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CHAPTER 5

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INLAND WETLAND MINERAL SOILS

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Coordinating Lead Authors

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Kimberly P. Wickland (USA) and Alex V. Krusche (Brazil)

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Lead Authors

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Randall K. Kolka (USA), Ayaka W. Kishimoto-Mo (Japan), Rodney A. Chimner (USA) and8

Yusuf Serengil (Turkey)

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Contributing Authors

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Stephen Ogle (USA) and Nalin Srivastava (TFI TSU)

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Review Editors

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Irineu Junior Bianchini (Brazil) and Michelle Garneau (Canada)

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Contents

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5.1

Introduction ..............................................................................................................................................5

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5.2

Land remaining in a land-use category ....................................................................................................8

5.2.1

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CO2 emissions and removals .......................................................................................................919

5.2.1.1

Biomass and dead organic matter ................................................................................................920

5.2.1.2

Soil carbon .................................................................................................................................10

5.2.2

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CH4 emissions from managed lands with IWMS ......................................................................16

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5.2.2.1

Choice of method.......................................................................................................................16

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5.2.2.2

Choice of emission factors.........................................................................................................1724

5.2.2.3

Choice of activity data ...............................................................................................................1825

5.2.2.4

Uncertainty assessment..............................................................................................................18

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5.3

Land converted to a new land-use category ...........................................................................................18

5.3.1

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CO2 emissions and removals .....................................................................................................1928

5.3.1.1

Biomass and dead organic matter ..............................................................................................1929

5.3.1.2

Soil carbon .................................................................................................................................19

5.3.2

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CH4 emissions ...........................................................................................................................2031

5.3.2.1

Choice of method and emission factors .....................................................................................2032

5.3.2.2

Choice of activity data ...............................................................................................................2033

5.3.2.3

Uncertainty assessment..............................................................................................................20

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5.4
5.4.1

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Completeness, reporting and documentation..........................................................................................21
Completeness .............................................................................................................................21

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Annex 5A.1 Estimation of default stock change factors for long-term cultivated Cropland andrewetting with Inland Wetland Mineral Soil carbon emissions/removals ..............................................22

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Annex 5A.2 Estimation of CH4 emission factors for managed lands with Inland Wetland Mineral
Soils, or dry mineral soils, where the water table has been raised .........................................................2340

Appendix 5a.1

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Future methodological development .........................................................................27

References ......................................................................................................................................................... 28

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Equations45

Equation 5.1 Annual CH4 emissions from rewetted and created wetlands on managed lands with IWMS ...........1746

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Tables48

Table 5.1 Updated and new guidance provided in Chapter 5 ...................................................................................6

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Table 5.2 Default reference soil organic carbon stocks (SOCREF) for Wetland Mineral Soilsa under native
vegetation (0-30 cm depth). ...................................................................................................................................12

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Table 5.3 Relative stock change factors for land-use (FLU) for long term cultivation on Cropland with IWMS
over 20 years) and rewetting of cropland with IWMS (over 20 years and 40 years) ............................................13

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Table 5.4 Default emission factors for CH4 from managed lands with IWMS where water table level has beenraised ......................................................................................................................................................................18

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Table 5A.1.1 Studies used for the derivation of default SOC stock change factors ..............................................22

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Table 5A.2 .1 CH4 emissions from restored and created wetlands with IWMS where water table level has beenraised, and natural wetlands, used to derive default value for EFCH4 ....................................................................23

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Table 5A.2.2 CH4 emissions from temperate, created/rewetted wetlands and natural wetlands with IWMS ........26

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Table 5A.2.3 CH4 emissions from temperate, rewetted, created and natural wetlands with IWMS, stratified byperiod of inundation ...............................................................................................................................................26

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Boxes

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Box 5.1 Distribution of Wetland Mineral Soils........................................................................................................7

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Box 5.2 Management activities on Inland Wetland Mineral Soils ...........................................................................8

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5.1

INTRODUCTION

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This chapter provides supplementary guidance for estimating and reporting greenhouse gas (GHG) emissions
and removals from managed lands with Inland Wetland Mineral Soils (IWMS) for all land-use categories (seeChapter 1 and decision tree in Chapter 1 in this supplement for what is specifically covered in this chapter in
relationship to other chapters in this supplement). Wetland mineral soil (WMS) information for Tier 1 default
methods is found in Table 2.3, Chapter 2, Volume 4 of the 2006 IPCC Guidelines for National Greenhouse Gas
Inventories (2006 IPCC Guidelines). This chapter covers “inland” managed lands with WMS; coastal lands with
WMS are addressed in Chapter 4 (Coastal Wetlands) of this supplement. The distinction between “inland” and“coastal” zones is defined in Chapter 4. Constructed wetlands with IWMS are addressed in Chapter 6(Constructed Wetlands for Wastewater Treatment) of this Supplement.

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Mineral soils are described as all soils that are not classified as organic soils in Annex 3A.5, Chapter 3, Volume
4 of the 2006 IPCC Guidelines. The 2006 IPCC Guidelines provide a default mineral soil classification for
categorizing mineral soil types based on the USDA taxonomy (Soil Survey Staff, 1999) in Figure 3A.5.3, andbased on the World Reference Base for Soil Resources Classification (FAO, 1998) in Figure 3A.5.4, where bothclassifications produce the same default IPCC soil types for Tier 1 methods. Under these soil classification
schemes, Wetland Soils (e.g. Wetland Mineral Soils) are classified as Aquic soil (USDA) or Gleysols (World
Reference Base), and are described as having restricted drainage leading to periodic flooding and anaerobic
conditions (Table 2.3, Chapter 2, Volume 4, 2006 IPCC Guidelines). They can occur in any of the six land-use
categories (Forest Land, Grassland, Cropland, Wetlands, Settlements and Other Land) depending upon thenational land-use classification system. Emissions and removals from areas of managed land with IWMS should
be reported in the land-use category under which they are classified, according to Volume 4 of the 2006 IPCC
Guidelines. Note that a change in management practice may, or may not, be accompanied by land-use conversion.
For higher tier methods, countries may use country-specific national classification systems as long as they aretransparently documented.

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For the purposes of this supplement, IWMS comprise those that have formed under restricted drainage, and may
or may not be artificially drained due to management activities. Guidance provided in this chapter applies to: (i)artificial drainage, defined here as the removal of free water from soils having aquic conditions to the extent thatwater table levels are changed significantly in connection with specific types of land-use (adapted from Soil
Survey Staff, 1999); (ii) to IWMS that have been artificially drained and subsequently allowed to re-wet(hereafter called “rewetting”); and (iii) the artificial inundation of mineral soils for the purposes of “wetland
creation.” There is no guidance provided for other IWMS such as saline IWMS (See Section 5.1.1 of thischapter) or reservoirs. Guidance on CH4 emissions from rice cultivation on IWMS is given in Chapter 5,
Volume 4 of the 2006 IPCC Guidelines. Guidance on carbon stock changes in Land Converted to Flooded Land1
with IWMS is given in Chapter 7, Volume 4 of the 2006 IPCC Guidelines2. This supplement does not update thisguidance.

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This chapter supplements guidance and methodologies in the 2006 IPCC Guidelines for emissions and removalsof carbon dioxide (CO2), and emissions of methane (CH4), and provides additional information to be used inapplying the methodologies. The review of the current literature suggests there is insufficient data to provide
robust emission factors and methodology to update the guidance on N2O emissions from IWMS provided in
Chapter 11, Volume 4 of the 2006 IPCC Guidelines at this time (see Appendix 5A of this chapter for additional
discussion). This chapter should be read in conjunction with Volume 4 of the 2006 IPCC Guidelines.

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This chapter updates the 2006 IPCC Guidelines for:

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Default reference soil organic carbon stocks (SOCREF) for IWMS under all climate regions (referring toTable 2.3, Chapter 2, Volume 4 of the 2006 IPCC Guidelines ,), to be used for Tier 1 methods in all six landuse categories.

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Default Soil Organic Carbon (SOC) stock change factor (FLU) for long-term cultivation of Cropland with
IWMS.

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This chapter gives new guidance not contained in the 2006 IPCC Guidelines, by:

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

Providing new default SOC stock change factors for land-use (FLU) for rewetting of drained IWMS classified
as Cropland.

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In the 2006 IPCC Guidelines, “Flooded Lands are defined as water bodies where human activities have caused changes in
the amount of surface area covered by water, typically through water level regulation.”

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Appendices 2 and 3 of Volume 4 of the 2006 IPCC Guidelines contain information on CO2 emissions from Land Converted
to Permanently Flooded Land and CH4 emissions from Flooded Land as a basis for future methodological development.

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Table 5.1 clarifies the scope and corresponding sections of this chapter, as well as guidance for IWMS provided
in the 2006 IPCC Guidelines and in other chapters of this supplement.

Providing methodologies and emission factors (EFs) for CH4 emissions from managed lands with drained
IWMS under any land-use category that has undergone rewetting, and from inland mineral soils that havebeen inundated for the purpose of wetland creation (Note: CH4 emissions from wetlands created for the
purpose of wastewater treatment are addressed in Chapter 6 of this supplement).

