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CHAPTER 5

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INLAND WETLAND MINERAL SOILS

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Coordinating Lead Authors

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

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Lead Authors

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

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Yusuf Serengil (Turkey)

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Contributing Authors

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Stephen Ogle (USA), Nalin Srivastava (IPCC)

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Contents

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Introduction ............................................................................................................................................. 4

5.1

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5.1.1

General background on Inland Wetland Mineral Soils and management activities ................... 5

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5.1.2

Reporting Inland Wetland Mineral Soils .................................................................................... 6

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5.2

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Land remaining in a land-use category ................................................................................................... 7
CO2 emissions and removals ...................................................................................................... 7

5.2.1

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5.2.1.1

Biomass and dead organic matter ............................................................................................... 7

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5.2.1.2

Soil carbon.................................................................................................................................. 821

CH4 emissions from managed lands with IWMS ..................................................................... 14

5.2.2

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5.2.2.1

Choice of method ..................................................................................................................... 14

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5.2.2.2

Choice of emission factors ....................................................................................................... 15

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5.2.2.3

Choice of activity data .............................................................................................................. 16

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5.2.2.4

Uncertainty assessment ............................................................................................................ 16

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5.3

Land converted to a new land-use category .......................................................................................... 16

5.3.1

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CO2 emissions and removals .................................................................................................... 16

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5.3.1.1

Biomass and dead organic matter ............................................................................................. 1629

5.3.1.2

Soil carbon................................................................................................................................ 17

5.3.2

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CH4 emissions .......................................................................................................................... 1831

5.3.2.1

Choice of method and emission factors .................................................................................... 18

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5.3.2.2

Choice of activity data .............................................................................................................. 1833

5.3.2.3

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

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5.4

Completeness, time series consistency, QA/QC, reporting and documentation.................................... 18

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5.4.1

Completeness............................................................................................................................ 18

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5.4.2

Developing a consistent time series.......................................................................................... 19

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5.4.3

Quality Assurance and Quality Control.................................................................................... 19

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5.4.4

Reporting and Documentation .................................................................................................. 20

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5.5

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Annex 5A.1
Estimation of default stock change factors for long-term cultivated cropland andwetland restoration with Wetland Mineral Soil C emissions/removals............................................................. 22

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Annex 5A.2
Estimation of CH4 emission factors for managed lands with Inland Wetland Mineral
Soils, or dry mineral soils, where the water table has been raised .................................................................... 23

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References ......................................................................................................................................................... 27

Future methodological development ..................................................................................................... 20

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Equations49

Equation 5.1 Annual CH4 Emissions from Restored and Created Wetlands on Managed Lands with IWMS ..... 1450

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Tables52

Table 5.1 Updated and new guidance provided in Chapter 5.................................................................................. 553
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Table 5.2 Default reference soil organic carbon stocks (SOCREF) for wetland mineral soilsa under native
vegetation (0-30 cm depth). .................................................................................................................................. 1055
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Table 5.3 Relative stock change factors for land-use (FLU) for long term cultivation on cropland with IWMS
(over 20 years) and wetland restoration of cropland with IWMS (over 20 years and 40 years) ........................... 1157
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Table 5.4 Default emission factors for CH4 from managed lands with IWMS where water table level has beenraised ..................................................................................................................................................................... 1559

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

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

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Table 5A.2.2 CH4 emissions from temperate restored, created and natural wetlands with IWMS, stratified byperiod of inundation .............................................................................................................................................. 25

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5.1

INTRODUCTION

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This chapter provides supplementary guidance for estimating and reporting greenhouse gas (GHG) emissions
and removals from managed lands with Inland Wetland Mineral Soils (IWMS) for all land-use categories.
Wetland mineral soils (WMS) are defined in 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 that are created or modified for
wastewater treatment are addressed in Chapter 6 (Constructed Wetlands – Wastewater Treatment) of thisSupplement.

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Mineral soils are described as all soils that are not classified as organic soils in Chapter 3 Annex 3A.5 of the2006 IPCC Guidelines. The 2006 IPCC Guidelines provide a default mineral soil classification for categorizing
mineral soil types based on the USDA taxonomy (USDA, 1999) in Figure 3A.5.3, and based on the World
Reference Base for Soil Resources Classification (FAO, 1998) in Figure 3A.5.4, where both classifications
produce the same default IPCC soil types. 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 ashaving restricted drainage leading to periodic flooding and anaerobic conditions (Chapter 2, Table 2.3, 2006
IPCC Guidelines). They can occur in any of the six land use categories.

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For the purposes of this Supplement, IWMS include those that have formed under restricted drainage, and may
or may not be artificially drained due to management activities. Artificial drainage is defined here as theremoval of free water from soils having aquic conditions to the extent that water table levels are changed
significantly in connection with specific types of land use (adapted from USDA, 1999). Additionally, guidance
provided in this chapter applies to IWMS that have been artificially drained and subsequently allowed to re-wet
for the purposes of “wetland restoration” and the artificial inundation of mineral soils for the purposes of“wetland creation”.

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This chapter supplements guidance and methodologies in the 2006 IPCC Guidelines for emissions and removalsof carbon dioxide (CO2), and emissions of methane (CH4), and provides additional information to be used inapplying the methodologies. This chapter should be read in conjunction with Volume 4 of the 2006 IPCC
Guidelines.

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This chapter updates the 2006 IPCC Guidelines for:

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Default reference soil organic carbon stocks (SOCREF) for IWMS under all climate regions (referring to2006 IPCC Guidelines Volume 4, Chapter 2, Table 2.3), to be used for Tier 1 methods in all six land-use
categories

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

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

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Providing new default SOC stock change factors for land-use (FLU) for wetland restoration on Cropland with
IWMS.

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Providing methodologies and emission factors for CH4 emissions from managed lands with IWMS under
any land-use category that have undergone wetland restoration, and from inland mineral soils that have beeninundated for the purpose of wetland creation (Note: CH4 emissions from wetlands created for the purposeof wastewater treatment are addressed in Chapter 6 of this Supplement).

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

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TABLE 5.1
UPDATED AND NEW GUIDANCE PROVIDED IN CHAPTER 5
IPCC Land-Use Category

Soil Organic
CarbonCH4 Emissions

Land Remaining in a Land-use Category
Forest Land

Updated
SOCREF for
IWMS

CroplandUpdated
SOCREF for
IWMS; SOC
stock change
factors forland-use (FLU)
for long-term
cultivation, andwetlandrestoration

Grassland

Updated
SOCREF for
IWMS

Settlements

EFCH4-IWMS for restored and created wetlands on
managed lands with mineral soils

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

Updated
SOCREF forIWMS;
SOC stockchange factors
for land-use(FLU) for longterm
cultivation, andwetlandrestoration

EFCH4-IWMS for restored and created wetlands on
managed lands with mineral soils*Existing guidance for managed lands that may have IWMS is provided in the 2006 IPCC Guidelines for: CO2, CH4, and N2O emissions
from rice cultivation (Croplands, Chapter 4), and CO2 and CH4 from Flooded Lands (reservoirs, impoundments; Appendix 3).

