.2; or,•Estimating total carbon stocks in perennial woody crops at regular time intervals (following Equation 3.2.3of the Forest land section).

Tier 3: Tier 3 approaches are either highly disaggregated Tier 2 approaches that are parameterized withcountry-specific carbon stock and carbon stock change values or they are country-specific methods such as useof models or repeated measurements of stocks such as those obtained using detailed forest inventories (seeSection 3.2.1.1.1). For example, well validated and species-specific growth models and detailed information on
harvest and pruning practices could be used to estimate annual growth rates, analogous to Equation 3.2.2. This
would require information on the area of woody biomass crops by species and age class, as well as data on
climate, soil and other growth limiting conditions for specific areas. Alternatively, periodic sampling-based stock
estimates (and associated models), similar to those used in detailed forest inventories could be applied toestimate stock changes as in Equation 3.2.3.

3.3.1.1.1.2 Choice of Emission/Removal Factors
Emission/removal factors for this methodology include the biomass accumulation (G) and loss rates (L). Table
3.3.2 provides default values for G and L across four general climate regions based on a published review ofcarbon stock research on agroforestry systems (Schroeder, 1994). Additional data in Table 3.3.2 highlightunderlying assumptions of the default data (e.g., time to harvest/maturity) and demonstrate how the defaults
were derived. The default annual growth rate (G) is derived by dividing biomass stocks at maturity by the timefrom crop establishment to harvest/maturity. The default annual loss rate is equal to biomass stocks at harvest,
which are assumed removed entirely in the year of removal. For an individual country, these defaults are highly
uncertain as they represent generic perennial woody biomass crop systems for broad climatic regions. Woody
crops vary greatly in their uses, growth and harvest rates, and degree of association with other non-woody crops
and thus the application of simple default factors will only coarsely approximate carbon changes.
When using the Tier 2 approach, biomass stocks, harvest cycles and carbon accumulation rates can be estimatedfrom country or region specific research results on perennial woody crop systems conducted by national experts.
Woody crops vary greatly, from annually harvested species used for green manure and fuel wood to potentiallylong-lived woody crops such as fruit orchards. It is important in deriving estimates of biomass accumulation
rates to recognize that net increases in biomass stocks will occur primarily during the first years following initialestablishment or regrowth of the woody crops. While some longer-lived orchard crops may not be subject to aregular removal and replanting cycle, losses due to pruning and tree replacement are likely to largely offset new
growth so that in mature crops net biomass stock increases will be near zero. Thus, at the country-level, net
increases in biomass carbon stocks would occur primarily where the area of cropland with woody crops isincreasing relative to other land uses having lower carbon stocks or where the proportion of land subject toremovals is less than the average dictated by the normal harvest frequency (e.g. if the land area is dominated byyoung, recently established woody crops). Conversely, net biomass losses at the country-level would occur when
woody crops are replaced by other annual cropland systems or when the harvest frequency of woody crops isincreasing.
To further improve estimates of carbon accumulation in perennial woody crop biomass, countries may conduct
field research to measure carbon stock changes or accumulation rates. Research studies should be based on
sound scientific principles and follow general approaches laid out by other similar studies (Dixon et al., 1993;
Schroeder, 1994; Schroth et al., 2002; and Masera et al., 2003). Results from field research should be compared

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Croplandto estimates of carbon accumulation rates from other sources to verify that they are within documented ranges.
Reported carbon accumulation rates may be modified based on additional data and expert opinion, provided
clear rationale and documentation are included in the inventory report.

3.3.1.1.1.3 Choice of Activity Data
Activity data in this section refer to estimates of land areas (AG, AL) of growing stock and harvested land inperennial woody crops. Chapter 2 provides general guidance on approaches for obtaining and categorising areaby different land use classes. For estimating emissions and removals from this source, countries need to obtainarea estimates for land in perennial woody crops, disaggregated as required to correspond to the available
emission factors and other parameters.
Tier 1: Under Tier 1, annual or periodic surveys are used in conjunction with the approaches outlined in
Chapter 2 to estimate the average annual area of established perennial woody crops and the average annual areaof perennial woody crops that are harvested or removed. The area estimates are further subdivided into generalclimate regions to match the default G and L values. Under Tier 1 calculations, international statistics such as
FAO databases, IPCC Guidelines and other sources can be used to estimate the area of land in perennial woody
crops.
Tier 2: For the Tier 2 method, more detailed annual or periodic surveys are used to estimate the areas of land indifferent classes of perennial woody biomass crops. Areas are further classified into relevant categories such that
all major combinations of perennial woody crop types and climatic regions are represented with area estimatesfor each. These area estimates must match any country-specific carbon accumulation and loss values developed
for the Tier 2 method. If country-specific finer resolution data are only partially available, countries areencouraged to extrapolate to the entire land base of perennial woody crops using sound assumptions from best
available knowledge.
Tier 3: Tier 3 requires high-resolution activity data disaggregated at sub-national to fine grid scales. Similar to
Tier 2, land area is classified into specific types of perennial woody crops by major climate and soil categories
and other potentially important regional variables (e.g., regional patterns of management practices). If possible,
spatially explicit area estimates are used to facilitate complete coverage of the perennial woody cropland andensure that areas are not over- or underestimated. Furthermore, spatially explicit area estimates can be related to
locally relevant carbon accumulation and removal rates, and restocking and management impacts, improving theaccuracy of estimates.

3.3.1.1.1.4 Uncertai nty Assessment
The following discussion provides guidance on approaches for assessing uncertainty associated with each tiermethod described in Section 3.3.1.1.1.1.
Tier 1: The sources of uncertainty when using the Tier 1 method include the degree of accuracy in land area
estimates and in the default carbon accumulation and loss rates. A published compilation of research on carbon
stocks in agroforestry systems was used to derive the default data provided in Section 3.3.1.1.1.2 (Schroeder,
1994). While defaults were derived from multiple studies, their associated uncertainty ranges were not includedin the publication. Therefore, a default uncertainty level of + 75% of the parameter value has been assigned
based on expert judgement. This information can be used with a measure of uncertainty in area estimates from
Chapter 2 of this Report to assess the uncertainty in estimates of carbon emissions and removals in croplandbiomass using the Tier 1 methodology for uncertainty analysis in Chapter 5.2 (Identifying and quantifying
uncertainties).
Tier 2: The Tier 2 method will reduce overall uncertainty because country-defined rates should provide moreaccurate estimates of carbon accumulation and loss for crop systems and climatic regions within nationalboundaries. It is good practice to calculate error estimates (i.e., standard deviations, standard error, or ranges) for
country-defined carbon accumulation rates and to use these variables in a basic uncertainty assessment. It is goodpractice for countries to assess error ranges in country-specific coefficients and compare them to those of default
carbon accumulation coefficients. If country-defined rates have equal or greater error ranges than default
coefficients, then it is good practice to use a Tier 1 approach and to further refine country-defined rates withmore field measurements.
Tier 2 approaches may also use finer resolution activity data, such as area estimates for different climatic regions
or for specific cropping systems within national boundaries. The finer-resolution data will reduce uncertainty
levels when associated with carbon accumulation factors defined for those finer-scale land bases (e.g., when areaof coffee plantations is multiplied by a coffee plantation coefficient, rather than by a generic agroforestry
default).
Tier 3: Tier 3 approaches will provide the greatest level of certainty relative to Tiers 1 and 2 approaches. It isgood practice to calculate standard deviations, standard errors, or ranges for all country-defined biomass growth

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and loss rates. It is also good practice to assess the measurement error in land area estimates for each land basecategory. Countries should consider developing probability density functions for model parameters to use inMonte Carlo simulations.

3.3.1.2

C HANGE IN CARB ON STOCKS IN SOILS

3.3.1.2.1 METHODOLOGICAL ISSUESThe IPCC Guidelines provide methods for estimating CO2 Emissions and Uptake by Soils from Land-Use andManagement (Section 5.3) that can be applied to all land uses, including cropland. The methodology considers
organic carbon stock changes (CO2 emissions or removals) for mineral soils, CO2 emissions from organic soils(i.e. peat soils) and emissions of CO2 from liming of agricultural soils.
In the IPCC Guidelines, carbon stocks are measured to a default depth of 30cm and do not include C in surface
residue (i.e. dead organic matter) or changes in inorganic carbon (i.e. carbonate minerals). In most cropland soils,
surface residue is either absent (due to incorporation with tillage) or represents a minor stock. Other depths may
be used at higher tiers, but depth must in all cases be used consistently over time.
The summary Equation 3.3.2 for estimating the change in organic carbon stocks in soils is shown below:
EQUATION 3.3.2
ANNUAL CHANGE IN CARBON STOCKS IN SOILS IN CROPLAND REMAINING CROPLAND∆CCCSoils = ∆CCCMineral – ∆CCCOrganic – ∆CCCLime
Where:∆CCCSoils = annual change in carbon stocks in soils in cropland remaining cropland, tonnes C yr-1
∆CCCMineral = annual change in carbon stocks in mineral soils, tonnes C yr-1
∆CCCOrganic= annual carbon emissions from cultivated organic soils (estimated as net annual flux), tonnes C yr-1
∆CCCLime = annual C emissions from agricultural lime application, tonnes C yr-1
For Tiers 1 and 2 methods, changes in dead organic matter and inorganic carbon should be assumed to be zero. Ifdead organic matter is included in a Tier 3 approach, measurements should be based on the lowest amounts
present during an annual cycle to avoid including fresh post-harvest residues that represent a transient organic
matter pool. Selection of the most suitable tier will depend on: 1) type and level of detail of activity data on
agricultural management and changes in management over time, 2) availability of suitable information toestimate base C stocks and stock change and emission factors, 3) availability of dedicated national inventory
systems designed for soils.
All countries should strive for improving inventory and reporting approaches by advancing to the highest tierpossible given national circumstances. It is good practice for countries to use a Tier 2 or Tier 3 approach if
carbon emissions and removals in cropland remaining cropland is a key category and if the subcategory of soilorganic matter is considered significant based on principles outlined in Chapter 5. Countries should use thedecision tree in Figure 3.1.1 to help with the choice of method.

3.3.1.2.1.1 Choice of Method
The method used to estimate carbon stock changes in mineral soils is different from the method used for organicsoils. It is also possible that countries will use different tiers to prepare estimates of the separate components on
this subcategory, given availability of resources. Thus, mineral soils, organic soils, and emissions from liming
are discussed separately below.

Mineral Soils
For mineral soils, the estimation method is based on changes in soil C stocks over a finite period followingchanges in management that impact soil C, as shown in Equation 3.3.3. Previous soil C stocks (SOC(0-T)) and soil
C stocks in the inventory year (SOC0) for the area of a cropland system in the inventory are estimated fromreference carbon stocks (Table 3.3.3) and stock change factors (Table 3.3.4), applied for the respective time
points. Here a cropland system refers to a specific climate, soil and management combination. Annual rates ofemissions (source) or removals (sink) are calculated as the difference in stocks (over time) divided by theinventory time period. The default time period is 20 years.

