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CHAPTER 5

INLAND MINERAL SOIL WETLANDS
Contents
5.1

Introduction ........................................................................................................................................... 1

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5.1.1

Inland Mineral Soil Wetlands ....................................................................................................... 2

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5.1.2

Guidance for Inland Mineral Soil Wetlands ................................................................................. 3

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5.1.3

Choice of Activity Data ................................................................................................................ 4

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5.1.4

Reporting Inland Mineral Soil Wetlands ...................................................................................... 4

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5.2

General Methods ................................................................................................................................... 6

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5.2.1

CO2 ............................................................................................................................................... 6

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5.2.2

Non-CO2 Emissions from IMS Wetlands ..................................................................................... 8

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5.3

Drainage, Creation, and Restoration of Inland Mineral Soil Wetlands ............................................... 11

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5.3.1

Introduction................................................................................................................................. 11

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5.3.2

Methodological Issues ................................................................................................................ 12

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5.4

Completeness, Time Series Consistency, Qa/Qc, and Reporting and Documentation ........................ 16

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5.5

Future Methodological Guidance ........................................................................................................ 17

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References ............................................................................................................................................................. 17

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5.1

INTRODUCTION

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This chapter provides guidance for estimating and reporting greenhouse gas emissions and removals fromManaged Inland Wetlands having Mineral Soils. This will be referred to as IMS wetlands (inland mineral soil
wetlands).
This chapter builds on the 2006 IPCC Guidelines for National Greenhouse Gas Inventories (2006 IPCC
Guidelines), Volume 4 chapter 2. Following the 2006 Guidelines, greenhouse gas emissions and removals can be
estimated in two ways: 1) Net changes in carbon stocks in the five IPCC C pools over time (used for most CO2
fluxes); and 2) Directly as gas flux rates to/from the atmosphere using emission factors (used for non-CO2
emissions and some CO2 emissions and removals).
These wetlands can occur in any of the six IPCC land classes. For example, a riverine wetland with trees may beclassified as a forest, while a marsh may be used for grazing and classified as grassland. The precise details of
this classification are specific to each country so it is not possible to say exactly how an inland wetland on
mineral soil may be classified. This guidance applies to all inland wetlands on mineral soils, however they are

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classified. The classification is important when reporting these emissions, and there is no intention to change inany way how land is classified, however there may be a need to sub-divide some land types to reflect differing
management actions.

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5.1.1

Inland Wetlands Having Mineral Soils meet the following two criteria:
1) Have Mineral Soils (i.e. not organic soils)
2) Do not meet the definition of Coastal Wetland
Mineral soils are those that do not fit the definition of organic soils. Organic soils are those that satisfy
requirements 1 & 2, or 1 & 3 below (FAO, 1998; 2006 IPCC Guidelines Vol. 4, Chap. 4 Glossary):
1) O horizon thickness ≥ 10 cm; a horizon of less than 20 cm must have 12% or more organic carbon
when mixed to a depth of 20 cm.
2) Soils that are never saturated for more than a few days must contain more than 20% organic C by
weight (i.e. about 35% organic matter).
3) Soils are subject to water saturation episodes and have either:a. At least 12% organic carbon by weight (i.e. about 20% organic matter) if the soil has no clay;orb. At least 18% organic carbon by weight (i.e. about 30% organic matter) if the soil has 60% ormore clay; orc. An intermediate, proportional amount of organic carbon for intermediate amounts of clay.
Coastal wetlands are covered in Chapter 4 of this Supplement.
Saline Inland Wetlands are a group of very specific Inland Wetlands. A review of the literature for potential
methods to estimate carbon stock changes and greenhouse gas fluxes was conducted for inland saline wetlands(i.e. saline wetlands not covered in Chapter Four). Also known as playas, pans, salt lakes, brackish wetlands,
salinas, and sabkhas (generally associated with coasts), saline wetlands are important parts of arid landscapes
across the globe (Shaw and Bryant 2011). Carbon stocks and greenhouse gas fluxeshave been little studied ininland saline wetlands. In a recent review of the literature characterizing known information on pans, playas andsalt lakes, carbon stocks and carbon dioxide, methane and nitrous oxide fluxes were not discussed (Shaw andBryant 2011), likely indicating little research carbon and greenhouse gas fluxes has been conducted. Because of
the briny nature of inland saline wetlands and their periodic flooding, saline wetlands are generally not
vegetated. A review of the broader literature on saline wetlands indicates that only one study has assessed soil C
in inland saline wetlands (Bai et al. 2007), and no studies have measured greenhouse gas fluxes or other biomass
categories from inland saline wetlands. The Bai et al. (2007) study was conducted in northeast China and foundrelatively low soil carbon stocks when compared to other wetlands in China. Although only a single study, thesoil carbon stocks found in Bai et al. (2007) of 41-47 Mg ha-1 to 30 cm are more similar to upland soils (Table
2.3 in the 2006 IPCC Guidelines) than freshwater mineral wetland soils (Table 5.1). At present the lack of dataon inland saline wetlands does not allow for default of carbon stock changes or greenhouse gas emission factors
to be given. However the same methods as described here for IMS wetlands can be used with nationallymeasured factors and applied to inland saline wetlands. Note that it is good practice for inventory compilers toaccount for all areas of inland saline wetlands as sub-categories of the six IPCC land classes, to ensure that allland is accounted.
Figure 1 in Chapter 1 shows a decision tree to orient the inventory compiler to what types of wetlands arecovered in this Chapter.

Inland Mineral Soil Wetlands

Mineral wetland soils are estimated to cover ~5.3% of the world’s land surface, or 7.26 x 106 km2 (Batjes, 2010).
The most important climate zone is boreal (2%), followed by Tropical Moist (0.67%), Cool Temperate Moist(0.63%), Tropical Wet (0.61%), Polar (0.60%), and Warm Temperate Moist (0.23%) soils (Batjes, 2010).
Climate zones with less than 0.20% mineral wetland soils include Cool and Warm Temperate Dry, Tropical Dry,and Tropical Montane.
Numerous inland wetland types have been described based on various criteria; the Ramsar Convention Wetland
Classification includes 24 inland wetland types alone. Wetland classification can be simplified by considering
broad generalizations of landform and hydroperiod (Semeniuk and Semeniuk, 1995, 1997). Inland mineral soil
wetlands (IMS wetlands) are found in a variety of landscape settings, including basins, channels, flats, slopes,
and highlands (Semeniuk and Semeniuk, 1995). It is common to find IMS wetlands adjacent to flowing waters

