ES_21_2 Spain, Canary Islands, Gran Canaria, Las Mesas (San Mateo) 2004 W.P. 9.1. Examples of prescribed burning and its effects UL-UFF.

ES_21_2 Spain, Canary Islands, Gran Canaria, Las Mesas (San Mateo) 2004

W.P. 9.1. Examples of prescribed burning and its effects

UL-UFF

Plot Description

Town: San Mateo. Gran CanariaPlace: Las MesasArea: 10,01 haGeneral slope: 20-30%Use: In the high part of the plot

exists a forest house occuped for the forest service firemen.

Objectives:

1. Wildfire prevention (diminishing the fuel load and change the forest structure to stablish shaded fuel breaks).

2. Fire prevention around structures.

Prescribed burning plots

Recreative area

Forest ServiceHouse

Plot Situation

Plot Description

Vegetation structure: Mixed reforested stand of native Canary Islands pine (Pinus canariensis) and introduced Pinus radiata species. Exist a vigorous shrub (Telline microphylla, Adenocarpus foliolosus, Pteridium aquilinum...)

MOTIVATION

Wildland fire regimes are changing in Gran Canaria and large wildland fires are more likely to occur. The prescribed burning as a tool to create fire resistant stands to allow wildland fire control. This was demonstrated by the wildland fire occur in Las Mesas (Agust 17th, 2004). The prescribed burn fuel breaks established around it in the previous months in which this fire was successfully anchor.

Prescription: Weather and fuel conditions in the burning day to have the wished effects

Variable Low Wished High

Temperature (ºC) 5 15 26

Air Relative Humidity (%) 30 45 65

Mid flame Wind speed (km/h) 2 15 25

Soil moisture 0 50 100

1-h fuel moisture (%) 5 7 10

10 and 100 h, Live herbaceous, Live woody and humus moisture 7 10 15

Rate of spread (km/h) 0,1 0,5 2,0

Flame length (m) 0,1 0,5 1,5

Fire type (1 = heat, 2 = rear, 3 = flank, 4 = circle) 2-3

PRESCRIPTION WINDOW (summary)

Prescription

Limitations: Above and below the plot a frequented road exists. It is necessary to control the traffic during the prescribed burning.

The plot places in the zone of influence of the sea of clouds. This phenomenon makes increase and diminish the relative humidity with what it is necessary to change the ignition pattern.

When the sea of clouds is for below the plot, the humidity is low. The ignition pattern is back fire or points. As it rises the pattern changes to strips. Finally one has to burn with pattern of flanks with superior humidity to 60-65%

Previously cut of the bushes is realized and pruning the trees. The fuel remains dry in the soil of the plot. In the day of burns clean lines of vegetation are realized to delimit the plot and to prevent the fire from escaping.

Plot preparation

Execution

First carries out a fire of test. The fire of test indicates the ignition patterns to use as well as the flame length.

This structure can behave as a model of fuel 11 or 12 (Rothermel 1972) with fuel load betwen 30-35 Tn/ha to 80 Tn/ha. This prescribed burning called “change structure " and they are more difficult to execute, slower and less economic.

With these fuel loads it’s necessary to bear the flame length in mind in order that the fire is not raised to canopy of the trees.

The ignition paterns are back fire and points and often strips.

Execution

Wildfire (Agust 17th, 2004).

On August 17, 2004 there was a wildfire below the zone treated by prescribed burning. This fire advanced directed by wind towards the forest service house and was stopped thanks to the zones treated by prescribed burning.

Wildfire (Agust 17th, 2004).

The wildfire burned 4,6 ha it has concerning the canopy of the trees. On having come to the treated zone it turned into a surface fire and could be extinguished by the forest services.

Wind Prescribed burning plots building

21:30

17:30 19:00

Wildfire effects

The effects of a wildfire are very different from those of a prescribed burning effects. The fire spread for the canopy of the trees killing to the majority of they. The soil met very affected. The vegetation is late very much in recovering. These fires cannot go out for the forest services.

Prescribed Burning Effects

The effects of the prescribed burning are different. First there is a decrease of the fuel load happening from a model 11-12 to a model 9. In addition there has been a change of structure increasing the height of the canopy.

This has been done by means of the thermal pruning. This tool is very related to the flame length. Many length of flame provokes too many thermal pruning, and the trees react sprouting. (Canary Island pine has eppicormic sprout under the bark).

On the other hand the good use of the managing of the fire allows to save the small repopulated plants. The vegetation recovers in a little time.

01 day later spring

10 months later winter

2 months later summer

Effects in the time