Chapter 5: Inland Wetland Mineral Soils

CHAPTER 5

INLAND WETLAND MINERAL SOILS

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

Lead Authors
Randall K. Kolka (USA), Ayaka W. Kishimoto-Mo (Japan), Rodney A. Chimner (USA) andYusuf Serengil (Turkey)

Contributing Authors
Stephen Ogle (USA) and Nalin Srivastava (IPCC TFI TSU)

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

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Chapter 5: Inland Wetland Mineral Soils

Contents

5 Inland Wetland Mineral Soils ............................................................................................................................... 5
5.1

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

5.2

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

5.2.1

CO2 emissions and removals....................................................................................................... 9

5.2.1.1

Biomass and dead organic matter ............................................................................................... 9

5.2.1.2

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

5.2.2

CH4 emissions from managed lands with IWMS...................................................................... 17

5.2.2.1

Choice of method ...................................................................................................................... 17

5.2.2.2

Choice of emission factors ........................................................................................................ 18

5.2.2.3

Choice of activity data .............................................................................................................. 18

5.2.2.4

Uncertainty assessment ............................................................................................................. 19

5.3

Land converted to a new land-use category ............................................................................... 19

5.3.1

CO2 emissions and removals..................................................................................................... 19

5.3.1.1

Biomass and dead organic matter ............................................................................................. 19

5.3.1.2

Soil carbon ................................................................................................................................ 20

5.3.2

CH4 emissions ........................................................................................................................... 21

5.3.2.1

Choice of method and emission factors .................................................................................... 21

5.3.2.2

Choice of activity data .............................................................................................................. 21

5.3.2.3

Uncertainty assessment ............................................................................................................. 21

5.4

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

5.4.1

Completeness ............................................................................................................................ 21

5.4.2

Reporting and Documentation .................................................................................................. 21

Annex 5A.1

Estimation of default stock change factors for long-term cultivated Cropland and rewettingwith Inland Wetland Mineral Soil carbon emissions/removals.................................................. 23

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 ........................................................... 24

Appendix 5a.1

Future methodological development .......................................................................................... 29

References ............................................................................................................................................................. 30

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Equations
Equation 5.1

Annual CH4 emissions from rewetted and created wetlands on managed lands
with IWMS......................................................................................................................... 17

TablesTable 5.1

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

Table 5.2

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

Table 5.3

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

Table 5.4

Default emission factors for CH4 from managed lands with IWMS where water table levelhas been raised ................................................................................................................... 18

Table 5A.1.1 Studies used for the derivation of default SOC stock change factors................................ 23
Table 5A.2.1 CH4 emissions from restored and created wetlands with IWMS where water table levelhas been raised, and natural wetlands, used to derive default value for EFCH4 ................. 24
Table 5A.2.2 CH4 emissions from temperate, created/rewetted wetlands and natural wetlands with
IWMS................................................................................................................................. 27
Table 5A.2.3 CH4 emissions from temperate, rewetted, created and natural wetlands with IWMS,
stratified by period of inundation ....................................................................................... 28

Boxes

5.4

Box 5.1

Distribution of Wetland Mineral Soils ................................................................................ 7

Box 5.2

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

Box 5.3

Example Calculations for SOC Stocks in Long-term Cultivated Croplands with Inland
Wetland Mineral Soils, and Rewetting of Long-Term Cultivated Croplands with Inland
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Chapter 5: Inland Wetland Mineral Soils

5 INLAND WETLAND MINERAL SOILS
5.1

INTRODUCTION

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). Information on Tier 1 default methods for Wetland Mineral
Soil (WMS) 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.
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.
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) 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 Box 5.1 of this Chapter), or reservoirs.
Guidance on methane (CH4) emissions from rice cultivation on IWMS is given in Chapter 5, Volume 4 of the2006 IPCC Guidelines. Guidance on carbon stock changes in Land Converted to Flooded Land1 with IWMS isgiven in Chapter 7, Volume 4 of the 2006 IPCC Guidelines2. This supplement does not update this guidance.
This chapter supplements guidance and methodologies provided in the 2006 IPCC Guidelines for emissions andremovals of carbon dioxide (CO2), and emissions of CH4, and provides additional information to be used in theapplication of the methodologies. Review of the current literature suggests there is insufficient data to provide
robust emission factors and methodology to update the guidance on nitrous oxide (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.
This chapter updates the 2006 IPCC Guidelines for:

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; and

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

This chapter gives new guidance not contained in the 2006 IPCC Guidelines by:1

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.

2

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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

providing new default SOC stock change factors for land-use (FLU) for rewetting of drained IWMS classified
as Cropland; and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 that CH4 emissions from wetlands created for the
purpose of wastewater treatment are addressed in Chapter 6 of this supplement).

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

Settlements

Updated SOCREF for IWMS

All land-use
conversions

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

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

Land Conversion to a New Land-use Category
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.
4
D Guidance on CH emissions from managed lands with IWMS does not apply to Flooded Land.
4

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Chapter 5: Inland Wetland Mineral Soils

BOX 5.1
DISTRIBUTION OF 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 the world’s WMS across climate
regions are as follows: boreal (moist plus dry): 2.07%; tropical moist: 0.67%; cool temperatemoist: 0.63%; tropical wet: 0.61%; polar (moist plus dry): 0.60%; and 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 of landscape 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 vascular plants, and/or bare ground.
Distribution of Gleysols (Wetland Mineral Soils; source: http://www.isric.org).

Dominant

AssociatedInclusions

Miscellaneous lands
FAO-GIS, February 1998

One 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, the carbon stocks
and CO2, CH4 and N2O fluxes were not discussed (Shaw and Bryant, 2011). A broader review ofthe 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 have yetmeasured GHG emissions and removals from saline IWMS. At present, the lack of data on saline
IWMS prevents the determination of their default carbon stock changes or GHG emission factors.
Countries are therefore encouraged to seek country-specific data in order to estimate changes incarbon pools in, and emissions and removals from, managed saline IWMS.