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(riparian wetland) and lake and pond margins. The hydroperiod, or degree of wetness over time, of IMS
wetlands range from inundated (covered by water) to saturated (water is at or just below the surface) to
unsaturated, and from permanent to seasonal or intermittent. Hydroperiod is directly related to climate(precipitation and evaporation), mechanisms of water discharge and recharge, and permeability of underlying
sediment. Hydroperiod can significantly impact wetland carbon and nitrogen cycling pathways and rates, and iscommonly altered by management activities. Therefore knowledge of wetland hydroperiod (inundated vs. uninundated, permanent vs. seasonal) is useful for inventories of emissions and removals, particularly CH4. An
additional characteristic that is used to classify IMS wetlands is dominant vegetation community, and can
include trees (forested wetland), woody shrubs, and/or emergent and non-emergent vascular plants. Vegetation
type and productivity is important to carbon cycling, and is commonly impacted by management activities. For
instance, emergent vascular plants can significantly enhance CH4 production and emission from wetland
sediments (Whiting et al., 1991; Whiting and Chanton, 1992, 1993).

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5.1.2

An important agricultural use of inland wetlands is rice cultivation, which is covered in the 2006 IPCC
Guidelines (Vol. 4, Chapter 5 – Croplands), and not addressed in this supplement. Other potentially important
agricultural uses of wetlands on mineral soils include lotus and mat rush cultivation, particularly in Asia (Seo etal., 2010; Maruyama et al., 2004). Currently there is little available information on C stock changes orgreenhouse gas emissions for this type of cultivation. Further research will be required to develop methodologies
for these types of cultivation practices. Indirect effects of agricultural activities include agricultural runoff toadjacent wetlands. Runoff would be expected to increase sedimentation rates, and may also alter greenhouse gas
fluxes, e.g. nitrogen-rich inputs from agricultural runoff may lead to higher N2O emissions (Bridgham et al.,2006). The impact of nitrogen fertilization on methane emissions is currently unclear as interactions arecomplex, and can affect both methane production and methane consumption (Bodelier, 2011).
Grazing is an important activity in wetlands within grassland or forest landscapes (Liu et al., 2009; Oates et al.,2008; Wang et al., 2009). The direct effects of livestock grazing on wetlands can be selective removal of plantbiomass, trampling of plants, changes in below-ground biomass and soil properties, nutrient inputs, and bacterial
contamination from animal waste. Overgrazing can influence biomass and carbon stocks. The intensity ofgrazing can also affect species composition and diversity. Reduction of aboveground biomass by grazing canaffect plant-mediated gas transport between soil and the atmosphere, which may alter greenhouse gas fluxes inwetlands. Grazed wetlands and wetlands receiving run-off from adjacent livestock grazing areas, may also alter
N2O (and NO) emissions from wetlands.
Forest management activities on forested wetlands can vary in management intensity depending on thesilvicultural system. The intensity may range from selective cutting treatments to large area clearcuts. It
represents a loss in biomass pools and can also alter the ecologic and hydrologic conditions of the site. Possible
consequences of harvesting in wetlands can be changes in water table, and changes in microclimatic conditions
such as increased solar radiation and evapotranspiration. Some of these changes can substantially affect primary
production, respiration, and fluxes of CO2, CH4, and N2O. Many studies have reported temporary increases inwater levels after harvesting from increased interception and decreased transpiration. The increase in water level
may result in decreasing decomposition rates but acceleration in CH4 and N2O emissions. This point is further
discussed below in rewetting. Another important point is the wetland ecosystem type where harvesting takes
place, for example seasonally flooded riparian ecosystems are known to have more soil and biomass carbon
content compared to upland ecosystems. Therefore, harvesting may be expected to cause larger carbon emissions
in these areas compared to dryer environments. A specific accounting method for harvesting in riparian
ecosystems is a topic for future improvement.

Guidance for Inland Mineral Soil Wetlands

In this Chapter guidance and methodologies mainly follow the 2006 IPCC Guidelines, in particular the genericguidance given in Volume 4 Chapter 2. This chapter provides additional information to be used in applying themethods in the 2006 IPCC Guidelines and should be read in conjunction with volume 4 of the 2006 Guidelines.
Management activities that impact CO2 and non-CO2 (CH4 and N2O) emissions include water level management
as well as activities that impact vegetation (such as grazing, vegetation removal, and cultivation, nutrient
amendments). Figure 1 shows a decision tree to guide inventory compilers on which Tier approach should be
used to report on Inland Wetlands on Mineral Soils. Table 5.1. clarifies the scope of the assessment, and thecorresponding sections of this chapter.

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SECTIONS ADDRESSING MAJOR GREENHOUSE GAS EMISSIONS FROM INLAND MINERAL
SOIL WETLANDS

Land-use category/GHG
IMS wetlands (General guidance)

CO2
Section 5.2.1

CH4
Section 5.2.2

N2O
IncludedElsewhere1
Section 5.3

Drainage, Restoration and Creation Section 5.3
Section 5.3
of IMS wetlands
Inland Saline Wetlands
No Guidance2
NOTES:
1
N2O emissions from FWMS wetlands are included in the estimation of indirect N2O fromagricultural or other run-off, and waste water.
2
No available information for providing default factors for inland saline wetlands however the same
methods as used for IMS wetlands can be used with national factors. Note that it is good practicefor inventory compilers to account for all areas of inland saline wetlands as sub-categories of thesix IPCC land classes.
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5.1.3

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5.1.4

Choice of Activity Data

IMS Wetlands may occur in any of the six IPCC land use classes described in volume 4 of the 2006 IPCC
Guidelines. It is good practice to follow the guidance given the 2006 Guidelines in categorising land. While theuse of this supplementary guidance does not ask for changes to the land classification required in the 2006
guidelines it may be necessary to sub-divide some categories according to ecosystem and management activities
especially where these involve changes in water level.
All areas should be estimated as accurately as possible. In a Tier 1 level some degree of aggregation can be
performed in the estimation of biomass. For example, initial land use of grassland and some types of croplands
can be aggregated and biomass estimations for both done with the same methodology. At higher level Tiers it isgood practice to use a matrix of initial land use and final wetlands types to estimate changes in biomass stocks.
Tier 1 assumes that transition from any land use to wetland occurs in the year of conversion, whereas in Tiers 2
and 3 biomass stocks are monitored during transitions years and expressed on an annual average basis.