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5.1.1

General background on Inland Wetland Mineral
Soils and management activities

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Wetland mineral soils (WMS), including both coastal and inland WMS, are estimated to cover ~5.3% of theworld’s land surface, or 7.26 x 106 km2 (Batjes, 2010). The distribution of the world’s WMS across climate
regions are as follows: Boreal (Moist plus Dry): 2.07%, Tropical Moist: 0.67%, Cool Temperate Moist: 0.63%,
Tropical Wet: 0.61%, Polar (Moist plus Dry): 0.60%, Warm Temperate Moist: 0.23% (Batjes, 2010). Climate
regions having less than 0.20% WMS include Cool and Warm Temperate Dry, Tropical Dry, and Tropical
Montane.

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IWMS can occur in any of the six IPCC land-use categories (Forest Land, Cropland, Grassland, Wetlands,
Settlements and Other Land). For example, depending on the national definitions, a riverine wetland with trees
may be classified as a Forest Land, while a marsh may be used for grazing and be classified as Grassland. IWMS
are found in a variety of landscape settings, including basins, channels, flats, slopes, and highlands (Semeniukand 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 dominant vegetation community, and can
include trees, woody shrubs, emergent and non-emergent vascular plants, and/or bare ground.

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Globally, more than 50% of lands with IWMS have been converted to other land uses, mostly by drainage(Bridgham et al., 2006). Drainage of IWMS is a common practice in the preparation of land for agriculture.
grazing, and forestry. Drainage leads to lower water levels which affects decomposition and vegetation
productivity, and can significantly reduce IWMS carbon (C) stocks over time (Bedard-Haughn et al., 2006;

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Huang et al., 2010; Page and Dalal, 2011). Hydrology of IWMS may be altered due to dredging of canals andditches through wetlands for flood control, navigation and transportation, (Mitsch and Gosselink, 2007);
management of river-floodplain systems through levee construction, channelization, flow manipulation by dams
(Dynesius and Nilsson, 1994); and water level control for wildlife management by dikes, weirs, control gates,and pumps (Mitsch and Gosselink, 2007). Dams for hydroelectric generation and flood control severely affectriparian wetlands in both upstream and downstream directions by minimizing the frequency and duration offlood pulses, which has impacts on sediment deposition and nutrient loading to wetlands (Brinson and Malvárez,2002; Noe and Hupp, 2005), and on vegetation communities (Nilsson and Berggren, 2000).

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

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A specific management activity that occurs on managed lands with IWMS is wetland restoration, where lands
with IWMS that were artificially drained are “re-wetted” by raising the water table level to pre-drainage
conditions. Active approaches to wetland restoration include filling or blocking of drainage ditches, breachinglevees, removal of dams and spillways, and contouring the land surface to mimic natural topography; passive
approaches include the elimination of water controls and allowing natural flood events (Aber et al., 2012). The
re-wetting of managed lands with IWMS is common in the conversion of agricultural lands back to wetlands,
and may occur when active regulation of river hydrology is discontinued. A related management activity that
occurs on mineral soils (wet or dry) is wetland creation, where lands are artificially inundated for the purposes of
supporting a wetland ecosystem (Aber et al., 2012). Wetlands are created for purposes such as water-quality
enhancement (treatment of wastewater, stormwater, acid mine drainage, agricultural runoff; Hammer, 1989),
flood minimization, and habitat replacement (Mitsch et al., 1998). Wetlands may be created unintentionallywhen regulation of river flows (i.e. large dam installation) results in periodic inundation of lands that did notexperience inundation prior to regulation (Chen et al., 2009; Yang et al., 2012). Wetland creation and restoration
are common activities in response to significant wetland loss and degradation on a global scale (Mitsch et al.,1998). There is great potential for increased carbon storage from restoring wetlands (Euliss et al., 2006;
Bridgham et al., 2006). Restored wetlands may also have higher emissions of CH4, potentially offsetting
increased carbon storage (Bridgham et al., 2006), although recent studies have suggested that created andrestored wetlands can be net C sinks, after accounting for CH4 emissions (Badiou et al., 2011; Mitsch et al.,2012).

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A specific type of land containing IWMS, Saline IWMS, is not covered in this chapter. Saline IWMS are
generally defined as having salinity >5000 mg L-1 when wet (Shaw and Bryant, 2011). Also known as playas,pans, salt lakes, brackish wetlands, salinas, and sabkhas, these lands are important parts of arid landscapes acrossthe globe (Shaw and Bryant, 2011). In a recent review of the literature characterizing known information onpans, playas and salt lakes, carbon stocks and CO2, CH4 and N2O fluxes were not discussed (Shaw and Bryant,2011). A review of the broader literature on lands containing saline IWMS indicates that only two studies haveassessed soil C in saline IWMS (Bai et al. 2007; Rodriguez-Murillo et al. 2011), and no studies have measured
GHG fluxes from saline IWMS. At present the lack of data on saline IWMS prevents the determination ofdefault C stock changes or GHG emission factors. If country specific data is available, it is good practice to usethat data to estimate C pools in, and fluxes from, managed saline IWMS.

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5.1.2

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IWMS can occur in any of the six broad IPCC land-use categories. While the 2006 IPCC Guidelines do provide
generic definitions, countries use their own country-specific definitions for classifying all land areas into thesesix broad land-use categories. Consequently, managed land with IWMS may be classified into any of the six
broad land-use categories depending upon the national land-use classification system. Emissions and removals
for areas of managed land on with IWMS should be reported in the land-use category under which they areclassified, according to Volume 4 of the 2006 IPCC Guidelines. Note that a change in management practice may,or may not, be accompanied by land conversion.

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LAND REMAINING IN A LAND-USE
CATEGORY

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

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5.2.1

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

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

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5.2.1.1

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Guidance for changes in the carbon pools in biomass (aboveground, belowground) and dead organic matter(dead wood, litter) is provided in the 2006 IPCC Guidelines, and remains unchanged for land remaining in aland-use category for managed lands with IWMS in this Supplement. For managed lands with IWMS classified
as land remaining in a land-use category in Forest Land, Cropland, Grassland, Settlements, or Other Land,changes in biomass and dead organic matter are to be determined using the guidance provided in thecorresponding chapters (Chapters 4-9) in Volume 4 of the 2006 IPCC Guidelines. It can be assumed that wetland
vegetation does not have substantially different biomass carbon densities than upland vegetation (e.g. Bridgham
et al., 2006).

