Reaserch topics: Fire effects on water quality, chemistry and nitrogen and carbon dynamics, Heavy metals soil and water contamination, Landscape recuperation after wildfires, Forest management, Forest fire meteorology, Climate change and behavior of climate extremes, Environmental modeling
Abstract: Cork oak, (Quercus suber) is widely distributed in the Mediterranean region, an area subject to frequent fires. The ash produced by burning can have impacts on the soil status and water resources that can differ according to the temperature reached during fire and the characteristics of the litter, defined as the dead organic matter accumulated on the soil surface prior to the fire. The aim of this work is to determine the physical and chemical characteristics of ash produced in laboratory experiments to approximate conditions typical of fires in this region. The litter of Quercus suber collected from two different plots on the Iberian Peninsula, Mas Bassets (Catalonia) and Albufeira (Portugal), was combusted at different temperatures for 2 h. We measured Mass Loss (ML per cent), ash colour and CaCO3 content, pH, Electrical Conductivity (EC) and the major cations (Ca2+, Mg2+, K+ and Na+) released from ash slurries created by mixing ash with deionized water. The results showed that ML per cent is higher at all temperatures in Albufeira samples compared to Mas Bassets samples, except at 550°C, and the rate of loss increases faster with temperature than the Mas Bassets samples. At 150°C the ash colour is yellowish, becoming reddish at 200-250°C and black at 300°C. Above 400°C the ash is grey/white. This thermal degradation is mostly observed in Albufeira litter. The formation of CaCO3 was identified at a lower temperature in Albufeira litter. At temperatures < 300°C, pH and EC values are lower, rising at higher temperatures, especially in Albufeira slurries. The concentration of cations at lower temperatures does not differ substantially from the unburned sample except for Mg2+. The cation concentration increases at medium temperatures and decrease at higher temperatures, especially the concentration of divalent cations. The monovalent cations showed a larger concentration at moderate temperatures, mainly in Albufeira ash slurries. The analysis of the Ca:Mg ratio also showed that for the same temperature, a higher severity results for Albufeira litter. Potential negative effects on soil properties are observed at medium and higher temperatures. These negative effects include a higher percentage of mass loss, meaning more soil may be exposed to erosion, higher pH values and greater cation release from ash, especially monovalalent cations (K+, Na+) in higher proportions than the divalent ions (Ca2+, Mg2+), that can lead to impacts on soil physical properties like aggregate stability. Furthermore, the ions in ash may alter soil chemistry which may be detrimental to some plants thus altering the recovery of these ecosystems after fire. Low intensity prescribed fire can be a useful tool to land management in these sites, due to the reduced effects of fire temperatures on the physical and chemical properties of surface litter, and can reduce the risk of high temperature wildland fires by reducing fuel loadings. From the perspective of water resources, lower fire temperatures produce fewer impacts on the chemistry of overland flow and there is less probability that the soil surface will be eroded.
Abstract: There is ample evidence of the citiesâ effects upon the local climate and, in particular,
upon temperature, by giving rise to the so-called âurban heat islandâ (UHI), which
has a strong negative impact upon human bioclimatic comfort and health.
In this study, temporal evolution of summer (June, July, August and September-
JJAS) temperature trends in Lisbon are studied. During the course of the 21st Century,
a temperature increase was found to have occurred in this city (most notably since
1980 and particularly as regards the mean minimum temperature), alongside an
increase in the number of nights in which the temperature has reached values higher
than 20 ºC and a reduction of the diurnal temperature range, all of which can be
attributed to urban growth and/or global warming.