Reporting Inland Mineral Soil Wetlands

As noted above, these inland wetlands may occur in any of the 6 IPCC land classes depending on the precise
national definitions used. Emissions should be reported in the land use category under which they are classified.
Note that a change in management practice may, or may not, result in the emissions being classified as “landconverted to” lands. For example, changes in harvesting trees in a wetland classified as forest would generally
not result in the emissions being reported as land use change while there would be a change in the management
and the guidance in this chapter.
Inventory compilers should also note that while the emission factors in this chapter are, in part, based on those
form pristine wetlands there is no intention for unmanaged wetlands to be reported. Methods applicable for thedrainage, creation and restoration of IMS wetlands are covered in section 5.3 while section 5.2 covers othermanagement uses of IMS wetlands. For Tier 1 it is assumed that these IMS wetlands reach an equilibrium state
after 10 years (inventory compilers are encouraged to us more appropriate periods for wetlands in their country ifsuch data is available). Thus after 10 years it is assumed that the impact of drainage, creation and restorationceases and the emissions would then be estimated following section 5.2.

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Figure 1 Decision tree to the inventory on Inland Wetlands on Mineral Soils
Start

Are detailed information
available on managed inland
wetlands with mineral soils?

Estimate emissions
using country-specificmethodology andemission factors(Tier 3).

Yes

No

Are historical and current
data available on the area ofmanaged inland wetlands
with mineral soils?

Yes

Were domestic studies
conducted on GHG emissions/removals on managed inland
wetlands
with mineral soils?

No

Are managed inland wetlands
with mineral soils a key category?

Yes

Estimate emissions
using default method
and country-specificdata (Tier 2).

No

Yes

Collect or compile
relevant datasets.

Estimate emissions using
default method andemission factors andnational activity data
(Tier 1)

No

Estimate emissions using
default emission factors
and activity data (Tier 1)

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5.2

GENERAL METHODS

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B IOMASS AND D EAD O RGANIC M ATTER

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The set of general equations to estimate the annual carbon stock changes on Managed Inland Wetlands are given
in Volume 4, Chapter 2 of the 2006 IPCC Guidelines.

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CHOICE OF METHOD AND TIER

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Management practices can significantly change mineral soil wetland C stocks, especially when flow is regulated
and sediment deposition rates change (McCarty and Ritchie 2002; Chmura et al. 2003). Changes in water tableaffect redox conditions in soils which affect decomposition rates and ultimately C stocks (Zdruli et al. 1995).
Restoration and rewetting of mineral soil wetlands can increase C stocks over time (Ballantine and Schneider(2009).

Figure 1.2 in Chapter 1 of Volume 4 of the 2006 Guidelines shows a decision tree for the identification of
appropriate Tiers for the inventory of land remaining in the same land-use category. Refer also to Figure 4.2 ofChapter 4 in Volume 1 of the 2006 Guidelines for assigning key categories.
Where there is no change in management or change in land-use the Tier 1 approach assumes no change inbiomass, dead wood or soil carbon in these wetlands. Following a change in management practices the biomass
and dead organic matter will not vary significantly after 10 years (Miller and Fujii, 2010), and this land area will
not fall into the definition of a key category (see Figure 1.2. in Chapter 1 of Volume 4 in the 2006 Guidelines for
guidance on defining key categories). Where there are significant changes in management, biomass stocks canchange accordingly. The Tier 1 approach of no change in biomass can be used if the land is not considered to bea key category, but if there is reliable data about rates of biomass change then countries should use a higher Tierto estimate emissions and removals associated with changes in biomass and dead organic matter. For Tier 2 and3, it is good practice to implement country-specific biomass and carbon stock inventories. If national data are notavailable for Tier 2, countries can use globally-compiled databases (e.g. FAO) and assume that wetland
vegetation does not have substantially different biomass carbon densities than upland vegetation (Bridgham etal., 2006). It is also good practice to use modern satellite imagery and field surveys to estimate sub-types ofWetlands, as outlined in Chapter 3 of the 2006 IPCC Guidelines. Where resources are not available to obtaincountry-specific data, wetland cover can also be derived from globally-compiled databases (e.g. WWF Global
Lakes and Wetlands Database – GLWD). Since several definitions exist for the classification of land as wetland(Mitsch and Gosselink, 2011), it is good practice that countries explicitly describe criteria of classification.

As stated in the 2006 Guidelines, Volume 1, Chapter 3 provides information on forest biomass uncertainties
associated with sample-based studies. FAO (2006) provides uncertainty estimates for forest carbon factors; basic
wood density (10 to 40%); annual increment in managed forests of industrialized countries (6 %); growing stock(industrialized countries 8%, nonindustrialized countries 30%); combined natural losses for industrializedcountries (15%); wood and fuelwood removals (industrialized countries 20%). The major sources of uncertainty
of wood density and biomass expansion factors are stand age, species composition, and structure. To reduce
uncertainty, countries are encouraged to develop country- or region specific biomass expansion factors and
BCEFs for FWMW. In case country- or regional-specific values are unavailable, the sources of default
parameters should be checked and their correspondence with specific conditions of a country should be
examined.
Uncertainty in dead organic matter pools is high relative to other carbon pools (Bradford et al. 2010). Deadorganic matter pools are dependent on the vegetation type (Currie and Nadelhoffer 2002), management (Scheller
et al. 2011), age of stand (if forested) (Sun et al. 2004), disturbance history (Tinker and Knight 2000) and thepresence of soil fauna (Hale et al. 2005). Errors as high as 100% are common when measuring DOM (Bradford
et al. 2009). For IMS wetlands it is highly unlikely that approaches other than inventory methods (Tier 2) will
be available to assess changes in DOM pools. Hence, good practice for inventory methods is critical for an
accurate assessment of DOM (see inventory discussion in Uncertainty Assessment in Soil C section – 5.2.3.5).
When no data on DOM are available, no change in DOM stocks can be assumed unless changes in DOM areassociated with a key category.

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TIER 1

Little information is available to conduct Tier 2 and Tier 3 soil C stock analyses for organic C in IMS wetlands.
For example, only two studies have assessed site specific changes in soil C pools following mineral soil wetland
drainage (Zdruli et al. 1995; Page and Dalal 2011). An alternative approach for Tier 1 could characterize thedirect soil emissions of CO2 by vegetation type, climate zone, management practices and soil type, however little
information is available to use a direct CO2 emission approach. Only four studies have assessed CO2 emissions
following a change in IMS wetlands (Danevcic et al. 2010; Fromin et al. 2010; Samaratini 2011; Sgouridis2011). Similarly, only three studies have measured direct emissions of CO2 following mineral soil wetland
restoration (Pfeifer-Meister 2008; Gleason et al. 2009). Because of the paucity of data on both changes in soil C
stock and on direct CO2 emissions, a Tier 1 approach based on annual multiple inventories is described to assesschanges in soil C stocks for mineral soil wetlands. If data from multiple inventories is not available, changes tosoil C stocks in IMS wetlands is assumed to be zero at Tier 1 level of estimation.