TABLE 5.1
UPDATED AND NEW GUIDANCE PROVIDED IN CHAPTER 5
IPCC Land-use
category

Soil Organic CarbonA,B (SOC)

CH4 emissionsC,DLand Remaining in a Land-use Category
Forest Land

Updated SOCREF for IWMS

CroplandUpdated SOCREF for IWMS; SOC stock change
factors for land-use (FLU) for long-term
cultivation, and rewetting of drained IWMS

Grassland

Updated SOCREF for IWMS

Wetlands

Updated SOCREF for IWMSb

Settlements

Updated SOCREF for IWMS

EFCH4-IWMS for rewetting ofdrained IWMS, and createdwetlands on managed lands withmineral soils

Land Conversion to a New Land-use Category
All land-use
conversions

Updated SOCREF for IWMS;
SOC stock change factors for land-use (FLU) for
long-term cultivation, and wetland rewetting

EFCH4-IWMS for rewetting ofdrained IWMS, and createdwetlands on managed lands withmineral soils

A The overall guidance as provided in Chapters 2 and 4-9 in the 2006 IPCC Guidelines will continue to apply along with elements mentioned in this table.
B Guidance on SOC will apply to all wetlands with IWMS except Flooded Land.
C Existing guidance on CH emissions from rice cultivation given in Chapter 5, Volume 4 of the 2006 IPCC Guidelines will continue to apply.
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D Guidance on CH emissions from managed lands with IWMS does not apply to Flooded Land.
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BOX 5.1
DISTRIBUTION OF WETLAND MINERAL SOILS

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Wetland mineral soils (WMS), including both coastal and inland WMS, are estimated to cover~5.3% of the world’s land surface, or 7.26 x 106 km2 (Batjes, 2010a). The distribution of theworld’s WMS across climate regions are as follows: Boreal (moist plus dry): 2.07%, Tropicalmoist: 0.67%, cool temperate moist: 0.63%, tropical wet: 0.61%, polar (moist plus dry): 0.60%,
warm temperate moist: 0.23% (Batjes, 2010a). Climate regions having less than 0.20% WMS
include cool and warm temperate dry, tropical dry, and tropical montane (See Figures 3A.5.1 and
3A.5.2, Chapter 3, Volume 4 of the 2006 IPCC Guidelines for climate zone definitions). Figure
5.1 shows the global distribution of gleysols (WMS) based on the World Reference Base for Soil
Resources (WRB) and the FAO/UNESCO soil map of the world. IWMS are found in a variety oflandscape settings, including basins, channels, flats, slopes, and highlands (Semeniuk and
Semeniuk, 1995). It is common to find IWMS adjacent to flowing waters and lake and pond
margins (riparian wetlands). Lands containing IWMS are often classified by predominant
vegetation community, and can include trees, woody shrubs, emergent and non-emergent vascularplants, and/or bare ground.

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Distribution of Gleysols (Wetland Mineral Soils; source: http://www.isric.org).

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A specific type of land containing IWMS, Saline IWMS, is not covered in this chapter. Saline
IWMS are generally defined as having salinity >5000 mg L-1 when wet (Shaw and Bryant, 2011).
Also known as playas, pans, salt lakes, brackish wetlands, salinas, and sabkhas, these lands areimportant parts of arid landscapes across the globe (Shaw and Bryant, 2011). In a recent review ofthe literature characterizing known information on pans, playas and salt lakes, carbon stocks andCO2, CH4 and N2O fluxes were not discussed (Shaw and Bryant, 2011). A review of the broader
literature on lands containing saline IWMS indicates that only two studies have assessed soil
carbon in saline IWMS (Bai et al., 2007; Rodriguez-Murillo et al., 2011), and no studies havemeasured GHG emissions and removals from saline IWMS. At present the lack of data on saline
IWMS prevents the determination of default carbon stock changes or GHG emission factors.
Countries are encouraged to seek country specific data to estimate changes in carbon pools in, andemissions and removals from, managed saline IWMS.

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BOX 5.2
MANAGEMENT ACTIVITIES ON INLAND WETLAND MINERAL SOILS

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Drainage of IWMS is a common practice in the preparation of land for agriculture, grazing, andforestry. Drainage leads to lower water levels, which increases decomposition and vegetation
productivity, but the balance generally favors decomposition leading to reduced IWMS carbon
stocks over time (Bedard-Haughn et al., 2006; Huang et al., 2010; Page and Dalal, 2011).
Hydrology of IWMS may be altered due to dredging of canals for navigation and ditches throughwetlands for flood control and to increase vegetation productivity, (Mitsch and Gosselink, 2007);
management of river-floodplain systems through levee construction, channelization, and flow
manipulation by dams (Dynesius and Nilsson, 1994); irrigation systems that lower water tables;
and water level control for wildlife management by dikes, weirs, control gates, and pumps (Mitschand Gosselink, 2007). Dams for hydroelectric generation and flood control influence newly createdriparian wetlands upstream and riparian wetlands by altering the frequency and duration of flood
pulses, which has impacts on sediment deposition and nutrient loading to wetlands (Brinson andMalvárez, 2002; Noe and Hupp, 2005, Nilsson and Berggren, 2000).

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An important agricultural use of lands with IWMS is rice cultivation, which is covered in the 2006
IPCC Guidelines (Chapter 5, Volume 4: Cropland), and is not addressed in this Supplement. Other
agricultural uses of lands with IWMS include lotus and mat rush cultivation, particularly in Asia
(Seo et al., 2010; Maruyama et al., 2004). Currently there is little available information on carbon
stock changes or GHG emissions for this type of cultivation. Grazing on lands with IWMS within
grassland or forest landscapes is widespread (Liu et al., 2009; Oates et al., 2008; Yao et al., 2012).
Forest management activities on Wetlands with forest can vary in management intensity dependingon the silvicultural system. The intensity may range from selective cutting treatments to large area
clearcuts. There is currently not enough available information about the impacts of grazing orforest management activities on carbon stock changes or GHG emissions on lands with IWMS toprovide new guidance.

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A specific management activity that occurs on managed lands with IWMS is “rewetting”, wherelands with IWMS that were drained are rewetted by raising the water table level to pre-drainage
conditions. Active approaches to rewetting include removal of drain tiles, filling or blocking ofdrainage ditches, breaching levees, removal of river dams and spillways, and contouring the land
surface to mimic natural topography; passive approaches include the elimination of water control
structures and allowing natural flood events (Aber et al., 2012). The rewetting of managed lands
with IWMS is common in the conversion of agricultural lands back to wetlands, and may occur
when active regulation of river hydrology is discontinued. A related management activity that
occurs on mineral soils (wet or dry) is wetland creation, where lands are artificially inundated forthe purposes of supporting a wetland ecosystem (Aber et al., 2012). Wetlands are created for
purposes such as water-quality enhancement (treatment of wastewater, stormwater, acid minedrainage, agricultural runoff; Hammer, 1989), flood minimization, and habitat replacement (Mitsch
et al., 1998). Wetlands may be created unintentionally when regulation of river flows (i.e. large
dam installation) results in periodic inundation of lands that did not experience inundation prior to
regulation (Chen et al., 2009; Yang et al., 2012). Wetland creation and rewetting of drained soils
are common activities in response to significant wetland loss and degradation on a global scale(Mitsch et al., 1998). There is great potential for increased carbon storage from rewetting wetlands(Euliss et al., 2006; Bridgham et al., 2006). Rewetted wetlands may also have higher emissions ofCH4, potentially offsetting increased carbon storage (Bridgham et al., 2006), although recent
studies have shown that created and rewetted wetlands can be net carbon sinks, after accounting
for CH4 emissions (Badiou et al., 2011; Mitsch et al., 2012).

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5.2

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LAND REMAINING IN A LAND-USE
CATEGORY

The 2006 IPCC Guidelines define land remaining in a land-use category as lands that have not undergone any
land-use conversion for a period of at least 20 years as a default period. The 2006 IPCC Guidelines provide
generic and land-use category specific guidance (Chapters 2 and Chapter 4-9, Volume 4) on stock changes in the
carbon pools (above-ground and below-ground biomass; dead wood and litter; and soil carbon), and non-CO2
emissions for land remaining in a land-use category for all land-use categories including those containing
mineral soils. This Chapter updates the 2006 IPCC Guidelines for guidance on SOC stock change factors andnon-CO2 emissions from managed lands with IWMS.

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5.2.1

CO 2 emissions and removals

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As explained in Chapter 2, Volume 4 of the 2006 IPCC Guidelines, CO2 emissions and removals from managed
lands are estimated on the basis of changes in the carbon stocks in the carbon pools: biomass (above and belowground biomass), dead organic matter (dead wood and litter) and soil organic carbon. The set of generalequations to estimate the annual carbon stock changes of carbon pools for land remaining in a land-use category
are given in Chapter 2, Volume 4 of the 2006 IPCC Guidelines, and also apply to managed lands with IWMS.

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Figure 1.2 in Chapter 1, Volume 4 of the 2006 IPCC Guidelines shows a decision tree for the identification of
appropriate methodological tiers for land remaining in a land-use category.

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5.2.1.1

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Guidance for changes in the carbon pools in biomass (above-ground, below-ground) and dead organic matter(dead wood, litter) is provided in the 2006 IPCC Guidelines, and remains unchanged for land remaining in aland-use category for managed lands with IWMS in this supplement. For managed lands with IWMS classified
as land remaining in a land-use category in Forest Land, Cropland, Grassland, Settlements, or Other Land,changes in biomass and dead organic matter are to be determined using the guidance provided in thecorresponding chapters (Chapters 4-9) in Volume 4 of the 2006 IPCC Guidelines. For lower Tier methods it may
be assumed that wetland vegetation does not have substantially different biomass carbon densities than uplandvegetation (e.g., Bridgham et al., 2006). However, if country specific data is available, it is good practice to usethat data to estimate biomass carbon densities.

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CHOICE OF METHOD AND EMISSION/REMOVAL FACTORS

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As explained in the 2006 IPCC Guidelines, inventories can be developed using Tiers 1, 2 and 3 methods. The
decision trees have been provided in the 2006 IPCC Guidelines to guide the selection of appropriate
methodological tier for the estimation of changes in carbon stocks of biomass and dead organic matter (Fig. 2.2
and Fig. 2.3, Chapter 2, Volume 4). In general it is good practice to use higher tier methods (Tiers 2 and 3) for
significant pools and subcategories within a key category i.e., those accounting for 25-30% ofemissions/removals for the overall key category (see Chapter 4, Volume 1 of the 2006 IPCC Guidelines).
Guidance on the choice of emission/removal factors for change in biomass and dead organic matter for the six
land-use categories are found in the sections on biomass and dead organic matter for land remaining in a landuse category in the appropriate Chapter(s) in Volume 4 of the 2006 IPCC Guidelines: Forest Land (Chapter 4),
Cropland (Chapter 5), Grassland (Chapter 6), Settlements (Chapter 8), and Other Land (Chapter 9). The Tier 1
methods will use the default emission factors, and parameters relating to biomass and dead organic matterprovided for specific land-use categories. These will also apply to managed lands with IWMS in any of theseland-use categories. Tier 2 methods will involve using country-specific emission factors and parameters alongwith activity data at suitable stratification, while Tier 3 methods involve detailed modeling or measurementbased frameworks using highly disaggregated data. There is no robust scientific information to support thedevelopment of emission factors for biomass and dead organic matter for specific management activities such as
drainage of lands with IWMS, rewetting of drained IWMS, or wetland creation. If there are reliable data for ratesof biomass and/or dead organic matter change upon drainage or rewetting/wetland creation, country-specificestimates may be derived using a Tier 2 method.

