Forest management approaches

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FORGEM
Distribution of Forest Management Approaches over Europe (Hengeveld et al., 2012)

To operate the ForGEM model at the European scale, a description of the most likely forest management at a particular location is required. The approach suggested by Duncker at al (2012) [1] is implemented in the forest management module of the ForGEM model. Duncker et al. (2012) present a framework for classifying different FMAs along a gradient of intensity of intervention with the natural processes in a forest. They distinguish five FMAs, differing in both objective and allowed silvicultural operations.

A map at the European scale with the most likely FMA's is presented in Hengeveld et al (2012) [2] The FMA framework thus allows to define management options across the continent.

The FMA's are implemented in ForGEM by quantifying the different forest intervention types. The intervention types and parameter values that characterize the FMA's are presented below.

FMA 1: unmanaged nature reserves

FMA 1 is defined as a strict nature reserve, without any management. In ForGEM this is implemented by only specifying General management parameters, but without any other interventions. In general, plots with exotic species would not be labelled as having an FMA1 type of management. But in case this happens, it means that non-indigenous species will remain in the stand and can only be eliminated by natural processes.


Intervention type: General management
Parameter name Value
cManagementInterval 999
cMinimumCuttingHeight -1
cMinimumHarvestDiameter -1
cLeaveDeadwoodAtHarvest 1
cLeaveBranchesAtHarvest 1
cLeaveFoliageAtHarvest 1

FMA 2: close-to-nature forestry

In FMA 2 forest management is allowed, but only aimed at enhancing the ecological functioning of the forest, with a low management intensity. The management cycle is therefore set to 10 years. Each time non-indigenous species are removed, according to Table Y. This more or less reflects the current natural range of the species and does not tolerate natural expansion of species outside their current range, for example due to climate change. Every 50 year a few gaps will be created to emulate small-scale natural disturbance processes. The total gap size is 5% of the simulated area. Gaps are between 200 and 800 m2 and at least 10m wide, with a preference for smaller gaps. Gaps are preferentially located at spots where most light reaches the forest floor. Existing gaps might thus be enlarged, or nothing is done if the gap is of sufficient size. Occurrence of natural regeneration is not a criterium. A gap will remain labelled as gap until the trees reach half their maximum attainable size. After that the area will be available for creation of a new gap. No soil scarification is applied and all (advanced) regeneration up to 5m tall is left untouched. Of the harvested wood (either from removal of certain species or the creation of gaps), 20% of the trees with a breast-height diameter of more than 15cm are extracted as harvest. The rest of the stem volume, branches and foliage of the felled trees remain in the forest.

General management
Parameter name Value
cManagementInterval 10
cMinimumCuttingHeight 5
cMinimumHarvestDiameter 15
cLeaveDeadwoodAtHarvest 0.8
cLeaveBranchesAtHarvest 1
cLeaveFoliageAtHarvest 1
Gap making
Parameter name Value
cMinGapSize 200
cMaxGapSize 800
cMinGapWidth 10
cThinningInterval 5
cGapAreaToMake 5
nTimesOfGapMaking 20
nYoungTreesMin 0
cConversion 0
cResetHeightCriterium 0.5
cSoilScarification 0
Gap size frequency 200m2 80%
Gap size frequency 800 m2 20%
Remove species
Parameter name Value
cInterval 1

FMA 3: combined objective forestry

FMA 3 is characterised as combined-objective forestry. Besides wood production, other functions as biodiversity, recreation and protection of soil and groundwater are integrated into the management. Forest management intensity is characterised as medium, implemented in ForGEM as a management cycle of 10 years. Regeneration of the simulated stand is done by a type of shelterwood felling. If the trees reach on average their target diameter (in general 60cm, see Table AA) the number of trees is reduced to about 25, depending on the tree species (Table AA). In case of a mixture, a weighted average is calculated. No soil scarification is applied, and all trees smaller than 5m are retained. At the next management intervention the density is reduced to 10 trees per ha. These trees will be left as seed source, and for biodiversity and recreational purposes. At the same time, the density of the natural regeneration is assessed. If this is below 2000 trees per ha, trees will be planted until this density is reached. This will be done with the tree species best adapted to the site, as assessed from the tree species map. After the regeneration reaches a height of 8m, the stand will be thinned every 10 years. A mixed stand is aimed at, with 60% of the basal area contributed by the dominant species. The dominant species is assessed based on the actual situation of the stand and may thus change over time. The remaining 40% is distributed over the other tree species that are present. The number of trees to be removed are based on the crown space that is needed per tree, which is based on Dutch yield tables. Trees are removed randomly. From the felled trees, only those with a minimum diameter of 10cm are extracted. However, 20% of them are left in the forest as deadwood for biodiversity purposes. No branches or foliage are extracted.