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CHOICE OF METHOD AND EMISSION/REMOVAL FACTORS

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As explained in the 2006 IPCC Guidelines, inventories can be developed using Tiers 1, 2 and 3 approaches. The
decision trees have been provided in the 2006 IPCC Guidelines to guide the selection of appropriate
methodological tiers for the estimation of changes in carbon stocks of biomass and dead organic matter (Volume
4, Chapter 2, Fig. 2.2 and Fig. 2.3). In general it is good practice to use higher Tier methods (Tiers 2 and 3) if
carbon stock changes in biomass or dead organic matter are key categories. Guidance on the choice ofemission/removal factors for change in biomass and dead organic matter for the six land-use categories are foundin the sections on biomass and dead organic matter for land remaining in a land use category in the appropriate
Chapter(s) in Volume 4 of the 2006 IPCC Guidelines: Forest Land (Chapter 4), Cropland (Chapter 5), Grassland(Chapter 6), Settlements (Chapter 8), and Other Land (Chapter 9). The Tier 1 methods will use the default
emission factors, and parameters relating to biomass and dead organic matter provided for specific land-use
categories. These will also apply to managed lands with IWMS in any of these land-use categories. Tier 2
methods will involve using country-specific emission factors and parameters along with activity data at suitabledisaggregation, while Tier 3 methods involve detailed modeling or measurement-based frameworks using highly
disaggregated data. There is no robust scientific information to support the development of emission factors forbiomass and dead organic matter for specific management activities such as drainage of lands with IWMS, or
wetland restoration and creation. If there are reliable data for rates of biomass and/or dead organic matter change
upon drainage or wetland restoration/creation, country-specific estimates may be derived using a Tier 2 method.

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CHOICE OF ACTIVITY DATA

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For Tier 1 methods, activity data consist of areas of managed lands with IWMS in land remaining in a land-use
category stratified by land-use category, climate region, soil type, and management practices. Total areas should
be determined according to approaches outlined in Chapter 3 of the 2006 IPCC Guidelines, and should beconsistent with those reported under other sections of the inventory. Stratification of land-use categories
according to climate region, based on default or country-specific classifications can be accomplished withoverlays of land-use on climate and soil maps. Although no organization catalogues changes in area as a result of
wetlands restored or created either nationally or globally, local activity data for restoration of managed lands

CO 2 emissions and removals

B IOMASS AND DEAD ORGANIC MATTER

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with IWMS or creation of wetlands may be obtained from agricultural, forestry, or natural resources agencies,
non-governmental conservation organizations, or other government sources. In addition, organizations such as
the Society for Ecological Restoration International (http://www.wer.org), Global Restoration Network(http://www.globalrestorationnetwork.org), Wetlands International (http://www.wetlands.org), and the Ramsar
Convention on Wetlands (http://www.ramsar.org) may be sources of information for wetland restoration projects.

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Higher tier methods may use activity data suitably stratified by criteria such as vegetation type (annual vs.
perennial species) and/or water table level and hydroperiod (continuously inundated vs. intermittently inundated).

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UNCERTAINTY ASSESSMENT

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

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5.2.1.2

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Soil C stocks in IWMS are influenced by changes in water level (drainage, re-wetting), management practices on
Cropland, Forest Land, and Grassland (including long-term cultivation, drainage to improve production, andgrazing), and wetland restoration 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 that can significantly change IWMS soil C stocks include management of river-floodplain systems
through the construction of dams, levees, and river channelization which can disconnect floodplains fromhydrologic interaction with rivers (Poff et al., 1997), reducing sediment deposition rates in floodplains (Hupp,
1992; Kleiss, 1996). Only a small number of studies, however, have quantified impacts of hydrologic alteration
on soil C accumulation rates in IWMS in floodplains (Noe and Hupp, 2005; Cabezas et al., 2009). Therefore it is
not possible to develop robust emission factors related to impacts of hydrologic alteration on soil C stocks of
IWMS in floodplains at this time. Similarly, very little information is available with regards to impacts of othercommon management practices, such as grazing, on IWMS soil C stocks. Therefore, guidance provided in this
Chapter is largely based on and updates the guidance in the 2006 IPCC Guidelines.

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

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Table 5.2 provides updated default soil organic carbon reference stocks (SOCREF) for IWMS (e.g. Wetland
soils) for use in any land-use category;

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Table 5.3 provides an updated stock change factor for land-use (FLU) associated with long term cultivationof Cropland with IWMS, and a new stock change factor for land use (FLU) for wetland restoration on
Cropland with IWMS.

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To account for changes in IWMS soil C stocks associated with changes in management on land remaining in aland-use category, countries need at a minimum, estimates of the area of managed land with IWMS in a landremaining in land-use category at the beginning and end of the inventory time period. If land-use andmanagement data are limited, aggregate data, such as FAO statistics on land-use (http://www.fao.org), can beused as a starting point, along with expert knowledge about the approximate distribution of land management
systems. Managed land with IWMS must be stratified according to climate regions, which can either be based on
default or country-specific classifications. This can be accomplished with overlays of land use on suitableclimate and soil maps.

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CHOICE OF METHOD

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

S OIL CARBON

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Tier 1The estimation method for mineral soils in land remaining in a land-use category, including IWMS, is based onchanges in soil organic C stocks over a finite period following changes in management that impact soil organic C.
Equation 2.25 (Chapter 2, 2006 IPCC Guidelines) is used to estimate change in soil organic C stocks in mineralsoils by subtracting the C stock in the last year of an inventory time period (SOC0) from the C stock at the
beginning of the inventory time period (SOC(0 –T)) and dividing by the time dependence of the stock change
factors (D). Soil organic C stocks (SOC) are estimated for the beginning and end of the inventory time periodusing default reference carbon stocks (SOCREF) and default stock change factors (FLU, FMG, FI ). In practice,country-specific data on land use and management must be obtained and classified into appropriate land
management systems, and then stratified by IPCC climate regions and soil types. The Tier 1 assumptions for C
stock changes in mineral soils in land remaining in a land-use category for specific land-use categories will also
apply to managed lands with IWMS in those land-use categories.

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Tier 2

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Tier 3

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A Tier 3 approach may also be developed using a measurement-based approach in which a monitoring network
is sampled periodically to estimate soil organic C stock changes. A much higher density of benchmark sites will
likely be needed 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.

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CHOICE OF EMISSION FACTORS

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Tier 1

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

Table 5.2 gives updated default reference SOC stocks (SOCREF) for IWMS1. Inventory compilers should use thestock change factors provided in the appropriate chapters addressing the six land-use categories (Chapters 4-9) inVolume 4 of the 2006 IPCC Guidelines in conjunction with the data in Table 5.2 for Tier 1 methods.

325

1

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

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TABLE 5.2
DEFAULT REFERENCE SOIL ORGANIC CARBON STOCKS (SOCREF) FOR WETLAND MINERAL SOILSA UNDER
NATIVE VEGETATION (0-30 CM DEPTH).
Climate Region

tonnes C ha-1

Error
(SD)

n

116

±94

6

Cold temperate, dry

87

B

±78

n/a

Cold temperate, moist

128

±55

42

Warm temperate, dry

74

±45

49

Warm temperate, moist

135

±101

28

Tropical, dry

22

±11

32

Tropical, moist

68

±45

55

Tropical, wet

49

±27

33

Tropical, montane

82

±73

12

BorealA

Batjes (2011) presents revised estimates of the 2006 IPCC Guidelines SOC stocks for wetland mineral soils (gleysols)
under natural vegetation based on an expanded version of the ISRIC-WISE database (Batjes, 2009) which contains 1.6
times the number of soil profiles of the databases used in the 2006 IPCC Guidelines SOC stocks estimate.