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BOX 5.2
MANAGEMENT ACTIVITIES ON INLAND WETLAND MINERAL SOILS

Drainage of IWMS is a common practice in the preparation of land for agriculture, grazing, andforestry. Drainage leads to lower water levels, which increases both 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). The
hydrology of IWMS may be altered in many ways: by dredging of canals for navigation andditches through wetlands for flood control and to increase vegetation productivity (Mitsch andGosselink, 2007); by management of river-floodplain systems through levee construction,
channelization, and flow manipulation by dams (Dynesius and Nilsson, 1994); by irrigation
systems that lower water tables; and by water level control for wildlife management by dikes,
weirs, control gates, and pumps (Mitsch and Gosselink, 2007). Dams for hydroelectric generationand flood control can create riparian wetlands upstream and influence existing riparian wetlands byaltering the frequency and duration of flood pulses, which impacts sediment deposition andnutrient loading to wetlands (Brinson and Malvárez, 2002; Noe and Hupp, 2005, Nilsson and
Berggren, 2000).
Grazing on lands with IWMS within grassland or forest landscapes is widespread (Liu et al., 2009;
Oates et al., 2008; Yao et al., 2010). Forest management activities on wetlands with forest canvary in management intensity depending on the silvicultural system. The intensity may range fromselective cutting treatments to large area clearcuts. There is currently not enough information
available about the impacts of grazing or forest management activities on carbon stock changes or
GHG emissions on lands with IWMS to allow us to provide new guidance.
One specific management activity that occurs on managed lands with IWMS is “rewetting”, wherelands with IWMS that were previously drained are subsequently rewetted by raising the watertable level to pre-drainage conditions. Active approaches to rewetting include the removal of draintiles, filling or blocking of drainage ditches, breaching levees, removal of river dams andspillways, 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 agriculturallands 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, wherelands are artificially inundated for the purposes of supporting a wetland ecosystem (Aber et al.,2012). Wetlands are created for various purposes such as water-quality enhancement (treatment ofwastewater, stormwater, acid mine drainage, agricultural runoff; Hammer, 1989), flood
minimization, and habitat replacement (Mitsch et al., 1998). Wetlands may be createdunintentionally when regulation of river flows (i.e. installation of large dams) results in periodic
inundation of lands that did not experience inundation prior to regulation (Chen et al., 2009; Yanget al., 2012). Wetland creation and rewetting of drained soils are common activities in response tosignificant wetland loss and degradation on a global scale (Mitsch et al., 1998). There is a great
potential for increasing carbon storage by the rewetting of wetlands (Euliss et al., 2006; Bridgham
et al., 2006). Rewetted wetlands may also have higher emissions of CH4, however, potentially
offsetting the increased carbon storage (Bridgham et al., 2006), although recent studies haveshown that created and rewetted wetlands can be net carbon sinks, even after accounting for CH4
emissions (Badiou et al., 2011; Mitsch et al., 2012).

5.2

LAND REMAINING IN A LAND-USE
CATEGORY

The 2006 IPCC Guidelines define “land remaining in a land-use category” as those lands that have notundergone any land-use conversion for a default period of at least 20 years. 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 organic matter), and nonCO2 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 reference stocks, SOC stockchange factors, and non-CO2 emissions from managed lands with IWMS.

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5.2.1

CO 2 emissions and removals

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.
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.

5.2.1.1

B IOMASS AND DEAD ORGA NIC MATTER

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, thechanges 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.

CHOICE OF METHOD AND EMISSION/REMOVAL FAC TORSAs explained in the 2006 IPCC Guidelines, inventories can be developed using Tier 1, 2 and 3 methods. The
decision trees have been provided in the 2006 IPCC Guidelines to guide the selection of the 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). The Tier 1 methods use the default emission factors along with parameters
relating to biomass and dead organic matter provided for specific land-use categories. These will also apply to
managed lands with IWMS in any of the land-use categories. For lower Tier methods it may be assumed thatwetland vegetation does not have substantially different biomass carbon densities than upland vegetation (e.g.
Bridgham et al., 2006). However, if country-specific data is available, it is good practice to use that data toestimate biomass carbon densities. There is currently no robust scientific information to support development ofemission factors for biomass and dead organic matter for specific management activities, such as drainage oflands with IWMS, rewetting of drained IWMS, or wetland creation. If there are reliable data for rates of biomass
and/or dead organic matter change upon drainage or rewetting/wetland creation, then country-specific estimates
may be derived using a Tier 2 method.

CHOICE OF ACTIVITY DATAFor 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. The total areas
should be determined according to the Approaches outlined in Chapter 3 of the 2006 IPCC Guidelines, andshould be consistent 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 accomplishedby overlays of land-use onto 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 wider scales where moredetailed soil information is lacking. Although no organisation 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 organisations,or other government sources. In addition, organisations such as the Society for Ecological Restoration(http://www.ser.org), the 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.
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 ASSESSME NT
Sources of uncertainty for the 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. Specific recommendations on how to reduce
uncertainties are included in the appropriate land-use category chapter in the 2006 IPCC Guidelines under which
managed lands with IWMS are classified.

5.2.1.2

S OIL CARBON

Soil carbon stocks in managed IWMS are primarily influenced by drainage and other management practices in
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 harvesting in forests that are prone to paludification(Lavoie et al., 2005), and the management of river-floodplain systems through the construction of dams, levees,
and river channelization which can disconnect floodplains from hydrologic interaction with rivers (Poff et al.,1997), thus reducing sediment deposition rates in floodplains (Hupp, 1992; Kleiss, 1996). Only a small numberof studies, however, have quantified the impacts of hydrologic alteration on soil carbon accumulation rates in
IWMS in floodplains (Noe and Hupp, 2005; Cabezas et al., 2009). Therefore, it is not possible to develop robust
emission factors relating to the impacts of hydrologic alteration on soil carbon stocks of IWMS in floodplains at
this time. Similarly, very little information is available on the impacts of other common management practices,such as grazing, on IWMS soil carbon stocks. Therefore, guidance provided in this chapter is largely based upon
and updates the guidance provided in the 2006 IPCC Guidelines.
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 is provided in Section 2.3.3, Chapter 2, Volume 4 of the 2006 IPCC Guidelines andshould be used along with the 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:

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

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

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 that is affected by changes in relevant management practices atthe beginning and end of the inventory time period. Two assumptions are made for mineral soils (see details in
Section 2.3.3.1, Chapter 2, Volume 4 of the 2006 IPCC Guidelines): (i) Over time, SOC reaches a spatiallyaveraged, stable value that is 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 onto suitable climate andsoil maps.