General management
Parameter name Value
cManagementInterval 10
cMinimumCuttingHeight 5
cMinimumHarvestDiameter 10
cLeaveDeadwoodAtHarvest 0.2
cLeaveBranchesAtHarvest 1
cLeaveFoliageAtHarvest 1


Additional planting
Parameter name Value
cLowestDensity 20
cDesiredDensity 20
cTimeSinceHarvest 1


Thinning
Parameter name Value
cThinningInterval 1
cMethod 1
cMainSpeciesTargetPercent 60


Shelterwood
Parameter name Value
cHeightCriterium 0.5
cSoilScarification 0
cTargetDiameter 60
cInterval 1
cGeneralDensity 25
cEndDensity 10

FMA 4: intensive even-aged forestry

FMA 4 is intensive even-aged management. In ForGEM, this is implemented as a 5-year management cycle. After clearfelling, the soil is prepared and planted with 3500 trees per hectare. At 6m height a tending is carried out, where numbers are reduced to 2000 trees per ha, where 20% admixture of other species is allowed. Thinnings are carried out every management cycle until the trees have reached the target diameter of 60cm. Thinnings are done using the crown space method. Only a small fraction (10%) of the harvested trees (>10cm) remain in the forest. 50% of the branches of the felled trees are removed, but no foliage.

General management
Parameter name Value
cManagementInterval 5
cMinimumCuttingHeight 2
cMinimumHarvestDiameter 5
cLeaveDeadwoodAtHarvest 0.1
cLeaveBranchesAtHarvest 0.5
cLeaveFoliageAtHarvest 1


Additional planting
Parameter name Value
cLowestDensity 35
cDesiredDensity 35
cTimeSinceHarvest 0
Tending
Parameter name Value
cMainSpeciesTargetPercent 80
Density at height 6m 20


Parameter name Value
Thinning
cThinningInterval 1
cMethod 1
cMainSpeciesTargetPercent 80


Clearcut
Parameter name Value
cHeightCriterium 0.5
cSoilScarification 1
cTargetDiameter 60

FMA 5: short rotation forestry

FMA 5 is more intensive than FMA 4. This is reflected by a 4-year management cycle, higher planting density (5000 trees per hectare), higher tending density (2500 per hectare) and an earlier harvest (target diameter 40cm). No admixture is allowed. All biomass is removed from the site, except half of the foliage.

General management
Parameter name Value
cManagementInterval 4
cMinimumCuttingHeight 2
cMinimumHarvestDiameter 0
cLeaveDeadwoodAtHarvest 0
cLeaveBranchesAtHarvest 0
cLeaveFoliageAtHarvest 0.5


Additional planting
Parameter name Value
cLowestDensity 50
cDesiredDensity 50
cTimeSinceHarvest 0


Tending
Parameter name Value
cMainSpeciesTargetPercent 100
Density at height 6m 25
Thinning
Parameter name Value
cThinningInterval 1
cMethod 1
cMainSpeciesTargetPercent 100
Clearcut
Parameter name Value
cHeightCriterium 0.5
cSoilScarification 1
cTargetDiameter 40

References

  1. Duncker, P. S., S. M. Barreiro, G. M. Hengeveld, T. Lind, W. L. Mason, S. Ambrozy, and H. Spiecker, 2012. Classification of forest management approaches: a new conceptual framework and its applicability to European forestry.
  2. Hengeveld, G. M., G.-J. Nabuurs, M. Didion, I. Van den Wyngaert, A. P. P. M. Clerkx, and M.-J. Schelhaas, 2012. A forest management map of European forests. Ecology and Society 17(4): 53..

Brus, D. J., G. M. Hengeveld, D. J. J. Walvoort, P. W. Goedhart, A. H. Heidema, G. J. Nabuurs, and K. Gunia. 2012. Statistical mapping of tree species over Europe. European Journal of Forest Research 131(1):145–157. http://dx.doi.org/10.1007/s10342-011-0513-5