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UL-UFF
ES_21_2 Spain, Canary Islands, Gran Canaria, Osorio
(Teror) 2002
W.P. 9.1. Examples of prescribed burning and its effects
Plot Description
Town: Teror. Gran Canaria
Place: Osorio
Area: 13,02 ha
General slope: 5-15%
Use: This zone is reforested
stand of laurel forest and is
visited by school estudents
and other visitors. The
Osorio Farm constitutes
Gran
Canaria’s
most
exquisite natural setting.
Objectives:
1. Wildfire prevention (diminishing the fuel load and change the forest
structure).
2. Accelerate the forest dynamics.
3. Trainning the firefighters service (2002 is the first year of prescribed
burning in Gran Canaria)
Plot Description
Vegetation structure: laurel forest reforested stands (Laurus
novocanariensis, Myrica faya,...) and vigorous understorey by ferms
(Pteridium aquilinum). In winter the dead ferms are very inflamable fuel.
MOTIVATION
In the 90s repopulations were realized by species
of laurel forest in the hillside of Osorio’s mountain.
During these years it has been growing other
plants (ferms, blackberry,... principally) that are
competing for the light, the nutrients and dthe
water against the planted vegetation. In many
zones the forest has stagnated. Also, these news
fuel structures are very vulnerable to the wildfires.
The prescribed fire accelerates the natural
dynamics of the laurel forest and makes it more
resistant to the fire.
Prescription: Weather and fuel conditions in the burning day to
have the wished effects
The plot have to be burned bearing the proximity
with the infrastructures (Osorio’s Farm) and the
management of the smoke.
PRESCRIPTION WINDOW (summary)
Variable
Low
Wished
High
Temperature (ºC)
5
15
26
Air Relative Humidity (%)
35
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
Limitations: The plot has the peculiarity to
inhabits of Osorio’s shrew (Crocidura Osorio) a
endemic species. In this moment not wise the
relation between the shrew and the fire.
2002 is the first year that ejecutes the prescribed
burning as fuel management tool. The fire is not
accepted even. There appear many problems:
social, permissions, conservacionist’s groups,...
Plot preparation: Preparation of the plot is not
done. One anchors the prescribed burning in the
existing ways.
Way
Execution
The accomplishment of prescribed
burning under laurel forest species is
complicated enough. These species are
very sensitive to the fire for what it is
necessary to fit the flame length not to
damage them.
This is done by the ignition pattern,
using the fire torch as scalpel from
firemen. With it we will look for low
flame lenghts, low times of fire
residence and the suctions.
Also de firemen uses the water ant the
hand tools for lowering the flame
lenght.
The seventeen parcels were burned in
diferent days, beggining with the
highest.
Way
Execution
In the opened zones of the plot the ignition pattern has been for
points or for strips. In these cases the flame lenght has been a bit
higher. Even this way the diferents reforested species have been
protected in the plot.
Effects
The prescribed burning has diminished
the fuel load and modified the forest
structure. In the zones of many plants,
the canopy have been closed
preventing the entry of light. This has
provoked the decrease of species as
the ferms.
In the most oppened zones the ferm
vegetation has grown very much. In the
first analysis it can seem that the
burning has not served. But it is a green
ferm stand without dead load fuel
below.
The majority of plants have supervived.
Some of them have lost leaves for
convection but they have not died. In
the spring they return to appear.
Effects in the time
01 week later autumn
17 months later spring
13 months later winter