B

No revised estimate was presented in Batjes (2011); values are from Table 2.3 of the 2006 IPCC Guidelines for
National Greenhouse Gas Inventories, Volume 4.

327
328
329
330

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

331

Forest Land (Chapter 4): Section 4.2.3, Tier 1 (when using Approach 1 activity data);332

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

333

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

334
335
336
337
338

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

339
340
341
342
343
344
345
346
347

Table 5.3 provides an updated Tier 1 default stock change factor for land use (FLU) that should 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 the Temperate/Boreal Moist
climate values in Table 5.5 (Chapter 5, 2006 IPCC Guidelines), but is lower than the Temperate/Boreal Dry
climate value. Consequently, this update should reduce bias associated with estimating soil C stock changes for
IWMS in dry climates. The method and studies used to derive the updated default stock change factor isprovided in Annex 5A.1 and References. The default time period for stock changes (D) is 20 years, andmanagement practices are assumed to influence stocks to 30 cm depth.

348
349
350
351
352
353
354
355

A new default stock change factor for land-use (FLU) following wetland restoration in Cropland with IWMS isalso provided in Table 5.3 for a Tier 1 approach. This factor applies to Cropland with IWMS where naturalhydrology has been restored, and crop production may or may not continue. Note that the factor applies to all
climate regions, with the caveat that this value is likely more representative of restoration activities in temperate
and boreal climates, as it is derived from studies limited to these regions (see Annex 5A.1 for method andstudies). The default time period for stock changes (D) is 20 years, however additional C gain from restoring
natural hydrology continues for another 20 years and will reach the reference carbon level after 40 years (i.e., thereference soil organic carbon stocks, Table 5.2).

356

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357
TABLE 5.3
RELATIVE STOCK CHANGE FACTORS FOR LAND-USE (FLU) FOR LONG TERM CULTIVATION ON CROPLAND WITH IWMS (OVER
20 YEARS) AND WETLAND RESTORATION OF CROPLAND WITH IWMS (OVER 20 YEARS AND 40 YEARS)
Factor value typeLand use (FLU)

Level

Long-term
cultivatedTemperature
regimeTemperate/
BorealMoisture
regimeDry and
Moist

Wetlandrestoration(20 years)

Wetlandrestoration(40 years)

1

0.71

0.80
Boreal,Temperate,and TropicalLand use (FLU)

Default

Error1

Description

41%

Represents
cropland with
IWMS thathas been
continuously
managedfor > 20years, topredominantly
annual crops.

10%

Dry and
Moist
1.0

N/A

Represents
cropland with
IWMS thathas undergone
wetlandrestoration(restoration ofnaturalhydrology)
and may or
may not be
under active
crop
production.

± two standard deviations, expressed as a percent of the mean.

358
359
360
361

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 wetland restoration (Table 5.3) for land remaining in a land-use
category:

362
363
364



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

365
366
367



The new stock change factors for long-term cultivation and wetland restoration of Cropland with IWMS in
this Supplement (Table 5.3) should be applied to Cropland remaining Cropland with IWMS taking accountof the following:

368
369
370
371

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

372
373

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

374
375
376
377
378

o

For Cropland with IWMS subject to wetland restoration, for a period of 0-20 years following
restoration, the final SOC stock (SOC0) is determined using FLU = 0.80 along with the other stockchange factors for management and input. The stock change factors for estimating the initial SOC
stocks (SOC(0-T)) will correspond to the Cropland land-use (long-term cultivated, perennial etc.),
management and input regimes before land-use conversion.

379
380
381
382
383

o

For the period between 20-40 years since the start of the restoration activity, FLU = 1 will be used
to estimate the final SOC stock (SOC0) along with appropriate stock change factors for
management and input. The stock change factors for estimating the initial stocks (SOC (0-T)) willcorrespond to the Cropland land-use (long-term cultivated, perennial etc.), management and input
regime at the start of the period.

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385
386

o

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

387
388
389
390
391
392

Tier 2

393
394
395

Tier 3396

CHOICE OF ACTIVITY DATA

397
398
399
400
401
402

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, at a minimum. Total areas should bedetermined according to approaches outlined in Chapter 3 of the 2006 IPCC Guidelines, and should beconsistent with those reported under other sections of the inventory. Stratification of land-use categories
according to climate region, based on default or country-specific classifications can be accomplished withoverlays of land-use on climate and soil maps.

403
404
405
406
407

Tier 1

408
409
410
411
412
413
414
415
416
417

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

418
419
420
421
422
423

Tier 2

424
425
426
427
428
429
430

Tier 3431

CALCULATION STEPS FOR TIER 1

432
433

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

434

Step 1: Organize data into inventory time periods based on the years in which activity data were collected.

435
436

Step 2: Determine areas of managed land on 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.

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 C stocks
can also be derived from country-specific data in a Tier 2 approach. Additional guidance is provided in Chapter
2, Section 2.3.3.1 (2006 IPCC Guidelines).
Constant stock change rate factors per se are less likely to be estimated in favour of variable rates that moreaccurately capture land-use and management effects. See Chapter 2, Section 2.3.3.1 for further discussion.

The Tier 1 approach requires area of managed land with IWMS for each land-use category stratified by climate
region and soil type. Available land cover/land-use maps, either country-specific maps or maps based on global
datasets such as IGBP_DIS (http://daac.ornl.gov), can be joined with soil and climate maps (country-specific, or
global maps such as ISRIC, http://www.isric.org, or FAO, http://www.fao.org) as an initial approach.

Tier 2 approaches are likely to involve a more detailed stratification of management systems, under therespective land-use category, than Tier 1 if sufficient data are available. This may include further divisions ofmanagement practices, and finer stratification of climate regions. At Tier 2, a higher spatial resolution of activity
data is required, and can be obtained by disaggregating global data in country-specific categories, or bycollecting country-specific activity data.
Tier 3 approaches may include the use of empirical, process-based or other types of models and/or direct
measurement-based inventories, in which case more detailed data on climate, soils, and management practices
are needed relative to Tier 1 and 2 methods. The exact requirements will be dependent on the model ormeasurement design. Examples of model input data include activity data on cropland management practices(crop type, tillage practices, fertilizer and organic amendments), climate, soil, biomass, and water table position(Ogle et al., 2010; Zhang et al., 2002).

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437
438

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).

439

Step 3: Classify land into the appropriate management system according to the respective land-use category.