Abstract: Carbon (C) and Nitrogen(N) are key nutrients in ecosystems health and the more affected by fire temperatures, because of their low temperatures of volatilization. After a wildfire, due higher temperatures reached, a great amount of C and N can be evacuated from the ecosystems and the percentage of C and N not vaporized is concentrated in ashes. Hence, the study of ash C and N is of major importance because will be linked with the capacity of ecosystem recuperation. The aim of this work is study the C, and C/N of three wildfires occurred in Mediterranean forests dominated by Quercus suber and Pinus pinea in Portugal. In the first wildfire, named âQuinta do Condeâ, we collected 30 samples, in the second, âQuinta da Areiaâ, 32 samples and the third, âCasal do Sapoâ 40 samples To estimate the consequences of wildfires in the parameters in study, we collected several
samples of unburned litter near burned areas, composed by the same vegetation. The results showed that wildfires induced in % of Total Carbon (%TC) ashes content a non significantly reduction in Quinta do Conde plot (at a p<0,05) and significantly in Quinta da Areia plot (p<0.001) and Casal do Sapo plot (p<0.001). In % of Total
Nitrogen (%TN) ashes content we observed in Quinta do Conde plot a significant increase (p<0.001), a non significant decrease in Quinta da Areia plot (at a p<0,05) and a significant reduce in Casal do Sapo plot (p<0.01). The The C/N ratio suffer a significant (p<0.001) reduction in Quinta do Conde and Quinta da Areia plots and at a p<0.01 in Casal do Sapo plot. In all parameters in study, wilfires induced a greater spatial variability, by the
analysis of the Coefficient of Variation. Our tests effectuated in laboratory with samples collected near wildfires occurrence and exposed to the temperature gradient (150º, 200º, 250º, 300º, 350º, 400º, 450º, 500º, 550ºC) fit with the results obtained. With temperature
gradient, we identified a decrease of %TC ash content of Quercus suber samples and a rise until the 300ºC in Pinus pinaster samples decreasing thereafter especially after the 400ºC. In %TN we identified a rise in both species reducing abruptly at 450ºC. C/N ratio decrease importantly after the 150ºC. Theses results showed us that wildfires can have different effects C and N litter resources, depending on the severity and temperature reached. Crossing the results obtained in laboratory simulations with the samples
collected in wildfires we will have an idea about the severity and temperature occurred in each wildfire. Overall, the lower severity were observed in Quinta do Conde plot and the higher in Casal do Sapo plot, being Quinta da Areia in a middle position. The C and N levels after a wildfire will determine the capacity of landscape recuperation and according the data obtained this will be higher in Quinta do Conde plot and lesser in Casal do Sapo plot. These hypothesis will be confirmed by field observation.
Abstract: Carbon, Nitrogen and Phosphorous are key elements in a healthy ecosystem but they are also very vulnerable to alteration or loss as a result of fire. In order to study the effects of fire on these nutrients we subjected leaf litter from two Quercus suber trees located in different plots on the Iberian Peninsula, Albuferia (Alb) and Mas Bassets (MB), to the temperatures of 150º, 200º, 250º, 300º, 350º, 400º, 450º, 500º and 550ºC in a muffle furnace for 2 hours to identify the temperature effects in relative percentage (%) on Total Carbon (TC), Total Nitrogen (TN), C/N ratio and the release of Water Soluble Phosphorous (WSP). The goal was to identify different vulnerabilities to fire effects between ecosystems. The results showed a decrease of % TC content in the ashes in relation to the unburned sample, mainly in the sample of Alb. At low temperatures the values are slightly higher than the control. At temperatures of 450ºC for the Alb litter and 500ºC for the MB litter, the %TC is less than 80% relative to the unburned sample. Both litter samples showed a rise in the content of %TN in relation to the unburned sample up to 400ºC, especially in the Alb sample, followed by an abrupt reduction also more evident in this sample. At 450ºC for the Alb sample and 500ºC for the MB sample, TN is nonexistent in the ashes. The C/N ratio decreases with increasing temperatures. At low temperatures, 150º-300ºC, C/N is higher in the Alb samples, and at higher temperatures this ratio is reduced. At 450ºC for the Alb sample and 500ºC for the MB sample, this ratio is zero because of the absence of TN. From 150ºC to 300ºC, both samples showed a rise in WSP in solution, decreasing thereafter. The effect of temperature is especially evident in the Alb litter, where at 300ºC the increase in WSP is 90-fold higher than the control sample. Overall it is observed that the effects of temperature are more severe on the Alb litter sample than the MB sample and that the environment has an important influence on the response to heating.
