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FORSEE : Indicateur évalué

Indicator 1.4.3: Carbon stock in the dead wood stock
Forest area covered (1995):
4956,1ha

Percentage of the total forest
area in Sousa Valley: 14,3 %

No of plots: 35

Cost

TOTAL COST: 2061,8 €

Costs/ha: 0,41 €

Costs/plot: 58,9 €

The total cost includes:

1- Data collection: 1793,5 €

2- Data analysis: 268,3 €

Results

Volume and biomass of logs and snags found in the 35 FORSEE devices

table

Sources : UTAD estimates

*1 device: 4 plots (1 IFN+3 satellites) and 2 transepts (T1, T2).

Remarks

The table above shows the average volume and average dry matter for:

a)Logs found in 11 devices - transepts T1 and T2;

b)Snags found in the 8 devices - IFN plots + satellites.

For the 11 devices where logs were found, the total volume is between 1,5 and 25,37 m3.ha-1 and the total dry matter between 0,53 and 9,99 ton. ha-1.

For the 8 devices where snags were found the total volume was between 0,44 and 9,23 m3.ha-1 and the total dry matter was between 0,74 and 4,453 ton.ha-1 .

Logs with a diameter ≥ 7,5 cm were found in 32% of the FORSEE devices. The average values and standard deviation reported in the table above do not take into account devices where was found logs with a diameter < 7, 5 cm.

Snags were found in 23% of the FORSEE devices.

Problems and improvement

The method of the line intercept is already well documented in forest and ecology literature. The main problems detected during the evaluation of this criterion were:

a) The transepts length (50 m) is too big for the size of the forest holdings in Sousa Valley. The small dimension of forest holdings and its fragmentation makes the transept cross different types of stands and sometimes different types of land use;

b) The classification of the decomposition status;

c) The conversion of volume in biomass using wood density values.

Further studies about density values of decayed wood are required. The values used by North Portugal, applied for Pinus pinaster and Eucalyptus globulus, are justly empirical being a percentage of an average density of the specific value of the species.

Comments and conclusion

The methodologies to estimate this indicator deserve further attention. They should be modified in order to be easily applied and to incorporate the complete assessment of logs. It would be of great interest the establishment of a working group of researchers on fuel inventory to define the best methods.

Carbon stock is one of the indicators of Criterion 1 considered by NP 4406 2003. NP 4406 2003 considers that one of the main functions in the forest ecosystems is the capacity of being a carbon sink. The increase of volume of the forest stands has positive consequences in the behaviour of this indicator though the effectiveness of this function is strongly limited by the use given to the products extracted from the forest.

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