440

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

441
442
443
444

Step 5: Assign a land-use factor (FLU), management factor (FMG), and C input levels (FI) based on the
management classification for the respective land-use category (Step 2). Values for FLU, FMG, and FI are provided
in the respective Chapters for land-use categories; an updated value for long-term cultivation FLU is given in
Table 5.3 for IWMS in Cropland.

445
446

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

447
448
449

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

450
451
452
453
454

Step 8: Estimate the average annual change in soil organic C stocks for managed land on IWMS remaining in aland-use category (ΔCMineral) by subtracting the ‘initial’ soil organic C stock (SOC(0-T)) from the final soil organic
C stock (SOC0), then dividing by the time dependence of the stock change factors (i.e. 20 years using the default
factors). If an inventory time period is greater than 20 years, then divide by the difference in the initial and final
year of the time period.

455

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

456
457

UNCERTAINTY ASSESSMENT

458
459
460
461
462
463
464
465
466
467
468
469
470
471
472

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 C 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 threeboard categories, while reducing bias (i.e., improve accuracy) is more likely to occur through the development of
a higher Tier inventory that incorporates country-specific information. An additional source of uncertainty arises
from the difficulty in accurately mapping wetlands; this has been an issue since inventory methods were firstdeveloped (Cowardin, 1982), and still continue even with advances in technology and remote sensing techniques(Hirano et al., 2003). Because mapping techniques tend to rely on vegetation and soils information, defining thearea of IWMS is especially difficult because their vegetation ranges from marsh to forested systems and soils
range from near organic to near non-wetland mineral across their range. Moreover, areas subjected to water tablevariation and flooding may increase or decrease frequently depending on interannual climate variability and on
management activities.

473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491

For Tier 1, uncertainties are provided with the reference C stocks in Table 5.2, and stock change factors in therespective land-use category Chapters (and Table 5.3 for the updated FLU). Uncertainties in land-use andmanagement data will need to be addressed by the inventory compiler, and then combined with uncertainties forthe default factors and reference C stocks using an appropriate method, such as simple error propagation
equations. If using aggregate land-use area statistics for activity data (e.g., FAO data), the inventory compiler
may have to apply a default level of uncertainty for the land area estimates (±50%). It is good practice for theinventory compiler to derive uncertainties from country-specific activity data instead of using a default level.
Default reference C stocks and stock change factors for mineral soils can have inherently high uncertainties,
particularly bias, when applied to specific countries. Defaults represent globally averaged values of land-use andmanagement impacts or reference C stocks that may vary from region specific values (Powers et al., 2004; Ogle
et al., 2006). Bias can be reduced by deriving country-specific factors using a Tier 2 method or by developing a
Tier 3 country-specific estimation system. The underlying basis for higher Tier approaches will be experiments
or soil C monitoring data in the country or neighboring regions that address the effect of land use andmanagement on soil C and/or can be used to evaluate model predictions of soil C change (e.g., Ogle et al., 2010).
In addition, it is good practice to further minimize bias by accounting for significant within-country differencesin land-use and management impacts, such as variation among climate regions and/or soil types, even at theexpense of reduced precision in the factor estimates (Ogle et al., 2006). Bias is considered more problematic forreporting stock changes because it is not necessarily captured in the uncertainty range (i.e., the true stock change
may be outside of the reported uncertainty range if there is significant bias in the factors).

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493
494
495

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

496

5.2.2

497
498
499
500
501
502
503
504

Methane (CH4) is produced in IWMS soils during anaerobic decomposition of organic matter, and emitted to theatmosphere after diffusion or ebullition (i.e. episodic release of gas bubbles from soils) through the water column,
or through plant-mediated transport. Several factors have been identified as important controls on CH4
production and emission, including water level, oxygen availability, temperature, vegetation community andproductivity, and microbial communities (Whiting and Chanton, 1993). Soil moisture content and water tablelevel are critical to determining whether CH4 is produced, and how much is emitted (Le Mer and Roger, 2001).
In a synthesis of CH4 flux from global hydromorphic organic soils, Jungkunst and Fiedler (2007) found that ingeneral when water table was greater than 0.1 m below the soil surface CH4 was not emitted.

505
506
507
508
509
510
511
512
513
514
515
516
517
518

Management activities on lands containing IWMS that alter the water table level can impact CH4 emissions. Two
common management activities that involve raising water table levels include the restoration of wetlands on
previously drained, cultivated, and/or degraded lands with IWMS, and the creation of wetlands on mineral soils(wet or dry). Wetland restoration often involves the cessation of active drainage by filling ditches and/or
removing drainage tiles, whereas wetland creation often involves active modification of hydrologic regime
where dry lands are purposely inundated. Both wetland restoration and wetland creation are often undertaken as
conservation efforts for habitat and wildlife. Studies have shown that raising water table levels on managed lands
with IWMS, through wetland restoration and 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 CH4
emissions as a result of raising the water table level on managed lands with IWMS; drainage and lowering watertables 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 todevelop guidance for CH4 fluxes for drained IWMS at this time.

519
520
521
522
523
524
525
526
527
528

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

529

5.2.2.1

530
531
532
533
534

Tier 1

CH 4 emissions from managed lands with IWMSC HOICE OF METHOD

CH4 emissions from managed lands with 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.

535
536
537
538

EQUATION 5.1
ANNUAL CH4 EMISSIONS FROM RESTORED AND CREATED WETLANDS ON MANAGED LANDSWITH IWMS

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

539

c

540
541

Where:

542

CH4-IWMS = Annual CH4 emissions from managed lands with mineral soil where

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management activities have raised the water table level to or above the land544

surface, kg CH4 yr-1

545
546

AIWMS, c = Total area of managed lands with mineral soil where the water table level has

547

been raised in climate region c, ha

548
549

EFCH4-IWMS,c = Emission factor from managed lands with mineral soil where water level has

550

been raised in climate region c, kg CH4 ha-1 yr-1.

551
552
553

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.

554
555
556
557
558
559
560
561

Tier 2

562
563
564
565
566
567
568
569
570
571
572

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
emission by facilitating transport from inundated soils to the atmosphere, and by providing substrate for CH4
production. Possible methods to determine the importance of these drivers to CH4 emission, and thus reduce
uncertainty in emission factors, include detailed field studies of CH4 emission and/or the use of models specificto carbon cycling in wet soils such as the Wetland-DNDC model (Zhang et al., 2002;
http://www.globaldndc.net).

573

5.2.2.2

574
575
576
577
578
579
580

Tier 1The 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 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 than intermittently
at above the land surface (Annex 5A.2). Seasonal and inter-annual changes in water table position, and duration
above the land surface, are determined by multiple variables including fluctuations in water source (ex. riverdischarge in the case of riparian wetlands) and precipitation.