Abstract: There is a lack of studies about the fire temperature effects on micro-elements release from litter, the organic matter on the soil surface. In order to contribute to this knowledge, a laboratory experiment was conducted by subjecting leaf litter of tree Mediterranean species, Quercus suber, Quercus robur and Pinus pinea to temperatures of 150º, 200º, 250º, 300º, 350º, 400º, 450º, 500º and 550ºC in a furnace for 2 hours to identify the release of aluminium (Al), iron (Fe) and zinc (Zn) from ashes. Subsequently, in a forest dominated by the mentioned species, mainly Quercus suber, we applied a prescribed fire in a plot (50 x 80 m). We collected litter samples before the fire, and the ashes following the fire in order to compare the results obtained in the laboratory experiment with prescribed fire with low to medium temperatures. The majority of ash collected is brownish or black, indicating incomplete combustion of the organic matter. The results showed that in laboratory experiments at low to medium temperatures (150º-350ºC) Al had higher levels in solution than unburned samples. In the prescribed fire, ashes released a significant higher quantity (p<0.01) of Al in solution in relation to litter, however with a lower spatial variability. The coefficient of variation (%CV) before fire was 76.48 and after 65.14. In the laboratory experiment, water leaches of ash produced at higher temperature showed decreases in Fe and Zn concentration relative to the unburned sample. After the prescribed fire we found a reduction of these elements in the ashes in relation to litter. For Fe a significant decrease occurred (p<0.01) in the concentration and the %CV decreased from 179.35 to 82.29. For Zn the reduction in the ash was more significant (p<0.0000) after prescribed fire and also the spatial variability decreased, % CV 90.32 before and 79.89 after. Overall, the results of this study show that laboratory experiments can simulate the effects of a prescribed fire on these metals. It is also important to point out that after prescribed fires the levels of Al in water resources could be higher in Mediterranean forests, inducing toxicity in the environment.
Abstract: Fire ash are majority composed by base cations, however the mineralized organic matter, led also available to transport a higher quantity of heavy metals that potentially could increase a toxicity in soil and water resources. The amount availability of these elements depend on the environment were the fire took place, burning temperature and combusted tree specie. The soil and water contamination from fire ash has been neglected, because the majority of studies are focused on base cations dynamic. Our research, beside contemplate major elements, is focused in to study the behavior of heavy metals released from ash slurries created at several temperatures under laboratory environment, prescribed fires and wildland fires. The results presented in these communication are preliminary and study the presence of Aluminium (Al3+), Manganese (Mn2+), Iron (Fe2+) and Zinc (Zn2+) of ash slurries generated in laboratory environment at several temperatures (150º, 200º, 250º, 300º, 350º, 400º,450º, 500º, 550ºC) from Quercus suber, Quercus robur, Pinus pinea and Pinus pinaster and from a low medium temperature prescribed fire in a forest dominated Quercus suber trees. We observed that ash produced at lower and medium temperatures (<300-400ºC) released in water higher contents of Al3+ than unburned sample, especially in Quercus species and Mn2+ in Pinus ashes. Fe2+ and Zn2+ showed a reduced concentration in test solution in relation to unburned sample at all temperatures of exposition. In the results obtained from prescribed fire, we identify a higher release of Al3+ and a decrease of the remain elements. The solubilization of these elements are related with pH levels and ash calcite content, because their ability to capture ions in solution. Moreover, the amount and the type of ions released in relation to unburned sample vary in each specie. In this study Al3+ release is related with Quercus species and
Mn2+ with Pinus species. Fire ashes can be an environmental problem, because at long term can increase soil acidity. After all base cations have being leached, pH values decrease, and the heavy metals remaining in the ash are easily transported with unknown impacts on soil and water resources. Research is needed in the study at long term of the effects of fire in metals accumulation in soil resources, and all these aspects will be discussed.
Abstract: After a fire the water soluble elements rises due the mineralization of organic matter. In order to understand this dynamic, we collected leaf litter before an application of a prescribed fire and thereafter the ashes produced, and analyzed the major cations (Ca2+, Mg2+, Na+, K+), S and SiO2, released in a Mediterranean forest. The prescribed fire was done conducted in a plot 50x80 m dominated by Quercus suber located in Gavarres Mountains, Iberian Peninsula, and it was of low and medium intensity, because the ash colors were brownish or black. To simplify our task, we applied a Factor Analysis (FA), extracted by the method of Principal Components (PCA) and rotated with the Varimax normalized method with the aim of observe the effects of fire application in the release of the nutrients. The results showed that the levels of water soluble ions were affected by the prescribed fire in the decreased order Na+ >SiO2 >Ca2+ > Mg2+> K+ and S. Although, in the great majority of the sample points, it was observed an increase of the water soluble elements and also a higher variability between points. Outliers were observed in two sample points after the prescribed fire due the higher fire intensity and the higher flammability of the Pinus pinea leaf litter, were we identified a greater amounts the water soluble elements analyzed.
