A complete Grassland inventory for Tier 1 has three elements: 1) carbon stock changes and non-CO2 (CH4, CO, N2O, NOx) emissions from biomass burning have been estimated for all Land Converted to Grassland and Grassland Remaining Grassland during the inventory time period; 2) inventory analysis addressed the impact of all management practices described in the Tier 1 methods; and 3) the analysis accounted for climatic and soil variation that affects emissions and removals (as described for Tier 1).
The latter two elements require assignment of management systems to grassland areas and stratification by climate regions and soil types. It is good practice for countries to use the same area classifications for biomass and soil pools in addition to biomass burning (to the extent that classifications are needed for these source categories). This will ensure consistency and transparency, allow for efficient use of land surveys and other data collection tools, and enable the explicit linking between changes in carbon stocks in biomass and soil pools, as well as non-CO2 emissions from biomass burning.
For biomass and soil C stock estimations, a Grassland inventory should address the impact of land-use change (Land Converted to Grassland) and management. However, in some cases, activity data or expert knowledge may not be sufficient to estimate the effects of management practices, such as extent and type of silvopastoral management, fertilizer management, irrigation, grazing intensity, etc. In those cases, countries may proceed with an inventory addressing land use alone, but the results will be incomplete and omission of management practices must be clearly identified in the reporting documentation for purposes of transparency. If there are omissions, it is good practice to collect the additional activity data on management for future inventories, particularly if biomass or soil C is a key source category.
C stock changes may not be computed for some grassland areas if greenhouse gas emissions and removals are believed to be insignificant or constant through time, such as non-woody grasslands where there are no management or land-use changes. In this case, it is good practice for countries to document and explain the reason for omissions.
For biomass burning, non-CO2 greenhouse gases should be reported for all controlled burns and wildfires on managed grasslands. This includes conversion of Forest Land to Grassland, where the amount of fuel available for burning is usually more significant than in the other land-use categories; emissions from burning of DOM and cleared tree biomass should be included in these estimates. Savannah burning also constitutes a large source of non-CO2 emissions from biomass burning. Biomass burning should be reported where wildfire on unmanaged land is followed by transition to managed land during the inventory reporting period.
Estimation of the area actually burnt is critical to the reliable calculation of non-CO2 greenhouse gas emissions. Remotely-sensed estimates of the area burnt need to be rigorously tested against ground data to ensure that areas burnt are accurately estimated. The use of regionally average statistics is likely to be highly unreliable for estimating the area burnt in a specific country.
In grasslands where fire management is changing the balance between grass and woody vegetation, the emissions of CO2 in fire may not be balanced by the re-fixation of an equivalent amount of C into biomass in the short-term. In such situations, net release of CO2 caused by burning should also be reported.
A complete Tier 2 inventory has similar elements as Tier 1, but incorporates country-specific data to estimate C stock change factors, reference soil C stocks, biomass density estimates (fuel load), and combustion and emission factors for biomass burning; to develop climate descriptions and soil categories; and to improve management system classifications. Moreover, it is good practice for a Tier 2 inventory to incorporate country-specific data for each component. Inventories are still considered complete, however, if they combine country-specific data with Tier 1 defaults.
In addition to Tiers 1 and 2 considerations, completeness of Tier 3 inventories will depend on the components of the country-specific evaluation system. In practice, Tier 3 inventories are likely to more fully account for emissions and removals for grasslands using more finely resolved data on climate, soils, biomass burning and management systems. It is good practice for inventory compilers to describe and document the elements of the country-specific system, demonstrating the completeness of the approach and data sources. If gaps are identified, it is good practice to gather additional data and further develop the country-specific system.
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