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Cropland

EQUATION 3.3.3
ANNUAL CHANGE IN CARBON STOCKS IN MINERAL SOILS FOR A SINGLE CROPLAND SYSTEM∆CCCMineral = [(SOC0 – SOC(0 –T)) ● A] / T
SOC = SOCREF ● FLU ● FMG ● FI
Where:∆CCCMineral = annual change in carbon stocks in mineral soils, tonnes C yr-1
SOC0 = soil organic carbon stock in the inventory year, tonnes C ha-1
SOC(0-T) = soil organic carbon stock T years prior to the inventory, tonnes C ha-1
T = inventory time period, yr (default is 20 yr)
A = land area of each parcel, ha
SOCREF = the reference carbon stock, tonnes C ha-1; see Table 3.3.3
FLU = stock change factor for land use or land-use change type, dimensionless; see Table 3.3.4
FMG = stock change factor for management regime, dimensionless; see Table 3.3.4
FI = stock change factor for input of organic matter, dimensionless; see Table 3.3.4
The types of land use and management factors supplied are very broadly defined and include: 1) a land use factor(FLU) that reflects C stock changes associated with type of land use, 2) a management factor (FMG) that forpermanent cropland represents different types of tillage and 3) an input factor (FI) representing different levels of
C inputs to soil. For cropland, FLU describes base C stocks for long-term cultivated soils, paddy rice cultivationand for temporary cropland set-asides, relative to native (uncultivated) soil C stocks. If the area was in other landuse (e.g. forest land, grazing land) at the beginning of the inventory period, then guidance provided under
Section 3.3.2, Land Converted to Cropland, should be followed.
The calculation steps for determining SOC0 and SOC(0-T) and net soil C stock change per ha of land area are as
follows:
Step 1: Select the reference carbon stock value (SOCREF), based on climate and soil type, for each area of land
being inventoried.
Step 2: Select the type of cropland use (long-term cultivated, paddy rice, set-aside) present at beginning of theinventory period (e.g. 20 years ago), together with tillage (FMG) and C input levels (FI). These factors,
multiplied by the reference soil C stock, provide the estimate of ‘initial’ soil C stock (SOC(0-T)) for theinventory period.
Step 3: Calculate SOC0 by repeating step 2 using the same reference carbon stock (SOCREF), but with land use,
tillage and input factors that represent conditions in the (current) inventory year.
Step 4: Calculate the average annual change in soil C stock for the area over the inventory period (∆CCCMineral)

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Example: For a Mollisol soil in a warm temperate moist climate, SOCREF is 88 tonnes C ha-1. On
an area of land under long-term annual cropping, previously managed with intensive tillage andlow C input level, the carbon stock at the beginning of the inventory period is calculated as(SOCREF ● FLU ● FMG ● FI, ) = 88 tonnes C ha-1● 0.71 ● 1 ● 0.91 = 56.9 tonnes C ha-1. Under thecurrent management of annual cropping with no tillage and medium C input level the carbon stockis calculated as 88 tonnes C ha-1 ● 0.71 ● 1.16 ● 1 = 72.5 tonnes C ha-1. Thus the average annualchange in soil C stock for the area over the inventory period is calculated as (72.5 tonnes C ha-1 –56.9 tonnes C ha-1) / 20 yrs = 0.78 tonnes C ha-1 yr-1.

TABLE 3.3.3
DEFAULT REFERENCE (UNDER NATIVE VEGETATION) SOIL ORGANIC C STOCKS (SOCREF)(TONNES C PER HA FOR 0-30 CM DEPTH)
HAC soils1

LAC soils2

Sandy soils3

Spodic soils4

Volcanic
soils5

Wetlandsoils6

Boreal

68

NA

10#

117

20#

146

Cold temperate, dry

50

33

34

NA

20#

Cold temperate, moist

95

85

71

115

130

Warm temperate, dry

38

24

19

NA

70#

Warm temperate, moist

88

63

34

NA

80

Tropical, dry

38

35

31

NA

50#

Tropical, moist

65

47

39

NA

70#

NA

#

RegionTropical, wet

44

60

66

130

87

88

86

Note: Data are derived from soil databases described by Jobbagy and Jackson (2000) and Bernoux et al. (2002). Mean stocks areshown. A default error estimate of 95% (expressed as 2X standard deviations as percent of the mean) are assumed for soil-climate
types. NA denotes ‘not applicable’ because these soils do not normally occur in some climate zones.
# indicates where no data were available and default values from IPCC Guidelines were retained.
1

Soils with high activity clay (HAC) minerals are lightly to moderately weathered soils, which are dominated by 2:1 silicate clay
minerals (in the World Reference Base for Soil Resources (WRB) classification these include Leptosols, Vertisols, Kastanozems,
Chernozems, Phaeozems, Luvisols, Alisols, Albeluvisols, Solonetz, Calcisols, Gypsisols, Umbrisols, Cambisols, Regosols; in USDA
classification includes Mollisols, Vertisols, high-base status Alfisols, Aridisols, Inceptisols).

2

Soils with low activity clay (LAC) minerals are highly weathered soils, dominated by 1:1 clay minerals and amorphous iron andaluminium oxides (in WRB classification includes Acrisols, Lixisols, Nitisols, Ferralsols, Durisols; in USDA classification includes
Ultisols, Oxisols, acidic Alfisols).

3

Includes all soils (regardless of taxonomic classification) having > 70% sand and < 8% clay, based on standard textural analyses (inWRB classification includes Arenosols,; in USDA classification includes Psamments).

4

Soils exhibiting strong podzolization (in WRB classification includes Podzols; in USDA classification Spodosols)

5

Soils derived from volcanic ash with allophanic mineralogy (in WRB classification Andosols; in USDA classification Andisols)

6

Soils with restricted drainage leading to periodic flooding and anaerobic conditions (in WRB classification Gleysols; in USDA
classification Aquic suborders).

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TABLE 3.3.4
RELATIVE STOCK CHANGE FACTORS (FLU, FMG, AND FI) (OVER 20 YEARS) FOR DIFFERENT MANAGEMENT ACTIVITIES ON
CROPLAND [SEE SECTION 3.3.7 FOR METHODS AND DATA SOURCES USED IN FACTOR DERIVATION]
Factor
value
type
Land
use
(FLU)

Land
use
(FLU)
Land
use
(FLU)
Tillage(FMG)

Tillage(FMG)

Tillage
(FMG)

Input
(FI)

Input
(FI)

Input
(FI)

Input
(FI)

Level

Longterm
cultivatedTemperature
regime’96
IPCC
default

Temperate

0.7,0.64

Tropical

0.6, 0.5

Paddy
rice

Temperate
andTropical

1.1

Set aside(< 20 yrs)

Temperate
andTropical

0.8

Temperate

Moisture
Regime1GPG
reviseddefault

Error2,3

Description

Dry

0.82

+ 10%

Wet

0.71

+ 12%

Dry

0.69

+ 38%

Wet

0.58

+ 42%

Represents area that has been continuously
managed for >20 yrs, to predominantly
annual crops. Input and tillage factors arealso applied to estimate carbon stockchanges. Land use factor was estimatedrelative to use of full tillage and nominal(‘medium”) carbon input levels.

Dry and
Wet

1.1

+ 90%

Dry

0.93

+ 10%

Wet

0.82

+ 18%

1.0

Dry and
Wet

1.0

NA

Tropical

0.9, 0.8

Dry and
Wet

1.0

NA

Temperate

1.05

Dry

1.03

+ 6%

Wet

1.09

+ 6%

Tropical

1.0

+ 10%

Full

ReducedTemperate

1.1

Tropical

1.1

No-tillTemperate

0.9

Tropical

0.8

Low

Dry

1.10

Wet

1.16

+ 8%

Dry

1.10

+ 6%

Wet

1.16

+ 4%
+ 8%

Dry

1.17

Wet

1.23

+ 8%

Dry

0.92

+ 4%

Wet

0.91

+ 8%

Dry

0.92

+ 4%

Wet

0.91

+ 4%

1.0

NA

Temperate

1.0

Dry andWet

Tropical

0.9

Dry and
Wet

1.0

NA

Dry

1.07

+ 10%

Wet

1.11

+ 10%

Dry

1.34

+ 12%

Wet

1.38

+ 8%

MediumHigh –
without
manureTemperate
andTropical

1.1High –
withmanureTemperate
andTropical

1.2Long-term (> 20 year) annual cropping of
wetland (paddy rice). Can include doublecropping with non-flooded crops. For
paddy rice, tillage and input factors are not
used.
Represents temporary set aside of annually
cropland (e.g. conservation reserves) orother idle cropland that has been
revegetated with perennial grasses.
Substantial soil disturbance with full
inversion and/or frequent (within year)
tillage operations. At planting time, little(e.g. <30%) of the surface is covered byresidues.
Primary and/or secondary tillage but with
reduced soil disturbance (usually shallow
and without full soil inversion). Normallyleaves surface with >30% coverage byresidues at planting.
Direct seeding without primary tillage,
with only minimal soil disturbance in theseeding zone. Herbicides are typicallyused for weed control.
Low residue return due to removal ofresidues (via collection or burning),
frequent bare-fallowing or production ofcrops yielding low residues (e.g.
vegetables, tobacco, cotton)
Representative for annual cropping withcereals where all crop residues are
returned to the field. If residues are
removed then supplemental organic matter(e.g. manure) is added.
Represents significantly greater crop
residue inputs due to production of highresidue yielding crops, use of green
manures, cover crops, improved vegetatedfallows, frequent use of perennial grasses
in annual crop rotations, but without
manure applied (see row below)
Represents high input of crop residues
together with regular addition of animal
manure (see row above).

1

Where data were sufficient, separate values were determined for temperate and tropical temperature regimes and dry and wet moistureregimes. Temperate and tropical zones correspond to those defined in the Chapter 3 introduction (3.1); wet moisture regime
corresponds to the combined moist and wet zones in the tropics and wet zone temperate region (see Figure 3.1.3); dry zone is the sameas defined Figure 3.1.3.

2+ two standard deviations, expressed as a percent of the mean; where sufficient studies were not available for a statistical analysis adefault, based on expert judgement, of + 50% is used. NA denotes ‘Not Applicable’, where factor values constitute defined reference
values.

3This error range does not include potential systematic error due to small sample sizes that may not be representative of the true impact
for all regions of the world.

4

The second value applies to the Aquic soil class as defined in the IPCC Guidelines. No significant differences were found for different
soil types in the updated estimates produced here for the Good Practice Guidance.

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Chapter 3: LUCF Sector Good Practice Guidance

Tier 1: For Tier 1, default reference carbon stocks and stock change factors are used (as shown in Equation
3.3.3) for major cropland systems in a country, stratified by the default climate and soil types (Equation 3.3.4).
For the aggregate area of cropland remaining cropland, stock changes can be calculated either by tracking
management changes and calculating stock changes on individual parcels of land (Equation 3.3.4B) or by
calculating aggregate soil carbon stocks at the start and end of the inventory period from more general data on
the area distribution of cropland systems (Equation 3.3.4A). Aggregate results will be the same with either
approach, the main difference being that attribution of the effects of specific changes in management require
activity data that tracks management changes on specific areas of land. Default values for this calculation are
described in Section 3.3.1.2.1.2.
EQUATION 3.3.4
ANNUAL CHANGE IN CARBON STOCKS IN MINERAL SOILS IN CROPLAND REMAINING CROPLAND∆CCCMineral = ∑c∑s∑i [(SOC0 – SOC(0-T)) ● A ] c,s,i / T(A)∆CCCMineral = [∑c∑s∑i (SOC0 ● A) c,s,i – ∑c∑s∑i (SOC(0-T) ● A) c,s,i ] / T(B)

Where:∆CCCMineral = annual change in carbon stocks in mineral soils, tonnes C yr-1
SOC0 = soil organic carbon stock in the inventory year, tonnes C ha-1
SOC(0-T) = soil organic carbon stock T years prior to the inventory, tonnes C ha-1
T = inventory time period, yr (default is 20 yr)
A = land area of each parcel, hac represents the climate zones, s the soil types, and i the set of major cropland systems that are present in acountry.
Example: The following example shows calculations for aggregate areas of cropland soil carbon
stock change using Equation 3.3.4B. In a warm temperate moist climate on Mollisol soils, there
are 1Mha of permanent annual cropland. The native reference carbon stock (SOCREF) for the regionis 88 tonnes C ha-1. At the beginning of the inventory calculation period (i.e. 20 yrs earlier) the
distribution of cropland systems were 400,000 ha of annual cropland with low carbon input levels
and full tillage and 600,000 ha of annual cropland with medium input levels and full tillage. Thus
initial soil carbon stocks for the area were: 400,000 ha ● (88 tonnes C ha-1 ● 0.71 ● 1 ● 0.91) +600,000 ha ● (88 tonnes C ha-1 ● 0.71 ● 1 ● 1) = 60.231 million tonnes C. In the (current)
inventory year, there are: 200,000 ha of annual cropping with full tillage and low C input, 700,000
ha of annual cropping with reduced tillage and medium C input, and 100,000 ha of annual
cropping with no-till and medium C input. Thus total soil carbon stocks in the inventory year are:200,000 ha ● (88 tonnes C ha-1 ● 0.71 ● 1 ● 0.91) + 700,000 ha ● (88 tonnes C ha-1 ● 0.71 ● 1.09
● 1) + 100,000 ha ● (88 tonnes C ha-1 ● 0.71 ● 1.16 ● 1) = 66.291 million tonnes C. Thus theaverage annual stock change over the period for the entire area is: (66.291 – 60.231) million tonnes
C / 20 yr = 6.060 million tonnes / 20 yr = 303,028 tonnes per year soil C stock increase.
Tier 2: For Tier 2, the same basic equations as in Tier 1 are used but country-specific values for reference
carbon stocks and/or stock change factors are used. In addition, Tier 2 approaches will likely involve a moredetailed stratification of management systems if sufficient data are available.
Tier 3: Tier 3 approaches, using a combination of dynamic models along with detailed soil C emission/stockchange inventory measurements, will likely not employ simple stock change or emission factors per se.
Estimates of emissions using model-based approaches derive from the interaction of multiple equations that
estimate the net change of soil C stocks within the models. A variety of models designed to simulate soil carbon
dynamics exist (for example, see reviews by McGill et al., 1996; Smith et al., 1997).
Key criteria in selecting an appropriate model are that the model is capable of representing all of the
management practices that are represented and that model inputs (i.e. driving variables) are compatible with theavailability of country-wide input data. It is critical that the model be validated with independent observations
from country or region-specific field locations that are representatives of the variability of climate, soil andmanagement systems in the country. Examples of appropriate validation data sets include long-term replicatedfield experiments (e.g. SOMNET, 1996; Paul et al., 1997) or long-term measurements of ecosystem carbon flux
for agricultural systems, using techniques such as eddy covariance (Baldocchi et al., 2001). Ideally, an inventory
system of permanent, statistically representative “on-farm” plots, that include major climatic regions, soil types,