Abstract: Fire severity is a product of the fire intensity and duration of the heat pulse and depends of biophysical conditions of the environment. Laboratory simulations can help us to understand the effects of fire temperature that could differ according to plant species. In this sense, to show and validate our methodology, leaf litter of four different Mediterranean species, Quercus suber, Quercus robur, Pinus pinea and Pinus pinaster, were subjected to different fire temperatures, 150º, 200º, 250º, 300º, 350º, 400º, 450º, 500º and 550ºC, throughout two hours in a muffle furnace. One of the main consequences of heating vegetation is the loss of mass. We measured the loss on ignition (LOI%) based on the mass height difference before and after heating samples, at the mentioned temperatures. Our results showed that up to 250ºC the LOI% is not substantial, rising abruptly between 250ºC-400ºC, and after 400-º450ºC the LOI% is higher than 90% in all species. Another excellent indicator of fire severity is the ash color, which also imparts also information about their chemical composition. The changes in ash color according the temperature gradient, can be measured with the help of the Munsell color chart and we observed that, generally, at low temperatures (150ºC) the colors were mainly yellowish, becoming reddish (200º-300ºC), black (300ºC), grey (350ºC) and white (>450ºC). However, this pattern is different according to the species under study and the thermal degradation is especially noticeable in Pinus leaf litter. The CaCO3 content of the ash is an indication of high fire severity. In order to analyze its presence in ash we used the Bernardâs calcimeter and after 350ºC we found carbonate in the ash, that increased with temperature gradient, mainly in the Pinus species.
Abstract: Fire temperatures can induce tree mortality. However in Mediterranean ecosystems,
plants are well adapted to fire effects and many have the capacity of resprouting and
others have an evasive strategy. Trees can support fire temperatures especially due the
bark that insulates their vital organs from temperatures. The aim of this work is study
the effects of a medium- high severity wildfire occurred in Portugal in Quercus suber
(resprouter) and Pinus pinaster (seeder) mortality and bark thickness. The wildfire
affected ± 40ha and scorched a great part of the analysed trees, especially Quercus. We
measured the Diameter at Breast Height (DBH) at 1.30 m, bark thickness (four
measurements in each tree), with bark gauge, and height with a clinometer (except when
the top was reached easily), of 202 trees (100 Quercus suber and 102 Pinus pinaster)
unburned trees located in the perimeter of burned area, as control plot. All Quercus
suber trees were not stripped. Inside the burned area we measured all the mentioned
variables, plus the mortality of 212 trees (102 Quercus suber and 110 Pinus pinaster).
In the case of Quercus suber, if they resprout, we observed the diameter and height of
their new branches (400 samples). In order to make a better comparison, the bark
thickness was subtracted from the DBH, to give the DBH without bark. The results
showed that in burned and unburned samples, DBH had a very good correlation with
bark thickness. r= 0.82, p<0.001 and r= 0.77, p>0.001 for unburned and burned Quercus
suber. r= 0.54 and p<0.001, r=0.62, p<0.001, for unburned and burned Pinus pinaster.
96% of all burned Quercus suber analysed survived to fire and all the alived trees
resprouted vigorously from the stem. In control area, the tree mean bark thickness was
3.61 cm (±1.33) and in burned area of 3.01 cm (±1.03), different significantly at a p>
0.001. The mean diameter of the new branches was 3.86 cm (±1.53) and the height was
84.57 cm (±28.70). The mean bark thickness of alive Quercus suber trees was 3.07 (±
0.97) and from dead trees was 1.00 (±0.26) different significantly at a p> 0.001. The
mean of DAP from alive trees was 44.51(±23.93) and from dead Quercus suber of
16.63 (±5.13) different significantly at a p>0.05. In relation to Pinus pinaster, 60.90%
of the trees survived (not totally scorched). In control plot the mean bark thickness was
4.35 cm (±0.96) and in burned area was 3.41 cm (±0.89) different significantly at a p>0.00000000001. The mean bark thickness of alived trees was 3.87 cm (±0.81) and of
dead trees was 2.89 cm (±0.69) different significantly at a p> 0.000000001. The average
of DAP from survived trees was 93.01 (±16.45) and from dead trees 78.30 (±18.42)
significantly different at a p> 0.0001. Beside the significant impacts of fire in Quercus
suber bark thickness, great part of trees survived due the low bark flammability.