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CHOICE OF ACTIVITY DATA

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For Tier 1 methods, activity data consist of areas of managed lands with IWMS in land remaining in a land-use
category stratified by land-use category, climate region, soil type, and management practices. Total areas should
be determined according to approaches outlined in Chapter 3 of the 2006 IPCC Guidelines, and should beconsistent with those reported under other sections of the inventory. Stratification of land-use categories
according to climate region, based on default or country-specific classifications can be accomplished withoverlays of land-use on climate and soil maps. A global GIS database that shows the spatial distribution ofgeneralized soil classes used for IPCC Tier 1 is available for download and use at http://isirc.org/data/ipccdefault-soil-classes-derived-harmonized-world-soil-data-base-ver-11. The database is derived from theHarmonized World Soil Data Base and FAO soil classifications, and includes the seven default IPCC soils
classes including Wetland Soils (termed “Wetland Soils” in the 2006 IPCC Guidelines, and “Wetland Mineral
Soils” in this Supplement) (Batjes, 2010b). This dataset may be used at national and broader scales where moredetailed soil information is lacking. Although no organization catalogues changes in area as a result of rewetting
or wetland creation either nationally or globally, local activity data for wetlands with rewetted IWMS may beobtained from agricultural, forestry, or natural resources agencies, non-governmental conservation organizations,or other government sources. In addition, organizations such as the Society for Ecological Restoration
International (http://www.ser.org), Global Restoration Network (http://www.globalrestorationnetwork.org),

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Wetlands International (http://www.wetlands.org), and the Ramsar Convention on Wetlands(http://www.ramsar.org) may be sources of information for rewetting and/or wetland creation projects.

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Higher Tier methods may use activity data suitably stratified by criteria such as vegetation type and/or watertable level and hydroperiod (e.g., continuously inundated vs. intermittently inundated).

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UNCERTAINTY ASSESSMENT

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Sources of uncertainty for changes in biomass and dead organic matter in managed lands with IWMS varydepending on the specific land-use category. In general, uncertainty can arise from 1) uncertainties in the
mapping of lands, land-use classification and/or management activity data, and 2) uncertainties in carbon gain
and loss, carbon stocks, and other parameters used for the estimation of carbon stock changes in biomass anddead organic matter such as biomass expansion factors. For specific recommendations for reducing uncertainties,
consult the appropriate land-use category chapter in the 2006 IPCC Guidelines under which managed lands with
IWMS are classified.

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5.2.1.2

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Soil carbon stocks in managed IWMS are primarily influenced by drainage and other management practices on
Cropland, Forest Land, and Grassland (including long-term cultivation, drainage to improve production, andgrazing), and rewetting after removal from active cropping and restoration of natural hydrologic conditions (e.g.,
removal of drainage tiles, plugging of drainage ditches, or similar activities). Other management practices thatcan significantly change IWMS soil carbon stocks include management of river-floodplain systems through theconstruction of dams, levees, and river channelization which can disconnect floodplains from hydrologic
interaction with rivers (Poff et al., 1997), reducing sediment deposition rates in floodplains (Hupp, 1992; Kleiss,
1996). Only a small number of studies, however, have quantified impacts of hydrologic alteration on soil carbon
accumulation rates in IWMS in floodplains (Noe and Hupp, 2005; Cabezas et al., 2009). Therefore it is notpossible to develop robust emission factors related to impacts of hydrologic alteration on soil carbon stocks of
IWMS in floodplains at this time. Similarly, very little information is available with regard to impacts of othercommon management practices, such as grazing, on IWMS soil carbon stocks. Therefore, guidance provided inthis chapter is largely based on and updates the guidance in the 2006 IPCC Guidelines.

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General information about mineral soil classification is provided in Chapters 2 and 3, Volume 4 of the 2006
IPCC Guidelines. The generic methodological guidance for estimation of changes in the carbon stocks in the
SOC pool in mineral soils provided in Section 2.3.3, Chapter 2, Volume 4 of the 2006 IPCC Guidelines andshould be used along with land-use category specific methodological guidance provided in Chapters 4 to 9,
Volume 4 of the 2006 IPCC Guidelines. This supplement updates the guidance on IWMS provided in the 2006
IPCC Guidelines with regard to the following:308



Table 5.2 provides updated default SOCREF for IWMS (e.g., wetland soils) for use in any land-use category;

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Table 5.3 provides an updated stock change factor for land-use (FLU) associated with long term cultivation of
Cropland with IWMS, and a new stock change factor for land-use (FLU) for rewetting of drained IWMS in
Cropland.

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To account for changes in IWMS SOC stocks associated with changes in relevant management practices on landremaining in a land-use category, countries need at a minimum, estimates of the area of managed land with
IWMS in a land remaining in land-use category affected by changes in relevant management practices at the
beginning and end of the inventory time period. Two assumptions are made for mineral soils (see details on
Section 2.3.3.1, Chapter 2, Volume 4 of the 2006 IPCC Guidelines): (i) over time, SOC reaches a spatiallyaveraged, stable value specific to the soil, climate, land-use and management practices; and (ii) SOC stockchanges during the transition to a new equilibrium SOC occurs in a linear fashion. If land-use and management
data are limited, aggregate data, such as FAO statistics on land-use (http://www.fao.org/home/en/), can be used
as a starting point, along with expert knowledge about the approximate distribution of land management systems.
Managed land with IWMS must be stratified according to climate regions, which can either be based on default
or country-specific classifications. This can be accomplished with overlays of land-use on suitable climate andsoil maps.

324

CHOICE OF METHOD

325
326
327
328

Inventories can be developed using a Tier 1, 2, or 3 approach, with each successive tier requiring more detail andresources than the previous one. A decision tree is provided for mineral soils in the 2006 IPCC Guidelines(Figure 2.4, Section 2.3.3.1, Chapter 2, Volume 4) to assist inventory compilers with selection of the appropriatetier for their soil carbon inventory.

S OIL CARBON

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331
332
333
334
335
336
337
338
339
340
341
342

Tier 1The estimation method for mineral soils in land remaining in a land-use category, including IWMS, is based onchanges in SOC stocks over a finite transition period following changes in management that impact SOC.
Equation 2.25 (∆Cmineral=(SOC0-SOC(0-T))/D; see Chapter 2, Volume 4 of the 2006 IPCC Guidelines for fullequation) is used to estimate change in SOC stocks in mineral soils by subtracting the SOC stock in the last yearof an inventory time period (SOC0) from the C stock at the beginning of the inventory time period (SOC(0 –T))and dividing by the time dependence of the stock change factors (D). SOC are estimated for the beginning andend of the inventory time period using default reference carbon stocks (SOCREF) (Table 5.2) and default stockchange factors (FLU, FMG, FI), based on the land-use (LU), management regime (MG) and input of organic matter(I) at the time of the inventory. In practice, country-specific data on land-use and management must be obtained
and classified into appropriate land management systems, and then stratified by IPCC climate regions and soil
types. The Tier 1 assumptions for carbon stock changes in mineral soils in land remaining in a land-use category
for specific land-use categories will also apply to managed lands with IWMS in those land-use categories.

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345
346

Tier 2

347
348
349
350
351
352
353
354

Tier 3

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356
357
358

A Tier 3 approach may also be developed using a measurement-based approach in which a monitoring network
is sampled periodically to estimate SOC stock changes. A much higher density of benchmark sites will likely beneeded than with models to adequately represent the combination of land-use and management systems, climate,and soil types. Additional guidance is provided in Section 2.3.3.1 of Chapter 2 of this supplement.

359

CHOICE OF EMISSION FACTORS

360
361
362
363

Tier 1

For Tier 2, the same basic equations are used as in Tier 1 (Equation 2.25), but country-specific information isincorporated to improve the accuracy of the stock change factors, reference C stocks, climate regions, soil types,
and/or the land management classification system.
Tier 3 approaches may use empirical, process-based or other types of models as the basis for estimating annual
carbon stock changes, such as the Century ecosystem model (Parton et al., 1987, 1994, 1998; Ogle et al., 2010),
or the Wetland-DNDC model (Zhang et al., 2002). Estimates from models are computed using equations that
estimate the net change of soil carbon. Key criteria in selecting an appropriate model include its capability ofrepresenting all of the relevant management practices/systems for the land-use category; model inputs (i.e.,
driving variables) are compatible with the availability of country-wide input data; and verification against
experimental, monitoring or other measurement data (e.g., Ogle et al.,2010).

Table 5.2 gives updated default reference SOC stocks (SOCREF) for IWMS3. Inventory compilers should use thestock change factors provided in the appropriate chapters addressing the six land-use categories (Chapters 4-9) inVolume 4 of the 2006 IPCC Guidelines in conjunction with the data in Table 5.2 for Tier 1 methods.

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3

These values are given under “wetland soils” in Table 2.3, Chapter 2, Volume 4 of the 2006 IPCC Guidelines.

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TABLE 5.2
DEFAULT REFERENCE SOIL ORGANIC CARBON STOCKS (SOCREF) FOR WETLAND MINERAL SOILSA UNDER NATIVEVEGETATION (0-30 CM DEPTH).
Climate region
Borealtonnes C ha-1

Standard
deviation

Error (95%
confidence
intervalB)

Number of sites

116

94

±99

6

Cold temperate, dry

87

C

n/a

Cold temperate, moist

128

Warm temperate, dry

D,E

D,E

n/aD

55

±17

42

74

45

±13

49

Warm temperate, moist

135

101

±39

28

Tropical, dry

22

11

±4

32

Tropical, moist

68

45

±12

55

Tropical, wet

49

27

±9

33

Tropical, montane

82

73

±46

12

n/a

ABatjes (2011) presents revised estimates (means, standard deviations) of the 2006 IPCC Guidelines SOC stocks for wetland mineral soils (gleysols) under naturalvegetation based on an expanded version of the ISRIC-WISE database (Batjes, 2009) which contains 1.6 times the number of soil profiles of the databases used in the2006 IPCC Guidelines SOC stocks estimate.
BThe 95% confidence interval is calculated from the mean, standard deviation, and the critical values of t distribution according to the degrees of freedom.
CNo revised estimate was presented in Batjes (2011); values are from Table 2.3, Chapter 2, Volume 4 of the 2006 IPCC Guidelines for National Greenhouse Gas
Inventories.
D”n/a” indicates information is not available.

