Forest management/Description: Difference between revisions

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|Description==== Timber demand ===
|Reference=Kallio et al., 2004; FAO, 2001a; FAO, 2001b; FAO, 2008;
In IMAGE 3.0, the extent of forest harvest is driven by timber demand per region. This timber demand is the sum of domestic/regional demand and timber claims by other regions (= export/trade). Trade assumptions for sawlogs and paper/pulp wood are adopted from  external models, such as EFI-GTM {Kallio, 2004 #1004}, where for fuel wood they are based on the TIMER model.  
|Description=The forest management module describes regional timber demand and the production of timber in the three different management systems clear felling, selective felling and forest plantations. Deforestation rates reported by {{abbrTemplate|FAO}} are used to calibrate deforestation rates in IMAGE, using a so called additional deforestion.  


=== Timber supply ===
===Timber demand===
In the model, felling in a region continues, until the timber demand has been met, using a stepwise procedure to attribute shares of the total demand to different management systems. First, the demand for timber will be met by the wood harvested in forests that have been converted to agriculture. Second, mature forest plantations (which are at the end of their rotation cycle) within that region can be harvested. The regional establishment of such plantations is scenario driven (see also Table 4.2.2.1). If the timber harvested from these plantations is still insufficient to meet the timber  demand, trees  from natural forests are harvested, applying either clearcut or selective cut.  
In IMAGE 3.0, the driver for forest harvest is timber demand per region. Timber demand is the sum of domestic and/or regional demand and timber claims by other regions (export/trade). Production and trade assumptions for saw logs and paper/pulp wood are adopted from external models, such as [[EFI-GTM model|EFI-GTM]] ([[Kallio et al., 2004]]), and domestic demand for fuelwood is based on the [[TIMER model]] (See Component [[Energy supply and demand]]).


=== Forest management types ===
Part of the global energy supply is met by fuelwood and charcoal, in particular in less developed world regions. Not all wood involved is produced from formal forestry activities, as it is also collected from non-forest areas, for example from thinning orchards and along roadsides ([[FAO, 2001b]]; [[FAO, 2008]]). As few reliable data are available on fuelwood production, own assumptions have been made in IMAGE. While fuelwood production in industrialized regions is dominated by large-scale, commercial operations, in transitional and developing regions smaller proportions of fuelwood volumes are assumed to come from forestry operations: 50% and 32% respectively.  
The share of each management system was derived from forest inventories taken for different world region (Arets et al., 2011), and used as model input (Table 4.2.2.1). Under selective cut, only a fraction of the trees (and thus stems and other tree pools) is logged (fraction is regional and time specific). The other trees remain in the forest. After logging only a fraction of the harvested wood can actually become removed (=fraction take away). Also this fraction is given by input/is scenario driven, i.e. regional specified and can vary over time (Table 4.2.2.1). In addition it depends on the overall wood demand (it equals 1 for wood fuel and the default value to industrial round wood). What is left behind in the forest represents losses/residues during tree harvesting (from tree damage and unusable tree parts) or left in the forest by purpose because of environmental concerns (e.g. biodiversity and nutrient supply). Trees can only be harvested in any forest management type once the rotation cycle of forest regrowth  has been completed (Table 4.2.2.1).  


=== Fuel Wood ===
===Timber supply & production in forests===
Part of the global energy demand is met by fuel wood, depending on the world region. Some of the fuel wood is harvested through formal forestry activities and can be coupled to the management systems described above. In addition,  fuel wood is produced and collected from non-forest areas; for example, from thinning orchards and along roadsides (FAO, 2001a; FAO, 2008). Reliable data on fuel wood production are scarce; therefore, assumptions have been made in IMAGE3.0. For the developed regions, it is assumed that fuel wood is produced on a large scale and, therefore, in IMAGE, all fuel wood demand is added to timber demand. In the transitional regions as well as in the developing regions, smaller fractions of the fuel wood demand are assumed to be met from forestry operations: 50% and 32%.
In IMAGE, felling in each region follows a stepwise procedure until timber demand is met, attributed to the three aforementioned management systems. The proportion for each management system is derived from forest inventories for different world regions ([[Arets et al., 2011]]) and used as model input (Figure Flowchart). Firstly, timber is harvested in forests that have been converted to agriculture. Secondly, timber from forest plantations at the end of their rotation cycle are harvested. Finally, trees from natural forests are harvested, applying clear felling and/or selective felling. In all management systems, trees can only be harvested when the rotation cycle of forest regrowth has been completed.