CHOICE OF METHOD
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.

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Chapter 5: Inland Wetland Mineral Soils

Tier 1The Tier 1 estimation method for mineral soils in land remaining in a land-use category, including IWMS, isbased on changes in SOC stocks over a finite transition period following such changes in management that
impact the SOC. Equation 2.25, Chapter 2, Volume 4 of the 2006 IPCC Guidelines (∆Cmineral=(SOC0-SOC(0-T))/D;
see the 2006 IPCC Guidelines for full equation) is used to estimate change in SOC stocks in mineral soils by
subtracting the SOC stock in the last year of an inventory time period (SOC0) from the C stock at the beginningof the inventory time period (SOC(0 –T)) and dividing by the time dependence of the stock change factors (D).
SOC stocks are estimated for the beginning and the end of the inventory time period using default reference
carbon stocks (SOCREF) (Table 5.2) and default stock change factors (FLU, FMG, FI), based on the land use (LU),
the management regime (MG) and the 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 region and soil type. The Tier 1 assumptions forcarbon 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.

Tier 2
For Tier 2, the same basic equations are used as in Tier 1 (Equation 2.25 in Chapter 2, Volume 4 of the 2006
IPCC Guidelines), but country-specific information is incorporated to improve the accuracy of the stock change
factors, reference SOC stocks, climate regions, soil types, and/or land management classification systems.

Tier 3Tier 3 approaches may use empirical, process-based or other types of models as the basis for estimating annual
carbon stock changes. Examples include the Century ecosystem model (Parton et al., 1987, 1994, 1998; Ogle etal., 2010), and the Wetland-DNDC model (Zhang et al., 2002). Estimates from models are computed using
equations that estimate the net change in soil carbon. Key criteria in selecting an appropriate model include its
capability to represent all of the relevant management practices/systems for the land-use category; model inputs(i.e. driving variables) that 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).
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.

CHOICE OF EMISSION F ACTORS
Tier 1
Table 5.2 gives updated default reference SOC stocks (SOCREF) for IWMS3. Inventory compilers should use thestock change factors provided in the appropriate chapters for 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.

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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Chapter 5: Inland Wetlands Mineral Soils

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

Standard
deviation

Error (95%
confidence
intervalB)

Number of sites

116

94

±99

6

Cold temperate, dry

87

C

n/a

D

n/a

D

n/aD

Cold temperate, moist

128

55

±17

42

Warm temperate, dry

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

Climate region
BorealA Batjes (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 compared to the databases
used in the 2006 IPCC Guidelines SOC stocks estimate.
B The 95% confidence interval is calculated from the mean, standard deviation, and the critical values of t distribution according to the degrees of freedom.
C No revised estimate was presented in Batjes (2011); values are from Table 2.3, Chapter 2, Volume 4 of the 2006 IPCC Guidelines .
D ”n/a” indicates that information is not available.

The updated SOCREF values for WMS presented in Table 5.2 for WMS should be used for calculating SOC stockchanges in IWMS when soils are classified as Wetland Soils, for land remaining in a land-use category in thefollowing sections of the 2006 IPCC Guidelines:Forest Land (Chapter 4): Section 4.2.3, Tier 1;Cropland (Chapter 5): Section 5.2.3, Tier 1; and

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

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. Similarly, default stock change factors for land-use (FLU), input (FI), andmanagement (FMG) that apply to managed land with IWMS in the Grassland Remaining Grassland land-use
category are presented in Table 6.2, Chapter 6, Volume 4 of the 2006 IPCC Guidelines.
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 those values inTable 5.5 of Chapter 5 of Volume 4 of the 2006 IPCC Guidelines for temperate/boreal moist climate but lower
than the temperate/boreal dry climate values. Consequently, this update should reduce uncertainties associatedwith estimating soil carbon stock changes for IWMS in dry climates. The method and studies used to derive theupdated default stock change factor are provided in Annex 5A.1. The default time period for stock changes (D)is 20 years, and management practices are assumed to influence stocks up to 30 cm depth, although greater
depths can also be affected. As a result, for Tier 1 and 2 methods, SOC stocks for mineral soils are computed to adefault depth of 30 cm. Greater soil depth may be selected and used at Tier 2, if data are available.
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 naturalhydrology has been restored, and where crop production may or may not continue. Note that the factor applies toall climate regions, with the caveat that this value is likely to be more representative of rewetting activities intemperate and boreal 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
natural hydrology continues for a further 20 years and will reach the reference SOC stock level (SOCREF values
in Table 5.2) after 40 years. It is also important to note that the long-term cultivation factor is used for areas that

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Chapter 5: Inland Wetland Mineral Soils

have been drained and are cultivated for crop production. If the high water table is restored, i.e. in the case ofrewetted Cropland, then FLU for rewetting should be used for two sets of 20 year periods (i.e. 0–20 and 21–40
years).

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)

Temperature
regimeTemperate/
BorealBoreal,temperate,
and tropical

Rewetting(Years 21–40)

Moisture
regimeDry andmoist

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, forpredominantly
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 percentage 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 (FLU) for rewetting are used for two sets of 20-year periods (i.e. 0–20 and 21–40 years since rewetting).

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:

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



The new stock change factors for long-term cultivation and rewetting of Cropland with IWMS provided inthis supplement (Table 5.3) should be applied to Cropland Remaining Cropland with IWMS, taking accountof the following:(i)

The new stock change factor for land-use (FLU) for Cropland with IWMS under long-term cultivationin this supplement should 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.

