‘CypFire’
Interaction between Cypress and Wildfires: Scientific
achievements
Dr. Gianni DELLA ROCCA
Institute for Sustainable Plant Protection – CNR, Italy
[email protected]
WHAT FLAMMABILITY MEANS?
Flammability: general ability of vegetation (fuel) to burn
Distinct aspects of combustion:
White & Zipperer (2010)
Ignitability – ease to ignition.
Sustainability – how well combustion will
proceed.
Combustion phases:
Pre-heating
Pre-Ignition (smoke)
Combustibility – velocity or intensity of
combustion.
Pyrolisis (red spots)
Flaming
Consumability – amount of combusted fuel.
Smoldering
Glowing
TO BE MORE FLAMABLE OR LESS FLAMMABLE… A TWIST
In previous studies, crown samples of C. sempervirens was classified as:
low or moderate flammable (Valette,1990; Neyisci and Intini, 2006),
not very flammable (Ganteaume et al., 2013),
highly flammable (Dimitrakopoulos and Papioannou, 2001; Liodakis et al., 2002)
Dimensions of plant flammability: individual plant portions, whole plant,
set of plants (woodland).
Methods & Devices for flammability characterization and its setting. Lack
of standardization!
Traits influencing the Flammability: i) physical properties (morphology,
surface/volume ratio, architecture), ii) primary chemical traits (water
content, percentage in lignin, mineral/ash content), and iii)
presence/abundance of secondary flammable metabolites (isoprenoids), iv)
the vegetation/fuel structure (e.g., fuel loading, arrangement, packing
ratio, porosity, dead : live ratio).
Ranking: comparison among whom?
Cupressus sempervirens var. sempervirens (sin.
var. horizontalis)
Cupressus sempervirens var. pyramidalis (sin. var.
fastigiata, var. stricta)
4
4
Assumptions
C. sempervirens var. horizontalis:
widespread and naturalized (throughout the
Mediterranean);
marked tolerance to drought and to high temperatures;
ability to go dormant during summer and;
to vegetate in highly-deteriorated and rocky soils;
cypress is adapted to the typical xero-Med climate and
can grow in conditions that are extremely unsuitable
(even lethal) for most tree species.
For these reasons, cypress can be properly compared
only to other Mediterranean species which have similar
ecological characteristics (grow in similar ecological
conditions).
Characterization of C. sempervirens var. horizontalis
In collaboration with the: Wildfire Laboratory – INIA, Madrid
(external and indipendet institution)
FUELS:
live fine fuel (Crown)
Ø < 0.6 cm
(FMC=96-120%)
Litter (FMC=10-12%)
DEVICES
PHRR
HRR
TTI
………
EPIRADIOMETER
(Valette, 1990)
250-400 °C
Time to smoke
Time to
pyrolisis
Time to ignition
Flame duration
Flame high
Smouldering
duration
Glowing
duration
MASS LOSS CALORIMETER
(Madrigal et al., 2012)
RMF
25-50 kW/m2
MOISTURE ANALYZER
FMC% - Moisture to extintion
Fuel bed ignition test,
simulating a fire brand / ember fall
BURNING TABLE
Surface fire propagation test
specie; LS Means
Current effect: F(5, 684)=187,32, p=0,0000
Results on stabilized litters
Effective hypothesis decomposition
Vertical bars denote 0,95 confidence intervals
45
40
Time of pyrolis (sec)
just few examples…
tempo incandesc
35
30
25
20
15
10
5
Cupressus glabra
Pinus halepensis
Pinus pinea
Cupressus sempervirens
Pinus pinaster
Quercus ilex
specie
specie; LS Means
specie; LS Means
Current effect: F(5, 661)=188,21, p=0,0000
Current effect: F(5, 26)=,47254, p=,79323
Effective hypothesis decomposition
Effective hypothesis decomposition
Vertical bars denote 0,95 confidence intervals
Vertical bars denote 0,95 confidence intervals
50
45
Time to Ignition
(sec)
35
130
30
25
110
100
90
20
80
15
70
10
Cupressus glabra
Pinus halepensis
Pinus pinea
Cupressus sempervirens
Pinus pinaster
specie
Quercus ilex
Ignition frequency (%)
120
freq fiamma
inizio fiamma
40
140
60
Cupressus glabra
Pinus halepensis
Pinus pinea
Cupressus sempervirens
Pinus pinaster
specie
Quercus ilex
Results on stabilized litters
Flame height (cm)
specie; LS Means
Current effect: F(5, 661)=36,192, p=0,0000
Effective hypothesis decomposition
Vertical bars denote 0,95 confidence intervals
23
22
21
H fiamma
20
19
18
17
16
15
14
Ash content (gr/gr)
Cupressus glabra
Pinus halepensis
Pinus pinea
Cupressus sempervirens
Pinus pinaster
specie
specie; LS Means
Current effect: F(5, 691)=174,90, p=0,0000
Effective hypothesis decomposition
Vertical bars denote 0,95 confidence intervals
0,14
0,12
peso ceneri
0,10
0,08
0,06
0,04
0,02
0,00
Cupressus glabra
Pinus halepensis
Pinus pinea
Cupressus sempervirens
Pinus pinaster
specie
Quercus ilex
Quercus ilex
MLC: Heat Release Rate (HRR)
High combustion delay
Cupressus sempervirens var. horizontalis
No surface fire propagation !
