Boxes

Box 4.1 Levels of detail 4.8

Box 4.2 Biomass conversion and expansion factors for assessing biomass and carbon in forests 4.13

Box 4.3 Examples of good practice approach in identification of lands converted to Forest Land 4.34

4 FOREST LAND 4.1 INTRODUCTION

This chapter provides methods for estimating greenhouse gas emissions and removals due to changes in biomass, dead organic matter and soil organic carbon on Forest Land and Land Converted to Forest Land. It builds on the Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories (1996IPCC Guidelines) and the Good Practice Guidance for Land Use, Land-Use Change and Forestry (GPG-LULUCF). The chapter:

• addresses all five carbon pools identified in Chapter 1 and transfers of carbon between different pools within the same land areas;

• includes carbon stock changes on managed forests due to human activities such as establishing and harvesting plantations, commercial felling, fuelwood gathering and other management practices, in addition to natural losses caused by fire, windstorms, insects, diseases, and other disturbances;

• provides simple (Tier 1) methods and default values and outline approaches for higher tier methods for the estimation of carbon stock changes;

• provides methods to estimate non-CO2 greenhouse gas emissions from biomass burning (other non-CO2 emissions such as N2O emissions from soils are covered in Chapter 11);

• should be used together with generic description of methods and equations from Chapter 2, and the approaches for obtaining consistent area data described in Chapter 3.

The Guidelines provide methods for estimating and reporting sources and sinks of greenhouse gases only for managed forests, as defined in Chapter 1. Countries should consistently apply national definitions of managed forests over time. National definitions should cover all forests subject to human intervention, including the full range of management practices from protecting forests, raising plantations, promoting natural regeneration, commercial timber production, non-commercial fuelwood extraction, and abandonment of managed land.

This chapter does not include harvested wood products (HWP) which are covered by Chapter 12 of this Volume.

Managed Forest Land is partitioned into two sub categories and the guidance and methodologies are given separately in two sections:

• Section 4.2 Forest Land Remaining Forest Land

• Section 4.3 Land Converted to Forest Land

Section 4.2 covers the methodology that applies to lands that have been Forest Land for more than the transition period required to reach new soil carbon levels (default is 20 years). Section 4.3 applies to lands converted to Forest Land within that transition period. The 20-year interval is taken as a default length of transition period for carbon stock changes following land-use change. It is good practice to differentiate national forest lands by the above two categories. The actual length of transition period depends on natural and ecological circumstances of a particular country or region and may differ from 20 years.

Unmanaged forests, which are brought under management, enter the inventory and should be included in the Land Converted to Forest Land. Unmanaged forests which are converted to other land uses enter the inventory under their post conversion land-use categories with the appropriate transition period for the new land-use category.

If there are no data on land conversion and the period involved are available, the default assumption is that all managed forest land belongs to the category Forest Land Remaining Forest Land and greenhouse gas (GHG) emissions and removals are estimated using guidance given in Section 4.2.

Relevant carbon pools and non-CO 2 gases

The relevant carbon pools and non-CO2 gases for which methods are provided are given below:

• Biomass (above-ground and below-ground biomass)

• Dead organic matter (dead wood and litter)

• Soil organic matter

The selection of carbon pools or non-CO2 gases for estimation will depend on the significance of the pool and tier selected for each land-use category.

Forest land-use classification

Greenhouse gas emissions and removals per hectare vary according to site factors, forest or plantation types, stages of stand development and management practices. It is good practice to stratify Forest Land into various sub categories to reduce the variation in growth rate and other forest parameters and to reduce uncertainty (Box 4.1). As a default, the Guidelines use the most recent ecological zone (see Table 4.1 in Section 4.5 and Figure 4.1 in this chapter) and forest cover (see Table 4.2 in Section 4.5 and Figure 4.2 in this chapter) classifications, developed by the Food and Agriculture Organization (FAO, 2001). National experts should use more detailed classifications for their countries, if available and suitable, given the other data requirements.