(ii)

The stock change factors for land-use (FLU) for Cropland with IWMS subject to rewetting should be
used for Cropland Remaining Cropland according to the following: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 used for estimating the initial SOC stocks (SOC(0-T)) willcorrespond to the Cropland land use (long-term cultivated, perennial, etc.) and management andinput regimes prior to rewetting.

o

For the next set of 20 years (i.e. 21–40 years since the initial year of rewetting), FLU = 1 should 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 the rewetted Cropland land-use (FLU = 0.8) and management and input regimes at 20
years following rewetting.

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Chapter 5: Inland Wetlands Mineral Soilso

For the period longer than 40 years following the initial year of rewetting, FLU will remain 1. Thechanges in SOC stocks as a result of 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 in the 2006 IPCC Guidelines.

Box 5.3 shows an example calculation using the stock change factors for land use (FLU) for Cropland with
IWMS under long-term cultivation, and for Cropland with IWMS subject to rewetting.

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.

Tier 3
In a Tier 3 approach, constant stock change rate factors per se are less likely to be estimated in favour of variable
rates that more accurately capture land use and management effects. See Section 2.3.3.1, Chapter 2, Volume 4 ofthe 2006 IPCC Guidelines for further discussion.

CHOICE OF ACTIVITY DATA
At a minimum, activity data consist of areas of managed lands with IWMS remaining in a land-use category
stratified by land-use category, climate region, soil type, and management practices. In addition, the areas of
Cropland with IWMS subject to rewetting need to be stratified by time since rewetting (0–20 or 21–40 years
since rewetting) for the correct application of stock change factors. If the compiler does not have sufficient
information to disaggregate areas of rewetted Cropland with IWMS by the time since conversion, all rewetted
Cropland with IWMS areas can be assumed to be within 0–20 years of rewetting, and thus FLU = 0.8 could beapplied to the entire rewetted Cropland with IWMS. Total areas should be determined according to theapproaches outlined in Chapter 3, Volume 4 of the 2006 IPCC Guidelines, and should be consistent with thosereported 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 with overlays of land use on climate
and soil maps. In the case of using methods such as models, and/or data as proxies for estimation, clear andcomplete documentation is encouraged for transparency.

Tier 1The Tier 1 approach requires area of managed land on IWMS for each land-use category stratified by climate
region and soil type. As an initial approach, available land cover/land-use maps, either country-specific or basedon global datasets such as IGBP_DIS (http://daac.ornl.gov), can be joined with soil and climate maps (countryspecific, or global maps such as ISRIC, http://www.isric.org, or FAO, http://www.fao.org/home/en). A global
GIS database that shows the spatial distribution of generalized soil classes used for IPCC Tier 1 is available fordownload and use at http://isirc.org/data/ipcc-default-soil-classes-derived-harmonized-world-soil-data-base-ver11. The database is derived from the Harmonized World Soil Database and FAO soil classifications, andincludes 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 atnational and broader scales where more detailed soil information is lacking.
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 a Tier 1 approach. Although no organisation catalogues changes in area asa result of rewetted or created wetlands either nationally or globally, local activity data for rewetting of managed
lands with IWMS or the creation of wetlands may be obtained from agricultural, forestry, or natural resources
agencies, non-governmental conservation organisations, or other government sources. In addition, organisations
such as the Society for Ecological Restoration (http://www.ser.org), the 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.

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

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Chapter 5: Inland Wetland Mineral Soils

Tier 3Tier 3 approaches may include the use of empirical, process-based or other types of models and/or direct
measurement-based inventories. In this case more detailed data on climate, soils, and management practices areneeded, as compared 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), as well as climate, soil, biomass, and water table
position (Ogle et al., 2010; Zhang et al., 2002).

CALCULATION STEPS FO R TIER 1
The steps for estimating SOC0, SOC (0-T) and net soil organic carbon stock change per hectare for managed landwith IWMS for land remaining in a land-use category are as follows:
Step 1: Organize data into time series according to the years in which activity data were collected.
Step 2: Classify land into the appropriate management system in accordance with its respective land-use
category.
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).
Step 4: Assign a native reference SOC stock value (SOCREF) for IWMS from Table 5.2, based on climate region.
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 relating to land-use categories; an updated value for long-term cultivation FLU
is given in Table 5.3 for IWMS in Cropland.
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.
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.
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 and then dividing by the time dependence of the stockchange factors (D) which is 20 years for default factors. If an inventory time period is greater than 20 years, thendivide by the difference in the initial and final year of the time period.
Step 9: Repeat steps 2 to 8 if there are additional inventory time periods.

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BOX 5.3
EXAMPLE CALCULATIONS FOR SOC STOCKS IN LONG-TERM CULTIVATED CROPLAND WITH IWMS, AND
REWETTING OF LONG-TERM CULTIVATED CROPLAND WITH IWMS

Assume an area with a cold temperate, dry climate. A crop is newly cultivated on an IWMS. For
the first 20 years after the initiation of cultivation, the SOC will decrease linearly by 71% (see 0.71
as default value in Table 5.3) down to a depth of 30 cm. From Table 5.2, it can be seen that thereference SOC for this climate region is 87 tonnes C ha-1. After 20 years of cultivation, the amountof SOC will be 61.8 tonnes C ha-1 (87 tonnes C ha-1 x 0.71 = 61.8 tonnes C ha-1), which representsa loss of 25.2 tonnes C ha-1 over the 20 years, or 1.26 tonnes C ha-1 yr-1. After 20 years, it isassumed that the SOC is stable at 61.8 tonnes C ha-1.
If we take this same soil and rewet it following drainage for crop production, the SOC will be 80%of the reference condition after 20 years, or 69.6 tonnes C ha-1 (87 tonnes C ha-1 x 0.80 = 69.6
tonnes C ha-1). The increase from 61.8 tonnes C ha-1 (from calculation above) is 7.8 tonnes C ha-1
or 0.39 tonnes C ha-1 yr-1 for the first 20 years. From year 21–40, the SOC will increase anadditional 20% (1.0–0.8 from Table 5.3) so that at year 40 the SOC is at the reference level of 87
tonnes C ha-1 (Table 5.2). In the Tier 1 method, the SOC is assumed to accrue linearly from years
21–40. The difference between the SOC at year 20 (69.6 tonnes C ha-1) and year 40 (87.0 tonnes
C ha-1) is 17.4 tonnes C ha-1, thus the annual accrual rate is 0.87 tonnes C ha-1 yr-1 between years
21 and 40.