Chapter 2 of Volume 4 of the 2006 Guidelines provides general information about mineral soil classification andsoil C stock estimations. The annual change in carbon stocks in mineral soils is calculated using Equation 2.25
(IPCC 2006, Volume 4 chapter 2). The Tier 1 approach is based on changes in soil C stocks over a finite periodof time, assuming (i) over time, soil organic C reaches a spatially-averaged, stable value specific to the soil,
climate, land-use and management practices and (ii) soil organic C stock changes during the transition to a new
equilibrium SOC occurs in a linear fashion (IPCC 2006). To account for changes in SOC, countries need toestimate wetland areas according to climate zones, management practices and soil types. Table 5.1 below gives
some updated reference soil organic carbon stocks that should be used in preference to those in the 2006
Guidelines in table 2.3 of volume 4, chapter 2.

TABLE 5.1. DEFAULT REFERENCE SOIL ORGANIC CARBON STOCKS FOR IMS WETLANDS.

Region

Depth

IPCC (2006),
Table 2.3a

Batjes, 2011b

Mg C
ha-1

Error

Mg C ha-Error

1

Boreal0-30cm

146*

131

116

94

Cold temperate, dry

0-30cm87

78

Cold temperate, moist

0-30cm

87*

78

128

55

Warm temperate, dry

0-30cm

88*

79

74

45

Warm temperate, moist

0-30cm

88*

79

135

101

Tropical, dry

0-30cm

86

77

22

11

Tropical, moist

0-30cm

86

77

68

45

Tropical, wet

0-30cm

86

77

49

27

Tropical, montane

0-30cm

86

77

82

73

a

SOC stocks for mineral soils under natural vegetation presented as Tier 1 values in Table 2.3 of the IPCC
2006 Guidelines for National Greenhouse Gas Inventories, Volume 4. They are derived from soil databases
described by Jobbagy and Jackson (2000) and Bernoux et al. (2002).
bThis study presents revised estimates of the IPCC 2006 SOC stocks for mineral soils under natural vegetation
based on an expanded version of the ISRIC-WISE database (Batjes, 2009) which contains 1.6 times thenumber of soil profiles of the databases used in the IPCC 2006 SOC stocks estimate.
*SOC stock estimates from IPCC 2006 that were not based on expert estimates (Batjes, 2011).

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For this assessment only new values of SOCref were found to support the derivation of general stock change
factors for IMS wetlands utilizing the second equation in 2.25 from the 2006 IPCC Guidelines. Inventory
compilers should use the data from the appropriate chapters of Volume 4 of the 2006 IPCC Guidelines in
conjunction with the data in table 5.1, above. If countries have data that can be used to derive stock change
factors or suitable literature values for these parameters for wetlands by climate region it is good practice to use
them.

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For Tier 2, it is good practice to conduct soil inventories for the appropriate classification of soils, but if data are
not available, aggregate data (e.g. FAO) can be used for general classification. To conduct a Tier 2 approach soil
C stocks need to be known at two periods in time and stock changes are simply a function of the difference in C
stock divided by the time period (years) (Equation 5.1).

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EQUATION 5.1
ANNUAL CHANGE IN ORGANIC CARBON STOCKS IN MINERAL SOILS
(

)

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Where:ΔCMineral = annual change in carbon stocks in mineral soils, tonnes C yr-1
SOC0 = soil organic carbon stock in the last year of an inventory time period, tonnes C
SOC(0-T) = soil organic carbon stock at the beginning of the inventory time period, tonnes C
SOC0 and SOC(0-T) are calculated using the SOC equation in the box where the reference carbon stocks and stockchange factors are assigned according to the land-use and management activities and corresponding areas at eachof the points in time (time = 0 and time = 0-T)
T = number of years between inventory time periods, yr

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5.2.2

Non-CO 2 Emissions from IMS Wetlands

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5.2.2.1

M ETHANE E MISSIONS FROM IMS W ETLANDS

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Methane is produced in soils of IMS during anaerobic decomposition of organic matter, and emitted to theatmosphere after diffusion or ebullition through the water column or through plant-mediated transport. Several
factors have been identified as important controls on methane production and emission, including water level,temperature, and vegetation community and productivity (Whiting and Chanton, 1993). Despite current
understanding of the processes involved in methane production and emission from wetlands, it remains difficult
to accurately predict methane emissions with a high degree of confidence. Studies show high spatial variability
in methane emissions across large areas that have similar climate, vegetation, and topography, and within small
areas that have microscale variation in topography (Ding et al., 2003; Saarnio et al., 2009). In addition, there arevery few studies of methane emissions from IMS wetlands in Europe (Saarnio et al., 2009), tropical regions(Mitsch et al., 2010), and certain regions of North America (Pennock et al., 2010). Therefore, the default
emission factors we present necessarily have large uncertainties.

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Because of lack of data at this time, the only reliable higher Tier approach to assess C stock changes in soils for
IMS wetlands is through repeated inventories. The repeated inventory (stock changes) approach works well forany of the disturbances and restoration activities discussed in this chapter. Inventory methods, if conducted withconsistent methods for measurement and analysis from year to year tend to be very accurate in assessing change(Gillespie 1999). As stated in the 2006 Guidelines, the precision of an inventory is increased and confidence
ranges are smaller with more sampling. If plot locations are not re-locatable, if measurement methods change orif lab analyses protocols are not consistent with time, uncertainty increases for inventories.
As indicated in the 2006 Guidelines, uncertainties in 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 to provide additional coverage. It is good practice to design a classification that
captures the majority of land-use and management activities with a sufficient sample size to minimize
uncertainty at the national scale.

TIER 1The basic equation to estimate CH4 emission is shown in Eq. 5.2, where wetland area subject to a particularhydroperiod is multiplied by the default emission factor, and by the annual fractional period that the wetland area
is inundated by water, if known. This allows for the incorporation of wetland hydroperiod, which may be
determined by natural causes or as a consequence of management activity. If the annual fractional period ofinundation is unknown, then a default fraction of 1 is assumed.