=== Establishing new plantations ===
===Selective logging===
Forest plantations are established with the purpose of growing wood in an efficient way. The expectation is that, in the future, more and more wood will be produced on plantations, as sustainability criteria may complicate the harvest from natural forests (Form, 2013). For this purpose, plantation planting rate scenarios have constructed by the FAO (Brown 2000; Carle and Holmgren 2008). In the IMAGE 3.0 model, forest plantations are assumed firstly to be established on abandoned agricultural land. Only when there is not enough abandoned land available forest plantations will be established on cleared forest areas. Once a forest plantation has been established, the land cannot be used for other purposes or be changed back to natural vegetation until the trees’ rotation cycle has been completed.
Under selective felling, only a - regional and time specific- fraction of the trees is logged and the other trees remain in the forest. After logging, a fraction of the harvested wood is removed from the forest to fulfil the demand. Biomass left behind in the forest represents losses/residues during tree harvesting (from tree damage and unusable tree parts) or left in the forest because of environmental concerns (biodiversity and nutrient supply). This fraction take-away is derived from literature, defined for industrial roundwood (see [[Arets et al., 2011]]) It is further adjusted to account for the demand for wood fuel, for which it equals unity.


=== Additional Deforestation ===
===Forest plantations===  
As aforementioned, land-use change is the major driver of global forest clearing. Apart from this process, however, there are also other causes of deforestation, not related to changes in food demand. In order for IMAGE 3.0 to be consistent with the deforestation rates per world region as reported by the FAO (2010), the category ‘additional deforestation’ has been introduced in the model, as an additional type of forest use.  
Forest plantations are established for efficient, commercially viable wood production. Their regional establishment in IMAGE 3 is scenario driven (see also Input/Output Table at [[Forest management|Introduction part]]), based on FAO. The expectation is that increasingly more wood will be produced in plantations because sustainability criteria may limit harvest from natural forests ([[Brown, 2000]]; [[Carle and Holmgren, 2008]]; [[FAO, 2012a]]). The development of forest plantations in IMAGE and [[LPJmL model|LPJmL]] is still under development, but expected to be available soon. Forest plantations are assumed to be established firstly on abandoned agricultural land. When sufficient abandoned land is not available, forest plantations are established on cleared forest areas. When a forest plantation has been established, the land cannot be used for other purposes or converted to natural vegetation until the tree rotation cycle has been completed.
 
The wood from forests cleared as a result of ‘additional deforestation’ is not used to fulfil the timber demand. Instead, in certain regions, mainly at higher latitudes, the wood is simply left behind;  in other -more tropical- regions it is burnt. The model assumes no recovery of natural vegetation for these areas, and no agricultural activities. In the model, additional deforestation for any particular region is allocated only after the timber demand has been met.


===Additional deforestation ===
Globally, conversion to agricultural land is the major driver of forest clearing, and timber harvest does not result in deforestation, if natural vegetation is regrowing. But there are other causes of deforestation not related to food demand and timber production, such as urbanisation, mining and illegal logging. These activities contribute to loss of forest area, increased degradation risks and a decline in the supply of forest services. To be consistent with the total deforestation rates per world region reported by the FAO ([[FAO, 2010|2010]]), IMAGE 3.0 introduces a category ‘additional deforestation’. IMAGE assumes no recovery of natural vegetation in these areas, and no agricultural activities.


|Flowchart=ForestManagementModel.png
|Flowchart=ForestManagementModel.png

Revision as of 15:05, 21 May 2014

Link to framework components overview

Parts of Forest management/Description

  1. Introduction page
  2. Model description
  3. Policy issues
  4. Data, uncertainty and limitations
  5. Overview of references
Component is implemented in:
Components:
Related IMAGE components
Projects/Applications
Key publications
References
Forest management module in IMAGE 3.0
Flowchart Forest management. See also the Input/Output Table on the introduction page. The option of forest plantations in IMAGE and LPJmL is still under development, and expected to be available soon.

Model description of Forest management

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