UNCERTAINTY ASSESSME NT
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 as a result ofdevelopment 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 different management activities, for example; this has been an issue since inventory
methods were first developed (Cowardin, 1982), and still continues even with advances in technology andremote sensing techniques (Arnesen et al., 2013). As mapping techniques tend to rely on vegetation and soils
information, defining the area of IWMS is especially difficult because their vegetation range from marsh toforested systems, and soils range from near organic to near non-wetland mineral. Moreover, the extent of areas
subject to water 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
and vegetation properties will remain consistent over time, even with interannual climate variability, and mappedareas should remain relatively unchanged.
For Tier 1, uncertainties are provided alongside the reference SOC stocks in Table 5.2, and stock change factors
in the respective 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, andcombined 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 need to apply a default level of uncertainty for the land area estimates (±50%). It isgood practice to apply country-specific uncertainty estimates to country-specific area estimates rather than use adefault level. Default reference SOC stocks and stock change factors for mineral soils can have inherently highuncertainties when applied to specific countries. The defaults represent globally averaged values of land-use andmanagement impacts or reference SOC stocks that may deviate 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 land
use 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, even

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Chapter 5: Inland Wetland Mineral Soils

at 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).
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 activities with a sufficient sample size to minimize uncertainty at the national scale.

5.2.2

CH 4 emissions from managed lands with IWMSManagement activities that alter the water table level on lands containing IWMS can impact CH4 emissions fromthose areas. Two common management activities that involve raising water table levels include the rewetting ofpreviously drained IWMS, and the creation of wetlands on wet or dry mineral soils. Both rewetting and wetland
creation are often undertaken as conservation efforts for habitat and wildlife. Studies have shown that raisingwater table levels on managed lands with IWMS, through rewetting and/or wetland creation, can increase CH4
emissions (Pennock et al., 2010; Badiou et al., 2011; Nahlik and Mitsch, 2010; Herbst et al., 2011; Yang et al.,2012). Here we provide guidance for estimating 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 a modeling study of global CH4 emissions, Spahni et al. (2011) suggest that
IWMS that are not inundated, but have 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.
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 the large spatial
variability, as well as to seasonal and interannual variability in the controlling factors such as water level andtemperature. 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 variations in topography (Ding et al.,
2003; Saarnio et al., 2009). In addition, there are very few studies into CH4 emissions from rewetted or createdwetlands 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 will necessarily havelarge uncertainties. Due to the relative lack of data on rewetted and created wetlands with IWMS, we haveincluded studies of CH4 emissions from natural wetlands on IWMS in the development of default emission
factors (see Annex 5A.2 for further details).

5.2.2.1

C HOICE OF METHOD

Tier 1CH4 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.

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

CH 4 IWMS   ( AIWMS  EFCH4  IWMS ) cc

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

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Chapter 5: Inland Wetlands Mineral Soils

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.

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 such as river discharge in the case of riparian wetlands, as well as evapotranspiration andprecipitation.

Tier 3
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
emissions, by facilitating transport from inundated soils to the atmosphere, and by providing a substrate for CH4
production. Possible methods to determine the importance of these drivers to CH4 emissions, and thus to 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).

5.2.2.2

C HOICE OF EMISSION FA CTORS

Tier 1The 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, as they were derived
from studies covering a range of inundation durations, therefore capturing a degree of variability in CH4emissions (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.

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

EFCH4-IWMS(kg CH4 ha-1 yr-1)

95% Confidence IntervalA

Number ofStudies

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 the t distribution, according to thedegrees of freedom. These are not expressed as a percentage of the mean.
B Bridgham et al. (2006)
C This study (Bridgham et al., 2006) is a synthesis of numerous studies; see publication for details.

5.2.2.3

C HOICE OF ACTIVITY DATAThe 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 organisation
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 the creation of wetlands may be obtained from agricultural,
forestry, or natural resources agencies, non-governmental conservation organisations, or other government
sources. In addition, organisations such as the Society for Ecological Restoration (http://www.ser.org), theGlobalRestoration
Network(http://www.globalrestorationnetwork.org),
Wetlands
International

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Chapter 5: Inland Wetland Mineral Soils(http://www.wetlands.org), and the Ramsar Convention on Wetlands (http://www.ramsar.org) may be used assources of information for rewetting and/or wetland creation projects. In addition to the above, Tier 2 and Tier 3
methods generally require the areas of managed lands with IWMS stratified by annual average water table level,
and the seasonal and/or interannual changes in inundation. For the development of country-specific emission
factors and models, areas may be further stratified by vegetation community composition, vegetation biomass,soil temperature, and previous land-use. 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
caused by 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.

5.2.2.4

U NCERTAINTY ASSESSMENT

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.

5.3

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 categoryspecific guidance (Chapters 2, Chapters 4-9, Volume 4) for estimating carbon stock changes in the carbon pools
and non-CO2 emissions from managed land on mineral soils for land converted to a new land-use category for allland-use categories. This chapter updates the guidance provided in the 2006 IPCC Guidelines 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.

5.3.1

CO 2 emissions and removals

The set of general equations used to estimate the annual carbon stock changes of carbon pools in land remaining
in a land-use category for managed lands with IWMS are given in Chapter 2, Volume 4 of the 2006 IPCC
Guidelines, and these will also apply to managed lands with IWMS for land converted to a new land-use
category.
Figure 1.3, Chapter 1, Volume 4 of the 2006 IPCC Guidelines presents a decision tree for the identification of
appropriate methodological Tier for the inventory of land converted to a new land-use category.