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369

The updated SOCREF values in Table 5.2 for WMS should be used for calculating SOC stock changes in IWMS
when soils are classified as “wetland soils”, for land remaining in a land-use category in the following sections in
the 2006 IPCC Guidelines:

370

Forest Land (Chapter 4): Section 4.2.3, Tier 1;371

Cropland (Chapter 5): Section 5.2.3, Tier 1;372

Grassland (Chapter 6): Section 6.2.3, Tier 1.

373
374
375
376
377

Default stock change factors for land-use (FLU), input (FI), and management (FMG) that apply to managed land on
IWMS in the Cropland Remaining Cropland land-use category are presented in Table 5.5 , Chapter 5, Volume 4of the 2006 IPCC Guidelines; default stock change factors for land-use (FLU), input (FI), and management (FMG)
that apply to managed land on IWMS in the Grassland Remaining Grassland land-use category are presented inTable 6.2, Chapter 6, Volume 4 of the 2006 IPCC Guidelines.

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384
385
386
387
388

Table 5.3 in this supplement provides an updated Tier 1 default stock change factor for land-use (FLU) thatshould be applied to Cropland with IWMS under “long-term cultivation.” Note that the updated factor applies
only to long-term cultivated land-use in the temperate or boreal dry and moist climate regions. All other default
stock change factors in the 2006 IPCC Guidelines are unchanged. The updated value is similar to theTemperate/Boreal Moist climate but lower than the Temperate/Boreal Dry climate values in Table 5.5, Chapter 5,
Volume 4 of the 2006 IPCC Guidelines. Consequently, this update should reduce uncertainties associated withestimating soil carbon stock changes for IWMS in dry climates. The method and studies used to derive theupdated default stock change factor is provided in Annex 5A.1. The default time period for stock changes (D) is
20 years, and management practices are assumed to influence stocks to 30 cm depth although lower depths canalso be affected. As a result, for Tier 1 and 2 methods, SOC stocks for mineral soils are computed to a default
depth of 30 cm. Greater soil depth can be selected and used at Tier 2 if data are available.

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391
392
393
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395

A new default stock change factor for land-use (FLU) following rewetting of Cropland with IWMS is also
provided in Table 5.3 for a Tier 1 approach. This factor applies to Cropland with IWMS where natural hydrology
has been restored, and crop production may or may not continue. Note that the factor applies to all climate
regions, with the caveat that this value is likely more representative of rewetting activities in temperate andboreal climates, as it is derived from studies limited to these regions (see Annex 5A.1 for method and studies).
The default time period for stock changes (D) is 20 years, however additional C gain from restoring naturalhydrology continues for another 20 years and will reach the reference SOC stock level after 40 years (i.e.,

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SOCREF values in Table 5.2). It is also important to note that the long-term cultivation factor is used for areasthat have been drained and are cultivated for crop production. If the high water table is restored, i.e., in the caseof rewetted Cropland, then FLU for rewetting are used for two sets of 20 year periods (i.e., 0-20 and 20-40 years).

399
TABLE 5.3
RELATIVE STOCK CHANGE FACTORS FOR LAND-USE (FLU) FOR LONG TERM CULTIVATION ON CROPLAND WITH IWMS OVER
20 YEARS) AND REWETTING OF CROPLAND WITH IWMS (OVER 20 YEARS AND 40 YEARS)
Factor value typeLand-use (FLU)

Land-use (FLU)

Management

Long-term
cultivatedB

Rewetting(Years 1-20)

Rewetting(Years 21-40)

Temperature
regimeTemperate/
BorealBoreal,Temperate,and Tropical

Moisture
regimeDry and
Moist

Default

0.71

0.80

ErrorA41%

10%

Dry and
Moist
1.0

N/A

Description
Represents
Cropland with
IWMS that has
been continuously
managed for > 20
years, topredominantly
annual crops.
Represents
cropland with
IWMS that has
undergone
rewetting(restoration ofnatural hydrology)
and may or may
not be under active
crop production.

A ± two standard deviations, expressed as a percent of the mean.
B The long-term cultivation factor is used for areas that have been drained and are cultivated for crop production. In the case of rewetted Cropland, stock-change factors forland-use (F) for rewetting are used for two sets of 20 year periods (i.e., 0-20 and 20-40 years since rewetting).
LU

400
401
402

The following are the key considerations in the application of the new stock change factors to Cropland with
IWMS subject to long-term cultivation and rewetting (Table 5.3) for land remaining in a land-use category:

403
404
405



The stock change factors for SOC in mineral soils provided for Forest Land, Cropland, Grassland, andSettlements in the 2006 IPCC Guidelines are applicable for all managed lands with IWMS classified as landremaining in a land-use category under any of the land-use categories.

406
407
408



The new stock change factors for long-term cultivation and rewetting of Cropland with IWMS in thisSupplement (Table 5.3) should be applied to Cropland remaining Cropland with IWMS taking account of
the following:

409
410
411
412

(i)

The new stock change factor for land-use (FLU) for Cropland with IWMS under long-term cultivationin this supplement will be used in place of the existing stock change factor for Cropland under longterm cultivation for all mineral soil types provided in Table 5.5, Chapter 5, Volume 4, in the 2006
IPCC Guidelines.

413
414

(ii)

The stock change factors for land-use (FLU) for Cropland with IWMS subject to rewetting are to be
used for Cropland remaining Cropland according to the following:

415
416
417
418
419
420

o

For Cropland with IWMS subject to rewetting, for the first 20 years following the initial year ofrewetting, the final SOC stock i.e., SOC stocks in the last year of an inventory time period (SOC0)
is determined using FLU = 0.80 along with the other stock change factors for management andinput. The stock change factors for estimating the initial SOC stocks (SOC(0-T)) will correspond to
the Cropland land-use (long-term cultivated, perennial etc.), management and input regimes prior
to rewetting.

421
422
423
424
425

o

For the next set of 20 years (i.e., 20-40 years since the initial year of rewetting), FLU = 1 will be
used to estimate the final SOC stock (SOC0) along with appropriate stock change factors for
management and input. The stock change factors for estimating the initial stocks (SOC (0-T)) willcorrespond to rewetted Cropland land-use (FLU = 0.8) management and input regimes at 20 years
following rewetting.

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o

For the period beyond 40 years following the initial year of rewetting, FLU will remain equal to 1.
The changes in SOC stocks due to changes in management/input regimes in Cropland with IWMS
may be estimated using appropriate stock change factors from Table 5.2, Chapter 5, Volume 4 inthe 2006 IPCC Guidelines.

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431
432
433
434
435

Tier 2

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439

Tier 3440

CHOICE OF ACTIVITY DATA

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451
452

Activity data consist of areas of managed lands with IWMS remaining in a land-use category stratified by landuse category, climate region, soil type, and management practices, at a minimum. The area of Cropland with
IWMS subject to rewetting need to be stratified by time since rewetting (0-20 or 20-40 years since rewetting) for
correct application of stock change factors. If the compiler does not have sufficient information to disaggregate
areas of rewetted Cropland with IWMS by time since conversion, all rewetted Cropland with IWMS areas could
be assumed to be within 0-20 years since rewetting and FLU = 0.8 could be applied to the entire rewetted
Cropland with IWMS. Total areas should be determined according to approaches outlined in Chapter 3, Volume
4 of the 2006 IPCC Guidelines, and should be consistent with those reported under other sections of theinventory. Stratification of land-use categories according to climate region, based on default or country-specificclassifications, can be accomplished with overlays of land-use on climate and soil maps. In the case of using
methods such as models, and/or use of data as proxies for estimation, clear and complete documentation is
encouraged for transparency.

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454
455
456
457
458
459
460
461
462
463

Tier 1The Tier 1 approach requires area of managed land on IWMS for each land-use category stratified by climate
region and soil type. Available land cover/land-use maps, either country-specific maps or maps based on global
datasets such as IGBP_DIS (http://daac.ornl.gov), can be joined with soil and climate maps (country-specific, or
global maps such as ISRIC, http://www.isric.org, or FAO, http://www.fao.org/home/en) as an initial approach. A
global GIS database that shows the spatial distribution of generalized soil classes used for IPCC Tier 1 isavailable for download and use at http://isirc.org/data/ipcc-default-soil-classes-derived-harmonized-world-soildata-base-ver-11. The database is derived from the Harmonized World Soil Data Base and FAO soil
classifications, and includes the seven default IPCC soils classes including Wetland Soils (termed “Wetland Soils”
in the 2006 IPCC Guidelines, and “Wetland Mineral Soils” in this supplement) (Batjes, 2010b). This dataset may
be used at national and broader scales where more detailed soil information is lacking.

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465
466
467
468
469
470
471
472
473

Classification systems for activity data for a Tier 1 inventory are provided in the respective land-use chapters ofthe 2006 IPCC Guidelines. Land-use activity data and management activity data specific to the respective landuse category are typically required for the Tier 1 approach. Although no organization catalogues changes in area
as a result of rewetted or created wetlands either nationally or globally, local activity data for rewetting ofmanaged lands with IWMS or creation of wetlands may be obtained from agricultural, forestry, or natural
resources agencies, non-governmental conservation organizations, or other government sources. In addition,organizations such as the Society for Ecological Restoration International (http://www.wer.org), Global
Restoration
Network(http://www.globalrestorationnetwork.org),
Wetlands
International(http://www.wetlands.org), and the Ramsar Convention on Wetlands (http://www.ramsar.org) may be sources of
information for rewetting and wetland creation projects.

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476
477
478
479

Tier 2

A Tier 2 approach involves the estimation of country-specific stock change factors. It is good practice to derivevalues for a higher resolution classification of management and climate if there are significant differences in thestock change factors among more disaggregated categories based on an empirical analysis. Reference SOC
stocks can also be derived from country-specific data in a Tier 2 approach. Additional guidance is provided in
Section 2.3.3.1, Chapter 2, Volume 4 of the 2006 IPCC Guidelines.
Constant stock change rate factors per se are less likely to be estimated in favour of variable rates that moreaccurately capture land-use and management effects. See Section 2.3.3.1, Chapter 2, Volume 4 for further
discussion.

Tier 2 approaches are likely to involve a more detailed stratification of management systems, under therespective land-use category, than Tier 1 if sufficient data are available. This may include further divisions ofmanagement practices, and finer stratification of climate regions. At Tier 2, a higher spatial resolution of activity
data is required, and can be obtained by disaggregating global data in country-specific categories, or bycollecting country-specific activity data.