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and management systems and system changes, would be established where repeated measures of soil carbon
stocks could be made over time. Recommended re-sampling frequencies in most cases should not be less than 3
to 5 years (IPCC, 2000b). Where possible, measurements of soil carbon stocks should be made on an equivalentmass basis (e.g. Ellert et al., 2001). Procedures should be implemented to minimize the influence of spatial
variability with repeated sampling over time (e.g. Conant and Paustian 2002). Such inventory measurements
could be integrated with a model-based methodology.

Organic Soils
The basic methodology for estimating carbon stock change in organic (e.g. peat-derived) soils is to assign anannual loss rate of C due to the drainage and other perturbations such as tillage of the land for agricultural
production. Drainage and tillage stimulate the oxidation of organic matter previously built up under a largely
anoxic environment. The area of cropland organic soils under each climate type is multiplied by the emission
factor to derive an estimate of annual C emissions, as shown in Equation 3.3.5 below:
EQUATION 3.3.5
CO2 EMISSIONS FROM CULTIVATED ORGANIC SOILS IN CROPLAND REMAINING CROPLAND∆CCCOrganic= ∑c (A ● EF) c
Where:∆CCCOrganic = CO2 emissions from cultivated organic soils in cropland remaining cropland, tonnes C yr-1
A = land area of organic soils in climate type c, ha
EF = emission factor for climate type c (see Table 3.3.5), tonnes C ha-1 yr-1
Tier 1: For Tier 1, default emission factors (Table 3.3.5) are used along with area estimates for cultivatedorganic soils within each climate region present in the country (Equation 3.3.5). Area estimates can be developed
using the guidance in Chapter 2.
Tier 2: The Tier 2 approach uses Equation 3.3.5 where emission factors are estimated from country-specificdata, stratified by climate region, as described in Section 3.3.2.1.3. Area estimates should be developed
following the guidance of Chapter 2.
Tier 3: Tier 3 approaches for organic soils will include more detailed systems integrating dynamic models andmeasurement networks as described above for mineral soils.

TABLE 3.3.5
ANNUAL EMISSION FACTORS (EF) FOR CULTIVATED ORGANIC SOILS
Climatic temperature regime

IPCC Guidelines default

Error #

(tonnes C ha-1 yr-1)#

Cold Temperate

1.0

+ 90%

Warm Temperate

10.0

+ 90%

Tropical/sub-tropical

20.0

+ 90%

Represents a nominal estimate of error, equivalent to two times standard deviation, as a percentage of the mean.

Lim ing
The IPCC Guidelines include application of carbonate containing lime (e.g. calcic limestone (CaCO3), or
dolomite (CaMg(CO3)2) to agricultural soils as a source of CO2 emissions. A simplified explanation of theprocess is that when carbonate lime is dissolved in soil, the base cations (Ca++, Mg++) exchange with hydrogenions (H+) on soil colloids (thereby reducing soil acidity) and the bicarbonate formed (2HCO3) can react further to
evolve CO2 and water (H2O). Although the liming effect generally has a duration of a few years (after whichlime is again added), depending on climate, soil and cropping practices, the IPCC Guidelines account foremission as CO2 of all the added carbonate carbon in the year of application. Thus the basic methodology issimply the amount of agricultural lime applied times an emission factor that varies slightly depending on thecomposition of the material added.

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Chapter 3: LUCF Sector Good Practice Guidance

EQUATION 3.3.6
ANNUAL CARBON EMISSIONS FROM AGRICULTURAL LIME APPLICATION∆CCCLime = MLimestone ● EFLimestone + MDolomite ● EFDolomite
Where:∆CCCLime = annual C emissions from agricultural lime application, tonnes C yr-1
M = annual amount of calcic limestone (CaCO3) or dolomite (CaMg(CO3)2), tonnes yr-1
EF = emission factor, tonnes C (tonne limestone or dolomite)-1 (These are equivalent to carbonate carbon
contents of the materials (12% for CaCO3, 13% for CaMg(CO3)2 )).
Tier 1: For Tier 1, the total amount of carbonate containing lime applied annually to cropland soil and an
overall emission factor of 0.12 can be used to estimate CO2 emissions, without differentiating between variable
compositions of lime material. Note that while carbonate limes are the dominant liming material used, oxides
and hydroxides of lime, which do not contain inorganic carbon, are used to a limited extent for agriculturalliming and should not be included here (CO2 is produced in their manufacture but not following soil application).
Tier 2: A Tier 2 approach could entail differentiation of different forms of lime and specific emission factors if
data are available, since different carbonate liming materials (limestone as well as other sources such as marl andshell deposits) can vary somewhat in their carbon content and overall purity.
Tier 3: A Tier 3 approach could entail a more detailed accounting of emissions stemming from lime
applications than is assumed under Tiers 1 and 2. Depending on climate and soil conditions, biocarbonate
derived from lime application may not all be released as CO2 in the soil or from drainage water – some can beleached and precipitated deeper in the soil profile or be transported to deep groundwater, lakes and oceans andsequestered. If sufficient data and understanding of inorganic carbon transformation for specific climate-soil
conditions are available, specific emission factors could be derived. However, such an analysis would likely
necessitate including carbon fluxes associated with primary and secondary carbonate minerals in soil and their
response to agricultural management practices.

3.3.1.2.1.2 Choice of Emission/Removal Factors
Mineral soils
When using either the Tier 1 or Tier 2 method, the following emission/removal factors are needed for mineralsoils: reference carbon stock (SOCREF); stock change factor for land-use change (FLU); stock change factor for
management regime (FMG); stock change factor for input of organic matter (FI).
Reference carbon stocks (SOCREF)
Soils under native vegetation that have not been subject to significant land use and management impacts are used
as a baseline or reference to which management-induced changes in soil carbon can be related.
Tier 1: Under Tier 1, it is good practice to use the default reference carbon stocks (SOCREF) provided in Table
3.3.3. These are updated from those provided in the IPCC Guidelines with the following improvements: i)estimates are statistically-derived from recent compilations of soil profiles under native vegetation, ii) ‘Spodic’soils (defined as boreal and temperate zone podzols in WRB classification, Spodosols in USDA classification)
are included as a separate category, iii) soils within the boreal climate region have been included.
Tier 2: For Tier 2, reference soil C stocks can be determined from measurements of soils, for example, as partof a country’s soil survey and mapping activities. Advantages include more representative values for anindividual country and the ability to better estimate probability distribution functions that can be used in a formal
uncertainty analysis. Accepted standards for sampling and analysis of soil organic carbon and bulk density
should be used and documented.
Stock change factors (FLU, FMG, FI)
Tier 1: Under Tier 1, it is good practice to use default stock change factors (FLU, FMG, FI) provided in Table
3.3.4. These are updated from the IPCC Guidelines, based on a statistical analysis of published research.
Definitions guiding the selection of appropriate factor values are provided in the table.

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Tier 2: For the Tier 2 method, stock change factors can be estimated from long-term experiments (e.g. Smith etal., 1996; Paul et al., 1997) or other field measurements (e.g. field chronosequences2) for a particular country or
region. To estimate stock change factors, information compiled from published studies and other sources should
include organic C stock (i.e. mass per unit area to a specified depth) or all information needed to calculate SOC
stocks, i.e. percent organic matter together with bulk density. If the percent organic matter and not the percent
organic carbon are reported, a conversion factor of 0.58 for the carbon content of soil organic matter can be used.
Other information that must be included is depth of measurement and time frame over which the management
difference has been expressed. In the absence of specific information upon which to select an alternative depth
interval, it is good practice to compare stock change factors at a depth of at least 30 cm (i.e. the depth used forTier 1 calculations). Stock changes over a deeper depth may be desirable if a sufficient number of studies areavailable and if statistically significant differences in stocks due to land management are demonstrated at deeper
depths. However, it is critical that the reference soil carbon stocks (SOCRef) and stock change factors be
determined to a common depth. Factor values should be compiled for major climate and/or soils types, at least to
the level of detail used in the Tier 1 method.

Organic soils
When estimating emissions from organic soils, an emission factor (EF) is required for different climatic regimes
where organic soils have been drained for cropland use.
Tier 1: For Tier 1, default emission factors, unchanged from the IPCC Guidelines, are provided in Table 3.3.5.
These factors are differentiated by major climate (temperature) regimes and assume that soils have been drained
prior to use as cropland. Organic soils used for paddy rice or minor crops grown under flooded conditions (e.g.
cranberry bogs, wild rice) are excluded.
Tier 2: For Tier 2, it is possible to derive emission factors from literature data on carbon losses from organicsoils. Estimates of carbon losses from cultivated organic soils are usually based on measurements of subsidencewith fewer studies based on direct measurements of CO2 fluxes (Klemedtsson et al., 1997; Ogle et al., 2003).
Processes that contribute to subsidence include erosion, compaction, burning, and decomposition. Only
decomposition losses should be included in the emission factor estimate. If using subsidence data, appropriate
regional conversion factors to determine the proportion of subsidence attributable to oxidation should be used,based on studies measuring both subsidence and CO2 flux. In the absence of such information, a default factor of
0.5 for oxidation-to-subsidence, on a gram-per-gram equivalent basis, is recommended based on a review byArmentano and Menges (1986). If available, direct measurements of carbon fluxes are recommended asproviding the best means of estimating emission rates from organic soils.

Lim ing
See Section 3.3.1.2.1.1.

3.3.1.2.1.3 Choice of Activity Data
Mineral Soils
The area of cropland under different management practices (A) is required for estimating mineral soil
emissions/removals.
For existing cropland, activity data should record changes or trends in management practices that affect soil
carbon storage, such as crop types and crop rotations, tillage practices, irrigation, manure application, residue
management, etc. Two main types of management activity data exist: 1) aggregate statistics compiled by country
or for administrative areas within countries (e.g. provinces, counties) or 2) point-based land use and management
inventories making up a statistically-based sample of a country’s land area. Either type of activity data could be
used for any of the three tiers, depending on their spatial and temporal resolution. For Tier 1 and Tier 2inventories, activity data should be stratified by major climatic regions and soil types, since reference soil C
stocks vary significantly according to these factors. For the broadly defined soil categories used in Tier 1,
national or even global soil maps can be used to delineate soil divisions within the cropland land area. For
application of dynamic models and/or a direct measurement-based inventory in Tier 3, similar or more detailed
knowledge of the combinations of climate, soil, topographic and management data are needed, but the exact
requirements will be in part dependent on the model used.
2

Chronosequences consist of measurements taken from similar but separate locations that represent a temporal sequence inland use or management, for example, years since deforestation. Efforts are made to control all other between-site
differences (e.g. by selecting areas with similar soil type, topography, previous vegetation). Chronosequences are often
used as a surrogate for experimental studies or measurements repeated over time at the same location.