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EQUATION 5.2
METHANE EMISSIONS FROM IMS WETLANDS
∑

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336
337
338
339
340
341
342
343
344
345

{

}

Where:MIMS = annual mass of methane emitted from IMS wetlands, kg yr-1
EF = annual emission factor, g C-CH4 m-2 yr-1
A = wetland area experiencing a particular hydroperiod, m2
T = annual fractional period of inundation, (dimensionless)
Table 5.2 gives default CH4 emission factors and error ranges for IMS wetlands that are permanently inundated,
specific for different climate zones.

TABLE 5.2 DEFAULT CH4 EMISSION FACTORS FOR PERMANENTLY INUNDATED IMS WETLANDS

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349
350
351

RegionEmission factor EFCH4(g CH4-C m-2 yr-1)

Range(g CH4-C m-2 yr-1)

References

Boreal5.04

2.52 – 7.55

Bridgham et al., 2006

Temperate Cool

33.5

4.21 – 80.0

Bridgham et al., 2006; Altor
and Mitsch, 2005; Kim et al.,
1998; Badiou et al., 2011

Temperate Warm

43.9

7.69 - 182

Bridgham et al., 2006; Yu et al.,2008; Pulliam, 1993

Tropical

91.7

6.70 - 350

Devol et al., 1990; Smith et al.,
2000; Nahlik and Mitsch, 2010

Several studies of CH4 emissions from seasonally inundated IMS wetlands have been conducted, especially intemperate regions. If a wetland is known to be seasonally inundated and is located in a temperate or tropicalregion, an alternative is to apply the following default emission factors (Table 5.3) to the total wetland area tocalculate an annual emission.
TABLE 5.3 DEFAULT CH4 EMISSION FACTORS FOR SEASONALLY INUNDATED IMS WETLANDS
RegionEmission factor EFCH4(g CH4-C m-2 yr-1)

Range(g CH4-C m-2 yr-1)

References

Temperate

16.7

0.13 – 46.8

Bridgham et al., 2006; Altor
and Mitsch, 2005; Pennock etal., 2010; Gleason et al., 2009;
Morse et al., 2012; Danevcic etal., 2010; Song et al., 2009;
Ding and Cai, 2007; Song et al.,
2003; Bartlett et al., 1993

Tropical

135

9.5 - 350

Nahlik and Mitsch, 2010;
Bartlett et al., 1993

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CALCULATING STEPS FO R TIER 1

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TIER 2

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TIER 3377

5.2.2.2

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390
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392

Nitrous oxide (N2O) is an important greenhouse gas.The microbial processes involved in production of N2O are
nitrification (nitrifier denitrification, in particular) and denitrification. Therefore, N2O emissions vary withclimate, soil-water conditions and management. Due to complexity of the interactions between these factors,
N2O shows very high spatial and temporal variations; even diurnal variations.

393
394
395

EQUATION 5.3
N2O EMISSIONS FROM IMS WETLANDS

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397
398
399
400
401

Step 1: Determine the area of wetland experiencing a particular hydroperiod; if hydroperiod is unknown thenassume permanent inundation (Tinundation=1). Using equation 5.2, the appropriate EFCH4 (Table 5.2), and theannual fractional period of inundation, estimate the annual CH4 emission from that area of wetland. If a wetland
is known to be seasonally inundated, an alternative is to apply the appropriate EFCH4 (Table 5.3), setting
Tinundation=1.
Step 2: Repeat Step 1 for each wetland area experiencing a particular hydroperiod.
Step 3: Sum the annual CH4 emissions from each wetland area to calculate a total annual CH4 emission from
IMS wetlands.

Tier 2 calculations use country-specific emission factors and parameters, to reflect regionally important wetland
types and hydrologic dynamics. For example if seasonally-inundated wetlands are a dominant IMS wetland typeof the country, it is recommended that wetland hydroperiod be determined.

Tier 3 calculations include site-specific determinations of methane emissions from dominant wetland types, or
may include approaches such as dynamic modeling of methane fluxes (Saarnio et al., 2009). Models based on
simple regressions (Christensen et al., 1996; Saarnio et al., 1997; Juutinen et al., 2003) or sophisticated processbased models (Walter and Heimann, 2000; Kettunen, 2003; Cui et al., 2005) can be applied to specific wetland
ecosystems, however these models require input data sets that may be difficult to obtain.

N ITROUS O XIDE E MISSIONS FROM IMS W ETLANDS

A wetland system can be a major N2O source or sink as a result of ecologic conditions and microbial activity.
The increase in anthropogenic nitrogen discharge to the natural environment may enhance the N2O flux to theatmosphere. Generally, wetlands with low N availability are considered relatively minor sources of N2O (Durand
et al., 2010). Relatively high N2O emissions from IMS wetlands are associated with agricultural runoff (Phillips
and Beeri, 2008; DeSimone et al., 2010), and livestock runoff (Chen et al., 2011; Oates et al., 2008; Jackson etal., 2006; Holst et al., 2007; Walker et al., 2002).In order to avoid double-counting N2O emitted from the use offertilizers, and urine and dung deposition from grazing animals, it is suggested to follow 2006 Guidelines(Volume 4, Chapter 11) for estimating N2O emissions from those IMS wetlands receiving agricultural or otherrunoff.

Where
NIMS = N2O emissions form IMS wetlands, kg yr-1
EF = Emission Factors (see Table 5.4 for defaults) kg km-2 yr-1
A = Area of IMS wetlands km-2

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TABLE 5.4 EMISSION FACTORS FOR ESTIMATING N2O EMISSIONS FROM IMS WETLANDS.
RegionEmission factor EFN2O

Uncertainty
range

Reference/Comments

Polar
BorealTemperate

Tropical155-231 kg km-2 yr-1

Wang et al., 2009. In China
Eutrophic conditions

0-1367 kg km-2 yr-1

Hasegawa et al., 2000 Paddy
field

0.5 kg km-2 yr-1

Vilain et al., 2010. Riparianbuffer

-0.2-0.9 kg ha-1 yr−1

0.8

Boeckx and Cleemput, 2006
Riparian buffer

4.07 kg ha-1 yr−1
2.09 kg ha-1 yr−1

1.72

4.07 kg ha-1 yr−1
2.09 kg ha-1 yr−1

1.72

Jiang et al, 2009 (Marsh)
Jiang et al, 2009 (Rice field)
Fertilizer application
Jiang et al, 2009 (Conversion ofMarsh to rice field)
Jiang et al, 2009 (Conversion ofMarsh to dryland)

4.07 kg ha-1 yr−1
4.90 kg ha-1 yr−1_

1.72

15.7 g m-2 h-1
98.9 g m-2 h-1
138.8 g m-2 h-1
429.5 g m-2 h-1

0.79

0.79

1.52_
-177.6–163.1-265.1–2101.4-278.0–437.0
71.0–1641.1

Wang et al.,2006. In China
Eutrophied conditions

403
404

5.3

405

DRAINAGE, CREATION, AND RESTORATIONOF INLAND MINERAL SOIL WETLANDS

406
407

This section provides some additional methodological guidance for cases when the water table is changed (either
raised or lowered) through drainage, restoration and creation of IMS wetlands.