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Tier 3488

CALCULATION STEPS FOR TIER 1

489
490

The steps for estimating SOC0 and SOC (0-T) and net soil organic carbon stock change per hectare for managed
land on IWMS for land remaining in a land-use category are as follows:

491

Step 1: Organize data into time series according to the years in which activity data were collected.

492
493

Step 2: Classify land into the appropriate management system in accordance with its respective land-use
category.

494
495
496
497

Step 3: Determine areas of managed land with IWMS under each land-use category for lands remaining in that
land-use category, disaggregated according to climate region at the beginning of the first inventory time period.
The first year of the inventory time period will depend on the time step of the activity data (0-T; e.g., 5, 10, or 20
years ago).

498

Step 4: Assign a native reference SOC stock value (SOCREF) for IWMS from Table 5.2 based on climate region.

499
500
501
502

Step 5: Assign a land-use factor (FLU), management factor (FMG), and organic matter input factor (FI) based on
the management classification for the respective land-use category (Step 2). Values for FLU, FMG, and FI areprovided in the respective chapters for land-use categories; an updated value for long-term cultivation FLU isgiven in Table 5.3 for IWMS in Cropland.

503
504

Step 6: Multiply the appropriate stock change factors (FLU, FMG, FI) by SOCREF to estimate an ‘initial’ SOC stock(SOC(0-T)) for the inventory time period.

505
506
507

Step 7: Estimate the final SOC stock (SOC0) by repeating Steps 1 to 5 using the same SOCREF, but with landuse, management, and input factors that represent conditions for the managed land in the last (year 0) inventory
year.

508
509
510
511

Step 8: Estimate the average annual change in SOC stocks for managed land on IWMS remaining in a land-use
category (ΔCMineral) by subtracting the SOC(0-T) from SOC0, then dividing by the time dependence of the stockchange factors (D) (i.e. 20 years using the default factors). If an inventory time period is greater than 20 years,
then divide by the difference in the initial and final year of the time period.

512

Step 9: Repeat steps 2 to 8 if there are additional inventory time periods.

513

UNCERTAINTY ASSESSMENT

514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531

Three broad sources of uncertainty exist in soil C inventories: 1) uncertainties in land-use and management
activity, and environmental data; 2) uncertainties in reference soil carbon stocks if using a Tier 1 or 2 approach,or initial conditions if using a Tier 3 approach; and 3) uncertainties in the stock change/emission factors for Tier
1 or 2 approaches, model structure/parameter error for Tier 3 model-based approaches, or measurement
error/sampling variability associated with Tier 3 measurement-based inventories. In general, precision of an
inventory is increased and confidence ranges are smaller with more sampling to estimate values for the threebroad sources of uncertainty, while reducing bias (i.e., improve accuracy) is more likely to occur through thedevelopment of a higher tier inventory that incorporates country-specific information. An additional source of
uncertainty arises from the difficulty in accurately mapping wetlands for the purposes of classification under soil
or vegetation types and management activities, for example; this has been an issue since inventory methods werefirst developed (Cowardin, 1982), and still continue even with advances in technology and remote sensing
techniques (Arnesen et al., 2013). Because mapping techniques tend to rely on vegetation and soils information,
defining the area of IWMS is especially difficult because their vegetation ranges from marsh to forested systems
and soils range from near organic to near non-wetland mineral across their range. Moreover, areas subjected towater table variation and flooding may increase or decrease frequently depending on interannual climate
variability and management activities. However, given no dramatic changes in hydrology, wetland soil andvegetation properties will remain consistent over time, even with interannual climate variability, and mappedareas should remain relatively unchanged.

532
533
534

For Tier 1, uncertainties are provided with the reference SOC stocks in Table 5.2, and stock change factors in therespective land-use category chapters in the 2006 IPCC Guidelines and Table 5.3 for the updated FLU.
Uncertainties in land-use and management data will need to be addressed by the inventory compiler, and thenTier 3 approaches may include the use of empirical, process-based or other types of models and/or direct
measurement-based inventories, in which case more detailed data on climate, soils, and management practices
are needed relative to Tier 1 and 2 methods. The exact requirements will be dependent on the model ormeasurement design. Examples of model input data include activity data on cropland management practices(crop type, tillage practices, fertilizer and organic amendments), climate, soil, biomass, and water table position(Ogle et al., 2010; Zhang et al., 2002).

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540
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545
546
547
548
549
550

combined with uncertainties for the default factors and reference SOC stocks using an appropriate method, suchas simple error propagation equations. If using aggregate land-use area statistics for activity data (e.g., FAO data),
the inventory compiler may have to apply a default level of uncertainty for the land area estimates (±50%). It isgood practice to apply country-specific uncertainty estimates for country-specific area estimates instead of using
a default level. Default reference SOC stocks and stock change factors for mineral soils can have inherently highuncertainties when applied to specific countries. Defaults represent globally averaged values of land-use andmanagement impacts or reference SOC stocks that may vary from region specific-values (Powers et al., 2004;
Ogle et al., 2006). Bias can be reduced by deriving country-specific factors using a Tier 2 method or bydeveloping a Tier 3 country-specific estimation system. The underlying basis for higher Tier approaches will be
experiments or soil carbon monitoring data in the country or neighbouring regions that address the effect of landuse and management on soil carbon and/or can be used to evaluate model predictions of soil carbon change (e.g.,
Ogle et al., 2010). Further reduction in bias can be obtained by accounting for significant within-country
differences in land-use and management impacts, such as variation among climate regions and/or soil types, evenat the expense of reduced precision in the factor estimates (Ogle et al., 2006). Bias is considered more
problematic for reporting stock changes because it is not necessarily captured in the uncertainty range (i.e., thetrue stock change may be outside of the reported uncertainty range if there is significant bias in the factors).

551
552
553
554

Uncertainties in land-use activity statistics may be reduced through a better national system, such as developing
or extending a ground-based survey with additional sample locations and/or incorporating remote sensing toprovide additional coverage. It is good practice to design a classification that captures the majority of land-use
and management activity with a sufficient sample size to minimize uncertainty at the national scale.

555

5.2.2

556
557
558
559
560
561
562
563
564
565
566

Management activities on lands containing IWMS that alter the water table level can impact CH4 emissions. Two
common management activities that involve raising water table levels include rewetting of previously drained
IWMS, and the creation of wetlands on mineral soils (wet or dry). Both rewetting and wetland creation are often
undertaken as conservation efforts for habitat and wildlife. Studies have shown that raising water table levels on
managed lands with IWMS, through rewetting and/or wetland creation, can increase CH4 emissions (Pennock etal., 2010; Badiou et al., 2011; Nahlik and Mitsch, 2010; Herbst et al., 2011; Yang et al., 2012). Here we provide
guidance for CH4 emissions as a result of raising the water table level on managed lands with IWMS; drainage
and lowering water tables typically results in lower or negligible CH4 emissions (Morse et al., 2012). In amodeling study of global CH4 emissions, Spahni et al. (2011) suggest that IWMS that are not inundated, buthave soil moisture content above a critical threshold, can still be a net CH4 source. Due to the lack of studies,
however, we are unable to develop guidance for CH4 emissions from drained IWMS at this time.

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568
569
570
571
572
573
574
575
576
577

Although our current understanding of the processes involved in CH4 production and emission is improving, itremains difficult to estimate CH4 emissions with a high degree of confidence due mainly to large spatial
variability, and to seasonal and interannual variability in controlling factors such as water level and temperature.
Studies show high spatial variability in CH4 emissions across large areas that have similar climate, vegetation,and topography, and within small areas that have microscale variation in topography (Ding et al., 2003; Saarnio
et al., 2009). In addition, there are very few studies of CH4 emissions from rewetted or created wetlands on
managed lands with IWMS in Europe (Saarnio et al., 2009), tropical regions (Mitsch et al., 2010), and certain
regions of North America. Therefore, the default emission factors we present necessarily have large uncertainties.
Due to the relative lack of data on rewetted and created wetlands with IWMS, we included studies of CH4
emissions from natural wetlands on IWMS in the development of default emission factors (see Annex 5A.2 forfurther details).

578

5.2.2.1

579
580
581
582
583

Tier 1

CH 4 emissions from managed lands with IWMSC HOICE OF METHOD

CH4 emissions from managed lands on IWMS, or dry mineral soils, where management activities have resulted
in the water table being raised to, or above, the land surface are estimated using a simple emission factor
approach (Equation 5.1), stratified by climate region. The default methodology considers boreal, temperate, andtropical climate regions.

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587

EQUATION 5.1
ANNUAL CH4 EMISSIONS FROM REWETTED AND CREATED WETLANDS ON MANAGED LANDS WITH
IWMS

CH 4 IWMS   ( AIWMS  EFCH 4  IWMS ) c

588

c

589
590

Where:

591
592

CH4-IWMS = Annual CH4 emissions from managed lands on IWMS where management activities haveraised the water table level to or above the land surface, kg CH4 yr-1

593
594

AIWMS, c = Total area of managed lands with mineral soil where the water table level has
been raised in climate region c, ha

595
596

EFCH4-IWMS, c = Emission factor from managed lands with mineral soil where water table level has
been raised in climate region c, kg CH4 ha-1 yr-1

597
598

The area of managed lands with IWMS, or dry mineral soil, where water table level has been raised, should be
stratified by climate region (boreal, temperate, or tropical), and the appropriate emission factor applied.

599
600
601
602
603
604
605
606

Tier 2The Tier 2 approach uses country-specific emission factors based on information on important parameters suchas water table level and hydroperiod. It is good practice when developing and using country-specific emission
factors to consider the water table position and its relationship to CH4 emissions. Annual CH4 emissions from
IWMS are generally larger when the water table is continuously at or above the land surface, rather thanintermittently at or below the land surface (Annex 5A.2). Seasonal and interannual changes in water table
position, and duration above the land surface, are determined by multiple variables including fluctuations inwater source (e.g., river discharge in the case of riparian wetlands), evapotranspiration and precipitation.