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Chapter 3: LUCF Sector Good Practice Guidance

Globally available land use and crop production statistics such as FAO databases (http://apps.fao.org) provide
annual compilations of total land area by major land-use types, with some differentiation of management
systems, (e.g., irrigated vs. non-irrigated cropland), area in ‘permanent’ crops (i.e. vineyards, orchards), and landarea and production for major crops (e.g. wheat, rice, maize, sorghum, etc.). Thus FAO or similar country-total
data would require additional in-country information to stratify areas by climate and soil types. If suchinformation has not already been compiled, an initial approach would be to overlay available land cover/land use
maps (of national origin or from global datasets such as IGBP_DIS) with soil maps of national origin or global
sources such as the FAO Soils Map of the World. Where possible, land areas associated with cropping systems(e.g. rotations and tillage practice), rather than simply area by crop, should be delineated and associated with theappropriate management factor values. [Note: This is applicable to the cropland biomass section as well since themethodology uses area-based estimates for specific crop types such as FAO classified “permanent crops”.] Refer
to Chapter 2 of this report.
National land-use and resource inventories, comprised of a collection of permanent sample points where data arecollected at regular intervals, have some advantages over aggregate agricultural and land-use statistics. Inventory
points can more readily be associated with a particular cropping system and the soil type associated with theparticular location can be determined by sampling or by referencing the location to a suitable soil map. Inventory
points selected based on an appropriate statistical design also enable estimates of the variability associated withactivity data, which can be used as part of a formal uncertainty analysis. An example of a point-based resource
inventory that includes cropland is the National Resource Inventory in the U.S. (Nusser and Goebel, 1997).

Organic Soils
The area of cultivated organic soils by climate regime (A) is required to estimate organic soil emissions. Similar
databases and approaches as those outlined above can be used for deriving area estimates. An overlay of soils
maps showing the spatial distribution of histosols (i.e. organic soils) with land use maps showing cropland area
can provide initial information on areas with organic soils under agricultural use. In addition, because organicsoils usually require extensive artificial drainage to be used for agricultural purposes, country-specific data on
drainage projects combined with soil maps and surveys can be used to get a more refined estimate of relevant
areas.

3.3.1.2.1.4 Uncertai nty Assessment
A formal assessment of uncertainty requires that uncertainty in per area emission/sequestration rates as well as
uncertainty in the activity data (i.e. the land areas involved in land-use and management changes), and theirinteraction be estimated. Where available, estimates of the uncertainty of the revised global default values
developed in this report are provided in the tables; these can be used with the appropriate estimates of variability
in activity data to estimate uncertainty, using the guidance provided in Chapter 5 of this report. Inventory
agencies should be aware that simple global defaults have a relatively high level of uncertainty associated withthem when applied to specific countries. In addition, because the field studies available to derive the global
defaults are not evenly distributed across climate regions, soil types and management systems, some areas –particularly in tropical regions – are underrepresented. For the Tier 2 methods, probability density functions (i.e.
providing mean and variance estimates) can be derived for stock change factors, organic soil emission factors
and reference C stocks as part of the process of deriving region- or country-specific data. For example, Ogle et al.
(2003) applied linear mixed-effect models to derive probability density functions for US specific factor values
and reference carbon stocks for agricultural soils. Activity data from a statistically-derived land use andmanagement inventory system should provide a basis to assign estimates of uncertainty to areas associated withland-use and management changes. Combining emission and activity data and their associated uncertainties canbe done using Monte-Carlo procedures to estimate means and confidence intervals for the overall inventory(Ogle et al., 2003; Smith and Heath, 2001) – see Chapter 5 of this report.

3.3.1.3

N ON -CO 2 GREENH OUSE GAS EMISSIO NSNITROUS OXIDEThe IPCC Guidelines and GPG2000 already address the following non-CO2 emission sources:•

N2O emissions from application of mineral and organic fertilisers, organic residues and biological nitrogen
fixation (IPCC Guidelines, Chapter 4 Agriculture);•

N2O, NOx, CH4 and CO emissions from on-site and off-site biomass burning (IPCC Guidelines, Chapter 4
Agriculture); and•N2O emissions from cultivation of organic soils.

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It is good practice to follow the existing IPCC Guidelines and GPG2000 and continue to report these emissions
under the Agriculture sector.

METHANE
Methane emissions from rice paddies are addressed in the IPCC Guidelines and GPG2000 and should bereported under the Agriculture sector.
Changes in the rate of methane oxidation in aerobic soils are not addressed at this time. The limited current
information indicates that the CH4 sink is small as compared to the CH4 sources from flooded soils such as ricepaddies. As more research is done and additional information becomes available, a fuller consideration of the
impact of various activities on methane oxidation should be possible.

3.3.2

Land Converted to Cropland

The conversion of land from other uses and from natural states to cropland will, in most cases, result inemissions of CO2 from both biomass and soils, at least for some years following conversion, as well as N2O andCH4 emissions from the soil. Possible exceptions are the irrigation of formerly arid lands, which can result in net
carbon gains in soils and biomass, and conversion of degraded lands to cropland. The calculation of carbon
emissions from conversion of forest land and grassland to cropland is found in the IPCC Guidelines in Section
5.2.3 (Forest and Grassland Conversion) and Section 5.3 (CO2 Emissions and Uptake from Soils). Whenestimating emissions and removals from land-use conversions to cropland, it is good practice to consider threesubcategories: change in carbon stocks in biomass (Section 3.3.2.1), change in carbon stocks in soil (Section
3.3.2.2), and emissions of nitrous oxide (Section 3.3.2.3). Methodological guidance is provided below for eachof these subcategories.
It is good practice to estimate emissions/removals from ‘land converted to cropland’ using the methods
described in this subsection for a period sufficient for the carbon stock changes to occur following land-use
conversion. However, biomass and soil pools respond differently to land-use conversions and therefore, time
periods are different for equilibrium carbon stocks to be reached. Changes in carbon in biomass pools are
estimated using the method in Section 3.3.2.1 below for the first time period following the land-use conversion
to cropland.3 After this time period, countries should estimate carbon stock changes in biomass using methods
described under Section 3.3.1.1 Cropland Remaining Cropland, Change in carbon stocks in biomass. Since thedefault inventory period for changes in soil carbon is 20 years, this period of time should be used in area
accounting for conversions to cropland.
The summary equation for carbon stock change in Land Converted to Cropland is shown below in Equation
3.3.7. In addition, methodologies based on emissions coefficients are discussed for N2O. Table 3.3.6 summarises
the tiers for each of the carbon subcategories, as well as for the N2O subcategory.
EQUATION 3.3.7
TOTAL CHANGE IN CARBON STOCKS IN LAND CONVERTED TO CROPLAND∆CLC = ∆CLCLB + ∆CLCSoils
Where:∆CLC = total change in carbon stocks in land converted to cropland, tonnes C yr-1
∆CLCLB = change in carbon stocks in living biomass in land converted to cropland, tonnes C yr-1
∆CLCSoils = change in carbon stocks in soil in land converted to cropland, tonnes C yr-1

3

The time period will depend on the frequency with which countries collect data. For example, if land use surveys arecollected on a five-year cycle, e.g., 1990, 1995, 2000, then a land conversion that takes place in 1992 will be captured by
the 1995 data collection and thus recorded using the methods below in the inventory report that employs survey data for
1995.

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3.3.2.1

C HANGE IN CARB ON STOCKS LIVING BIOMASSThis section provides good practice guidance for calculating carbon stock change in biomass due to theconversion of land from natural conditions and other uses to cropland, including deforestation and conversion of
pasture and grazing lands to cropland. The methods require estimates of carbon in living biomass stocks prior toand following conversion, based on estimates of the areas of lands converted during the period between land use
surveys. As a result of conversion to cropland, it is assumed (in Tier 1) that the dominant vegetation is removed
entirely, resulting in near zero amounts of carbon remaining in biomass. Some type of cropping system isplanted soon thereafter, increasing the amount of carbon stored in biomass. The difference between initial andfinal biomass carbon pools is used to calculate carbon stock change from land-use conversion and in subsequent
years accumulations and losses in perennial woody biomass in cropland are counted using methods in section
3.3.1 Croplands remaining Croplands.

3.3.2.1.1 METHODOLOGICAL ISSUES
The methodology estimates carbon stock change in living biomass. Currently, there is not sufficient information
to provide a basic approach with default parameters to estimate carbon stock change in dead organic matter poolsin land converted to cropland4. In addition, the methodology below considers carbon stock change inaboveground biomass only because limited data are available on belowground carbon stocks in perennial
cropland.
TABLE 3.3.6
TIER DESCRIPTIONS FOR SUBCATEGORIES UNDER LAND CONVERTED TO CROPLAND (LC)Tier
Sub
-categories

4

Tier 1

Tier 2Tier 3

Biomass

Use default coefficients to estimate
carbon stock change in biomass
resulting from land use conversions
and for carbon in biomass that
replaces cleared vegetation during
the year of land use transition.

Use at least some country-specificcarbon stock parameters to estimate
carbon stock changes from land use
conversion to cropland. Apportion
carbon from biomass removal toburning, decay, and other nationally
important conversion processes.
Estimate non-CO2 trace gas emissions
from the portion of biomass burned
both on-site and off-site. Use area
estimates that are disaggregated tonationally relevant climate zones andother boundaries to match countryspecific carbon stock parameters.

Use country-specificapproach at finespatial scale (e.g.,modeling,
measurement).

Carbon stocks
in Soil

For change in soil carbon frommineral soils use default
coefficients. The areas must be
stratified by climate and soil type.
For change in soil carbon fromorganic soils use default
coefficients and stratify the areas byclimatic region. For emissions fromliming, use default emission factors.

For both mineral and organic soils use
some combination of default and or
country-specific coefficients and area
estimates of increasingly finer spatial
resolution. For emissions from liming,
use emission factors differentiated byforms of lime.

Use country-specificapproach at finespatial scale (e.g.,modeling,
measurement)

Nitrous Oxide
from soiloxidation
duringconversion

Use default parameters and coarse
spatial disaggregation

Use of country-specific parameters andincreased spatial disaggregation

Use country-specificapproach at finespatial scale (e.g.,modeling,
measurement) andreport under
LULUCF croplandremaining cropland

Any litter and dead wood pools (estimated using the methods described in Section 3.2.2.2) should be assumed oxidized
following land conversion.

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Cropland

3.3.2.1.1.1 Choice of Method
The IPCC Guidelines describe increasingly sophisticated alternatives that incorporate greater detail on the areasof land converted, carbon stocks on lands, and removal of carbon resulting from land conversions. Good practiceguidance reflects this in a tiered methodology with the choice of tier depending on data availability and national
circumstances. All countries should strive for improving inventory and reporting approaches by advancing to thehighest tier possible given national circumstances. It is good practice for countries to use a Tier 2 or Tier 3
approach if carbon emissions and removals in land converted to cropland is a key category and if thesubcategory of living biomass is considered significant based on principles outlined in Chapter 5. Countries
should use the decision tree in Figure 3.1.2 to help with the choice of method.
Tier 1: The Tier 1 method follows the approach in IPCC Guidelines Section 5.2.3. Forest and Grassland
Conversion where the amount of biomass that is cleared for cropland is estimated by multiplying the forest area
converted in one year by the average carbon stock in biomass in the forest prior to conversion. It is good practiceto account completely for all land conversions to cropland. Thus, this section elaborates on the method such thatit includes each initial land use, including but not limited to forests.
Equation 3.3.8 summarises the major elements of a first order approximation of carbon stock change from landuse conversion to cropland. Average carbon stock change on a per area basis is estimated for each type of
conversion. The average carbon stock change is equal to the carbon stock change due to the removal of biomass
from the initial land use (i.e., carbon in biomass immediately after conversion minus the carbon in biomass prior
to conversion), plus carbon stocks from one year of growth in cropland following conversion. As stated in the
IPCC Guidelines, it is necessary to account for any vegetation that replaces the vegetation that was cleared
during land use conversion. The IPCC Guidelines combine carbon in biomass after conversion and carbon inbiomass that grows on the land following conversion into a single term. In this method, they are separated into
two terms, CAfter and ∆CGrowth to increase transparency. At Tier 1, carbon stocks in biomass immediately afterconversion (CAfter) are assumed to be zero, i.e., the land is cleared of all vegetation before planting crops.
Average carbon stock change per area for a given land use conversion is multiplied by the estimated area oflands undergoing such a conversion in a given year. In subsequent years, change in biomass of annual crops isconsidered zero because carbon gains in biomass from annual growth are offset by losses from harvesting andchange in biomass of perennial woody crops are counted following the methodology in Section 3.3.1.1 (Change
in carbon stocks in biomass, in: Cropland Remaining Cropland).
The basic steps in estimating carbon stock change in biomass from land conversion to cropland are as follows:(i)

Estimate the average area of land undergoing a transition from non-cropland to cropland during ayear (Aconversion), separately for each initial land use (i.e., forest land, grasslands, etc.) and final crop
type (i.e., annual or perennial woody).