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

581
TABLE 5.4
DEFAULT EMISSION FACTORS FOR CH4 FROM MANAGED LANDS WITH IWMS WHERE WATER TABLE LEVEL HAS BEEN
RAISED

Climate Domain

EFCH4-IWMS-1

Uncertainty Range-1(kg CH4 ha yr )(95% Confidence Interval)

Boreal76

10 – 142

Temperate237

103 - 371

Tropical

900

345 - 1454

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5.2.2.3

C HOICE OF ACTIVITY DATA

583
584
585
586
587
588
589
590
591
592
593
594
595
596

Tier 1 method requires data on areas of managed lands with IWMS where the water table level has been raised,
for instance as in wetland restoration or wetland creation, stratified by climate region. Although no organization
catalogues changes in area as a result of wetlands restored or created either nationally or globally, local activity
data for restoration of managed lands with IWMS or creation of wetlands may be obtained from agricultural,
forestry, or natural resources agencies, non-governmental conservation organizations, or other government
sources. In addition, organizations such as the Society for Ecological Restoration International(http://www.wer.org), Global Restoration Network (http://www.globalrestorationnetwork.org), Wetlands
International (http://www.wetlands.org), and the Ramsar Convention on Wetlands (http://www.ramsar.org) may
be sources of information for wetland restoration projects. In addition to the above, Tier 2 and Tier 3 methods
generally require areas of managed lands with IWMS stratified by annual average water table level, and seasonal
and/or inter-annual changes in inundation. Areas may be further stratified by vegetation community composition,
vegetation biomass, soil temperature data, and previous land use, for the development of country-specificemission factors and models. Remote sensing can be used for detection of areas of inundation, and for mappingof vegetation.

597

5.2.2.4

598
599
600
601

Ranges of uncertainty for EFCH4-IWMS are provided in Table 5.4 for each climate region. The major sources of
uncertainty in these values are the small number of studies on which the estimates are based, and the
combination of studies with different inundation periods (continuously inundated and intermittently inundated).
The development of country-specific emission factors will aid in reducing uncertainty.

U NCERTAINTY ASSESSMENT

602
603

5.3

604

LAND CONVERTED TO A NEW LAND-USE
CATEGORY

605
606
607
608
609
610
611

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

612

5.3.1

613
614
615

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

616
617

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

618

5.3.1.1

619
620
621

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 have to be used.

622

CHOICE OF METHOD AND EMISSION/REMOVAL FACTORS

623
624
625

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 have to be used.

5.16

CO 2 emissions and removals

B IOMASS AND DEAD ORGANIC MATTER

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626

CHOICE OF ACTIVITY DATA

627
628
629
630
631

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 have to be used.

632

UNCERTAINTY

633
634
635

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

636

5.3.1.2

637
638
639
640
641
642
643

Conversion of land with IWMS to other land uses can increase (in Forest Land, for example, Volume 4, Chapter
4 in 2006 IPCC Guidelines) or decrease SOC stocks (in Cropland, for example, Chapter 5 of Volume 4 in 2006
IPCC Guidelines). In general, the guidance provided in section 5.2.1.2 also applies to lands converted to a newland-use category for managed lands with IWMS. However, there are specific applications of the new SOC
stock change factors for wetland restoration 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 have to be used.

644

CHOICE OF METHOD

645
646
647

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

648

CHOICE OF EMISSION/REMOVAL FACTORS

649
650
651
652

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

653
654
655



The stock change factors for SOC changes in mineral soils provided for Forest, Cropland, Grassland, andSettlements 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;

656
657
658



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

S OIL CARBON

659
660
661
662

(i)

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

663
664

(ii)

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

665
666
667
668
669

o

For land-use conversion to Cropland with IWMS subject to wetland restoration the final SOC
stock (SOC0) is determined using FLU = 0.80 for a period of 0-20 years following restoration alongwith the relevant stock change factors corresponding to the management and input regimes afterland-use conversion. The stock change factors for estimating the initial SOC stocks (SOC(0-T)) willcorrespond to the land-use, management and input regimes before land-use conversion.

670
671
672
673
674
675
676

o

For Cropland with IWMS subject to restoration undergoing land-use conversion to any other landuse category, FLU values of 0.8 or 1 are to be used for a period of 20-40 years or more than 40
years since the start of the restoration activity respectively along with relevant stock change factors
corresponding to the management/input regime before conversion. The stock change factors forland use, management and input for the new land-use category (e.g., Forest Land or Grassland)
will be used to determine the final SOC stock (SOC0) along with relevant stock change factors
corresponding to the management and input regimes following land-use conversion.

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677
678

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

679

CHOICE OF ACTIVITY DATA

680
681
682
683

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

684

UNCERTAINTY

685
686
687

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

688

5.3.2

689
690
691

The guidance provided in section 5.2.2 also applies to lands converted to a new land-use category for managed
lands with IWMS. The guidance in sections pertaining to land converted to a new land-use category in the 2006
IPCC Guidelines have to be used.

692

5.3.2.1

693
694
695

The guidance provided in section 5.2.2 also applies to lands converted to a new land-use category for managed
lands with IWMS. The guidance in sections pertaining to land converted to a new land-use category in the 2006
IPCC Guidelines have to be used.

696

5.3.2.2

697
698
699
700

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

701

5.3.2.3

702
703
704

The guidance provided in section 5.2.2 also applies to lands converted to a new land-use category for managed
lands with IWMS. The guidance in sections pertaining to lands converted to a new land-use category in the 2006
IPCC Guidelines have to be used.

705

5.4

COMPLETENESS, TIME SERIESCONSISTENCY, QA/QC, REPORTING AND
DOCUMENTATION

708

5.4.1

Completeness

709
710
711

Complete GHG inventories will include estimates of carbon stock changes and emissions and sinks of GHG
from all managed land with IWMS for which methodological guidance is provided in the 2006 IPCC Guidelines
and this Supplement.

712
713
714
715
716
717

Because multiple activities or land uses (e.g., cropping, forest) may occur on land with IWMS, countries areencouraged to monitor land use changes and activities to avoid double counting. For example, if a forested
wetland has been reported as a forest it should be reported as a forest during the entire time series. Also, when
inputs from other land uses such as drainage waters carrying nitrogen from Croplands to managed lands with
IWMS it is good practice to ensure that sources are accounted for under the proper land use where they are
produced.

718
719

It is good practice to disaggregate the type of managed lands with IWMS according to national circumstancesand employ country-specific emission factors if possible. It is suggested that flooded lands, peatlands, and

706
707

5.18

CH 4 emissions

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

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721

coastal wetlands are clearly excluded from land with IWMS and this separation is applied consistently
throughout the reporting period.

722
723
724
725

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

726

5.4.2

727
728
729
730
731
732
733
734
735
736

General guidance on consistency in time series is given in Chapter 7 of this Supplement. It is essential for theconsistency of time series that estimation methods are comparable from one year to another in the time series.
The classification of land, criteria for using activity data and emission factors and inventory methods should beconsistent with the Generic Methodologies described in Volume 2 of the 2006 IPCC Guidelines and in this 2013
Supplement. It is expected that when countries use country-specific data, changes in methods and/or emission or
removal factors occur between years as a result of the development of new methodologies and/or availability of
new information. In these cases inventory agencies should assure that new developments do not create
methodological artefacts that do not represent real changes in trends (see Section 7.6.2 I). It is good practice torecalculate the entire time series when new country-specific methodologies are developed as well as document,
preferably on a peer-review basis, the consistency between different methods.