However, samples with lower bark thickness and DAP died, probably because the lower
protection of their vital organs. The bark thickness of Pinus pinaster was higher than
Quercus suber bark in control and burned plot. Beside the significant differences
observed between bark thickness of control plot and burned plot, the fire did not
consume âenough barkâ to kill Pinus pinaster trees. Also, the bark was very thick and
this could be a reason why many trees survived. Only Pinus pinasters with small DAP
and consequent bark thickness died.
Abstract: One of the most visible effects of fires in the landscape is the presence of ash. His
properties are very variable according to burning temperature and specie affected. Also,
the available nutrients to landscape recover after a fire is contained in ash. Hence, it is
of major importance study the type and amount of ash water soluble elements in order
to evaluate the effects these ions in soil solution and availability to plant growth. The
aim of this study is study the effects of a wildfire occurred in ash elements release
Calcium (Ca2+), Magnesium (Mg2+), Sodium (Na+), Potassium (K+), Aluminum (Al3+),
Manganese (Mn2+), Iron (Fe2+), Zinc (Zn2+), Phosphorous (P), Silica (SiO2) and Sulfur
(S) in a Quercus suber and Pinus pinaster stand located in Portugal. Forty samples of
ash were collected in the burned area and twenty five of litter as control plot near
burned area in order to observe the effects of fire in water soluble elements. The results
showed that the fire induced a significant increase of Ca2+ (p<0.001), Mg2+ (p<0.001),
Na+ (p<0.001), K+ (p<0.001), SiO2 (p<0.001) and S (p<0.001) and a significant
decrease in Al3+ (p<0.001), Mn2+ (p<0.001), Fe2+ (p<0.001) and Zn2+ (p<0.001). In P
we identified a non-significant decrease at a p<0.05. Principal Component Analysis
(PCA) of all variables grouped water soluble elements in three distinct groups. First,
highly affected (Ca2+, Mg2+, Na+, SiO2 and S), moderately and non affected (K+, P) and
negatively affected (Al3+, Mn2+, Fe2+ and Zn2+). The wildfire induced also a greater
variability in the release of these elements. The behavior of water soluble ions is related
with the ash pH and CaCO3 content. Further discussions will be made about these
issues.
Abstract: Ash colour is widely used technique to estimate burning severity. Normally, the
presence of gray/white colours is an indicator of severe burn. Ash properties changes
with temperature and burned specie. After a wildfire, the temperatures produced and the
diversity of affected species will produce a heterogeneous mosaic of severities, because
each species respond differently to similar burning temperatures. Also, CaCO3 ash
content is evidence of high burning severity and as ash colour; their content is different
according to burning temperature and affected specie. The aim of this work is based on
the colour and CaCO3 content of the ash produced in laboratory conditions, throughout
a temperature gradient, (150, 200, 250, 300, 350, 400, 450, 500 and 550ºC) classify the
burning severity of two plots affected by wildfires in Portugal, composed by Pinus
pinaster and Quercus suber trees. The samples of both species to laboratory fire
simulations were collected near lagoa de Albufeira (Lat 38º31âN, Lon 09º 08â W) and
the real ash were collected nearby this plot in two different stands, Quinta do Conde
(Lat 38º34âN, Lon 09º02â W) and Casal do Sapo (Lat 38º 33â, Lon 09º03â). The
wildfires occurred in forest with very similar plant composition and structure with the
area where samples for laboratory fire simulations were collected. Ash colour was
identified with the Munsell color chart and CaCO3 content with the Bernardâs
calcimeter. The results showed that at 150ºC âashâ showed a yellowish colour, became
reddish at 200-250ºC for Pinus pinaster and only in the first temperature to Quercus
suber. At 250-300ºC for Quercus suber and 300ºC for Pinus pinaster, present a black