5.3.1.1

B IOMASS AND DEAD ORGA NIC MATTERThe 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 should be used.

CHOICE OF METHOD AND EMISSION/REMOVAL FAC TORSThe 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 should be used.

CHOICE OF ACTIVITY D ATA
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 should be used.

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Chapter 5: Inland Wetlands Mineral Soils

UNCERTAINTY
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 should be used.

5.3.1.2

S OIL CARBON

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

CHOICE OF METHOD
The guidance provided in Section 5.2.1.2 also applies to land 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 should be used.

CHOICE OF EMISSION/R EMOVAL FACTORSThe guidance provided in Section 5.2.1.2 also applies to all land 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:

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.



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

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

(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:oFor 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 used for estimating the initial SOC stocks(SOC(0-T)) should correspond to the land use, management and input regimes before the land-use
conversion.

o

For Cropland with IWMS subject to rewetting undergoing land-use conversion to any other landuse category, FLU = 1 should be used for a period of 21–40 years, or more than 40 years since thefirst year of rewetting activity respectively, along with relevant stock change factors corresponding
to the management and 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) should be
used to determine the final SOC stock (SOC0) along with relevant stock change factors
corresponding to the management and input regimes following the land-use conversion.

o

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

CHOICE OF ACTIVITY D ATA
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 the time since rewetting

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Chapter 5: Inland Wetland Mineral Soils(0–20 or 21–40 years since rewetting) for the correct application of stock change factors. If the compiler does nothave sufficient information to disaggregate the areas of rewetted Cropland with IWMS by the time sinceconversion, all the areas of rewetted Cropland with IWMS can be assumed to be within 0–20 years of rewetting,and therefore FLU = 0.8 may be applied to the entire rewetted Cropland with IWMS. The guidance provided in
Section 5.2.1.2 also applies to land converted to a new land-use category for managed lands with IWMS.

UNCERTAINTY
The guidance provided in Section 5.2.1.2 also applies to land 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 land converted toa new land-use category in the 2006 IPCC Guidelines should also be used.

5.3.2

CH 4 emissions

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

5.3.2.1

C HOICE OF METHOD AND EMISSION FACTORSThe guidance provided in Section 5.2.2 also applies to land converted to a new land-use category for managed
lands with IWMS.

5.3.2.2

C HOICE OF ACTIVITY DA TA

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 land converted to a new land-use category for managed lands
with IWMS.

5.3.2.3

U NCERTAINTY ASSESSMENT

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

5.4

COMPLETENESS, REPORTING AND
DOCUMENTATION

5.4.1

Completeness

It is good practice to disaggregate the types 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 that this separation is appliedconsistently throughout the reporting period.
Where guidance not provided for IWMS in this Chapter for some lands, some climates, some carbon pools, andsome GHGs, it is the result of a lack of relevant data that allow the development of emission factors. Countries
are encouraged to develop new research and accounting practices to fill gaps to better account for changes incarbon stocks and GHG emissions and removals from drained wetlands, rewetted wetlands, or created wetlands
on lands with IWMS.
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 also be consistent withthe generic methodologies described in Volume 4 of the 2006 IPCC Guidelines and in this supplement. Chapter
6, Volume 1 of the 2006 IPCC Guidelines and Chapter 7 of this supplement provide general guidance on theissues concerning Quality Assurance and Quality Control (QA/QC).

5.4.2

Reporting and Documentation

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

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Chapter 5: Inland Wetlands Mineral Soils

EMISSION FACTORSThe scientific basis for 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.

ACTIVITY DATA
Sources of all activity data used in the calculations including data sources, databases and soil map references,
should be recorded, as well as communications with industry subject to any confidentiality considerations. This
documentation should include the frequency of data collection and estimation, estimates of accuracy andprecision, and reasons for any significant changes in emission levels.

TREND ANALYSIS
Any significant fluctuations in emissions between years should be explained. A distinction should be madebetween changes in activity levels and changes in emission factors, parameters and methods from year to year,
and the reasons for these changes documented. If different emission factors, parameters and methods are used for
different years, then the reasons for this should be explained and documented.

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Chapter 5: Inland Wetland Mineral Soils

Annex 5A.1

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

Default stock change factors that were computed using a dataset of experimental results for land use are provided
in Table 5.3. The land-use factor for long-term cultivation represents the loss of SOC that occurs after 20 yearsof continuous cultivation. The rewetting factor represents the effect of the restoration of natural hydrology ofcultivated 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 up to 40 years. Experimental data (citations listed below, and provided in the list of references) wereanalysed in linear mixed-effects models, accounting for both fixed and random effects (Ogle et al., 2005). Fixed
effects included depth and the number of years since a management change. For depth, data were not aggregatedbut 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, despite those measurements being made on
the same plots. Consequently, random effects were used to account for the dependencies in times-series data andamong data points representing different depths from the same study. If significant, a country-level random
effect was used to assess an additional uncertainty associated with applying a global default value to a specificcountry. This is included in the default uncertainties. The long-term cultivation factor represents the average lossof SOC at 20 years or longer time period following cultivation of IWMS. Users of the Tier 1 method canapproximate 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 cultivated cropland, 20 and 40 years after the first yearof 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,
Montana, Iowa, USA

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, USA

LC

van Wesemael et al., 2010

Belgium

LC

Wang et al., 2012

Sanjiang Plain, China

LC, R

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Chapter 5: Inland Wetlands Mineral Soils

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

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 emissions 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 temperate
climate regions. Thus, studies of CH4 emission from natural IWMS were included to derive emission factors
from boreal and tropical regions, and to supplement the number of studies in 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 that noemissions occurred during cold seasons and/or by applying mean daily fluxes to part or all of the annual perioddepending on the climate region and/or specific recommendations made by the study authors.
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
ClimateregionBorealTemperate