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412
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414
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416
417
418
419
420
421
422
423
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425

5.3.1

Introduction

Drainage and restoration of wetlands are very common management activities that may result directly frommanagement or may be part of land use conversion from, or to, wetlands. Management activities that commonlyoccur on wetlands include agriculture, grazing, and forestry.
Draining of mineral wetlands generally leads to other land uses such as agriculture, grazing or forestry, althoughwetlands may be drained and still meet the criteria for wetlands. Following limited drainage, wetlands can bevery productive even if still meeting the wetland criteria. Drainage leads to lower water tables which affectprocesses like decomposition, above and belowground productivity, and organic matter and nutrient
mineralization. Drainage can lead to changes in vegetation, soil carbon stocks, and greenhouse gas fluxes.
Although some wetlands have been drained for centuries, drainage increased tremendously approximately 100
years ago with the onset of modern agriculture and the growth of urban environments. Globally, approximately
54% of mineral soil wetlands have been converted to other land uses, mostly by drainage (Bridgham et al.,2006).
Restoration is “the process of assisting the recovery of an ecosystem that had been degraded, damaged, or
destroyed” (SER 2004). Wetland restoration is a common activity in response to significant wetland loss anddegradation on a global scale. Wetland restoration can take many forms, including: invasive species removal,

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conversion of agricultural lands back to wetlands, filling or blocking ditches, reducing nutrient and sedimentlevels, to name a few. There is large potential for increased carbon storage from restoring mineral soil wetlands.
For instance, Bridgham et al. (2006) estimated that mineral soil wetlands are currently losing roughly 45 Mt C
yr-1 of carbon sequestration potential from wetland conversion. This potential to sequester more carbon has beenborne out by many restoration studies (Euliss et al. 2006, Gleason et al. 2009, Ballantine and Schneider 2009,
Card et al. 2010, Badiou et al. 2011). Badiou et al. (2011) estimated from their study of 22 wetlands that
restored wetlands were accumulating 2.7 Mg C ha-1 yr-1 as soil organic carbon. Ballantine and Schneider (2009)
surveyed 35 restored wetlands in New York and found that 17% (6% to 23%) of the reference carbon stock had
accumulated over a 55 year chronosequence. Ballantine and Schneider (2009) also summarized the literatureand found that wetlands recovered about 50% of their reference soil carbon after 55 years, whereas plant
standing biomass reached reference conditions at 55 years. Time to recover soil C after wetland restoration
varies greatly depending upon the amount of soil C lost, soil wetness, vegetation, and hydrogeomorphic setting.
For instance, Card et al. (2010) estimated that it would only take 7-11 years after restoration in riparian wetlands
to come back to reference conditions.

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477
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5.3.2

Although restored wetlands tend to increase their ability to sequester carbon, restored wetlands may also increase
their emissions of CH4 and N2O, and so could increase their climate change impacts despite storing more carbon(Bridgham et al. 2006). This is especially true for mineral wetlands, which can have relatively large CH4
emissions. For example, peatlands occupy 32% more land then mineral wetlands, but emit 46% less CH4(Bridgham et al. 2006). Much less information exists for trace gas emissions compared to soil carbon contents in
restored wetlands. In general, emissions of CH4 and N2O are affected by hydroperiod, vegetation, and substratequality and quantity. A few studies in seasonal wetlands have found that restoration had little impact on either
CH4 or N2O emissions (Gleason et al. 2009, Pfeifer-Meister 2008). Conversely, other studies, especially inrestored wetlands with permanent or semi-permanent hydroperiods, were found to have increased CH4 and/or
N2O (Badiou et al. 2011).
Data is still sparse to document how wetland restoration affects emissions of total greenhouse gas emissions (seesummaries by Roulet 2000, Bridgham et al. 2006). Few studies of restoration effects on mineral wetlands havebeen conducted. Badiou et al. (2011) measured greenhouse gas fluxes across a range of prairie potholes in
Canada and calculated that they would sequester approximately 3.25 Mg CO2 equivalents ha-1 yr-1, even after
accounting for an increase in CH4 and N2O emissions. Gleason et al. (2009) found no significant difference inCO2, CH4, or N2O exchange between cropland and restored prairie pothole wetlands on cropland 16 years after
restoration.

Methodological Issues

The primary challenges to wetland restoration and creation are the development of wetland hydrology and theestablishment of vegetation (US EPA, 2003). Wetlands are restored or created for a variety of reasons, including
water-quality enhancement (treatment of wastewater, stormwater, acid mine drainage, agricultural runoff;
Hammer, 1989), flood minimization, and habitat replacement (Mitsch et al., 1998). Wetlands created for the
purposes of wastewater treatment are not covered in this Chapter; please refer to Chapter 6 (ConstructedWetlands) in this Supplement for guidance on these types of wetlands. Flooding of land to create reservoirs iscovered in Chapter 7 of Volume 4 of 2006 Guidelines.
The inventory of greenhouse gas emissions requires the assessment of all 5 IPCC carbon pools as well as
emissions of non-CO2 gases, stratified by climatic zones and conversion types. For example, the initial raising of
the water table might result in death of all or part of the living biomass, with transfers to dead organic matter andlitter pools or decomposition and losses to the atmosphere. However, with time, original vegetation mightcolonize the wetland, increasing living biomass pool again. Thus, changes and transfers in C pools will vary
according to the stage of the conversion until a new steady state is achieved.
The appropriate Tier to be used in the inventory can be decided based on Figure 1.3 of Chapter 1 of Volume 4 inthe 2006 Guidelines.
When a new wetland is created transfers of C among pools can be abrupt or follow different transitional stages
until a new steady state is achieved. For this reason, all carbon pools and exchanges among them have to beaccounted for in the first year of conversion and in the subsequent 9 years. The 10 year transitional stage isassumed based on studies of vegetation recovery during wetland restorations but might not apply for every land
use change. Countries are encouraged to establish monitoring programs in representative plots of key categories
to determine which time frame is more appropriate.

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5.3.2.1

B IOMASS

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493
494
495
496
497
498
499
500
501
502
503
504
505

TIER 1.

