|Summary||On forest carbon cycle||
How to run
|General description||Examples for model output||
DETAILED MODEL DESCRIPTION
CASMOFOR models both the carbon dynamics, as well as the economics of carbon sequestration of afforested areas. At the heart of the model is a set of accounting functions that are described in the sections for carbon pools, processes that bring about changes in these pools, and external forces that affect these processes. Model parameters can also be checked when running the software, or by clicking here. The accounting functions only make sense after the boundaries of the system are defined. Within these boundaries, all inputs to the system, and outputs from the system, are counted. The system boundaries can be seen on the flowchart of the modelled system. For the whole system, the second law of thermodynamics applies, i.e. all changes within the system are equal to the difference between the sum of all inputs and the sum of all outputs. Note that this requirement has been used to check whether the system functions properly.
In order to assess carbon sequestration, one needs either field measurements, or models, or both. CASMOFOR can be used if no field measurements are available, or if they cannot be taken, e.g. when predictions are made. Such predictions are, e.g., necessary when planning afforestations. The aims of afforestation programs may be numerous, and one aim can be sequestering carbon. CASMOFOR was designed to help users estimate the carbon sequestration potentials of various afforestation programs. By making it possible to quickly compare different variants or options, CASMOFOR is an ideal decision supporting tool.
One needs a complete modelling of the carbon cycle if carbon sequestration is to be estimated correctly and accurately. In the system of forests and forestry, there are many pools (like biomass, dead wood biomass, wood products, soil etc.), and their carbon content is increased and decrased by many processes (e.g., growth, mortality, timber harvest etc.). The overall resultant of these processes change the overall carbon content of the system, since this system is open: it can absorb and emit carbon. Depending on all the processes, the overall carbon content of the whole system can either increase (in which case the system removes carbon from the air) or decrease (when the system emits carbon to the air).
The ultimate objective of using the model is to estimate how much carbon is removed from, or emitted to, the air by the system. Thus, the focus of the model is not any traditional characteristics of the forests, such as the tree volume, but the amount of carbon in all pools and processes, i.e. the carbon cycle of forests and forestry. Therefore, the amount of all substances that contain carbon in various pools (e.g., biomass, soil) and that pass through these pools by many processes is converted to, and is handled as, amounts of carbon.
However, there are many types of pools and very complicated processes in a forestry system. These together with the spatial dimensions and spatial diversity of pools, and the time scale of the processes render it very difficult to asses the amounts of carbon in the various parts of the system over time. This difficulty is recognized by CASMOFOR, which was designed to predict the amount of carbon fixed by the forest. After the establishment of the stands, and after several years or decades of growing, the amount of carbon actually fixed can be more accurately estimated e.g. by measuring in samples.
CASMOFOR does not attempt to be as scientific as theoretically possible. Rather, it focuses on practical approaches, by which practical and feasible estimates can be made and which concentrate on the most important pools and processes, i.e. those where the most carbon can be found. The ultimate aim of forestations in terms of carbon is to fix air carbon and to keep it within the forestry system in the medium term (i.e. over several decades). Therefore, those pools and processes are of greatest importance where most carbon can be found at this time scale.
Because of the above, not all processes and pools are modelled with the same level of accuracy (or uncertainty). "Well" modelled processes and pools are the ones whose modelling is developed best and where most data (constants, functions, empirical values) are available. Attempts were made to incorporate all bits of information in the biological part of the model that are available in the literature so that modelling of the biological processes, which play the most important role in the system, is as accurate as possible. In addition, an attempt was made throught developing this help to document all important information on the whole model, and to indicate the accuray/uncertainty of various modelling methods for the user to be able to judge the level of understanding that could be used in the model.
As it was noted above, CASMOFOR was designed so that it can be used for modelling the carbon cycle of forestation programs in Hungary. This means that all information stored in the model are for Hungarian species and site conditions (see specifications at the description of the respective pools and processes below). Although there are many models worldwide that are currently used for similar purposes (e.g. CO2FIX, GORCAM), their parametrization may be difficult because of their structure that is not approppriate to use with data available for the Hungarian conditions. CASMOFOR can be regarded as the model that is ideal for the Hungarian conditions because of its structure and parameters that was tailored for Hungarian conditions.
However, if the forestry system (e.g. thinning regimes, growth data etc.) is similar in another country, and only data are different, the structure of CASMOFOR can be used in this country so that data in the model are replaced with those that are used in that country.
The information content of the model (i.e. growing characteristics of various species, thinning regimes, biomass expansion factors etc.) is stored in various files. One single file (cai.xls) contains growth data, expressed as tC/ha, and derived from growth data expressed as m3*ha-1*yr-1 (see details here), wood density and carbon content (in file CAI create.xls). Another file (nevmodel.xls) contains thinning regime data (timing and intensity of thinnings). All other data are stored in the "knowledge base" file of the model (kb.xls). Together with user.xls, which is used to provide the model with structural data (area by species) of any forest that is present at the start of running the model, all files were designed so that the user itself can modify the data to fit them to actual afforestation situations. (Please note that the intent is that the data in kb.xls are changed on request by the developer, and some area and/or biomass data in user.xls by the user for specific scenarios. Should the user want to replace/modify any other data, originally specific to the general Hungarian forestry conditions, please contact the developer of CASMOFOR, Zoltan Somogyi, how to do it.)
It must also be noted that all forestry processes in the model start at the planting of trees and end at the final cut of trees. Any processes (e.g. soil preparation before planting, or erosion before planting or after clearcut etc.) that are not part of the normal afforestation system from planting to final cut are not modelled in CASMOFOR. Although these processes may be important sources of emissions (e.g. much carbon can be emitted from the soil during ploughing), they are outside the scope of CASMOFOR).
The flowchart of the carbon fluxes (processes) and pools of a typical Hungarian forestry system can be seen below. Help on any process or pool can be obtained either by looking for them in this help system, or by clicking on the approppriate part of the flowchart when running CASMOFOR, where the flowchart is also shown.
Note that CASMOFOR was programmed as (a) a system of MS Excel based spreadsheets, and (b) by using MS Visual Basic (for Excel). The intent with all this was that (i) the use of the system is user-friendly, (ii) the parametrization of the model is easy for the user, (iii) both the structure of the system and parameters are transparent, and (iv) the whole system can easily be chedked, fixed and developed further. Finally, note also that great effort was made to document the model (its structure and knowledge base, all pools and processes etc.) so that the model is transparent, and that any modifications or development can later be made by either the author or users.
Note also that a lot of useful documents, data, and links can be found in the help system of the CD version.
Links to other carbon models:
CASMOFOR is an accounting-type of model. It models many processes and pools based on the physical or biological processes in the forests, then sums them up. It acocunts for every molecule of carbon dioxide that enters or leaves the system. For details of the accounting system, see the accounting functions.
As it was mentioned above, CASMOFOR is already parametrized for the Hungarian conditions. Thus, modelling the carbon cycle of Hungarian forests can be better done by CASMOFOR than by any other model.
The various parameters, the structure of the model (pools, processes, external forces etc.), and information on accuracy and sources of error can be found in the detailed description of the model (see also Table of contents).
In this section, some general characteristics of the model are provided.
See also the disclaimer.
This webpage was last modified by Zoltan Somogyi 29 June 2014.