color and at 350-400ºC are dark gray for Pinus and only in the first temperature for
Quercus suber. The major differences are observed after the 450ºC, where the ash
produced from Quercus are light gray and from Pinus are white. CaCO3 was identified
at 350ºC in both species, however the contents in Pinus pinaster were always higher at
all temperatures than in Quercus suber. In Quinta do Conde (N=30) the great part of the
ash colour was black (46.66%) (chroma value 2.1), followed by very dark gray
(26.66%) (chroma value 3.1) and very dark brown (chroma value 2.2) and dark gray
(chroma value 4.1) with 13.33%. On average the ash contains 6.56% of CaCO3. In Casal do Sapo (N=40) the colour most common of the ash was dark gray (52.50%)
(chroma value 4.1), followed by very dark gray (17.5%) (chroma value 3.1) and black
(chroma value 2.1) and light gray (chroma value 6.1 and 7.2) with 10% each one. The
mean content of % of ash CaCO3 was 19.16%. According the ash colour we observed
that in Quinta do Conde plot that 70% of the area was affected by a medium severity,
17% for a medium/high severity and 13% for a reduced severity. In Casal do Sapo
52.5% of the interest area was affected by a medium/high severity, 27.5% by a medium
severity and 20% by a high severity. The relations between ash chroma value and
CaCO3 content are very positive in laboratory simulations and in the ash collected from
wildfires. The temperatures occurred in Quinta do Conde plot were not higher than
400ºC and in Casal do Sapo were always superiors to 350-400ºC and in some parts can
reached temperatures of 500-550ºC. In both plots the higher severities were identified in
Pinus pinaster ash.
Abstract: Fire intensity has important effects on the biogeochemical cycling and availability of
carbon and nitrogen in ecosystems. Both nutrients are fundamental for the health and
productivity of the forest. The objective of this work is to evaluate the dynamics of carbon
and nitrogen in leaf litter of three mediterranean species, (Quercus suber, Quercus
robur, Pinus Pinea) when exposed for 2 hours to temperatures of 150, 200, 250, 300,
350, 400, 450, 500 and 550žC in a laboratory environment. The results show that ash
of the three species created by heating litter samples for 2 hours at low and medium
temperatures (150-350ž) contains a higher percentage of carbon than unburned samples.
This may be a result of the formation of charcoal. At high temperatures an abrupt
reduction of carbon in the ash is observed. Comparing all species, the litter from Pinus
pinea is most affected by the higher temperatures. The percentage of nitrogen and carbon
in the ash is higher at low and medium temperatures, compared to the control. The
proportion of both nitrogen and carbon increases up to 350žC, decreases significantly
at temperatures higher than 400žC, and drops to levels close to zero in the Quercus
robur samples and is totally absent in the ash of the other species. Nitrogen volatilizes
at low temperatures (200žC), so the increase at low and medium temperatures, must be
a result of their high presence than other elements. Once again, the Pinus pinea is the
species more affected by heating. The response of the C:N is different from species to
species; all show a reduction up to 350-400žC, but after this temperature, the C:N in
the Quercus robur sample stabilizes until reaching 500žC and grew abruptly at 550žC.
The C:N of Pinus pinea shows an increase at 400žC and an abrupt decrease at 550žC
due to the total loss of nitrogen. In the Quercus suber, the C:N decreases until 450žC
and is zero at 500 and 550žC, because no nitrogen exists in the sample. The highest
values of C:N are observed in the Pinus pinea and the lowest in Quercus suber.
Abstract: (1) GRAM (Grup de Recerca Ambiental Mediterrà nea), Departament de Geografia FÃsica i
Anà lisi Geográfica Regional, Facultat de Geografia i Història, Universitat de Barcelona, C/
Montalegre, 6. 08001 Barcelona. (2) USGS, 3215 Marine Street, Boulder, Colorado, USA.
(Daviolas@gmail.com).
