## Equations For Soil Carbon

Where:

ACSoils = annual change in carbon stocks in soils, tonnes C yr-1

ACMineral = annual change in organic carbon stocks in mineral soils, tonnes C yr-1

LOrganic = annual loss of carbon from drained organic soils, tonnes C yr-1

ACInorganic = annual change in inorganic carbon stocks from soils, tonnes C yr-1 (assumed to be 0 unless using a Tier 3 approach)

Equation 2.25

Annual change in organic carbon stocks in mineral soils

^CMineral d

SOC = ^ ^¡SOCREFCst • FLUCsi * FMGCr!i • FIC^ • Ac,s,i ) c, s,i

(Note: T is used in place of D in this equation if T is > 20 years, see note below)

Where:

AC . , = 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(o-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 stock change factors are assigned according to the land-use and management activities and corresponding areas at each of the points in time (time = 0 and time = 0-T)

T = number of years over a single inventory time period, yr

D = time dependence of stock change factors which is the default time period for transition between equilibrium SOC values, yr. Commonly 20 years, but depends on assumptions made in computing the factors FLU, FMG and FI. If T exceeds D, use the value for T to obtain an annual rate of change over the inventory time period (0-T years).

c = represents the climate zones, 5 the soil types, and i the set of management systems that are present in a country.

SOCref = the reference carbon stock, tonnes C ha-1 (Table 2.3)

Flu = stock change factor for land-use systems or sub-system for a particular land-use, dimensionless

[Note: Fnd is substituted for FLU in forest soil C calculation to estimate the influence of natural disturbance regimes.

Fmg = stock change factor for management regime, dimensionless

FI = stock change factor for input of organic matter, dimensionless

A = land area of the stratum being estimated, ha. All land in the stratum should have common biophysical conditions (i.e., climate and soil type) and management history over the inventory time period to be treated together for analytical purposes.

Equation 2.26 Annual carbon loss from drained organic soils (CO2)

Where:

L = annual carbon loss from drained organic soils, tonnes C yr-1

A = land area of drained organic soils in climate type c, ha

Note: A is the same area (Fos) used to estimate N2O emissions in Chapter 11, Equations 11.1 and 11.2 EF = emission factor for climate type c, tonnes C ha-1 yr-1

E. EQUATIONS FOR BIOMASS BURNING

Where:

Lfire = amount of greenhouse gas emissions from fire, tonnes of each GHG e.g., CH4, N2O, etc.

Mb = mass of fuel available for combustion, tonnes ha-1. This includes biomass, ground litter and dead wood. When Tier 1 methods are used then litter and dead wood pools are assumed zero, except where there is a land-use change (see Section 2.3.2.2).

Cf = combustion factor, dimensionless (default values in Table 2.6)

Gef = emission factor, g kg-1 dry matter burnt (default values in Table 2.5)

Note: Where data for MB and Cf are not available, a default value for the amount of fuel actually burnt (the product of MB and Cf ) can be used (Table 2.4) under Tier 1 methodology. 