607
608
609
610
611
612
613
614
615
616

A Tier 3 approach involves a detailed consideration of the dominant drivers of CH4 emission from IWMS,
including but not limited to water table position, seasonal changes in inundation, temperature of soils,
importance of CH4 ebullition, and vegetation community dynamics. CH4 ebullition is a poorly quantified
component of CH4 emission from inundated soils, but has been shown to be a significant contributor to annual
CH4 emission in some systems (Wilson et al., 1989). Vegetation can have important implications for CH4
emission by facilitating transport from inundated soils to the atmosphere, and by providing substrate for CH4
production. Possible methods to determine the importance of these drivers to CH4 emission, and thus reduce
uncertainty in emission factors, include detailed field studies of CH4 emission and/or the use of models specificto carbon cycling in wet soils such as the Wetland-DNDC model (Zhang et al., 2002; http://www.globaldndc.net).

617

5.2.2.2

618
619
620
621
622
623

Tier 1

Tier 3

C HOICE OF EMISSION FACTORSThe default emission factors for IWMS (EFCH4-IWMS), stratified by climate region, are provided in Table 5.4. The
Tier 1 emission factors do not distinguish between continuous and intermittent inundation. The emission factors
were derived from studies covering a range of inundation duration, therefore capturing a degree of variability in
CH4 emission (Annex 5A.2). The uncertainties in the EFs can be reduced by using country-specific EFs thatincorporate information on water table position and period of inundation at higher Tier levels.

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625
TABLE 5.4
DEFAULT EMISSION FACTORS FOR CH4 FROM MANAGED LANDS WITH IWMS WHERE WATER TABLELEVEL HAS BEEN RAISEDClimate Region

EFCH4-IWMS-1-1

95% Confidence IntervalA

Number ofStudies(kg CH4 ha yr )Boreal

76

±76B

1C

Temperate

235

±108

21

Tropical

900

±456

18

AThe 95% confidence interval is calculated from the mean, standard deviation, and the critical values of t distribution according to thedegrees of freedom. These are not expressed as a percentage of the mean.
B Bridgham et al. (2006)
CThis study (Bridgham et al., 2006) is a synthesis of numerous studies; see publication for details.

626

5.2.2.3

C HOICE OF ACTIVITY DATA

627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642

The Tier 1 method requires data on areas of managed lands with IWMS where the water table level has beenraised, for instance as in rewetting or wetland creation, stratified by climate region. Although no organization
catalogues changes in area as a result of rewetting or wetland creation either nationally or globally, local activity
data for rewetting of managed lands with IWMS or creation of wetlands may be obtained from agricultural,
forestry, or natural resources agencies, non-governmental conservation organizations, or other government
sources. In addition, organizations such as the Society for Ecological Restoration International(http://www.wer.org), Global Restoration Network (http://www.globalrestorationnetwork.org), Wetlands
International (http://www.wetlands.org), and the Ramsar Convention on Wetlands (http://www.ramsar.org) may
be sources of information for rewetting and/or wetland creation projects. In addition to the above, Tier 2 and Tier
3 methods generally require areas of managed lands with IWMS stratified by annual average water table level,and seasonal and/or interannual changes in inundation. Areas may be further stratified by vegetation community
composition, vegetation biomass, soil temperature data, and previous land-use, for the development of countryspecific emission factors and models. The use of Synthetic Aperture Radar (SAR) on the Japanese Satellite JERS,
for example, can improve the accuracy of the quantification of inundated areas, by overcoming the bias causedby clouds in more common satellite imagery on the visible spectrum (e.g., Landsat images). Also, higher
resolution satellite images (e.g., QuickBird) can reduce uncertainties in land-use and vegetation classifications.

643

5.2.2.4

644
645
646
647
648

Estimates of uncertainty for EFCH4-IWMS, as ± 95% Confidence Interval, are provided in Table 5.4 for eachclimate region. Major sources of uncertainty in these values are the small number of studies on which theestimates are based, and the combination of studies with different inundation periods (continuously inundated
and intermittently inundated). The development of country-specific emission factors will aid in reducing
uncertainty.

U NCERTAINTY ASSESSMENT

649
650

5.3

651
652
653
654
655
656
657
658

LAND CONVERTED TO A NEW LAND-USE
CATEGORY

The 2006 IPCC Guidelines define land converted to a new land-use category as lands that have been converted
in the last 20 years as a default period. The 2006 IPCC Guidelines provide generic and land-use category
specific guidance (Chapters 4-9, Chapters 2, Volume 4) for carbon stock changes in the carbon pools and nonCO2 emissions from managed land on mineral soils for land converted to a new land-use category for all land-use
categories. This chapter updates the 2006 IPCC Guidelines for guidance on changes in SOC stocks and non-CO2
emissions from managed lands with IWMS that have been classified as land converted to a new land-use
category in all six land-use categories.

659

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660

5.3.1

CO 2 emissions and removals

661
662
663

The set of general equations to estimate the annual C stock changes of C pools for land remaining in a land-use
category for managed lands with IWMS are given in Volume 4, Chapter 2 of the 2006 IPCC Guidelines, and will
also apply to managed lands with IWMS for land converted to a new land-use category.

664
665

Figure 1.3 in Volume 4, Chapter 1 of the 2006 IPCC Guidelines shows a decision tree for the identification of
appropriate methodological Tiers for the inventory of land converted to a new land-use category.

666

5.3.1.1

667
668
669

The guidance provided in section 5.2.1.1 also applies to lands converted to a new land-use category for managed
lands with IWMS. The guidance in sections pertaining to land converted to a new land-use category in the 2006
IPCC Guidelines are to be used.

670

CHOICE OF METHOD AND EMISSION/REMOVAL FACTORS

671
672
673

The guidance provided in section 5.2.1.1 also applies to lands converted to a new land-use category for managed
lands with IWMS. The guidance in sections pertaining to land converted to a new land-use category in the 2006
IPCC Guidelines are to be used.

674

CHOICE OF ACTIVITY DATA

675
676
677
678
679

The activity data consist of areas of managed lands with IWMS in land converted to a new land-use category
stratified by land-use category, climate region, soil type, and management practices, at a minimum. The guidance
provided in Section 5.2.1.1 also applies to lands converted to a new land-use category for managed lands with
IWMS. The guidance in sections pertaining to land converted to a new land-use category in the 2006 IPCC
Guidelines are to be used.

680

UNCERTAINTY

681
682
683

The guidance provided in Section 5.2.1.1 also applies to lands converted to a new land-use category for managed
lands with IWMS. The guidance in sections pertaining to lands converted to a new land-use category in the 2006
IPCC Guidelines are to be used.

684

5.3.1.2

685
686
687
688
689
690
691

Conversion of land on IWMS to other land-uses can increase (in Forest Land, for example, Volume 4, Chapter 4
in 2006 IPCC Guidelines) or decrease SOC stocks (in Cropland, for example, Chapter 5 of Volume 4 in 2006
IPCC Guidelines). In general, the guidance provided in section 5.2.1.2 also applies to lands converted to a newland-use category for managed lands with IWMS. However, there are specific applications of the new SOC stockchange factors for rewetting depending on the specific land-use conversion (see Choice of Emission/Removal
Factors below for details). The guidance in sections pertaining to land converted to a new land-use category in
the 2006 IPCC Guidelines are to be used.

692

CHOICE OF METHOD

693
694
695

The guidance provided in section 5.2.1.2 also applies to lands converted to a new land-use category for managed
lands with IWMS. The guidance in sections pertaining to land converted to a new land-use category in the 2006
IPCC Guidelines are to be used.

696

CHOICE OF EMISSION/REMOVAL FACTORS

697
698
699
700

The guidance provided in section 5.2.1.2 also applies to all lands converted to a new land-use category for
managed lands with IWMS in any land-use category, including the updated SOCREF for IWMS (Table 5.2) andthe updated and new stock change factors (FLU, Table 5.3). The following are the key considerations in theapplication of stock change factors for managed lands with IWMS:

701
702
703



The stock change factors for SOC stock changes in mineral soils provided for Forest, Cropland, Grassland,
and Settlements in the 2006 IPCC Guidelines are applicable for all land-use conversions (both to and from)involving managed lands with IWMS classified under any of the land-use categories;

704
705
706



The new stock change factors for long-term cultivation and wetland rewetting of Cropland with IWMS in
this supplement (Table 5.3) can be applied to land-use conversions involving Cropland taking account of thefollowing:

B IOMASS AND DEAD ORGANIC MATTERS OIL CARBON

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707
708
709
710

(i)

The new stock change factor for land-use (FLU) for Cropland with IWMS under long-term
cultivation in this supplement will be used in place of the existing stock change factor for Croplandunder long-term cultivation for all mineral soil types provided in Table 5.5, Chapter 5, Volume 4in the 2006 IPCC Guidelines.

711
712

(ii)

The stock change factors for land-use (FLU) for Cropland with IWMS subject to rewetting can beused for land-use conversions involving Cropland in the following ways:

713
714
715
716
717

o

For land-use conversion to Cropland with IWMS subject to rewetting the final SOC stock (SOC0)
is determined using FLU = 0.80 for a period of 0-20 years following the first year of rewetting
along with the relevant stock change factors corresponding to the management and input regimes
after land-use conversion. The stock change factors for estimating the initial SOC stocks (SOC(0-T))
will correspond to the land-use, management and input regimes before land-use conversion.

718
719
720
721
722
723
724

o

For Cropland with IWMS subject to rewetting undergoing land-use conversion to any other landuse category, FLU = 1 be used for a period of 20-40 years or more than 40 years since the first yearof rewetting activity respectively, along with relevant stock change factors corresponding to the
management/input regime before conversion. The stock change factors for land-use, management
and input for the new land-use category (e.g., Forest Land or Grassland) will be used to determine
the final SOC stock (SOC0) along with relevant stock change factors corresponding to the
management and input regimes following land-use conversion.

725
726

o

The guidance in sections pertaining to land converted to a new land-use category in the 2006 IPCC
Guidelines are to be used.

727

CHOICE OF ACTIVITY DATA

728
729
730
731
732
733
734
735

The activity data consist of areas of managed lands with IWMS in land converted to a new land-use category
stratified by land-use category, climate region, soil type, management practices, and time since conversion, at aminimum. The area of Cropland with IWMS subject to rewetting need to be stratified by time since rewetting (020 or 20-40 years since rewetting) for correct application of stock change factors. If the compiler does not havesufficient information to disaggregate areas of rewetted Cropland with IWMS by time since conversion, allrewetted Cropland with IWMS areas could be assumed to be within 0-20 years since rewetting and FLU = 0.8
could be applied to the entire rewetted Cropland with IWMS. The guidance provided in Section 5.2.1.2 also
applies to lands converted to a new land-use category for managed lands with IWMS.