(ii)

For each type of land use transition to cropland, use Equation 3.3.8 to estimate the resulting change
in carbon stocks. Default data in Section 3.3.2.1.1.2 for CAfter, CBefore, and ∆CGrowth can be used toestimate the total stock change on a per area basis for each type of land use transition. The estimate
for stock change on a per area basis can then be multiplied by the appropriate area estimates fromstep 1.

(iii)

Estimate the total carbon stock change from all land-use conversions to cropland by summing theindividual estimates for each transition.

The default assumption for Tier 1 is that all carbon in biomass is lost to the atmosphere through decay processes
either on- or off-site. As such, Tier 1 calculations do not differentiate immediate emissions from burning andother conversion activities.
EQUATION 3.3.8
ANNUAL CHANGE IN CARBON STOCKS IN LIVING BIOMASSIN LAND CONVERTED TO CROPLAND∆CLCLB = AConversion ● (LConversion + ∆CGrowth)
LConversion = CAfter – CBefore
Where:∆CLCLB = annual change in carbon stocks in living biomass in land converted to cropland, tonnes C yr-1
AConversion = annual area of land converted to cropland, ha yr-1
LConversion = carbon stock change per area for that type of conversion when land is converted to cropland,
tonnes C ha-1

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Chapter 3: LUCF Sector Good Practice Guidance∆CGrowth = changes in carbon stocks from one year of cropland growth, tonnes C ha-1
CAfter= carbon stocks in biomass immediately after conversion to cropland, tonnes C ha-1
CBefore= carbon stocks in biomass immediately before conversion to cropland, tonnes C ha-1
Tier 2: The Tier 2 calculations are structurally similar to Tier 1, with these distinctions. First, Tier 2 relies on atleast some country-specific estimates of the carbon stocks in initial and final land uses rather than the defaults
provided in Section 3.3.2.1.1.2. Area estimates for land converted to cropland are disaggregated at finer spatial
scales to capture regional and crop systems variations in country-specific carbon stocks values.
Second, Tier 2 may modify the assumption that carbon stocks immediately following conversion are zero. This
enables countries to take into account land use transitions where some, but not all, vegetation from the originalland use is removed.
Third, under Tier 2, it is good practice to apportion carbon losses to burning and decay processes if applicable.
Emissions of carbon dioxide occur as a result of burning and decay in land-use conversions. In addition, nonCO2 trace gas emissions occur as a result of burning. By partitioning losses to burning and decay, countries canalso calculate non-CO2 trace gas emissions from burning. The IPCC Guidelines Workbook provides step-by-step
instructions for estimating carbon removals from burning and decay of biomass on-site and off-site and for
estimating non-CO2 trace gas emissions from burning (pages 5.7-5.17). Below is guidance on estimating carbon
removals from burning and decay and Section 3.2.1.4 of this chapter provides further guidance on estimating
non-CO2 trace gas emissions from burning.
The basic equations for estimating the amount of carbon burned or left to decay are provided in Equations 3.3.10
and 3.3.11 below. This methodology addresses burning for the purposes of land clearing. Non-CO2 emissions
from burning for management of cropland remaining cropland are covered in the Agriculture chapter of
GPG2000. The default assumption in Equations 3.3.10 and 3.3.11 is that only aboveground biomass, is burned
or decays. Countries are encouraged to use additional information to assess this assumption, particularly for
decaying belowground biomass. Equations 3.3.10 and 3.3.11 estimate the amount of carbon in biomass removed
during a land use conversion to cropland that is burned (on-site and off-site) or that decays, respectively. The
basic approach can be modified to address other conversion activities as well to meet the needs of national
circumstances. Both equations use as an input the total amount of carbon in biomass removed during land
clearing (∆Cconversion) (Equation 3.3.9), which is equivalent to area of land converted (AConversion) multiplied by the
carbon stock change per area for that type of conversion (LConversion in Equation 3.3.8).
The portion of biomass removed is sometimes used as wood products. In the case of wood products, countries
may use the default assumption that carbon in wood products is oxidized in the year of removal. Alternatively,
countries may refer to Appendix 3a.1 for estimation techniques for carbon storage in harvested wood products,
which may be accounted for provided carbon in the product pool is increasing.
EQUATION 3.3.9
CHANGE IN CARBON STOCKS AS A RESULT OF CLEARING BIOMASS IN A LAND USE CONVERSION∆Cconversion = Aconversion ● Lconversion
Where:∆Cconversion = change in carbon stocks as a result of clearing biomass in a land use conversion, tonnes C
AConversion = area of land converted to croplands from some initial use, ha
LConversion = carbon stocks removed when land is converted from some initial use to cropland, tonnes C ha-1
(from Equation 3.3.8)
EQUATION 3.3.10
CARBON LOSSES FROM BIOMASS BURNING, ON-SITE AND OFF-SITE
Lburn onsite = ∆Cconversion ● ρburned on site ● ρoxid
Lburn offsite = ∆Cconversion ● ρburned off site ● ρoxid
Where:
Lburn = carbon losses from biomass burned, tonnes C∆Cconversion = change in carbon stocks as a result of a clearing biomass in a land use conversion, tonnes Cρburned on site = fraction of biomass that is burned on-site, dimensionless

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Croplandρoxid = fraction of biomass that oxidizes when burned, dimensionlessρburned off site = fraction of biomass that is burned off-site, dimensionless

EQUATION 3.3.11
CARBON LOSSES FROM BIOMASS DECAY
Ldecay = ∆Cconversion ● ρdecay

ρdecay = 1 – (ρburned on site + ρburned off site )Where:
Ldecay = carbon losses from biomass decay, tonnes C∆Cconversion = change in carbon stocks as a result of a clearing biomass in a land use conversion, tonnes Cρdecay = fraction of biomass that is left on-site to decay, dimensionlessρburned on site = fraction of biomass that is burned on-site, dimensionlessρburned off site = fraction of biomass that is burned off-site, dimensionless
It is good practice for countries to use the terms Lburn on site and Lburn off site as inputs to estimate non-CO2 trace gas
emissions from burning following guidance provided in Section 3.2.1.4.
Tier 3: The Tier 3 method is similar to Tier 2, with the following distinctions: rather than relying on averageannual rates of conversion, countries can use direct estimates of spatially disaggregated areas converted annuallyfor each initial and final land use; carbon densities and soil carbon stock change are based on locally specificinformation, which makes possible a dynamic link between biomass and soil; and biomass volumes are based on
actual inventories.

3.3.2.1.1.2 Choice of Emission/Removal Factors
Tier 1: Default parameters are provided in both the IPCC Guidelines and in this report to enable countries withlimited data resources to estimate emissions and removals from this source. The first step in this methodology
requires parameters for carbon stocks before conversion for each initial land use (CBefore) and after conversion(CAfter). It is assumed that all biomass is cleared when preparing a site for cropland use, thus, the default for CAfteris 0 tonnes C ha-1. Table 3.3.7 provides default carbon stock values for CBefore in either forest or grassland land
uses prior to clearing.
In addition, a value is needed for carbon stocks after one year of growth in crops planted after conversion(∆CGrowth). Table 3.3.8 provides defaults for ∆CGrowth. Separate defaults are provided for annual non-woody crops
and perennial woody crops. For lands planted in annual crops, the default value of ∆CGrowth is 5 tonnes of C per
hectare, based on the original IPCC Guidelines recommendation of 10 tonnes of dry biomass per hectare (drybiomass has been converted to tonnes carbon in Table 3.3.8). Default carbon stocks from one year of growth inperennial woody crops the same as those in Table 3.3.2. The total accumulation of carbon in perennial woody
biomass will, over time, exceed that of the default carbon stock for annual cropland. However, default values
provide in this section are for one year of growth immediately following conversion, which usually give lower
carbon stocks for perennial woody crops compared to annual crops.
TABLE 3.3.7
DEFAULT BIOMASS CARBON STOCKS REMOVED DUE TO LAND CONVERSION TO CROPLAND
Carbon stock in biomass before conversion (CBefore)(tonnes C ha-1)

Error range #Forest land

See Tables 3A.2 and 3A.3 in Annex 3A.1 for carbon stocks in a range offorest types by climate regions. Stocks are in terms of dry matter. Multiply
values by a carbon fraction (CF) 0.5 to convert dry matter to carbon.

See Section 3.2.2(Land Converted toForest land)

Grassland

See Table 3.4.2 for carbon stocks in a range of grassland types by climate
regions.

+ 75%

Land-use category#

Represents a nominal estimate of error, equivalent to two times standard deviation, as a percentage of the mean.

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Chapter 3: LUCF Sector Good Practice Guidance

TABLE 3.3.8
DEFAULT BIOMASS CARBON STOCKS PRESENT ON LAND CONVERTED TO CROPLAND
IN THE YEAR FOLLOWING CONVERSION

Carbon stock in biomass after
one year (∆CGrowth)(tonnes C ha-1)

Error range#

5

+ 75%

Temperate (all moisture regimes)

2.1

+ 75%

Tropical, dry

1.8

+ 75%

Tropical, moist

2.6

+ 75%

Tropical, wet

10.0

+ 75%

Crop type by climate region
Annual cropland
Perennial cropland#Represents a nominal estimate of error, equivalent to two times standard deviation, as a percentage of the mean.

Tier 2: Tier 2 methods should include some country-specific estimates for biomass stocks and removals due toland conversion, and also include estimates of on- and off-site losses due to burning and decay following land
conversion to cropland. These improvements can take the form of systematic studies of carbon content andemissions and removals associated with land uses and land-use conversions within the country and a reexamination of default assumptions in light of country-specific conditions.
Default parameters for emissions from burning and decay are provided, however countries are encouraged todevelop country-specific coefficients to improve the accuracy of estimates. The IPCC Guidelines use a general
default of 0.5 for the proportion of biomass burned on-site for both forest and grassland conversions. Researchstudies suggest that the fraction is highly variable and could be as low as 0.2 (Fearnside 2000, Barbosa andFearnside, 1996, and Fearnside, 1990). Updated default proportions of biomass burned on site are provided inTable 3A.13 for a range of forest vegetation classes. These defaults should be used for transitions from forest
land to cropland. For non-forest initial land uses, the default proportion of biomass left on-site and burned is 0.35.
This default takes into consideration research, which suggests the fraction should fall within the range 0.2 to 0.5(e.g. Fearnside, 2000; Barbosa and Fearnside, 1996; and Fearnside, 1990). It is good practice for countries to use
0.35, or another value within this range provided the rationale for the choice is documented. There is no default
value for the amount of biomass taken off-site and burned; countries will need to develop a proportion based onnational data sources. In Equation 3.3.10., the default proportion of biomass oxidized as a result of burning is 0.9,
as originally stated in the IPCC Guidelines.
The method for estimating emissions from decay assumes that all biomass decays over a period of 10 years. For
reporting purposes countries have two options: to report all emissions from decay in one year, recognizing that inreality they occur over a 10 year period, or report all emission from decay on an annual basis, estimating the rate
as one tenth of the totals in Equation 3.3.11. If countries choose the latter option, they should add a
multiplication factor of 0.10 to Equations 3.3.11.
Tier 3: Under Tier 3, all parameters should be country-defined using more accurate values rather than thedefaults.