After a fire, the ash produced by the combustion of the vegetation is very rich in
available nutrients. Different fire intensities have different impacts on the type of ash
generated and thereafter in their chemical composition. The aim of this work is to
analyse the characteristics of the slurry produced by mixing water and ash generated
from three Mediterranean species heated for a period of 2 hours at 150, 200, 250,
300, 350, 400, 450, 500, 550žC - pH and electrical conductivity, minor elements (Fe,
Mn, Al and Zn), major elements (Ca, Mg and Na) and other components, SiO2 and
P2O5. Results show that pH is stable at low temperatures, except for a small decrease
at 300žC, and the electrical conductivity increased slightly. At 350žC both parameters
increased, mainly in the ash of Pinus pinea. The minor elements have high values
of solubilization at low temperatures and pH. The dissolution of the heavy metals is
quite variable from species to species. Major changes are noted in the leaf litter of
Pinus pinea (mainly in Mn) and Quercus suber (Al). All other components show no
clear trend. In general, the major elements in all species, have high levels of solubilization
at 350-450žC in a high pH environment, and showed an abrupt decrease at higher
temperatures. The main impacts are noted in Pinus pinea in the monovalent and divalent
cations, and results for the minor elements, demonstrated important differences
between species.The SiO2 shows a behavior similar to the major elements, but the
rate of decrease of the dissoloution is not as abrupt. The major impact of increasing
temperatures is found in the leaf litter of Quercus robur. Similar to Ca, the P2O5 has
higher rates of solubilization at 350žC, decreasing drastically at higher temperatures
for the Pinus pinea and Quercus robur, and at 450žC for Quercus suber. It is in this
species that the impacts of higher temperatures are more evident. The reduction in the
dissolution after 400-450žC may be related to the creation of insoluble components of
CaCO3, found in all the ashes at 400žC that affects all chemical components in different
ways. Their effect is more visible in major elements, SiO2 and P2O5 and less
in minor elements. The impact of the CaCO3 on the solubilization of the chemical
components is more evident in the ashes generated by Pinus pinea.
Abstract: Quercus suber (Q.S.) is a widely distributed tree species characteristic of the Mediterranean
region. This species is very important for the forest industry because of the
economic value of its bark and its adaptation to fire. However, this resilience depends
on fire severity and the magnitude of these fire impacts is important for the recovery
of Q.S. forests after fire. The physical and chemical properties of ash resulting from
the burning of the forest floor are indicators of the severity of fire effects on the forest.
The aim of this work is to observe the physical - Loss on Ignition (LOI %) and
ash color - and chemical (Calcite, pH, Electrical Conductivity (EC), release of Ca2+,
Mg2+, Na+ and K+) changes of leaf litter from two Q.S. plots exposed to 150ž, 200ž,
250ž, 300ž, 350ž, 400ž, 450ž, 500ž, and 550žC in a laboratory experiment. The Q.S.
plots were located in different forests of the Iberian Peninsula, Albufeira (Alb) located
in Sesimbra-Portugal and Mas Bassets (MB) located in Girona-Catalunya. The
results show that LOI% continues to change for Q.S. Alb up 400žC and for Q.S. MB
up to 450žC, thereafter the variations are not statistically significant. Comparing both
species, the LOI % of Q.S Alb litter is at all temperatures higher than that of the Q.S.
MB litter. Ash color at 150žC is brown, becoming reddish at 200-250žC and black
at 300žC. After this temperature, grey ashes are identified and they become whiter at
higher temperatures. Calcite appears in the Q.S. Alb ash at 350žC and in Q.S. MB at
400žC, and shows a tendency to increase with higher temperatures. Nevertheless, the
proportion is always higher in the Albufeira samples. The two locations show similar
pH and EC up to 300žC. The EC values are low, about 1 mS/cm3. Above 300 žC, both
values rise, mainly in the Q.S. Alb samples. The release of base cations shows a different
behavior between the two locations according to the temperature. The release of
Ca in both locations is not substantial at low fire temperatures (150-300žC), however
it rises abruptly at 350-400žC for Q.S. MB, decreasing subsequently. For Q.S. Alb,
an increase of Ca2+ is especially high at 500žC. The Mg in solution shows a reduced
solubility at low fire temperatures for both Q.S. locations. However, it increases exponentially
at 350žC in Q.S Alb followed by a reduction. The major dissolution of this
ion in Q.S. Alb. is observed at 400žC. Na in Q.S. Alb also exhibits a reduced solubility
at lower fire temperatures, but that rises abruptly at 350žC, and shows a reduction at
higher temperatures. For Q.S. MB this rise continues up to 500žC, decreasing thereafter.