736

UNCERTAINTY

737
738
739

The guidance provided in Section 5.2.1.2 also applies to lands converted to a new land-use category for
managed lands with IWMS where the water table has been raised. The guidance in sections pertaining to lands
converted to a new land-use category in the 2006 IPCC Guidelines are to be used.

740

5.3.2

741
742

The guidance provided in Section 5.2.2 also applies to lands converted to a new land-use category for managed
lands with IWMS.

743

5.3.2.1

744
745

The guidance provided in Section 5.2.2 also applies to lands converted to a new land-use category for managed
lands with IWMS.

746

5.3.2.2

747
748
749
750

The activity data consist of areas of managed lands with IWMS in land converted to a new land-use category
stratified by land-use category, climate region, soil type, and management practices, at a minimum. The guidance
provided in Section 5.2.2 also applies to lands converted to a new land-use category for managed lands with
IWMS.

751

5.3.2.3

752
753

The guidance provided in Section 5.2.2 also applies to lands converted to a new land-use category for managed
lands with IWMS.

5.20

CH 4 emissions

C HOICE OF METHOD AND EMISSION FACTORSC HOICE OF ACTIVITY DATAU NCERTAINTY ASSESSMENT

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5.4

COMPLETENESS, REPORTING AND
DOCUMENTATION

756

5.4.1

Completeness

757
758
759
760

It is good practice to disaggregate the type of managed lands with IWMS according to national circumstancesand employ country-specific emission factors if possible. It is suggested that flooded lands (including reservoirs),
peatlands, and coastal wetlands are clearly excluded from land with IWMS and this separation is appliedconsistently throughout the reporting period.

761
762
763
764

Guidance not provided for IWMS in this chapter for some lands, some climates, some carbon pools, and some
GHGs is the result of lack of relevant data to develop emission factors. Countries are encouraged to develop
new research and accounting practices to fill gaps to better account for changes in carbon stocks and GHG
emissions and removals from drained wetlands, rewetted wetlands, or created wetlands on lands with IWMS.

765
766
767
768
769

General guidance on consistency in time-series is given in Chapter 7 of this Supplement. The classification ofland, criteria for using activity data and emission factors and inventory methods should be consistent with thegeneric methodologies described in Volume 4 of the 2006 IPCC Guidelines and in this supplement. Chapter 6 inVolume 1 of the 2006 IPCC Guidelines and Chapter 7 of this supplement provide general guidance on the issues
concerning Quality Assurance and Quality Control (QA/QC).

770

5.4.2 Reporting and Documentation

771
772
773

General guidance on reporting and documentation is given in Chapter 8 of Volume 1 of the 2006 IPCC
Guidelines. Section 7.4.4, Chapter 7, Volume 4 of the 2006 IPCC Guidelines states the following for reportingand documentation:

774

EMISSION FACTORS

775
776
777

The scientific basis of new country-specific emission factors, parameters and models should be fully describedand documented. This includes defining the input parameters and describing the process by which the emission
factors, parameters and models were derived, as well as describing sources of uncertainties.

778

ACTIVITY DATA

779
780
781
782

Sources of all activity data used in the calculations (data sources, databases and soil map references) should berecorded plus (subject to any confidentiality considerations) communication with industry. This documentation
should cover the frequency of data collection and estimation, and estimates of accuracy and precision, andreasons for significant changes in emission levels.

783

TREND ANALYSIS

784
785
786
787

Significant fluctuations in emissions between years should be explained. A distinction should be made betweenchanges in activity levels and changes in emission factors, parameters and methods from year to year, and thereasons for these changes documented. If different emission factors, parameters and methods are used for
different years, the reasons for this should be explained and documented.

754
755

788
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790

Annex 5A.1

791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813

Estimation of default stock change factors for longterm cultivated Cropland and rewetting with
Inland Wetland Mineral Soil carbon
emissions/removals

Default stock change factors are provided in Table 5.3 that were computed using a dataset of experimental
results for land-use. The land-use factor for long-term cultivation represents the loss of SOC that occurs after 20
years of continuous cultivation. The rewetting factor represents the effect of the restoration of natural hydrology
of cultivated cropland with IWMS (such as through the removal of drainage tiles, or plugging of drainage
ditches), which may or may not have continued crop production. The influence of this change on IWMS SOC
stocks may continue for a period of time that may extend to 40 years. Experimental data (citations listed below,
and provided in reference list) were analyzed in linear mixed-effects models, accounting for both fixed andrandom effects (Ogle et al. 2005). Fixed effects included depth and number of years since the managementchange. For depth, data were not aggregated but included SOC 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 toaccount for the dependencies in times series data and among data points representing different depths from thesame study. If significant, a country level random effect was used to assess an additional uncertainty associatedwith applying a global default value to a specific country (included in the default uncertainties). The long-term
cultivation factor represents the average loss of SOC at 20 years or longer time period following cultivation of
IWMS. Users of the Tier 1 method can approximate the annual change in SOC storage by dividing the inventory
estimate by 20. The rewetting factor represents the average net gain in SOC after rewetting of cultivatedcropland at 20 and 40 years following the first year of rewetting. Variance was calculated for each of the factor
values, and can be used with simple error propagation methods or to construct probability distribution functions
with a normal density.
TABLE 5A.1.1
STUDIES USED FOR THE DERIVATION OF DEFAULT SOC STOCK CHANGE FACTORS
Study

Location

Stock Change Factor (LC= Long term cultivation;
R = Rewetting)Badiou et al., 2011

Saskatchewan, Alberta, Manitoba, Canada

LC, RBallantine et al., 2009

New York, USAR

Bedard-Haughn et al., 2006

Saskatchewan, Canada

LC

Besasie et al., 2012

Wisconsin, USA

LC, RDavid et al., 2009

Illinois, USALC

Euliss et al., 2006

North Dakota, South Dakota, Minnesota,

LC, R

Gleason et al., 2009

North Dakota, USAR

Huang et al., 2010

Sanjiang Plain, China

LC

Hunter et al., 2008

Louisiana, USA

LC, R

Jacinthe et al., 2001

Ohio, USALC

Lu et al., 2007

Lake Taihu, China

LC, R

Meyer et al., 2008

Nebraska, USA

LC, R

Morse et al., 2012

North Carolina, USA

LC

Norton et al., 2011

California, USALC

Wang et al., 2012

Sanjiang Plain, China

LC, R

van Wesemael et al., 2010

Belgium

LC

814
815
816

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819

Estimation of CH4 emission factors for managed
lands with Inland Wetland Mineral Soils, or dry
mineral soils, where the water table has been raised

820
821
822
823
824
825
826
827
828

The Tier 1 default emission factors in Table 5.4 were derived from the published studies listed in Table 5A.2.1.
The number of studies of CH4 emission from rewetted IWMS as a result of rewetting of drained IWMS, andfrom wetted mineral soils as a result of wetland creation, is very limited. They are also restricted to the temperate
climate regions. Thus studies of CH4 emission from natural IWMS were included to derive emission factors fromboreal and tropical regions, and to supplement the number of studies in the temperate region. Studies varied intheir reporting of emissions; some reported annual fluxes, while others reported seasonal fluxes or mean daily
fluxes. In the case of seasonal or daily flux reporting, an annual flux was estimated by assuming no emission
occurred during cold seasons and/or by applying mean daily fluxes to part or all of the annual period depending
on climate region and/or specific recommendation by study authors.

817

Annex 5A.2

818

TABLE 5A.2 .1
CH4 EMISSIONS FROM RESTORED AND CREATED WETLANDS WITH IWMS WHERE WATER TABLE LEVEL HAS BEEN RAISED, AND NATURALWETLANDS, USED TO DERIVE DEFAULT VALUE FOR EFCH4
ClimateregionWetlandtype

BorealNaturalwetlands

Temperate

Temperate

Restoredwetlands,
previous use
CroplandRestoredwetlands,
previous use
Cropland

Temperate

Restoredwetlands,
previous use
CroplandRestoredwetlands,
previous use
CroplandRestoredwetland,previous use
Cropland

Temperate

Createdwetlands,
riparian

Temperate

Temperate

Annualperiod ofinundation

CH4 emission(kg CH4 ha-1
yr-1)

CH4 Flux
measurement
methodCH4 Flux
reported

Canadaunspecified

76

Chamber, EC

AnnualBridgham etal., 2006

CanadaIntermittent

49

Chamber

Mean daily

Badiou etal., 2011

Location

Reference

AnnualCanadaIntermittent

349

Chamber(modified for
diurnal variation
as stated in study)

North Dakota, USA

Intermittent

142

Chamber

Mean daily

Gleason etal., 2009

North Carolina,
USA

Intermittent

7Chamber

AnnualMorse et al.,2012

Pennock etal., 2010

AnnualDenmark

Intermittent

110

EC

(minus emissions
from cattle on-site
as stated in study)

Herbst etal., 2011

AnnualChina

Intermittent

13

Chamber(diffusive andebullitive fluxes
combined)

AnnualTemperate

Createdwetlands

Ohio, USA

Continuous

402

ChamberTemperate

Naturalwetland,marsh

Nebraska

Continuous

800

EC

DRAFT Wetlands Supplement(mean of two
different years
from same site)

AnnualYang et al.,2012
Nahlik andMitsch,2010; Altor
and Mitsch,
2008
Kim et al.,
1999

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Temperate

Naturalwetlands,
marshes

Temperate

Naturalwetlands,
Carex
marshes

Temperate

Naturalwetland,riparian
Naturalwetlands,
Deyeuixa
marshesSanjiang Plain, NE
China

Continuous

468

Chamber

AnnualDing andCai, 2007

AnnualSanjiang Plain, NE
China

Ohio, USA

Continuous

Continuous

434

758

(as reported inDing and Cai,
2007)

Song et al.,2003

Chamber

AnnualNahlik andMitsch,2010

Chamber

AnnualSong et al.,
2003

Sanjiang Plain, NE
China

Intermittent

289

Chamber(as reported inDing and Cai,
2007)