Wetlandtype

Naturalwetlands
Restoredwetlands,
previous use
Cropland

Location

Annualperiod ofinundation

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

CH4 Flux
measurement
methodCanadaUnspecified

76

Chamber, EC

CanadaIntermittent

49

Chamber

CH4 Flux
reported

Reference

AnnualBridghamet al.,
2006

Mean daily

Badiou etal., 2011

AnnualTemperate

Temperate

Temperate

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

Temperate

Restoredwetland,previous use
Cropland

Temperate

Createdwetlands,
riparian

CanadaIntermittent

349

Chamber(modified for
diurnal variation
as stated instudy)

North Dakota, USA

Intermittent

142

Chamber

Mean daily

Gleason etal., 2009

North Carolina,
USA

Intermittent

7Chamber

AnnualMorse etal., 2012

Pennock etal., 2010

Annual (minus
Denmark

Intermittent

110

EC

emissions fromcattle on-site asstated in study)

Herbst etal., 2011

AnnualChina

Intermittent

13

Chamber(diffusive andebullitive fluxes
combined)

AnnualTemperate

Createdwetlands

Ohio, USA

Continuous

402

ChamberTemperate

Naturalwetland,marsh

Nebraska, USA

Continuous

800

EC

5.24

(mean of two
different years
from same site)

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

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Chapter 5: Inland Wetland Mineral Soils

TABLE 5A.2.1(CONTINUED)
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
Annualperiod ofinundation

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

Continuous

468

CH4 Flux
measurement
methodCH4 Flux
reported

Chamber

AnnualClimateregionWetlandtype

Temperate

Naturalwetlands,
marshes

Temperate

Naturalwetlands,
Carex
marshes

Temperate

Naturalwetland,riparian

Temperate

Naturalwetlands,
Deyeuixa
marshesSanjiang Plain, NE
China

Intermittent

289

Temperate

Naturalwetlands,
riparianGeorgia, USA

Intermittent

Temperate

Naturalwetlands,
marshesSanjiang Plain, NE
China

Temperate

Naturalwetlands,
marsh

Temperate

Naturalwetlands,
shrub swamp

Temperate

Naturalwetlands,
swampsGlobalIntermittent

113

Chamber

Mean daily

Temperate

Naturalwetlands,
marshesGlobalIntermittent

105

Chamber

Mean daily

Temperate

Naturalwetlands,
floodplains

GlobalIntermittent

72

Chamber

Mean daily

Temperate

Naturalwetlands

TropicalTropicalNaturalwetlands,
rainforest
swamp
Naturalwetlands,
alluvial
marsh

Location

Sanjiang Plain, NE
China

Reference

Ding andCai, 2007

AnnualSanjiang Plain, NE
China

Ohio, USA

Continuous

Continuous

434

758

Chamber

Chamber(as reported inDing and Cai,
2007)

Song etal., 2003

AnnualNahlik andMitsch,2010

AnnualChamber(as reported inDing and Cai,
2007)

Song etal., 2003

226

Chamber

AnnualPulliam,
1993

Intermittent

225

Chamber

AnnualHuang etal., 2010

Sanjiang Plain, NE
China

Intermittent

58

Chamber

AnnualSong etal., 2009

Sanjiang Plain, NE
China

Intermittent

3Chamber

AnnualSong etal., 2009

Continental USA

Costa Rica

Costa Rica

unspecified

ContinuousIntermittent

76

2930

3500

Chamber, EC

Chamber

Chamber

Bartlett
andHarriss,
1993
Bartlett
andHarriss,
1993
Bartlett
andHarriss,
1993

AnnualBridghamet al.,
2006

AnnualNahlik andMitsch,2011

AnnualNahlik andMitsch,20112013 Supplement to the 2006 IPCC Guidelines for National Greenhouse Gas Inventories: Wetlands

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Chapter 5: Inland Wetlands Mineral Soils

TABLE 5A.2.1(CONTINUED)
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
Annualperiod ofinundation

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

CH4 Flux
measurement
methodClimateregionWetlandtype

TropicalNaturalwetlands,
swampsGlobalIntermittent

297

Chamber

Mean daily

TropicalNaturalwetlands,
marshesGlobalIntermittent

419

Chamber

Mean daily

TropicalNaturalwetlands,
floodplains

GlobalIntermittent

328

Chamber

Mean daily

TropicalNaturalwetlands,
floodplains

Amazon, Upper
Negro Basin54

Chamber,Ebullition
funnelAnnualTropicalNaturalwetlands,
floodplains

Pantanal, Brazil(Arara-Azul)

Intermittent

516

Chamber

Mean daily

TropicalNaturalwetlands,
floodplains

Pantanal, Brazil(Bau)

Intermittent

1033

Chamber

Mean daily

TropicalNaturalwetlands,
floodplains

Pantanal, Brazil(Sao Joao)

Intermittent

510

Chamber

Mean daily

TropicalNaturalwetlands,
floodedforests

TropicalNaturalwetlands,
aquatic
macrophytes

TropicalNaturalwetlands,
floodedforests

Jau River basin
floodplains/Amazon

Intermittent

TropicalNaturalwetlands,
floodplains

Mojosbasin/Amazon

TropicalNaturalwetlands,
floodplains

LocationIntermittent

CH4 Flux
reported

AnnualSolimoes/Amazon
floodplain

Intermittent

567

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

AnnualReference
Bartlett
andHarriss,
1993
Bartlett
andHarriss,
1993
Bartlett
andHarriss,
1993
Belger etal., 2011
MaraniandAlvala,2007
MaraniandAlvala,2007
MaraniandAlvala,2007
MelackandForsberg,
2001
MelackandForsberg,
2001

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

306

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

Rosenqvist
et al.,
2002

Intermittent

948

Chamber

AnnualMelack etal., 2004

Roraima/ Amazon

Intermittent

1341

Chamber

AnnualMelack etal., 2004

TropicalNaturalwetlands,
floodplains

BananalIntermittent

954

Chamber

AnnualMelack etal., 2004

TropicalNaturalwetlands,
floodplains

OrinocoIntermittent

951

Chamber

AnnualMelack etal., 2004

5.26

Solimoes/Amazon
floodplain

Intermittent

184

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Chapter 5: Inland Wetland Mineral Soils

