Criteria for Evaluation and Selection of Parameters

The default values provided in many databases such as IPCC, FAO and EFDB are often based on a single or a few studies for a given forest or plantation type. The values normally provide global or national averages for a given parameter for a given land-use category or forest or plantation type. Often, multiple sources provide the values for a given parameter such as above-ground biomass growth rate or soil carbon density. For example, above-ground biomass growth rate for eucalyptus plantation is available from local, regional, national and international sources. Further, several studies may be available for a given region. It is important to ensure that extremely high or low values for a given carbon inventory parameter are not used, even if they are from the region. Thus, the carbon inventory expert may have to compare different values available, validate them and make expert judgment before selecting a value for calculation of carbon stocks or changes. It is important for the carbon inventory expert to stratify the project location or land-use category and to select appropriate default values. Further, even if a parameter is actually measured for a given location, it is desirable to compare the results with the values reported in literature to validate the measured values.

Values for the carbon inventory parameters are required at as disaggregated a level as possible. Given the high variability due to various biophysical factors, the location specificity of these values is important. However, it is also important to state here that for many parameters the average values may indeed be adequate for different situations. For example, a review of 160 studies (Cairns et al. 1997) on root to shoot ratios showed that the values were within a small range of 0.18-0.30, and thus using a mean value of 0.26 may be adequate for most studies. The criteria for selecting the values from published or unpublished sources could be based on biophysical and management systems. Some potential stratification criteria are given in Table 17.10.

Table 17.10 Criteria for data selection for different types of forests or plantations

Rainfall zone

Forest, plantation

Climate

(annual

type or dominant

Age of stand

Silviculture or

domain

rainfall, cm)

species

(years)

management system

- Tropical

- Humid (>200)

- Tropical wet

- <5

- Density of

- Subtropical

- Subhumid

- Tropical dry

- 5-10

plantations/forests

- Temperate

(100-200)

- Warm temperate dry

- 11-20

- Rates of fertilizer

- Boreal

- Semi-arid

- Warm temperate wet

- 21-100

application

(50-100)

- >100

- Thinning

- Tectona

- Acacia

- Irrigation

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