Temperate

Naturalwetlands,
riparianGeorgia, USA

Intermittent

226

Chamber

AnnualPulliam,
1993

Temperate

Naturalwetlands,
marshesSanjiang Plain, NE
China

Intermittent

225

Chamber

AnnualHuang etal., 2010

Temperate

Naturalwetlands,
marsh

Sanjiang Plain, NE
China

Intermittent

58

Chamber

AnnualSong et al.,2009

Temperate

Naturalwetlands,
shrub swamp

Sanjiang Plain, NE
China

Intermittent

3Chamber

AnnualSong et al.,2009

Temperate

Naturalwetlands,
swampsMean daily

Bartlett andHarriss,
1993

Temperate

Naturalwetlands,
marshes

Mean daily

Bartlett andHarriss,
1993

Temperate

Naturalwetlands,
floodplains

GlobalIntermittent

72

Chamber

Mean daily

Bartlett andHarriss,
1993

Temperate

Naturalwetlands

Continental USA

unspecified

76

Chamber, EC

AnnualBridgham etal., 2006

AnnualNahlik andMitsch,2011

AnnualNahlik andMitsch,2011

Mean daily

Bartlett andHarriss,
1993

Mean daily

Bartlett andHarriss,
1993

Temperate

TropicalTropicalNaturalwetlands,
rainforest
swamp
Naturalwetlands,
alluvial
marsh

TropicalNaturalwetlands,
swampsTropicalNaturalwetlands,
marshes

5.24

GlobalGlobal

Costa Rica

Costa Rica

GlobalGlobalIntermittent

Intermittent

ContinuousIntermittent

Intermittent

Intermittent

113

105

2930

3500

297

419

Chamber

Chamber

Chamber

Chamber

Chamber

Chamber

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TropicalNaturalwetlands,
floodplains

GlobalTropicalNaturalwetlands,
floodplains

Amazon, Upper
Negro Basin

TropicalNaturalwetlands,
floodplains

Pantanal, Brazil(Arara-Azul)

TropicalNaturalwetlands,
floodplains

Pantanal, Brazil(Bau)

TropicalNaturalwetlands,
floodplains

Pantanal, Brazil(Sao Joao)

TropicalNaturalwetlands,
floodedforests

TropicalIntermittent

Intermittent

Intermittent

Intermittent

328

Chamber

Mean daily

54

Chamber,Ebullition
funnelAnnualBelger etal., 2011

Mean daily

Marani andAlvala,2007

Mean daily

Marani andAlvala,2007

Chamber

Mean daily

Marani andAlvala,2007

Chamber(as reported in
Melack et al.,
2004)

516

1033

510

Chamber

Chamber

AnnualSolimoes/Amazon
floodplain

Intermittent

567

AnnualSolimoes/Amazon
floodplain

Intermittent

184

Chamber(as reported in
Melack et al.,2004)

Melack andForsberg,
2001
Melack andForsberg,
2001

AnnualRosenqvist
et al., 2002

Jau River basin
floodplains/Amazon

Intermittent

306

Chamber(as reported in
Melack et al.,2004)

TropicalNaturalwetlands,
floodplains

Mojosbasin/Amazon

Intermittent

948

Chamber

AnnualMelack etal., 2004

TropicalNaturalwetlands,
floodplains

Roraima/ Amazon

Intermittent

1341

Chamber

AnnualMelack etal., 2004

TropicalNaturalwetlands,
floodplains

BananalIntermittent

954

Chamber

AnnualMelack etal., 2004

TropicalNaturalwetlands,
floodplains

OrinocoIntermittent

951

Chamber

AnnualMelack etal., 2004

TropicalNaturalwetlands,
floodplains

Pantanal

Intermittent

949

Chamber

AnnualMelack etal., 2004

Solimoes/Amazon
floodplain

Continuous&Intermittent

404

Chamber

AnnualMelack etal., 2004

TropicalTropical

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830
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833
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836

Naturalwetlands,
aquatic
macrophytes
Naturalwetlands,
floodedforests

Intermittent

Bartlett andHarriss,
1993

Naturalwetlands,
floodedforest,

The climate region with the greatest number of studies is the temperate region, including natural andcreated/rewetted wetlands, and sites under continuous inundation and intermittent inundation. We tested for
differences in CH4 emission factors between wetland types (natural vs. created/rewetted) and hydrologic regime(continuous vs. intermittent inundation) using paired Student’s t-test, two-tailed, at a significance level of α=0.05
to: 1) determine whether it is valid to include studies of natural wetlands in the development of CH4 emission
factors from created/rewetted wetlands, and 2) determine whether there is a significant difference in CH4emission between continuously and intermittently inundated wetlands.

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There is no significant difference in the CH4 emissions for natural vs. created/rewetted wetlands located intemperate regions (Table 5A2.2; t-test value = 0.24). Therefore the inclusion of studies of natural wetlands in thedevelopment of the CH4 emission factors for created/rewetted wetlands on IWMS is valid for temperate regions.
There are not enough studies on created/rewetted wetlands on IWMS in the boreal or tropical regions to do thesame analysis; we make the assumption that there is similarly no significant difference between CH4 emissions
from natural and created/rewetted wetlands in boreal or tropical regions, and thus we include studies of natural
wetlands in the development of the CH4 emission factors.

845
TABLE 5A.2.2
CH4 EMISSIONS FROM TEMPERATE, CREATED/REWETTED WETLANDS AND NATURAL WETLANDS WITH IWMS
Climate region
Temperate

Wetland type

Mean CH4
emission(kg CH4 ha-1 yr-1)

Standard
deviation

95% confidence
intervalA

Number ofstudiesCreated/Rewetted

153

160

±148

7

Natural

136

99

±83

8

Note: Values are derived from studies of temperate wetlands listed in Table 5A.2.1.
A The 95% confidence interval is calculated from the mean, standard deviation, and the critical values of t distribution according to the degrees of freedom.

846
847
848
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850

There is a significant difference in CH4 emissions for temperate region wetlands (created/rewetted and natural
wetlands are combined) under the two hydrologic regimes (Table 5A2.2; t-test value = 6.47, p<0.0001). Thishighlights the importance of period of inundation in annual CH4 emission (Table 5A.2.3). The development ofcountry-specific emission factors that incorporate period of inundation will reduce uncertainties.

851
TABLE 5A.2.3
CH4 EMISSIONS FROM TEMPERATE, REWETTED, CREATED AND NATURAL WETLANDS WITH IWMS, STRATIFIED BY PERIOD OFINUNDATION

Climate region
Temperate

Annualperiod ofinundation

Mean CH4 emission(kg CH4 ha-1 yr-1)

Standard
deviation

95% confidence
intervalA

Numberof studies

Continuous

572

191

±125

5

Intermittent

126

108

±75

14

Note: Values are derived from studies of Temperate wetlands listed in Table 5A.2.1.
A The 95% confidence interval is calculated from the mean, standard deviation, and the critical values of t distribution according to the degrees of freedom.

852
853
854

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Appendix 5a.1 Future methodological development

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Lands with IWMS occupy significant areas in some countries and are important carbon stock compartments.
Conversion of this land to other uses and management practices potentially affect these stocks. However, at thetime of preparation of this supplement, except for changes in SOC stocks and CH4 emissions for rewetted/createdwetlands on lands with IWMS, and changes in SOC stocks as a result of long-term cultivation and rewetting on
Croplands with IWMS, little information was available to provide emission factors specific to different land-uses
and management practices, or to derive emission factors for N2O.

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Particular effort should be employed to differentiate multiple uses on lands with IWMS (e.g., wetland forest,
wetland grasslands) for future methodological improvements. A good example of the methodological approachnecessary for this task can be found in the United States Fish and Wildlife Service Report to the Congress (Dahl,
2011). This document describes how wetland inventories have been made in the United States and, although notproviding figures for SOC stock changes, gives reference for future work to obtain such data with the National
Wetland Condition Assessment (NWCA), with methods described in detail at www.epa.gov/wetlands/survey.
Another example of a methodological approach for assessing carbon stocks and GHG fluxes at a national level isfound in a United States Geological Survey Scientific Investigations Report 2010 (Zhu et al., 2010). While thisdocument describes SOC stock changes and GHG emissions from managed and unmanaged lands, it may serve
as a useful example for a national-level carbon assessment. Synthetically, surveys to quantify the areas of landon IWMS under different land-use and management practices in conjunction with carbon pool quantification
allows the future use of general equations for carbon stock-changes described in the 2006 IPCC Guidelines.

874
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876

Other databases are available that have flux information (mainly CO2 measured with the eddy covariancetechnique) at the ecosystem level, including IWMS (e.g., www.ghg-europe.eu, fluxnet.ornl.gov,
ameriflux.ornl.gov, www.tern-supersites.net.au, fluxnet.ccrp.ec.gc.ca).

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New research is needed to fill a number of gaps for IWMS. Additional studies are needed to evaluate the effectof IWMS conversion on SOC stock changes following conversion to Grassland, Forest Land, Settlements andOther Land. Moreover, new research is needed to understand the effect of IWMS conversion on other carbon
stocks (biomass, dead organic matter) as well as CH4 and N2O fluxes. Although we were able to develop
guidance for IWMS CH4 fluxes for some climate regions, specific guidance for climate and region combinations
would improve our estimates of CH4 fluxes. New research assessing N2O fluxes following conversion of IWMS
to other land-uses, especially Cropland, would add considerably to our ability to assess GHG impacts anddevelop Tier 2 methods for GHG fluxes. N2O emissions from IWMS are typically very low, unless there is asignificant input of organic or inorganic nitrogen from runoff. Such inputs typically result from anthropogenic
activities such as agricultural fertilizer application (Hefting et al., 2006; Phillips and Beeri, 2008; DeSimone etal., 2010), or Grassland management (Chen et al., 2011; Oates et al., 2008; Liebig et al., 2012; Jackson et al.,2006; Holst et al., 2007; Walker et al., 2002). The review of the current literature suggests there is insufficient
data to provide robust emission factors and methodology to estimate N2O emissions from IWMS at this time. We
suggest that N2O emissions be more thoroughly addressed in future updates of this guidance as research on this
topic progresses. For future methodological improvement of N2O emission factors, it is important to avoid
double-counting N2O emissions already accounted for properly according to 2006 IPCC Guidelines, Chapter 11.

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Fully functional models that consider the influence of changes in hydrology on carbon cycling and GHG fluxes
cannot be developed or tested until more databases are available for IWMS. Process-based models like WetlandDNDC (Zhang et al., 2002) have substantial capabilities but have not been tested or calibrated across IWMS.
Future model testing and development on IWMS could lead to Tier 3 approaches for IWMS.

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