737

5.4.3

738
739
740
741
742
743
744
745

Chapter 6 in Volume 1 of the 2006 IPCC Guidelines and Chapter 7 of this Supplement provide general guidanceon the issues concerning Quality Assurance and Control (QA/QC). All steps in the inventory should be clearly
documented for revision by inventory compilers and non-inventory reviewers. It is good practice for countries toverify the applicability of default emission factors and activity data to their specific inventories and special
attention should be given to cross-referencing country-specific data to values reported in the scientific literatureor reported by other countries. Classification of land use based on remotely obtained information has progressed
rapidly and it is good practice for countries to search for available imagery which can improve the accuracy ofarea estimates and reduce uncertainties in activity data.

Developing a consistent time series

Quality Assurance and Quality Control

746

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747

5.4.4

Reporting and Documentation

748
749
750

General Guidance on Reporting and Documentation is given in Chapter 8 of Volume 1 of the 2006 IPCC
Guidelines. Section 7.4.4 in Chapter 7 of Volume 4 of the 2006 IPCC Guidelines states the following for
Reporting and Documentation:

751

EMISSION FACTORS

752
753
754

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

755

ACTIVITY DATA

756
757
758
759

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

760

TREND ANALYSIS

761
762
763
764

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

765
766

5.5

767
768
769
770
771
772

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

773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789

Particular effort should be employed to differentiate multiple uses on lands with IWMS (e.g. forested wetlands,
wet grasslands) for future methodological improvements. A good example of the methodological approachnecessary for this task can be found in USFWS (United States Fish and Wildlife Service) Report to the Congress
entitled “Status and Trends of Wetlands in the Conterminous United States – 2004 to 2009”(http://www.fws.gov/wetlands/Documents/Status-and-Trends-of-wetlands-in-the-Conterminuous-United-States2004-to-2009.pdf). This document describes how wetland inventories have been made in the United States and,
although not providing figures for C stock changes, gives reference for future work to obtain such data at 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 C stocks and GHG
fluxes at a national level is found in the USGS (United States Geological Survey) Scientific Investigations
Report 2010-5233 entitled “A Method for Assessing Carbon Stocks, Carbon Sequestration, and Greenhouse-Gas
Fluxes in Ecosystems of the United States Under Present Conditions and Future Scenarios” (Zhu et al., 2010;
http://pubs.usgs.gov/sir/2010/5233). While this document describes C stock changes and GHG emissions frommanaged and unmanaged lands, it may serve as a useful example for a national-level C assessment.
Synthetically, surveys to quantify the areas of land with IWMS under different land use and management
practices in conjunction with C pools quantification allows the future use of general equations for C stockchanges described in the 2006 IPCC Guidelines.

790
791
792
793
794
795
796
797
798
799

New research is needed to fill a number of gaps for IWMS. Additional studies are needed to evaluate the effectof IWMS conversion on soil C stock changes following conversion to Grassland, Forest Land, Settlements andOther Lands. Moreover, new research is needed to understand the effect of IWMS conversion on other C stocks(biomass, dead organic matter) as well as CH4 and N2O fluxes. Although we were able to develop guidance for
IWMS CH4 fluxes for some climate regions, specific guidance for climate and region combinations would
improve our estimates of CH4 fluxes. New research assessing N2O fluxes following conversion of IWMS toother land uses, especially Croplands, 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 from anthropogenic activities
such as agricultural fertilizer application (Hefting et al., 2006; Phillips and Beeri, 2008; DeSimone et al., 2010),

5.20

FUTURE METHODOLOGICAL DEVELOPMENT

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800
801
802
803
804
805
806

or Grassland management (Chen et al., 2011; Oates et al., 2008; Liebig et al., 2011; Jackson et al., 2006; Holstet al., 2007; Walker et al., 2002). The review of the current literature suggests there is insufficient data toprovide robust emission factors and methodology to estimate N2O emissions from IWMS at this time. We
suggest that N2O emissions be addressed in future updates of this guidance as research on this topic progresses.
For future methodological improvement of N2O emission factors, it is important to avoid double-counting N2Oemission already included in the estimates of indirect N2O from agricultural or other runoff, and waste water (seeVolume 4, Chapter 11 of the IPCC 2006 IPCC Guidelines)

807
808
809
810

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

811
812
813

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817

Estimation of default stock change factors for longterm cultivated Cropland and wetland restoration
with Inland Wetland Mineral Soil Cemissions/removals

818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837

Default stock change factors are provided in Table 5.3 that were computed using a dataset of experimental
results for land use. The land-use factor for long-term cultivation represents the loss of carbon that occurs after
20 years of continuous cultivation. The wetland restoration factor represents the effect of the restoration ofnatural hydrology of cultivated cropland with IWMS (such as through the removal of drainage tiles, or plugging
of drainage ditches), which may or may not have continued crop production. The influence of this change on
IWMS carbon stocks may continue for a period of time that may extend to 40 years. Experimental data (citations
listed below, and provided in reference list) were analyzed in linear mixed-effects models, accounting for both
fixed and random effects (Ogle et al. 2005). Fixed effects included depth and number of years since themanagement change. For depth, data were not aggregated but included C stocks measured for each depth
increment (e.g., 0-5 cm, 5-10 cm, and 10-30 cm) as a separate point in the dataset. Similarly, time series data
were not aggregated, even though those measurements were conducted on the same plots. Consequently, random
effects were used to account for the dependencies in times series data and among data points representing
different depths from the same study. If significant, a country level random effect was used to assess anadditional uncertainty associated with applying a global default value to a specific country (included in thedefault uncertainties). The long-term cultivation factor represents the average loss of carbon at 20 years or longer
time period following cultivation of IWMS. Users of the Tier 1 method can approximate the annual change incarbon storage by dividing the inventory estimate by 20. The wetland restoration factor represents the average
net gain in carbon after restoration of cultivated cropland at 20 and 40 years following restoration. Variance wascalculated for each of the factor values, and can be used with simple error propagation methods or to constructprobability distribution functions with a normal density.