Box 4.1

Levels of detail

Stratification of forest types into homogeneous sub-categories, and if possible at regional or subregional level within a country, reduces the uncertainty of estimates of greenhouse gas emissions and removals. For simplicity and clarity, this chapter discusses estimation of emissions and removals at national level and for a relatively small number of subcategories of Forest Land. This level of detail is designed to match the available sources of default input data, carbon contents and other assumptions. It is important, however, for users of these Guidelines to understand that they are encouraged to carry out the greenhouse gas emissions inventory calculations at a finer level of detail, if possible. Many countries have more detailed information available about forests and land-use change than were used in constructing default values in this Chapter. These data should be used, if suitable, for the following reasons:

1. Geographic detail at regional rather than national level

Experts may find that greenhouse gas estimation for various regions within a country are necessary to capture important geographic variations in ecosystem types, biomass densities, fractions of cleared biomass which are burnt, etc.

2. Finer detail by subcategory

Experts may subdivide the recommended land-use categories and subcategories to reflect important differences in climate, ecology or species, forest types, land-use or forestry practices, fuelwood gathering patterns, etc.

In all cases, working at finer levels of disaggregation does not change the basic nature of the method of estimations, although additional data and assumptions will generally be required beyond the defaults provided in this Chapter. Once greenhouse gas emissions are estimated, using the most appropriate level of detail determined by the national experts, results should also be aggregated up to the national level and the standard categories requested in these Guidelines. This will allow for comparability of results among all participating countries. Generally, the data and assumptions used for finer levels of detail should also be reported to ensure transparency and repeatability of methods.

Terminology

The terminology used in the methods for estimating biomass stocks and changes need to be consistent with the terminologies and definitions used by the Food and Agriculture Organization (FAO). FAO is the main source of activity data and emission factors for forest and other land-use categories in Tier 1 level calculations. Examples of terminology from FAO are: biomass growth, mean annual increment, biomass loss, and wood-removal. The Glossary in Annex 4A. 1 includes definitions of these terminologies.

Chapter 4: Forest Land

Figure 4.1 Global ecological zones, based on observed climate and vegetation patterns (FAO, 2001). Data for geographic information systems available at http://www.fao.org.

Figure 4.1 Global ecological zones, based on observed climate and vegetation patterns (FAO, 2001). Data for geographic information systems available at http://www.fao.org.

Forest World Original Cover

Figure 4.2 Global forest and land cover 1995. Original spatial resolution of the forest data is 1 km2 (analysis U.S. Geological Survey (Loveland et al., 2000) and FAO (2001)). Data for geographic information systems available at http://edc.usgs.gov.

Figure 4.2 Global forest and land cover 1995. Original spatial resolution of the forest data is 1 km2 (analysis U.S. Geological Survey (Loveland et al., 2000) and FAO (2001)). Data for geographic information systems available at http://edc.usgs.gov.

4.2 FOREST LAND REMAINING FOREST LAND

This section deals with managed forests that have been under Forest Land for over 20 years (default), or for over a country-specific transition period. Greenhouse gas inventory for Forest Land Remaining Forest Land (FF) involves estimation of changes in carbon stock from five carbon pools (i.e., above-ground biomass, below-ground biomass, dead wood, litter, and soil organic matter), as well as emissions of non-CO2 gases. Methods for estimating greenhouse gas emissions and removals for lands converted to Forest Land in the past 20 years (e.g., from Cropland and Grassland) are presented in Section 4.3. The set of general equations to estimate the annual carbon stock changes on Forest Land are given in Chapter 2.

4.2.1 Biomass

This section presents methods for estimating biomass gains and losses. Gains include total (above-ground and below-ground) biomass growth. Losses are roundwood removal/harvest, fuelwood removal/harvest/gathering, and losses from disturbances by fire, insects, diseases, and other disturbances. When such losses occur, below-ground biomass is also reduced and transformed to dead organic matter (DOM).

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