3.3.2.1.1.3 Choice of Activity Data
All tiers require estimates of land areas converted to cropland. The same area estimates should be used for bothbiomass and soil calculations on land converted to cropland. Higher tiers require greater specificity of areas. To
be consistent with IPCC Guidelines, at a minimum, the area of forest and natural grassland converted to croplandshould be identified separately for all tiers. This implies at least some knowledge of the land uses prior toconversion; this may require expert judgment if Approach 1 in Chapter 2 is used for land area identification.
Tier 1: One type of activity data is needed for a Tier 1 approach: separate estimates of areas converted tocropland from initial land uses (i.e., forest land, grassland, settlement, etc.) to final crop type (i.e., annual or
perennial) (Aconversion). For example, countries should estimate separately the area of tropical moist forest
converted to annual cropland, tropical moist forest converted to perennial cropland, tropical moist grassland
converted to perennial cropland, etc. The methodology assumes that area estimates are based on a one-year timeframe. If area estimates are assessed over longer time frames, they should be converted to average annual areas
to match the default carbon stock values provided above. If countries do not have these data, partial samples may
be extrapolated to the entire land base or historic estimates of conversions may be extrapolated over time basedon the judgement of country experts. Under Tier 1 calculations, international statistics such as FAO databases,

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Cropland

IPCC Guidelines and other sources, supplemented with sound assumptions, can be used to estimate the area ofland converted to cropland from each initial land use. For higher tier calculations, country-specific data sources
are used to estimate all possible transitions from initial land use to final crop type.
Tier 2: Countries should strive to use actual area estimates for all possible transitions from initial land use to
final crop type. Full coverage of land areas can be accomplished either though analysis of periodic remotelysensed images of land use and land cover patterns, through periodic ground-based sampling of land use patterns,
or hybrid inventory systems. If finer resolution country-specific data are partially available, countries areencouraged to use sound assumptions from best available knowledge to extrapolate to the entire land base.
Historic estimates of conversions may be extrapolated over time based on the judgment of country experts.
Tier 3: Activity data used in Tier 3 calculations should be a full accounting of all land use transitions tocropland and be disaggregated to account for different conditions within a country. Disaggregation can occur
along political (county, province, etc.), biome, climate, or on a combination of these parameters. In many cases
countries may have information on multi-year trends in land conversion (from periodic sample-based or
remotely sensed inventories of land use and land cover).

3.3.2.1.1.4. Uncertainty Assessment
Tier 1: The sources of uncertainty in this method are from the use of global or national average rates of
conversion and coarse estimates of land areas converted to cropland. In addition, reliance on default parameters
for carbon stocks in initial and final conditions contributes to relatively high degrees of uncertainty. The default
values in this method have corresponding error ranges associated with them. A published compilation ofresearch on carbon stocks in agroforestry systems was used to derive the default data provided in Section
3.3.2.1.1.2 (Schroeder, 1994). While defaults were derived from multiple studies, their associated uncertainty
ranges were not included in the publication. Therefore, a default uncertainty level of +/- 75% of the carbon stock
has been assumed based on expert judgement.
Tier 2: Actual area estimates for different land use transitions will enable more transparent accounting andallow experts to identify gaps and double counting of land areas. The Tier 2 method uses at least some countrydefined defaults, which will improve the accuracy of estimates, because they better represent conditions relevantto the country. Use of country-specific values should entail sufficient sample sizes and or use of expert judgment
to estimate uncertainties, which, together with uncertainty estimates on activity data derived using the advice in
Chapter 2 should be used in the approaches to uncertainty analysis described in Chapter 5 of this report.
Tier 3: Activity data from a land use and management inventory system should provide a basis to assign
estimates of uncertainty to areas associated with land-use changes. Combining emission and activity data andtheir associated uncertainties can be done using Monte-Carlo procedures to estimate means and confidence
intervals for the overall inventory.

3.3.2.2

C HANGE IN CARB ON STOCKS IN SOILS

3.3.2.2.1 METHODOLOGICAL ISSUESLand conversion to cropland can occur from unmanaged land, including native, relatively undisturbed
ecosystems (e.g. forest land, grassland, savanna, wetland) and from land managed for other uses (e.g. managed
forest, managed grazing land). The more intensive management entailed in cropland use (i.e. high removal of
harvested biomass, often frequent soil disturbance by tillage) will usually result in losses of C in soil organic
matter and dead organic matter (surface litter and coarse woody debris). Any litter and dead wood pools(estimated using the methods described in Section 3.2.2.2) should be assumed oxidized following land
conversion and changes in soil organic matter C stocks should be estimated as described below.
The total change in carbon stocks in soils on Lands Converted to Cropland is shown in Equation 3.3.12 below:
EQUATION 3.3.12
ANNUAL CHANGE IN CARBON STOCKS IN SOILS IN LAND CONVERTED TO CROPLAND∆CLCSoils = ∆CLCMineral – ∆CLCOrganic – ∆CLCLiming
Where:∆CLCSoils = annual change in carbon stocks in soils in land converted to cropland, tonnes C yr-1
∆CLCMineral = change in carbon stocks in mineral soils in land converted to cropland, tonnes C yr-1

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Chapter 3: LUCF Sector Good Practice Guidance∆CLCOrganic = annual C emissions from cultivated organic soils converted to cropland (estimated as net
annual flux), tonnes C yr-1
∆CLCLiming = annual C emissions from agricultural lime application on land converted to cropland, tonnes
C yr-1
Criteria for selecting the most suitable estimation method are similar to that outlined for permanent croplandsoils. Key factors include type of land conversion and the longevity of the conversion, and availability of suitablecountry-specific information to estimate reference soil C stocks and stock change and emission factors.
All countries should strive for improving inventory and reporting approaches by advancing to the highest tierpossible given national circumstances. It is good practice for countries to use a Tier 2 or Tier 3 approach if
carbon emissions and removals in land converted to cropland is a key category and if the subcategory of soilorganic matter is considered significant based on principles outlined in Chapter 5. Countries should use thedecision tree in Figure 3.1.2 to help with the choice of method.

3.3.2.2.1.1 Choice of Method
Mineral Soils
The Tier 1 method is based on the IPCC Guidelines (CO2 Emissions and Uptake by Soils from Land-Use andManagement, Section 5.3), using Equation 3.3.3, following land conversion. Tier 1 methods rely on default
values for reference C stocks and stock change factors and relatively aggregated data on the location and rates ofland-use conversion.
For Tier 1, the initial (pre-conversion) soil C stock (SOC(0-T)) is determined from the same reference soil C
stocks (SOCREF) used for all land uses (Table 3.3.3), together with stock change factors (FLU, FMG, FI) appropriate
for the previous land use as shown in Table 3.3.9 (also see Sections 3.2.1.3 (Forest soils) and 3.4.1.2 (Grassland
soils)). For unmanaged land, as well as for managed forest and grazing land with low disturbance regimes, soil C
stocks are assumed equal to the reference values (i.e. land use, management and input factors equal 1). Current(SOC0) soil C stocks on land converted to cropland are estimated exactly as for permanent cropland, i.e., using
the reference carbon stocks (Table 3.3.3) and stock change factors (Table 3.3.9). Thus, annual rates of emissions(source) or removals (sink) are calculated as the difference in stocks (over time) divided by the inventory time
period (default is 20 years).
The calculation steps for determining SOC0 and SOC(0-T) and net soil C stock change per ha of land area are as
follows:
Step 1: Select the reference carbon stock value (SOCREF), based on climate and soil type, for each area of land
being inventoried.
Step 2: Calculate the pre-conversion C stock (SOC(0-T)) of land being converted into cropland, based on thereference carbon stock and previous land use and management, which determine land use (FLU),
management (FMG) and input (FI ) factors. Note that where the land being converted is forest or native
grassland, the pre-conversion stocks will be equal to the native soil carbon reference stocks.
Step 3: Calculate SOC0 by repeating step 2 using the same reference carbon stock (SOCREF), but with land use,
tillage and input factors that represent conditions in the land converted to cropland.
Step 4: Calculate the average annual change in soil C stock for the area over the inventory period (∆CCCMineral ).
Example: For a forest on volcanic soil in a tropical moist environment: SOCRef = 70 tonnes C ha-1.
For all forest soils (and for native grasslands) default values for stock change factors (FLU , FMG ,FI) are all 1; thus SOC(0-T) is 70 tonnes C ha-1. If the land is converted into annual cropland, withintensive tillage and low residue C inputs then SOC0 = 70 tonnes C ha-1 ● 0.58 ● 1 ● 0.91 = 36.9
tonnes C ha-1. Thus the average annual change in soil C stock for the area over the inventory
period is calculated as (36.9 tonnes C ha-1 – 70 tonnes C ha-1) / 20 yrs = -1.7 tonnes C ha-1 yr-1.
The IPCC Guidelines also provide estimates for C stock change associated with the transient land-use
conversion to cropland represented by shifting cultivation. In this case, the stock change factors are different
from those used if the conversion is to permanent cropland, and change in soil C stocks will depend on thelength of the fallow (vegetation recovery) cycle. The soil carbon stocks calculated for shifting cultivation
represent an average over the crop-fallow cycle. Mature fallow denotes situations where the non-croplandvegetation (e.g. forest, savanna) recovers to a mature or near mature state prior to being cleared again forcropland use, whereas in shortened fallow vegetation recovery is not attained prior to re-clearing. If land already

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Croplandin shifting-cultivation is converted to permanent cropland (or other land uses) the stock factors representing
shifting cultivation would provide the ‘initial’ C stocks in the calculations of changes following conversion.
The Tier 2 method for mineral soils also uses Equation 3.3.3, but involves country or region-specific reference C
stocks and/or stock change factors and more disaggregated land use activity data.

Organic Soils
Tier 1 and Tier 2 approaches for organic soils that are converted from other land uses to cropland within theinventory period are treated the same as long-term cropped organic soils, i.e., they have a constant emission
factor applied to them, based on climate regime (see Equation 3.3.5 and Table 3.3.5). In Tier 2, emission factors
are derived from country or region-specific data.

Mineral and organic s oils
For both mineral and organic soils, Tier 3 methods will involve more detailed and country-specific models
and/or measurement-based approaches along with highly disaggregated land use and management data. Tier 3
approaches for estimating soil C change from land-use conversions to cropland should employ models and data
sets that are capable of representing transitions over time between different land use and vegetation types,
including forest, savanna, grasslands, cropland. The Tier 3 method needs to be integrated with estimates ofbiomass removal and the post-clearance treatment of plant residues (including woody debris and litter), as
variation in the removal and treatment of residues (e.g. burning, site preparation) will affect C inputs to soilorganic matter formation and C losses through decomposition and combustion. It is critical that models bevalidated with independent observations from country or region-specific field locations that are representative of
the interactions of climate, soil and vegetation type on post-conversion change in soil C stocks.

Lim ing
If agricultural lime is applied to cropland converted from other land uses then the methods for estimating CO2
emissions from liming are the same as described for Cropland Remaining Cropland, in Section 3.3.1.2.1.1.

3.3.2.2.1.2 Choice of Emission/Removal Factors
Mineral soils
The following variables are needed when using either the Tier 1 or Tier 2 method:
Reference carbon stocks (SOCREF)
Tier 1: Under Tier 1, it is good practice to use the default reference carbon stocks (SOCREF) provided in Table
3.3.3. These are updated from those provided in the IPCC Guidelines with the following improvements: i)estimates are statistically-derived from recent compilations of soil profiles under native vegetation, ii) ‘Spodic’soils (defined as boreal and temperate zone podzols in WRB classification, Spodosols in USDA classification)
are included as a separate category, iii) soils within the boreal climate region have been included.
Tier 2: For the Tier 2 method, reference soil C stocks can be determined from measurements of soils, forexample, as part of a country’s soil survey and mapping activities. It is important that reliable taxonomic
descriptions of measured soils be used to group soils into the classes defined in Table 3.3.3 or if a finer
subdivision of reference soil C stocks is used definitions of soil groupings need to be consistently and well
documented. Advantages to using country-specific data for estimating reference soil C stocks include moreaccurate and representative values for an individual country and the ability to better estimate probability
distribution functions that can be used in a formal uncertainty analysis.
Stock change factors (FLU, FMG, FI)
Tier 1: Under Tier 1, it is good practice to use default stock change factors (FLU, FMG, FI) provided in Table
3.3.9. These are updated from the IPCC Guidelines, based on a statistical analysis of published research.
Definitions guiding the selection of appropriate factor values are provided in the table. Stock change factors areused in estimating both post- (SOC0) and pre-conversion (SOC(0-T)) stocks; values will vary according to land
use and management conditions before and after the conversion. Note that where forest land or native grasslands
are converted to cropland use, the stock change factors all have the value of one, such that the pre-conversion
soil carbon stocks are equal to the native vegetation reference values (SOCREF).
Tier 2: For the Tier 2 method, estimation of country-specific stock change factors for land-use conversion tocropland will typically be based on paired-plot comparisons representing converted and unconverted lands,
where all factors other than land-use history are as similar as possible (e.g. Davidson and Ackermann, 1993).
Ideally several sample locations can be found that represent a given land use at different times since conversion– referred to as a chronosequence (e.g. Neill et al., 1997). There are few replicated long-term experiments ofland- use conversions and thus stock change factors and emission factors for land-use conversions will have

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greater uncertainty than for permanent cropland. In evaluating existing studies or conducting new measurements
it is critical that the plots being compared have similar pre-conversion histories and management as well as
similar topographic position, soil physical properties and be located in close proximity. As for permanent
cropland, required information includes C stock (i.e. mass per unit area to a specified depth) for each land use(and time point if a chronosequence). As previously described under Cropland Remaining Cropland, in theabsence of specific information upon which to select an alternative depth interval, it is good practice to compare
stock change factors at a depth of at least 30 cm (i.e. the depth used for Tier 1 calculations). Stock changes overa deeper depth may be desirable if a sufficient number of studies are available and if statistically significant
differences in stocks due to land management are demonstrated at deeper depths. However, it is critical that thereference soil carbon stocks (SOCRef) and stock change factors (FLU, FMG, FI) be determined to a common depth.