814

Annex 5A.1

815
816

TABLE 5A.1.1
STUDIES USED FOR THE DERIVATION OF DEFAULT SOC STOCK CHANGE FACTORS
Study

Location

Stock Change Factor (LC =Long term cultivation; WR =Wetland restoration)

Badiou et al., 2011

Saskatchewan, Alberta, Manitoba,

LC, WR

Ballantine et al., 2009

New York, USAWR

Besasie et al., 2011

Wisconsin, USA

LC, WR

Bedard-Haughn et al., 2006

Saskatchewan, Canada

LCDavid et al., 2009

Illinois, USALC

Euliss et al., 2006

North Dakota, South Dakota,

LC, WR

Gleason et al., 2009

North Dakota, USAWR

Huang et al., 2010

Sanjiang Plain, China

LC

Hunter et al., 2008

Louisiana, USA

LC, WR

Jacinthe et al., 2001

Ohio, USALC

Lu et al., 2007

Lake Taihu, China

LC, WR

Meyer et al., 2008

Nebraska, USA

LC, WR

Morse et al., 2012

North Carolina, USA

LC

Norton et al., 2011

California, USALC

Wang et al., 2012

Sanjiang Plain, China

LC, WR

van Wesemael et al., 2010

Belgium

LC

838
839
840

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843

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

844
845
846
847
848

The Tier 1 default emission factors in Table 5.4 were derived from the published studies listed in Table 5A.2.1.
The number of studies of CH4 emission from re-wetted IWMS as a result of wetland restoration, and from wetted
mineral soils as a result of wetland creation, is very limited. They are also restricted to the temperate climate
regions. Thus studies of CH4 emission from natural IWMS were included to derive emission factors from boreal
and tropical regions, and to supplement the number of studies in the temperate region.

841

Annex 5A.2

842

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

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

Canadaunspecified

76

Bridgham et al.,2006

CanadaIntermittent

49

Badiou et al., 2011

CanadaIntermittent

349

Pennock et al.,2010

North Dakota, USA

Intermittent

142

Gleason et al., 2009

North Carolina,
USA

Intermittent

7

Morse et al., 2012

Temperate

Restored wetland,previous use
CroplandDenmark

Intermittent

110

Herbst et al., 2011

Temperate

Created wetlands,
riparian

China

Intermittent

13

Yang et al., 2012

Climate Region

Wetland Type

BorealNaturalwetlands

Temperate

Temperate

Temperate

Temperate

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

Location

Reference

Temperate

Created wetlands

Ohio, USA

Continuous

402

Nahlik and Mitsch,
2010; Altor and
Mitsch, 2008

Temperate

Natural wetland,marsh

Nebraska

Continuous

800

Kim et al., 1998

Temperate

Natural wetlands,
marshesSanjiang Plain, NE
China

Continuous

468

Ding and Cai, 2007

Temperate

Natural wetlands,
Carex marshes

Sanjiang Plain, NE
China

Continuous

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Temperate

Natural wetlands,
Deyeuixa marshes

Sanjiang Plain, NE
China

Continuous

289Song et al., 2003

Temperate

Natural wetland,
riparian

Ohio

Continuous

758

Nahlik and Mitsch,2010

Temperate

Natural wetlands,
riparianGeorgia, USA

Continuous

266

Pulliam, 1993

Temperate

Natural wetlands,
marshesSanjiang Plain, NE
China

Continuous

225

Huang et al., 2010

Temperate

Natural wetlands,
marsh

Sanjiang Plain, NE
China

Intermittent

58Song et a., 2009

Temperate

Natural wetlands,
shrub swamp

Sanjiang Plain, NE
China

Intermittent

3Song et a., 2009

Temperate

Natural wetlands,
swampsGlobalIntermittent

113

Bartlett and Harriss,
1993

Temperate

Natural wetlands,
marshesGlobalIntermittent

105

Bartlett and Harriss,
1993

Temperate

Natural wetlands,
floodplains

GlobalIntermittent

72

Bartlett and Harriss,
1993

Temperate

Natural wetlands

Continental USA

unspecified

76

Bridgham et al.,2006

TropicalNatural wetlands,
rainforest swamp

Costa Rica

Continuous

2930

Nahlik and Mitsch,
2011

TropicalNatural wetlands,
alluvial marsh

Costa Rica

Intermittent

3500

Nahlik and Mitsch,
2011

TropicalNatural wetlands,
swampsGlobalIntermittent

297

Bartlett et al., 1993

TropicalNatural wetlands,
marshesGlobalIntermittent

419

Bartlett et al., 1993

TropicalNatural wetlands,
floodplains

GlobalIntermittent

328

Bartlett et al., 1993

TropicalNatural wetlands,
floodplains

Amazon, Upper
Negro Basin

Intermittent

54Belger et al., 2011

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TropicalNatural wetlands,
floodplains

Pantanal, Brazil(Arara-Azul)

Intermittent

516

Marani et al. 2007

TropicalNatural wetlands,
floodplains

Pantanal, Brazil(Bau)

Intermittent

1033

Marani et al. 2007

TropicalNatural wetlands,
floodplains

Pantanal, Brazil(Sao Joao)

Intermittent

510

Marani et al. 2007

TropicalNatural wetlands,
flooded forests

Solimoes/Amazon
floodplain

Intermittent

567

Melack andForsberg, 2001

TropicalNatural wetlands,
aquatic
macrophytes

Solimoes/Amazon
floodplain

Intermittent

184

Melack andForsberg, 2001

TropicalNatural wetlands,
flooded forests

Jau River basin
floodplains/Amazon

Intermittent

306

Rosenqvist et al.,2002

TropicalNatural wetlands,
floodplains

Mojosbasin/Amazon

Intermittent

948

Melack et al., 2004

TropicalNatural wetlands,
floodplains

Roraima/ Amazon

Intermittent

1341

Melack et al., 2004

TropicalNatural wetlands,
floodplains

BananalIntermittent

954

Melack et al., 2004

TropicalNatural wetlands,
floodplains

OrinocoIntermittent

951

Melack et al., 2004

TropicalNatural wetlands,
floodplains

Pantanal

Intermittent

949

Melack et al., 2004

Solimoes/Amazon
floodplain

Continuous &Intermittent

404

Melack et al., 2004

TropicalNatural wetlands,
flooded forest,
aquatic
macrophytes,

849
850
851

Studies for temperate region sites are roughly equal in number for continuous inundation and intermittent
inundation, so the emission factors were compared for the two hydrologic regimes (Table 5A2.2).

852
TABLE 5A.2.2
CH4 EMISSIONS FROM TEMPERATE RESTORED, CREATED AND NATURAL WETLANDS WITH IWMS, STRATIFIED BY PERIODOF INUNDATION

Climate region

Annual Period
of Inundation

EF(kg CH4 ha-1 yr-1)

95%
confidence
intervalnTemperate

Continuous

455

182

8

Intermittent

93

65

11

Note: Values are derived from studies of Temperate wetlands listed in Table 5A.2.1, n = number of studies.

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854
855
856

There is a significant difference in EF for the two hydrologic regimes (ANOVA, p<0.000). This highlights theimportance of period of inundation in annual CH4 emission. The development of country-specific emission
factors that incorporate period of inundation will reduce uncertainties.

857
858

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References

860
861

Aber JS, Pavri F, Aber SW. Environmental Cycles and Feedback. Wetland environments: A Global Perspective.
John Wiley & Sons, Ltd.

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