2099
Box 2.2.9: Estimating carbon gains and losses from logging 2100
A model that illustrates the fate of live biomass and subsequent CO2 emissions 2101
when a forest is selectively logged is shown below.
2102
from active logging concessions). The regrowth factor or rate accounts for a gain in 2119
carbon resulting from the regeneration of new trees to fill the gap and potential 2120
enhanced growth of residual trees. The regrowth rate can only be applied to the 2121
area of gaps and a relatively narrow zone extending into the forest around the gap 2122
that would likely benefit from additional light and not to the total area under 2123
logging. The quantities in (1) above can be expressed on an area basis (i.e., t 2124
C/ha) or on a m3 of extracted timber per ha.
2125
(2)
C
deadbiomass C
dead,loggingdamage WoodDecomp ositionFac tor
2126
In areas undergoing selective logging, dead wood cannot be ignored because 2127
logging increases the size of this pool. The change in the dead wood pool should 2128
be estimated to account for decomposition that occurs over time. Research has 2129
shown that dead wood decomposes relatively slowly in tropical forests and hence 2130
this pool has a long turnover time. The damaged wood is assumed to enter the 2131
dead wood pool, where it starts to decompose, and each year more dead wood is 2132
added from harvesting, but each year some is lost because of decomposition and 2133
resulting emissions of carbon. Decomposition of dead wood is modeled as a simple 2134
exponential function based on mass of dead wood and a decomposition coefficient 2135
(proportion decomposed per year that can range from about <0.05 to 0.15 per 2136
year).
2137
(3)
C
woodproducts C
timberextraction proportion
woodproducts2138
Not all of the decrease in live biomass due to logging is emitted to the atmosphere 2139
as a carbon emission because a relatively large fraction of the harvested wood 2140
goes into long term wood products. However, even wood products are not a 2141
permanent storage of carbon—some of it goes into products that have short lives 2142
(some paper products), some turns over very slowly (e.g. construction timber and 2143
furniture), but all is eventually disposed of by burning, decomposition or buried in 2144
landfills.
2145
In addition to quantifying the changes in Eq. 1, two other pieces of information are 2146
needed to fully estimate the total net emissions of CO2—these are the amount of 2147
timber extracted per unit area per year and the total area logged per year. Total 2148
emissions are then estimated as the product of total change in carbon stocks (from 2149
Eq.1), the timber extraction rate and the total area logged.
2150
Creating a national look-up table 2151
A cost-effective method for Approach A and Approach B stratifications may be to create 2152
a ―national look-up table‖ for the country that will detail the carbon stock in each 2153
selected pool in each stratum. Look-up tables should ideally be updated periodically to 2154
account for changing mean biomass stocks due to shifts in age distributions, climate, 2155
and or disturbance regimes. The look up table can then be used through time to detail 2156
the pre-deforestation or degradation stocks and estimated stocks after deforestation and 2157
degradation. An example is given in Box 2.2.10.
2158 2159
2160
Box 2.2.10: A national look up table for deforestation and degradation 2161
The following is a hypothetical look-up table for use with approach A or approach B 2162
stratification. We can assume that remote sensing analysis reveals that 800 ha of 2163
lowland forest were deforested to shifting agriculture and 500 ha of montane forest 2164
were degraded. Using the national look-up table results in the following:
2165
The loss for deforestation would be 2166
154 t C/ha – 37 t C/ha = 117 t C/ha x 800 ha =93,600 t C.
2167
The loss for the degradation would be 2168
130 t C/ha – 92 t C/ha = 38 t C/ha x 500 ha =19,000 t C 2169
(Note that degradation will often have been caused by harvest and therefore 2170
emissions will be decreased if storage in long-term wood products, rather than by 2171
fuelwood extraction, was included—that is the harvested wood did not enter the 2172
atmosphere.) 2173
2174 2175 2176 2177
2.3 ESTIMATION OF SOIL CARBON STOCKS
2178
Tim Pearson, Winrock International, USA 2179
Nancy Harris, Winrock International, USA 2180
David Shoch, The Nature Conservancy, USA 2181
Sandra Brown, Winrock International, USA 2182
2183
Florian Siegert, Universitry of Munich, Germany 2184
Hans Joosten, Wetlands International, The Netherlands 2185
2.3.1 Scope of chapter
2186
Chapter 2.3 presents guidance on the estimation of the organic carbon 2187
component of soil of the forests being deforested and degraded. Guidance is 2188
provided on: (i) which of the three IPCC Tiers to be used, (ii) potential methods 2189
for the stratification by Carbon Stock of a country’s forests and (iii) actual 2190
Estimation of Carbon Stocks of Forests Undergoing Change.
2191
IPCC AFOLU divides soil carbon into three pools: mineral soil organic carbon, organic soil 2192
carbon, and mineral soil inorganic carbon. The focus in this section will be on only the 2193
organic carbon component of soil.
2194 2195
In Section 2.3.2 explanation is provided on IPCC Tiers for soil carbon estimates.
2196
In Section 2.3.3 the focus is on how to generate a good Tier 2 analysis for soil carbon.
2197
In Section 2.2.4 guidance is given on the estimation of emissions as a result of land use 2198
change in peat swamp forests.
2199 2200
2.3.2 Explanation of IPCC Tiers for soil carbon estimates
2201
For estimating emissions from organic carbon in mineral soils, the IPCC AFOLU 2202
recommends the stock change approach but for organic carbon in organic soils such as 2203
peats, an emission factor approach is used (Table 4.5). For mineral soil organic carbon, 2204
departures in carbon stocks from a reference or base condition are calculated by 2205
applying stock change factors (specific to land-use, management practices, and inputs 2206
[e.g. soil amendment, irrigation, etc.]), equal to the carbon stock in the altered condition 2207
as a proportion of the reference carbon stock. Tier 1 assumes that a change to a new 2208
equilibrium stock occurs at a constant rate over a 20 year time period. Tiers 2 and 3 2209
may vary these assumptions, in terms of the length of time over which change takes 2210
place, and in terms of how annual rates vary within that period. Tier 1 assumes that the 2211
maximum depth beyond which change in soil carbon stocks should not occur is 30 cm;
2212
Tiers 2 and 3 may lower this threshold to a greater depth.
2213
Tier 1 further assumes that there is no change in mineral soil carbon in forests remaining 2214
forests. Hence, estimates of the changes in mineral soil carbon could be made for 2215
deforestation but are not needed for degradation. Tiers 2 and 3 allow this assumption to 2216
change. In the case of degradation, the Tier 2 and 3 approaches are only recommended 2217
for intensive practices that involve significant soil disturbance, not typically encountered 2218
in selective logging. In contrast, selective logging of forests growing on organic carbon 2219
soils such as the peat-swamp forests of South East Asia could result in large emissions 2220
caused by practices such as draining to remove the logs from the forest (see Section 2221
2.3.3 for further details on this topic).
2222
Table 2.3.1: IPCC guidelines on data and/or analytical needs for the different 2223
Tiers for soil carbon changes in deforested areas.
2224
Soil carbon
pool Tier 1 Tier 2 Tier 3
Organic