EFI : European Forest Institute
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Le réseau pour la gestion durable des forêts cultivées.

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FORSEE : Indicateur évalué

Indicator 1.2: Forest Growth

Cost

Total
€4720
Marginal €220
Shared €4500
Total Cost/ha €0.13

These costs include:

Data processing
Purchase maps
Computer software

Results

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Table 1.2a: Map of Current Wood Volume

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Current wood volume was calculated stump to tip using generalised models for Picea sitchensis developed from the Irish NFI. In the absence of other national volume models, the two models were assumed to be relevant to all other species in the pilot zone area;

The models where applied to small trees (Equation 1);

Tree with DBH > 12cm

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And large trees (Equation 2);

Trees with DBH ≤ 12cm

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Table 1.2a: Volume Equation Parameter

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Remarks

The generated map indicates that 43% of the forest area has a volume less than 50m3 / ha. This low volume is a result of a significant proportion of young stands in the pilot zone. The map shows that volume varies across the area, however there is a predominance of low volume stands in the south eastern area of the pilot zone. These stands can be found on more productive soils and show a move of forestry into these areas in recent years, in line with national policy.

The new NFI data is capable of generating volume equations for trees of less than merchantable timber volume, albeit with an increase relative error due to the inherent variability of smaller tree characteristics.

Problems and improvements

One particular weakness of this analysis is the application of a volume model for Picea sitchensis to all the species in the region. This was the case due to the lack of national models for any of the other species planted in the pilot zone. In an attempt to estimate the potential impact such an assumption would have on the reported total volume for the region, species specific volume equations were taken from literature (Table 1.2b) for comparison.

Table 1.2b: Volume Equations taken from Zianis et. al., 2005

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This analysis indicated an overall 6% variation between using the national Picea sitchensis equation for all species and using non-national species specific equations. The development of nationally specific volume equations for all species would improve confidence in the volume estimates.

Remarks and conclusions

The forest resource in the pilot zone area has a predominantly small volume. However the map indicates that the low volume stands are not concentrated in any particular part of the pilot area but are well-distributed across it.

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Project co-financed by European Union
A community initiative ERDF
INTERREG the IIIB Atlantic Area