Establishing the initial parameters in CO^IX model A CO2FIX file needs to be prepared for each species or group of species with supporting parameters. Parameterization is an important step in estimating carbon stocks. Initial parameters need to be specified for each module. The growth of stem biomass (Bs) is expressed as a function of age. The values are initially derived from yield tables and further refined with data from inventories. The biomass allocation coefficients (F) for foliage, branches and roots are expressed as a function of the age of the tree. Like the growth rates of the stem, the F-parameters have to be refined through destructive sampling. The data used to determine the parameter values are based on scientific and peer-reviewed literature. The CO2FIX model description and its user manual give the data sources and references to research studies on which the model parameters were developed.
Parameterization The following aspects need to be considered in parameterization of the CO2FIX model:
• The CO2FIX manual should be consulted for implementing the model and for its parameterization.
• The factors influencing carbon stocks can be captured using the data and parameters from yield tables, local studies, official publications and peer-reviewed literature on vegetation, soil and climate of the region.
• It is a good practice to assess the mean, median and range for each parameter required in the CO2FIX model from local studies and published literature relevant to the region.
• Multiple model runs should be done to calibrate the parameters and the model projections compared with actual data on carbon pools to assess the robustness of the parameters.
Estimation of changes in the carbon stock of tree biomass Most yield tables report only merchantable stem volume and exclude information on the branch and leaf biomass. In such situations, the CO2FIX model could be used to estimate the changes in total above-ground tree biomass:
• Estimates of stem volume from yield tables or other studies to be collected and incorporated under the species files in the CO2FIX model.
• The projections of CO2FIX model are in the time steps of 1 year and follow the "Gain-Loss" approach, which takes into account growth and loss of tree biomass during the year from harvest and disturbances such as fire and pests. The annual change in the tree carbon stock is reflected in the ex ante estimation (pre-i mplementation phase). The growth parameters reflect the annual increases and losses in above-ground tree biomass due to thinning, harvests and disturbance
• The harvested biomass from thinning and harvest is subtracted from the existing biomass, and the slash and deadwood from the harvests are added to the soil module since these are expected to decompose over time.
Estimation of carbon stock changes in non-tree shrub biomass The shrub biomass can be estimated by modelling the non-tree woody perennial species as a cohort of species. The data on shrubs can be collected from local studies or published literature and used for parameterizing shrub growth in the model to estimate shrub biomass and projected change in its stock of carbon.
Estimation of carbon stock changes in below-ground biomass In the CO2FIX model, the relation between below-ground biomass and above-ground biomass is expressed as a fraction of stem biomass for each species.
Estimation of carbon stock changes in deadwood In the CO2FIX model, deadwood is included in coarse woody litter (stems and stumps) and, to a lesser extent, in the short fine woody litter (fine and coarse branches, coarse roots). Estimation of cartoon stock changes in litter The data on estimates of litter from literature can be used to parameterize the CO2FIX model. Data on litter can be input either directly into the model or estimated using the biomass module through biomass turnover, natural mortality, management mortality and logging slash. Estimation of changes in soil organic carbon CO2FIX uses the Yasso model for modelling soil carbon dynamics. The Yasso model (see, e.g. Liski et al. 2005) describes the decomposition and dynamics of soil carbon and calibrates the total stock of soil carbon without distinguishing between soil layers. The model uses parameters from the soil module, deadwood and litter parameters from the biomass module and climate parameter inputs under the general parameters tab. The soil module consists of two tabs, namely general parameters and cohort parameters. The parameters for the soil module are under the soil main menu. The user needs to provide climate parameters for the site. The model has been tested in evaluating the effects of climate on decomposition rates of litter in a wide range of ecosystems. Steps in using the graphical user interface CONFIX V. 3.1.0 Model The following broad steps can be adopted to enter data and to generate outputs:
Step 1: Open a new project by clicking the "New" option in the file menu
Step 2: Go to the data menu and scroll down to general parameters; define the project scenario and enter the general parameters Step 3: Select the data menu and scroll down to biomass; as you click, a new window appears; enter the input parameters related to biomass parameters
Step 4: In the data menu, go to "Soil" and define general and cohort parameters Step 5: Define the products, bioenergy, finance and carbon credit sections if these are relevant to the project goals Step 6: Go to "View" and get any of the following outputs
° Carbon stock ° Financial ° Carbon credit
Step 7: Go to the "File" menu and export the output file to a desired location and in the desired format
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