No litter ignition !
Bulk density effect > 60 kg/m3
(threashold)
Quercus ilex subsp. ilex and Quercus faginea
Pinus pinea
MAIN RESULTS
Comparison among species belonging to the same
vegetation belt and climate zone
Cypres adopts a ‘water saving’ strategy faced to the drought. In summer
time its leaves have a higher water content than those of many other
strictly Mediterraneran tree species.
Cypress leaves and litter are slow to ignite (low ignitability) but release
an high amount of energy during the combustion (high combustibility).
Litter is dense (compact), retains humidity and allow an low oxygen
circulation, consequently it is really hard to catch fire.
Cypress leaves have a high mineral content that essentially
indicates that there is less mass to burn (low consumability).
The flammable isoprenoids (expecially MT) are stored superficially in leaf
glands in cypress. During the thermal decomposition of the fuel, are early
dispersed, poorly contributing to the flammability phases.
For further details
(Scientific papers)
Brief remarks on the cypress at the plant level and at stand level
Absence of understory in cypress stands
i) ‘mulching action’ exerted by the thick layer of the litter; ii) supposed acidity
and the allelopathic effect of the litter, which prevent the germination of other
plants; iii) marked shading, which reduces the amount of light reaching the soil.
Cypresses can limit the risk of surface fires involving litter or understory, compared to
other tree species which, instead, allow the development of a continuous layer of
understory vegetation.
 reduced circulation of
air within the crowns;
 maintenance of a
humidity inside
(both these factors
reduces flammability)
Thickness of the crown
The flames develop easily and rapidly in a tree with a crown that is
not very dense and well-aired. Common cypresses (var. horizontalis)
has a rather thick crown compared to other conifers (e.g. pines).
Cypress crowns are also capable to retaining part of the radiating
heat of the fire that delay the loss of humidity of the surrounding
vegetation, thus slowing down the advance of the fire.
How to realize an effective multi-row cypress barrier ?
It is a still empirical task….
Previous and consolidated experiences are based on windbreaks
Cypress barrier
Woodland
2,50 m
2,50 m
Cypress plantation strategy
2,50 m 2,50 m
Variabile
7 Cypress
rows
Woodland
7 Cypress
rows
Forest Track
8m
Service Trail – the width depends on the topography
Forest Track
Woodland
Cypress plantation
realized in Siena
8m
Cypress plantation realized in Siena
CONCLUSIONS
Selected C. sempervirens var. horizontalis have a good potential
as effective complementary means to control low-medium
intense wildfire in the Mediterranean environment and can
really contribute to the reduction of the initial fire risk.
Cypress may be planted along the access roads to the
woodlands, among the plantations of other highly flammable
species, to make green low-ignitable barriers, to slow down or
prevent the quick spread of fire making easier its control.
THE IMPORTANCE OF A CORRECT
COMMUNICATION WITH MASS MEDIA
IGNIFUGO – UNINFLAMMABLE ????
Popular Science
CAUTION !!!!!!!
On this topic a lively debate
(partially unjustified) arose…
Responsible declarations
«Sciences et Avenir» April 2017
THANK YOU FOR YOUR ATTENTION
Dr. Gianni DELLA ROCCA
[email protected]