According Official Data from the Regional Ministry of Agriculture, the Average Forest

ELECTRONIC SUPPLEMENTAL MATERIAL

APPENDIX S2: Forest biomass in Catalonia―Description

This appendix gives technical details on the figures calculated and criteria considered for estimating the forest biomass technically available for Catalonia, as well as intensities and rotation period considered in our simulations.

To estimate the forest biomass, data were processed from the Spanish National

Forest Inventory (IFN3 and 2; Villanueva 2005), the Land Cover Map of Catalonia

(CREAF 2009; Ibañez and Burriel 2010) and the OrGest map (Vericat and others 2010;

Piqué and others 2011).The following constraints were applied to define the final technically available forest biomass (859,000 hectares):

- Canopy cover fraction (FCC) over 70%

- Main species, whose occupancy area is larger than 1.000 hectares, were

selected

- Protected areas were excluded

- Accessibility, as buffer distances described in Table S2.1

Forest managers from the Autonomous Government were consulted to help establish the accessibility conditions required for exploitable areas (Table S2.1).

Table S2.1: Buffer Distances (Expressed in Meters) for Slope Classes and Regions of Catalonia

Buffer distance from General Central Catalonia Pyrenean area forest roads Slope <30 % 400 400 500 Slope 30-60 % 75 150 300 Slope >60 % 35 75 75 Available biomass can be split into two categories: energy uses (primary forest biomass) and industrial uses (packaging, construction, and so on). The assumptions for splitting the available forest biomass are shown in Table S2.2.

Table S2.2: Assumptions for Differentiation of Biomass Use

Biomass for energy Biomass for industrial use Stem + thick branch biomass of conifer trees under Stem from conifer species over DC20 cm

Thick branch biomass of conifer trees over DC20

Stem + thick branch biomass of Quercus species Acronyms: DC20 refers to the diameter class of 20 cm.

Current bioenergy trends and thermal conversion technologies allow the use of wood chips from full trees. In this full-tree harvesting system, trees are felled and extracted without being delimbed or topped. This harvesting system is perceived as better for the creation of fire suppression opportunities, with good potential synergies with understory grazing. The calculations of the harvesting potential for bioenergy

(stem plus thick-branch biomass as shown in Table S2.2) have been obtained by adopting this harvesting system as reference. However, the full-tree system might not be used in practice in every biomass exploitation due to technical (terrain or stand difficulties, skillness of companies, intermediate storage availability, and so on), environmental (nutrient exports) or economic reasons (not enough critical mass to justify this harvesting system over the full-stem harvesting system in which trees are felled, delimbed and topped at forest).

We thus calculated technically available forest biomass feedstock of

2,714,100 m3 per year on 859,000 hectares for both industrial and energy uses, allowing a sustainable biomass extraction rate (BER) of 3.16 m3/ha/y. Specifically, 989,600 m3 per year are classified as energy assortments and 1,724,500 m3 per year as industrial assortments. However, the current exploitation in Catalonia is between 600,000 and

880,000 m3, (average of 705.900 m3 per year, meaning a BER of 0.82 m3/ha/y in the technically available surface, 859.000 ha) according to Autonomous Government databases for 2000–2010 period (GENCAT 2013), so the current exploitation could be increased almost four- fold to match available growing volumes.

 BER [industry uses] = available forest biomass feedstock per year (1,724,500

m3/y)/ technically available surface (859.000 ha) = 2.1 m3/ha/y

 BER [energy uses] = available forest biomass feedstock per year (989,600

m3/y)/ technically available surface (859.000 ha) = 1.15 m3/ha/y

3  BER [total] = BER [industry uses] + BER [energy uses] = 3.16 m /ha/y

Forest harvesting intensity has been simplified, for the whole region to two intensity levels: 1) high intensity level (High-Int) and 2) low intensity level (Low-Int)

(that is, half of the high-intensity treatment). One assumption for the high-intensity level is that all the technically available biomass per year is effectively harvested (2,714,100 m3//year). The period between harvests (or rotation period), area to be treated each year, and harvesting intensity are interrelated. Thus, rotation period was chosen as a function of the profitability of the harvest for forest companies, which usually need to harvest more than 45 fresh tons per hectare. This dictates a rotation period between harvests of

22 years, with a mean intensity of 25.4 m3/ha of biomass for energy and 44.1 m3/ha for industry uses, totalizing 69.5 m3/ha. This figures were calculated according to the following expressions:  High-Int [industry uses] = [available forest biomass feedstock per year

(1,724,500 m3/yr) * rotation period (22 y)] / technically available surface

(859.000 ha) = 44.16 m3/ha

 High-Int [energy uses] = [available forest biomass feedstock per year (989,600

m3/y) * rotation period (22 y)] / technically available surface (859.000

ha) = 25.4 m3/ha

3  High-Int [total] = H-Int [industry uses] + H-Int [energy uses] = 69.5 m /ha

The low-intensity harvesting level imply half of the amount of harvested material per hectare (34.75 m3/ha), but also a higher amount of harvested (treated) area per year when the total harvest of 2,714,100 m3/year is to be reached. The period of time between harvests will be, logically, half of the time when applying a high intensity level.

References

CREAF (2009) Land cover map of Catalonia, 3rd edn. http://www.creaf.uab.cat/mcsc/usa/index.htm.

Ibañez JJ, Burriel JA (2010) Mapa de cubiertas del suelo de Cataluña: características de la tercera edición y relación con SIOSE. In: Actas del XIV Congreso Nacional de Tecnologías de la Información Geográfica, Sevilla.

Piqué M, Vericat P, Cervera T, Baiges T, Farriol R (2011) Tipologies forestals arbrades. Sèrie: Orientacions de gestió forestal sostenible per a Catalunya (ORGEST). Centre de la Propietat Forestal. Departament d’Agricultura, Ramaderia, Pesca, Alimentació i Medi Natural. Generalitat de Catalunya, Barcelona.

Vericat P, Piqué M, Koua O, Pla M (2010) Mapa de formacions forestals pures i mixtes de Catalunya a partir del Mapa Forestal de España 1:50.000 digitalizado. Centre Tecnològic Forestal de Catalunya, Solsona.

Villanueva JA (2005) Tercer Inventario Forestal Nacional (1997–2007). España. Ministerio de Medio Ambiente, ICONA, Madrid.