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510
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512
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514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529

TIER 2

530
531
532

TIER 3533

5.3.2.2

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535
536
537
538
539
540
541

Dead Organic Matter and Litter summed constitute the Dead Organic Matter pool. These pools vary greatly
according to the type of initial land use (Forest, Crop, Grassland or Other Uses) and the rates of transfers fromother pools to the DOM pool will also be quite different depending on the velocity of the conversion and thetypes of Other Land Use Converted to Wetland. For example, after rewetting of a forest leaves might fall anddecompose while trunks will remain as DOM, whereas grasses might be all decomposed in the first year of
conversion. If anaerobic conditions develop after complete rewetting, decomposition might slow down after the
initial phases of transition.

In a Tier 1 approach changes in biomass carbon stock wetland creation are calculated using Equation 2.15 from
Chapter 2 of Volume 4 of the 2006 Guidelines. For simplicity, in Tier 1 it can be assumed that once the land isrewetted all the vegetation will initially die and the resulting plant organic matter will decompose, with theecosystem reaching a new steady-state immediately after the conversion. Average C stock changes are calculated
from the difference between initial and final stocks. Default values for biomass carbon stocks for each type ofother land use (Forest, Grassland, Cropland) can be obtained from their respective chapters in Volume 4 of the2006 Guidelines. After this transition period of 10 years the land is assumed to have reached a new equlibrium
state and would be reported in a “land remaining” category (e.g. forest land remaining forest land,or grassland
remaining grassland).
Tier 1 requires the estimation of biomass stocks in land before and after the conversion to Wetland. Althoughrewetting will cause variable death rates depending on the type of living biomass prior to conversion, at this levela simple assumption can be made that all biomass is lost and the ecosystem achieves a new steady-state in theyear of conversion. Hence, biomass stock after conversion is zero. Initial biomass is estimated using the methods
provided in the 2006 Guidelines for each type of Land cover, that is, Chapter 4 for Forest, Chapter 5 for
Cropland and Chapter 6 for Grassland. Annual change in biomass carbon stock is calculated using Equations
2.15 and 2.16 from Chapter 2 of Volume 4 of 2006 Guidelines. Since biomass after conversion is assumed to bezero, ∆CCONVERSION term in equation 2.15 also equals to zero. If data is not available, countries might use
global biomass stocks datasets and emission/removal factors suggested in the referred respective chapters.
Tier 2 uses country-specific data for each climatic, ecosystem type and management practice to estimate biomasschanges following Land conversion to Wetland. In this case the Tier 1 assumption of a new steady-state
condition in the first year is replaced by the monitoring of the transitions in time of average carbon pools.
Equations 2.5 and 2.6 from Chapter 2 of Volume 4 of the 2006 Guidelines are used. To estimate biomass poolssuggested methods and respective equations are the same as those in Section 5.2.1.above.
It is good practice to implement country-specific biomass and carbon stock inventories. If national data are notavailable for Tier 2, countries can use globally-compiled databases (e.g. FAO) and assume that wetland
vegetation does not have substantially different biomass carbon densities than terrestrial vegetation (Bridgham etal., 2006). It is also good practice to use modern satellite imagery and field surveys to estimate sub-types ofWetlands, as delineated in Chapter 3 of the 2006 IPCC Guidelines. Where resources are not available to obtaincountry-specific data, wetland cover can also be derived from globally-compiled databases (e.g. WWF Global
Lakes and Wetlands Database – GLWD). Since several definitions exist for the classification of land into the
Wetland category (Mitsch and Gosselink, 2011), it is good practice that countries explicitly describe criteria ofclassification.
Under a Tier 2 approach empirical data is used to evaluate the evolution in time of biomass stocks in Other Land
Converted to Wetland immediately after the conversion and in the following 9 years of succession. It is goodpractice to obtain country-specific data from each previous kind of vegetation (forest, crop and grassland) undereach climatic region and to subsequently follow changes in biomass stocks according to management practices
under the Land Converted to Wetland. In biomass carbon stock changes accounted for longer periods of time,
results are converted to average annual values.

Tier 3 uses country and ecosystem specific data to model the evolution of biomass carbon stocks in time, fromthe conversion year until a new steady-state is reached

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Because average DOM stock changes will depend on the stage of the transition from one type of land use toanother it is good practice to follow the transitional process until a new steady-state is reached. Estimates should
be expressed on an annual average basis for consistency. Given the variability of the DOM stock, there are nodefault values for this carbon pool and is good practice that countries strive to obtain country specific data.

551

5.3.2.3

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Few studies have assessed the carbon implications of restoring and creating IMS wetlands. In general, therestoration and creation of IMS wetlands leads to increases in soil C stocks over time (Badiou et al. 2011; Wolfet al. 2011; Ballantine and Schneider 2009; Meyer et al. 2008; Wiggington et al. 2000). Research on C dynamics
in created wetlands is sparse with only a few a studies addressing C stocks in soils or greenhouse gas fluxes (Shaet al. 2011; Wolf et al. 2011; Ahn and Peralta 2009). Although there are more data on C pools and fluxes fromwetland restoration studies, many do not report bulk density so that stocks can be calculated (e.g. Hartman et al.
2008), measurement systems such as eddy covariance include landscape components other than restored
wetlands (e.g. Herbst et al. 2011), or difficulty in interpreting numbers to make independent calculations (e.g. Lu
et al. 2007). The most detailed analysis of both soil c stocks and greenhouse gas fluxes in restored wetlands has
been conducted in the Prairie Pothole Region of Canada and the United States (Badiou et al. 2011; Card et al.
2010; Gleason et al. 2009; Euliss et al. 2006).

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For simplicity Tier 1 assumes that a new steady-state is achieved in the first year of conversion while it is more
likely that the transition for this new state will take longer and countries are encouraged to use Tiers 2 and 3 toobtain more accurate estimations. If countries choose to use Tier 1 method after the first year this land should beclassified as Wetland Remaining Wetland.

TIER 1
Tier 1 characterises the direct soil emissions of CO2 by climate zone, management practices and soil type,whereas for non-CO2 emissions, Tier 1 estimates include factors of climate zone, management practices andinundation regime Equation 5.4 gives the method that is applicable to CO2, CH4 and N2O. Emissions are
estimated by multiplying the emission rate for pristine wetlands by an adjustment factor AF. Values of F aregiven in table 5.5. Emission rates for pristine wetlands for CH4 are given in tables 5.2 and 5.3 and for N2O intable 5.4 with emission rates for CO2 listed in table 5.6, below.