Organic soils
Tier 1 and Tier 2 choice of C emission factors from organic soils recently converted to cropland should observe
the same procedures for deriving emission factors as described earlier under the Cropland Remaining Croplandsection.
TABLE 3.3.9
RELATIVE SOIL STOCK CHANGE FACTORS (FLU, FMG, FI) FOR LAND-USE CONVERSIONS TO CROPLAND
Factorvalue typeLand use

Land use
Land use,
Management,& Input
Land use,
Management,& Input
Land use,
Management,& Input#

Level
Native forest or
grassland(non-degraded)
Shifting cultivation– Shortened fallow
Shifting cultivation– Mature fallow

Climateregime

IPCC
Guidelines
default

Error#

Definition

Temperate

1NA

Tropical1NA

Tropical

0.64

+ 50%

Tropical

0.8

+ 50%

Represents native or long-term, nondegraded and sustainably managed forestand grasslands.
Permanent shifting cultivation, where
tropical forest or woodland is cleared forplanting of annual crops for a short time(e.g. 3-5 yr) period and then abandoned toManaged forest

See Equation 3.2.14 and accompanying text

Managed grassland

See default values in Table 3.4.5

CroplandSee default values in Table 3.3.4

Represents a nominal estimate of error, equivalent to two times standard deviation, as a percentage of the mean. NA denotes ‘Not
Applicable’, where factor values constitute defined reference values.

3.3.2.2.1.3 Choice of Activity Data
Mineral and Organic Soils
At a minimum, countries should have estimates of the areas of land converted to cropland during the inventory
period. If land use and management data are limited, aggregate data, such as FAO statistics on land conversions,can be used as a starting point, along with knowledge of country experts of the approximate distribution of land
use types (e.g. forest land and grassland areas and their respective soil types) being converted and knowledge ofthe types of cropland practices being used on land converted to cropland. More detailed accounting can beaccomplished either through analysis of periodic remotely sensed images of land use and land cover patterns,
through periodic ground-based sampling of land use patterns, and/or hybrid inventory systems. Estimates ofland-use conversions to cropland should be stratified according to major soil types, as defined for Tier 1, orbased on country-specific stratifications if employed in Tier 2 or 3 approaches. This can be based on overlays
with suitable soil maps and spatially-explicit data of the location of land conversions.

3.3.2.2.1.4 Uncertai nty Assessment
Because most conversions to cropland uses entail losses from soil carbon stocks, the most critical data from thestandpoint of reducing overall uncertainty is accurate estimates of the land area being converted to cropland. Dueto their high native soil carbon stocks and potential for large losses, conversions to cropland occurring onorganic soils, as well as wetland mineral soils and volcanic soils, are of particular importance. Reducing
uncertainty in the estimates of stock change and emission factors for lands recently (<20 yrs) converted tocropland can best be accomplished from direct monitoring of C stocks (and emissions) before and after (for a

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period of several year) conversion to cropland, at the same location. However, data based on indirect estimates,
so-called chronosequences, in which land converted to cropland at different times in the past and at different
locations, are more common. Use of estimates based on chronosequences will have a higher uncertainty thandirect monitoring over time. In constructing and evaluating chronosequences it is important to select areas which
are as similar as possible with respect to original vegetation, soil type and landscape position – i.e. the maindifference being time since conversion. Estimates should be based on more than one chronosequence. Overall
uncertainty assessment will require combining uncertainties associated with stock change and emission factors
and activity data concerning land areas converted to cropland.

3.3.2.3

N ON -CO 2 GREENH OUSE GAS EMISSIO NSThis section deals with the increase in N2O emissions arising from the conversion of forest land, grassland, andother land to cropland. An increase in N2O emissions can be expected following the conversion of forest land,grassland and other land to cropland. This is a consequence of the enhanced mineralisation (conversion to
inorganic form) of soil organic matter (SOM) that normally takes place as a result of that conversion. The
mineralisation results not only in a net loss of soil C and hence a net CO2 emission (Section 3.3.2.2.1.2) but also
in associated conversion of nitrogen previously in the SOM to ammonium and nitrate. Microbial activity in thesoil converts some of the ammonium and nitrate present to N2O. Thus an increase in this microbial substratecaused by a net decrease in SOM can be expected to give an increase in net N2O emissions. The approach here is
to use the same emission factor (EF1) as that used for direct emissions from agricultural land which has been incultivation for a long time (see Agriculture, GPG2000), and has the same logical basis, i.e. that N converted into
inorganic form in the soil, as a result of mineralisation, is all of equal value as a substrate for the organisms
producing N2O by nitrification and denitrification, no matter what the organic source is, soil organic matter inthis case of land-use conversion to cropland, or plant roots and crop residues from cultivation after harvest, oradded organic manures as in the case of the N2O emissions addressed in the IPCC Guidelines, Chapter 4
Agriculture and GPG2000.
Guidance on estimating trace gas emissions (N2O, NOx, CH4 and CO) from on-site and off-site biomass burning
is provided in Section 3.2.1.4.
The rate of methane oxidation in aerated topsoils can change due to conversion to cropland. The reduction inoxidation is not addressed in this report, however, due to limited information. In the future, as more data become
available, it may be possible to provide a fuller consideration of the impact of various activities on methane
oxidation rates.

3.3.2.3.1 METHODOLOGICAL ISSUESNITROUS OXIDE FROM MINERAL SOILS
3.3.2.3.1.1 Choice of Method
The total emissions of N2O are equivalent to the sum of all N2O emissions from land use conversions as shownin Equation 3.3.13 and 3.3.14. These are emissions from mineralisation of soil organic matter resulting fromconversion of forest land, grassland, settlements or other land to cropland.
EQUATION 3.3.13
TOTAL ANNUAL EMISSIONS OF N2O FROM MINERAL SOILS IN LAND CONVERTED TO CROPLAND
Total N2O-Nconv = ∑i N2O-Nconv,iWhere:
Total N2O-Nconv = total annual emissions of N2O from mineral soils in land converted to cropland, kg
N2O-N yr-1
N2O-Nconv,i = N2O emissions from land conversion type i, kg N2O-N yr-1
Emissions from fertilisation: N2O emissions from nitrogen application in the preceding land use (managed forest
or grassland) and new land use (cropland) are calculated elsewhere in the inventory (GPG 2000) and should not
be reported here, to avoid double counting.

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EQUATION 3.3.14
N2O EMISSIONS AS A RESULT OF THE DISTURBANCE ASSOCIATED WITH LAND-USE CONVERSIONOF FOREST LAND, GRASSLAND, OR OTHER LAND TO CROPLAND
N2O-Nconv = N2Onet-min-N
N2Onet-min-N = EF1 ● Nnet-min
Where:
N2O-Nconv = N2O emissions as a result of the disturbance associated with land-use conversion of forest
land, grassland, or other land to cropland, kg N2O-N yr-1
N2Onet-min-N = additional emissions arising from the land-use change, kg N2O-N yr-1
Nnet-min = N released annually by net soil organic matter mineralisation as a result of the disturbance, kg N yr-1
EF1 = IPCC default emission factor used to calculate emissions from agricultural land caused by added N,
whether in the form of mineral fertilisers, manures, or crop residues, kg N2O-N/kg N. (The default
value is 0.0125 kg N2O-N/kg N)
Note: Multiply N2O-Nconv by 44/28 and10-6 to obtain N2O emissions in Gg N2O yr-1
The N released by net mineralisation, Nnet-min, can be calculated following the calculation of the soil C
mineralised over the same period (20 years). The default method assumes a constant C:N ratio in the soil organic
matter over the period, thus:
EQUATION 3.3.15
ANNUAL NITROGEN RELEASED BY NET SOIL ORGANIC MINERALISATION AS A RESULT OF THE
DISTURBANCE (BASED ON SOIL C MINERALISED)
Nnet-min = ∆CLCMineral ● 1 / C:N ratio
Where:
Nnet-min = annual N released by net soil organic matter mineralisation as a result of the disturbance, kg N yr-1
∆CLCMineral = values obtained from Equation 3.3.12 (see also Section 3.3.2.2.1.1)), where applied to anarea of land converted to cropland (see Section 3.3.2.2.1.), kg C yr-1
C:N ratio = the ratio by mass of C to N in the soil organic matter (SOM), kg C (kg N)-1
Tier 1: Use default values and minimal spatial disaggregation with Equations 3.3.13 and 3.3.14
Tier 2: Actual measurements of locally specific C:N ratios in SOM will improve the calculations of N2Oemissions after conversion.
Tier 3: Tier 3 comprises a more dynamic way of simulating emissions using process models, based on locallyspecific data, possibly spatially explicit, taking into account local characteristics of the land use conversion tocropland.

3.3.2.3.1.2 Choice of Emission Factor
The following factors are needed:•

EF1: The emission factor for calculating emissions of N2O from N in the soil. The global default value is0.0125 kg N2O-N/kg N, based on the general default emission factor used for N2O emissions in Chapter 4(Agriculture) of the IPCC Guidelines.

•

C released is calculated using Equation 3.3.3.

•

C:N ratio: The ratio of C to N in soil organic matter is by default 15. This reflects the somewhat greater
C:N ratio found in forest or grassland soils compared to most cropland soils where C:N ratios typicallyaround 8-12.

The box below highlights ways in which further refinement of emissions estimates may be made, by analogy
with the equivalent text in GPG2000.

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BOX 3.3.1
GOOD PRACTICE IN DERIVATION OF COUNTRY-SPECIFIC EMISSION FACTORSIn situations where higher-tier methods may be possible, the following points apply:
Good practice requires the measurement of N2O emissions by individual sub-source category (e.g.
synthetic fertiliser (FSN), animal manure (FAM), crop residue mineralisation (FCR) and (in thepresent context of land-use conversion to cropland), mineralisation of soil organic N (FOM-min).
For N2O emission factors to be representative of environmental and management conditions within
the country, measurements should be made in the major crop growing regions within a country, inall seasons, and if relevant, in different geographic and soil regions and under different
management regimes. Soil factors such as texture and drainage condition, temperature andmoisture will affect EFs (Firestone and Davidson, 1989; Dobbie et al., 1999).
Validated, calibrated, and well-documented simulation models may be a useful tool to develop
area-average N2O emission factors on the basis of measurement data.
Regarding measurement period and frequency, N2O emission measurements should be taken overan entire year (including fallow periods), and preferably over a series of years, in order to reflect
differences in weather conditions and inter-annual climatic variability. Measurements should befrequent during the initial period after land conversion.

3.3.2.3.1.3 Choice of Activity Data
Aconv: The area of land being converted is required. For Tier 1 the Aconv is a single value, but for Tier 2 it isdisaggregated by the types of conversions.