TABLE 5A.2.1(CONTINUED)
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
Location

Annualperiod ofinundation

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

TropicalNaturalwetlands,
floodplains

Pantanal

Intermittent

TropicalNaturalwetlands,
floodedforest,aquatic
macrophytes,
open water

Solimoes/Amazon
floodplain

Continuous&Intermittent

ClimateregionWetlandtype

CH4 Flux
measurement
methodCH4 Flux
reported

949

Chamber

AnnualMelack etal., 2004

404

Chamber

AnnualMelack etal., 2004

Reference

The climate region with the greatest number of studies is the temperate region, including natural andcreated/rewetted wetlands, and sites under continuous and intermittent inundation. We tested for differences inCH4 emission factors between wetland types (natural vs. created/rewetted wetlands under intermittent inundation)and hydrologic regime (continuous vs. intermittent inundation) using paired Student’s t-test, two-tailed, at asignificance level of α=0.05 to: 1) determine whether it is valid to include studies of natural wetlands in thedevelopment of CH4 emission factors from created/rewetted wetlands; and 2) determine whether there is asignificant difference in CH4 emission between continuously and intermittently inundated wetlands.
There is no significant difference in the CH4 emissions for natural vs. created/rewetted wetlands underintermittent inundation located in temperate regions (Table 5A2.2; t-test value = 0.24). Therefore the inclusion ofstudies of natural wetlands in the development of the CH4 emission factors for created/rewetted wetlands on
IWMS is valid for temperate regions. As there are not sufficient studies on created/rewetted wetlands on IWMS
in boreal or tropical regions to carry out the same analysis, we make the assumption that, as above, there is no
significant difference between the CH4 emissions from natural and created/rewetted wetlands in boreal or
tropical regions, and thus include studies of natural wetlands in the development of the CH4 emission factors.
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

7B

Natural

136

99

±83

8C

Note: All 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.
B The studies used to determine this value are listed in Table 5A.2.1: Altor and Mitsch, 2008 and Nahlik and Mitsch, 2010 (mean value for the same system determined by
two studies); Gleason et al., 2009; Pennock et al., 2010; Badiou et al., 2011; Herbst et al., 2011; Morse et al., 2012; and Yang et al., 2012.
C The studies used to determine this value are listed in Table 5A.2.1; Pulliam, 1993; Bartlett and Harriss, 1993 (n=3 wetland types); Song et al., 2003; Song et al., 2009 (n=2wetland types); Huang et al., 2010.

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 5A.2.3; t-test value = 6.47, p<0.0001). Thishighlights the importance of the period of inundation in annual CH4 emissions. Thus, the development ofcountry-specific emission factors that incorporate the period of inundation will reduce uncertainties.

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Chapter 5: Inland Wetlands Mineral Soils

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

5B

Intermittent

126

108

±75

14C

Note: All 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 the t distribution, according to the degrees of freedom.
B The studies used to determine this value are listed in Table 5A2.1; Kim et al., 1999; Song et al., 2003 (Carex marshes); Ding and Cai, 2007; Altor and Mitsch, 2008;
Nahlik and Mitsch, 2010.
C The studies used to determine this value are listed in Table 5A2.1; Pulliam, 1993; Bartlett and Harriss, 1993 (n=3 wetland types); Song et al., 2003 (Deyeuxia marshes);
Song et al., 2009 (n=2 wetland types); Huang et al., 2010; Badiou et al., 2011; Pennock et al., 2010; Gleason et al., 2009; Morse et al., 2012; Herbst et al., 2011; Yang etal., 2012.

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Chapter 5: Inland Wetland Mineral Soils

Appendix 5a.1 Future methodological development
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 can potentially affect these stocks. However, atthe time of preparation of this supplement, except for changes in SOC stocks and CH4 emissions in
rewetted/created wetlands 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 todifferent land uses and management practices, or to derive emission factors for N2O.
Particular effort should be made to differentiate between multiple uses on lands with IWMS (e.g. wetland forest
and wetland grasslands) for future methodological improvements. A good example of the methodologicalapproach necessary for this task can be found in the United States Fish and Wildlife Service Report to theCongress (Dahl, 2011). This document describes how wetland inventories have been made in the United Statesand, although not providing figures for SOC stock changes, gives reference for future work to obtain such datawith 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 is found in a United States Geological Survey Scientific Investigations Report(Zhu et al., 2010). This document describes SOC stock changes and GHG emissions from managed andunmanaged lands and it may serve as a useful example for a national-level carbon assessment. Surveys thatquantify the areas of land on IWMS under different land use and management practices, in conjunction withcarbon pool quantification, allow the future application of the general equations for carbon stock changes that aredescribed in the 2006 IPCC Guidelines.
Other databases are available that contain 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 and fluxnet.ccrp.ec.gc.ca).
New research is needed to fill a number of gaps for IWMS. Additional studies are needed to evaluate the effectsof IWMS land-use conversion on SOC stock changes following conversion to Grassland, Forest Land,
Settlements and Other Land. Moreover, new research is needed to understand the effect of IWMS conversion onother carbon stocks (biomass, dead organic matter) as well as CH4 and N2O fluxes. Although we were able todevelop guidance for CH4 fluxes from IWMS 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 and develop Tier 2 methods for GHG fluxes. N2O emissions from IWMS are typically very low,
unless there is a significant input of organic or inorganic nitrogen from runoff. Such inputs typically result fromanthropogenic activities such as agricultural fertilizer application (Hefting et al., 2006; Phillips and Beeri, 2008;
DeSimone et al., 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). A review of the current literature suggests there isinsufficient data to provide robust emission factors and methodology to estimate N2O emissions from IWMS at
this time. We suggest that N2O emissions should be more thoroughly addressed in future updates to thisguidance, 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 Chapter 11,
Volume 4 of the 2006 IPCC Guidelines.
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 such as
Wetland-DNDC (Zhang et al., 2002) have substantial capabilities but have not been tested or calibrated acrossIWMS. Future model testing and development on IWMS could lead to development of Tier 3 approaches forIWMS.

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