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590
591
592

S OIL C ARBON

EQUATION 5.4
SOIL EMISSIONS FROM DRAINAGE, CREATION, AND RESTORATION OF IMS WETLANDS

Where:
Ep,l = Emissions from Soil from management, restoration or creation of IMS wetlands, (tonnes)
With:
p = gas (CO2, CH4 or N2O)
l is land use type.
AFp,l = Adjustment Factor to account for drainage, creation and restoration for gas p and land type l,(+ve = emission, -ve = removal) Table 5.5 provides default values. (dimensionless)
EFp = Emission Factor of pristine wetland for gas p
Al = area of land type l (ha)Table 5.5 provides emission adjustment factors based on the data reported in the studies above. However, thenumbers were obtained from many different approaches, such as modelling by Li et al. (2004), gaseous fluxes
measurements by Page and Dalal (2011) and biomass changes measured by Ballantine and Schneider (2009).
Countries are encouraged to develop their own studies based on local climate and vegetation types.

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TABLE 5.5. SOIL EMISSION ADJUSTMENT FACTORS DUE TO DRAINAGE OR RESTORATION OF IMS WETLANDSTO BE USED IN EQUATION 5.4 (DIMENSIONLESS) (TO BE COMPLETED)RegionBorealDeforestation/Drainage

Restoration

CO2

CH4

CO2

CH4

N2O

+3

-1

-1.2

+7

-7

Li et al., 2004*

-3

-0.7
to +1

+0.3
to
+10

Badiou et al, 2011+

N2O

Source+9Temperate

+1

-0.25
to -1

+0 to
+30

Page & Dalal,
2011++000Gleason et al., 2009#

North
America

+0.2
5

-0.4

Euliss et al. 2006†

Canada+0.2-0.3

Euliss et al. 2006†-0.2

Mckenna, 2003**

Humid
Sub-Tropical

+2

-1

+8

-1.5

+47

-1

Li et al., 2004*

Humid

-8

Craft et al., 2003††

Continental-0.6
to 0.7

Ballantine &Schneider, 2009‡

Global+1

Bridgham et al.,
2006***

Notes:* Values based on a process-based model, Wetland-DNDC+

Praire potholes, long-term restoration (> years)++

Melaleuca freshwater forests# Wetland Croplands compared to Wetland Grasslands†

Aquatic croplands, values computed as OC over a period of 10 years††

1 year old restored marsh** Woodland converted to upland grass wetland 6 years before the study‡

Depressional wetlands with 10 to 50 years of restoration*** Estimates based on losses of wetland area only

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SourceBorealTemperate

North
America
CanadaHumid
Sub-Tropical
Humid
Continental
GlobalNotes:To be completed
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TIER 2 AND 3

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5.4

Little information is available to conduct Tier 2 and Tier 3 soil C stock analyses for Lands Converted to IMS
wetlands unless in the Prairie Pothole Region of Canada and the United States (see below). Outside of thisregion single studies have been done in New York (Ballantine and Schneider 2009), Virginia (Wolf et al. 2011),
North Carolina (Morse et al. 2012), South Carolina (Wiggington et al. 2000), Florida (Schipper and Reddy
1994), Louisiana (Hunter et al. 2008), Ohio (Zhang and Mitsch 2007), Nebraska (Meyer et al. 2008), and Oregon(Pfeifer-Meister 2008) within the United States, and in Denmark (Herbst et al. 2011) and China (Lu et al. 2007).
Although there are several studies listed from the east coast of the United States, the wetland types are very
different ranging from riparian bottomland hardwood ecosystems in South Carolina (e.g. Wiggington et al. 2000)
to marsh ecosystems in New York (Ballantine and Schneider 2009).
Due to the number of studies that have assessed soil C stock changes resulting from the restoration of prairie
pothole wetlands, a direct rate change for this Region is reasonable. Most recently Badiou et al. (2011)
calculated the mean soil C sequestration rate for the Canadian part of the Prairie Pothole Region to be 2.70 Mg C
ha-1 yr-1 which is slightly lower than the 3.05 Mg C ha-1 yr-1 found by Euliss et al. (2006) for semi-permanent
prairie potholes in the United States part of the Prairie Pothole Region. Based on the large number of wetlands
assessed in both studies, 2.7 to 3.1 Mg C ha-1 yr-1 are reasonable bounds for estimating soil C stock changes inprairie pothole wetlands. For IMS wetlands other than prairie potholes, estimation of soil carbon stock changes
due to management activity requires a two-step approach. Stocks are first estimated in previous land use
according to their respective matrix of vegetation, climate and management practices and methodologies
described in the appropriate Chapters of Volume 4 of the 2006 Guidelines (e.g. Chapter 4 if the original land use
is Forest). Then stocks are estimated in the newly wetted soils employing the methods described in Section 5.2.3(Soil Carbon).

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

Consistent reporting is a major issue for IMS wetlands because multiple activities or land uses may occur. In
addition to managed peatlands and flooded land already given in IPCC 2006, a complete carbon inventory on
this land use should include CO2, and non-CO2 emissions and removals from Wetlands Converted to Other land
uses and activities of wetland management (i.e. biomass burning, harvesting).

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The countries selecting other land uses in inland mineral wetlands should not change during the whole reporting
period to avoid double accounting. For example, if a forested wetland has been reported as a forest it should bereported as a forest during the whole series. It is suggested that flooded lands, peatlands, and coastal wetlands
are clearly excluded from IMS wetlands and this separation is applied consistently throughout the reporting
period.
It is good practice to disaggregate the type of IMS wetlands according to national circumstances and employ
national emission factors if possible. Carbon stocks and fluxes are highly variable for wetland type. It is also
good practice to apply methods that separate riparian ecosystems from upland ecosystems considering theusually larger biomass stocks in riparian ecosystems.

5.5

FUTURE METHODOLOGICAL GUIDANCEIMS wetlands are significant compartments in carbon cycle. However, accounting carbon emissions andremovals is challenging due to diversity in this land use. The diversity is not only caused by soil and climaticconditions but also seasonality of water table. Changes in water table affect CO2 and CH4 emissions and N2O insome cases considerably. Besides, mineral wetlands are reported under other land uses when they fit under thedefinition of forest, agriculture, or grassland.
It is clear that removal of biomass in wetlands with human activities like harvesting, or grazing would affect thestocks or fluxes of carbon different than upland conditions. Particular effort should be employed to differentiate
multiple uses in relation with wetlands (i.e. forested wetlands, wet grasslands) for future methodologicalimprovements.

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