3.3.3

CompletenessA complete data series for land area estimates contains, at a minimum, the area of land within country
boundaries that is considered cropland during the time period covered by land use surveys or other data sources
and for which greenhouse gas emission and removals are estimated in the LULUCF sector. The total area
covered by the cropland inventory methodology is the sum of land remaining in cropland and land converted tocropland during the time period. This inventory methodology may not include some cropland areas where
greenhouse gas emissions and removals are believed to be insignificant or constant through time, such as nonwoody cropland where there are no management or land-use changes. Therefore, it is possible for the total
cropland area for which estimates are prepared to be less than the total area of cropland within country
boundaries. In this case, it is good practice for countries to document and explain the difference in cropland areain the inventory and total cropland within their boundaries. Countries are encouraged to track through time thetotal area of land in cropland within country boundaries, keeping transparent records on which portions are used
to estimate carbon dioxide emissions and removals. As addressed in Chapter 2, all cropland areas, including
those not covered by the emissions inventory, should be part of the consistency checks to help avoid double
counting or omission. When summed with area estimates for other land uses, the cropland area data series will
enable a complete assessment of the land base included in a countries’ LULUCF sector inventory report.
Countries that use Tier 2 or 3 methods for cropland biomass and soil pools should include more detail in theirinventory on the cropland area data series. For example, countries may need to stratify the cropland area bymajor climate and soil types, including both the inventoried and non-inventoried cropland areas. When stratified
land areas are used in the inventory, it is good practice for countries to use the same area classifications for boththe biomass and soils pools. This will ensure consistency and transparency, allow for efficient use of land
surveys and other data collection tools, and enable the explicit linking between carbon dioxide emissions andremovals in biomass and soil pools.

3.3.4

Developing a Consistent Time Series

To maintain a consistent time series, it is good practice for countries to maintain records on the cropland areasused in inventory reports over time. These records should track the total cropland area included in the inventory,
subdivided by land remaining in cropland and land converted to cropland. Countries are encouraged to include
an estimate of the total cropland area within country boundaries. To ensure that area estimates are treatedconsistently through time, land use definitions should be clearly defined and kept constant. If changes are madeto land use definitions, it is good practice to keep transparent records of how the definition changed. Consistent

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definitions should also be used for each of the cropland types and management systems included in the inventory.
In addition, to facilitate the proper accounting of carbon emissions and removals over several periods,
information on historic land conversions can be utilized. Even if a country cannot rely on historic data for current
inventories, improvements to current inventory practices to provide the ability to track land conversions acrosstime will have benefits in future inventories.

3.3.5

Reporting and Documentation

The categories described in Section 3.3 can be reported using the reporting tables in Annex 3A.2. The estimates
under the cropland category can be compared with the reporting categories in the IPCC Guidelines as follows:•

Carbon dioxide emissions and removals in biomass in cropland remaining cropland to IPCC Reporting
Category 5A, Changes in woody biomass;•

Carbon dioxide emissions and removals in soils in cropland remaining cropland to IPCC Reporting
Category 5D, Changes in soil carbon; and•Carbon dioxide emissions and removals resulting from land-use conversions to cropland to IPCC
Reporting Category 5B for biomass, IPCC Reporting category 5D for soils, and IPCC Reporting Category
5E for non-CO2 gases.

It is good practice to maintain and archive all information used to produce national inventory estimates.
Metadata and data sources for information used to estimate country-specific factors should be documented andboth mean and variance estimates provided. Actual databases and procedures used to process the data (e.g.
statistical programs) to estimate country-specific factors should be archived. Activity data and definitions used tocategorise or aggregate the activity data must be documented and archived. Procedures used to categorise
activity data by climate and soil types (for Tier 1 and Tier 2) must be clearly documented. For Tier 3 approaches
that use modelling, model version and identification must be documented. Use of dynamic models requires that
copies of all model input files as well as copies of model source code and executable programs be permanently
archived.

3.3.6

Inventory Quality Assurance/Quality Control(QA/QC)

It is good practice to implement quality control checks and external expert review of inventory estimates anddata. Specific attention should be paid to country-specific estimates of stock change and emission factors toensure that they are based on high quality data and verifiable expert opinion.
Specific QA/QC checks across the cropland methodology include:
Cropland remaining cropland: Cropland soil estimates may be based on area data that includes both perennial
woody crops and annual crops, while biomass estimates are based on area data for perennial woody crops only.
Therefore, the area estimates underlying biomass and soils estimates in cropland remaining cropland may differ,with biomass estimates based on a smaller land area than soil estimates. This will be true in most cases, except incountries where cropland is comprised entirely of perennial woody crops or management and land use isconstant on annual crops.
Lands converted to cropland: Aggregate area totals for land converted to cropland should be the same in thebiomass and soils estimations. While biomass and soil pools may be disaggregated to different levels of detail,the same general categories should be used to disaggregate the area data.
For all soil carbon stock change estimates using Tier 1 or Tier 2 methods, total areas for each climate-soil typecombination must be the same for the start (year(0-T)) and the end (year(0)) of the inventory period (see Equation
3.3.4).

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3.3.7

Estimation of Revised GPG Tier 1 Defaults for
Mineral Soil C Emissions/Removals for Cropland(see Table 3.3.4)

Cropland management factors were computed for tillage, input, set-aside, and land use conversion fromgrassland or forest land. The land use conversion factor represents the loss of carbon that occurs after 20 years ofcontinuous cultivation. Tillage factors represent the impact of changing management from a conventional tillage
system, in which the soil is completely inverted, to conservation practices, including no-till and reduced till. Notillage is direct seeding without tillage of the soil. Reduced tillage involves some tillage, but does not involve full
inversion of the soil and typically leaves more than 60% of the soil surface covered by residue, including
practices such as chisel, mulch, and ridge tillage. The input factors represent the effect changing carbon input tothe soil by planting more productive crops, cropping intensification, or applying amendments; input factors
include cropping systems categorised as low, medium, high, and high w/manure amendments. Low input factors
represent low residue crops, rotations with bare-fallow, or cropping systems in which the residue is burned or
removed from the field. Medium input cropping systems represent cereals in which the residue is returned to thefield or rotations receiving organic amendments that otherwise would be considered low input due to residue
removal. High input rotations have high residue-yielding crops, cover crops, improved vegetated fallow, or years
with grass cover, such as hay or pasture in the rotation. Tillage and input factors represent the effect on C stocks
after 20 years since the management change. Set-aside factors represent the effect of temporary removal ofcropland from production and placing it into grass vegetation for a period of time that may extend to 20 years.
The data were synthesized in linear mixed-effects models, accounting for both fixed and random effects. Fixed
effects included depth, number of years since the management change, and the type of management change (e.g.,
reduced tillage vs. no-till). For depth, data were not aggregated but included C stocks measured for each depth
increment (e.g., 0-5 cm, 5-10 cm, and 10-30 cm) as a separate point in the dataset. Similarly, time series data
were not aggregated, even though those measurements were conducted on the same plots. Consequently, random
effects were used to account for the interdependence in times series data and the interdependence among data
points representing different depths from the same study. Data were transformed with a natural log
transformation if model assumptions were not met for normality and homogeneity of variance (back-transformed
values are given in the tables). Factors represent the effect of the management practice at 20 years for the top 30
cm of the soil, with the exception of the land use conversion factor, which represents the average loss of carbon
at 20 years or longer time period following cultivation. Users of this carbon accounting method can approximate
the annual change in carbon storage by the dividing the inventory estimate by 20. Variance was calculated foreach of the factor values, and can be used to construct probability distribution functions with a normal density.

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REFERENCES USED FOR THE ANALYSIS IN SECTION 3.3.7
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Angers, D.A., M.A. Bolinder, M.R. Carter, E.G. Gregorich, C.F. Drury, B.C. Liang, R.P. Voroney, R.R. Simard,
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Angers, D.A., R.P. Voroney, and D. Cote. (1995). Dynamics of soil organic matter and corn residues affected bytillage practices. Soil Science Society of America Journal 59:1311-1315.
Baer, S.G., C.W. Rice, and J.M. Blair. (2000). Assessment of soil quality in fields with short and long term
enrollment in the CRP. Journal of Soil and Water Convservation 55:142-146.
Balesdent, J., A. Mariotti, and D. Boisgontier. (1990). Effect of tillage on soil organic carbon mineralization
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Barber, R.G., M. Orellana, F. Navarro, O. Diaz, and M.A. Soruco. (1996). Effects of conservation and conventionaltillage systems after land clearing on soil properties and crop yield in Santa Cruz, Bolivia. Soil and Tillage
Research 38:133-152.
Bauer, A., and A.L. Black. (1981). Soil carbon, nitrogen, and bulk density comparisons in two cropland tillage
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Bayer, C., J. Mielniczuk, T.J.C. Amado, L. Martin-Neto, and S.V. Fernandes. (2000). Organic matter storage in asandy clay loam Acrisol affected by tillage and cropping systems in southern Brazil. Soil and Tillage Research
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Bayer, C., J. Mielniczuk, L. Martin-Neto, and P.R. Ernani. (2002). Stocks and humification degree of organic matter
fractions as affected by no-tillage on a subtropical soil. Plant and Soil 238:133-140.
Beare MH, Hendrix PF, Coleman DC. (1994). Water-stable aggregates and organic matter fractions in conventionaland no-tillage soils. Soil Science Society of America Journal 58: 777-786.
Beyer, L. (1994). Effect of cultivation on physico-chemical, humus-chemical and biotic properties and fertility of
two forest soils. Agriculture, Ecosystems and Environment 48:179-188.
Black, A.L., and D.L. Tanaka. (1997). A conservation tillage-cropping systems study in the Northern Great Plains of
the United States. Pages 335-342 in Paul, E.A., K. Paustian, E.T. Elliott, and C.V. Cole, editors. Soil Organic
Matter in Temperate Agroecosystems: Long-term Experiments in North America. CRC Press. Boca Raton, FL.
Bordovsky, D.G., M. Choudhary, and C.J. Gerard. (1999). Effect of tillage, cropping, and residue management on
soil properties in the Texas rolling plains. Soil Science 164:331-340.
Borin, M., C. Menini, and L. Sartori. (1997). Effects of tillage systems on energy and carbon balance in northeastern Italy. Soil and Tillage Research 40:209-226.
Borresen, T., and A. Njos. (1993). Ploughing and rotary cultivation for cereal production in a long-term experimenton a clay soil in southeastern Norway. 1. Soil properties. Soil and Tillage Research 28:97-108.
Bowman, R.A., and R.L. Anderson. (2002). Conservation Reserve Program: Effects on soil organic carbon andpreservation when converting back to cropland in northeastern Colorado. Journal of Soil and Water
Conservation 57:121-126.
Bremer, E., H.H. Janzen, and A.M. Johnston. (1994). Sensitivity of total, light fraction and mineralizable organic
matter to management practices in a Lethbridge soil. Canadian Journal of Soil Science 74:131-138.
Burke, I.C., W.K. Lauenroth, and D.P. Coffin. (1995). Soil organic matter recovery in semiarid grasslands:
implications for the Conservation Reserve Program. Ecological Applications 5:793-801.
Buschiazzo, D.E., J.L. Panigatti, and P.W. Unger. (1998). Tillage effects on soil properties and crop production in
the subhumid and semiarid Argentinean Pampas. Soil and Tillage Research 49:105-116.
Buyanovsky, G.A., C.L. Kucera, and G.H. Wagner. (1987). Comparative analysis of carbon dynamics in native andcultivated ecosystems. Ecology 68:2023-2031.
Buyanovsky, G.A., and G.H. Wagner. (1998). Carbon cycling in cultivated land and its global significance. Global
Change Biology 4:131-141
Cambardella, C.A., and E.T. Elliott. (1992). Particulate soil organic-matter changes across a grassland cultivation
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REFERENCES USED FOR THE ANALYSIS IN SECTION 3.3.7 (CONTINUED)
Campbell CA, Zentner RP. (1997). Crop production and soil organic matter in long-term crop rotations in the semiarid northern Great Plains of Canada. Pages 317-334 in: E.A. Paul, E.T. Elliott, K. Paustian, and C.V. Cole.
Soil organic matter in temperate agroecosystems: Long-term experiments in North America. CRC Press, Boca
Raton, FL.
Campbell, C.A., V.O. Biederbeck, G. Wen, R.P. Zentner, J. Schoenau, and D. Hahn. (1999). Seasonal trends inselected soil biochemical attributes: Effects of crop rotation in the semiarid prairie. Canadian Journal of Soil
Science 79:73-84.
Campbell CA, Bowren KE, Schnitzer M, Zentner RP, Townley-Smith L (1991) Effect of crop rotations andfertilization on soil organic matter and some biochemical properties of a thick black Chernozem. Canadian
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