The monovalent cation K demonstrates the same behavior as the other cations,
a reduced solubilization at lower fire temperatures, increasing dramatically at 350žC
for Q.S.Alb and 450žC for Q.S. MB. The Q.S. located in different forests respond
differently when exposed to the same fire temperatures. At lower temperatures, these
differences are not substantial. However, at medium and high temperatures, the behavior
of the parameters is more heterogeneous and the impacts depend on the element
under analysis. In general, the major impacts of fire temperature are more evident in
the Q.S.Alb location.
Abstract: In order to evaluate the degree of solutes release according to temperature and the relations
between these it is applied a clusters analysis. It was exposed to different temperatures
(150ž, 200ž, 250ž, 300ž, 350ž, 400ž, 450ž, 500ž and 550žC) in laboratory
environment leaf litter samples of three mediterranean species (Quercus suber, Quercus
robur and Pinus pinea) during 2 hours and posteriorly mixed with destiled water
to create an ash slurry. The paramethers analysed are pH, electrical conductivity(EC),
major ions (Ca2+, Mg2+ and N+), minor ions (Al3+, Fe2+, Mn2+ and Zn2+), other
compounds (P2O5 and SiO4) and the Calicite (CaCO3) of the ashes because is an
important component who determine the solubility of the compounds.With the aim of
identify the proximity between temperatures - taking in consideration the parameters
in analysis - it is applied a clusters model (Joining - tree clustering), the single linkage
method as amalgamation rule and r-pearson as distance of measure with the objective
of identify the correlations between temperatures. The cut line for group formation is
at the distance of 0.15. The results show that in Quercus suber leaf litter, the formation
of three groups, the first composed by the temperatures 150ž, 200ž, 250ž, 300ž,
350ž and 400žC, the second by 450žC and the third by 500ž and 550žC. In relation to
Quercus robur, itâs identified three groups too, first (150ž, 200ž, 250ž, 300ž and 350ž
C), second (400žC) and third (450ž, 500ž and 550žC). The same number of clusters
are finded in Pinus pinea, first (150ž, 200ž, 250ž, 300ž and 350ž C), second (400 and
450žC) and third (500ž and 550žC). It can be noted that for the three species, the
composition is different and itâs related to different impacts with the temperature. Of
all species, the more reduced impacts are found in Quercus suber litter (low variation
until 400žC, first group), and higher in the others, mainly in Pinus pinea. The model
shows that with the increasing of the fire temperatures, the homogeneity is lower and
the impacts on solutes release rising exponentialty but in different degrees depending
on the specie in analysis. This rising is abrupter in Pinus pinea leaf litter, and lower
in Quercus suber. This analisys indicates that fire temperatures have heterogeneous
impacts on solute release in mediterranean forests and that, as much higher is the fire
temperature, higher the heterogeneity between effects of the temperature.
Abstract: Wildfires near residential locations threaten human properties and lives. Although, these effects are extended to water and soil quality. Ashes chemical properties play an essential role on the ecosystems recover after a wildfire and the type and amount of solutes release. This study is a preliminary approach to the effects of ashes in water pH and Electrical Conductivity (EC) of three wildfires occurred in Portugal (Setubal peninsula) near urban areas, in forests dominated by Quercus suber and Pinus pinaster. Samples were collected in three different plots. The first named âQuinta do Condeâ with 6x13m (30 samples), the second âQuinta da Areiaâ with 15x35m (32 samples) and the third âCasal do Sapoâ with 9x27m (40 samples). We collected samples of unburned litter(6 samples in Quinta do Conde and Casal do Sapo and 5 in Quinta da Areia) in the contiguous area where wildfires occurred to compare the effects of fire on pH and EC released with unburned litter. The wildfire where Quinta do Conde samples were collected, was of little dimensions (±3 ha) and affected mainly understory vegetation. In the other two wildfires the burned area was higher (Quinta da Areia with ±15 ha and Casal do Sapo with ±20 ha), all understory vegetation were combusted as tree canopy. The results obtained showed that in the wildfire in âQuinta do Condeâ, the pH of the water released by the ash slurries were significantly higher (p<0.0001) in relation to unburned litter. Same results were observed in âQuinta da Areiaâ (p<0.0001) and in âCasal do Sapoâ (p<0.0001). In relation to EC, we identified although a higher salinity in the water released by the combusted organic matter in relation to control samples, in all plots. âQuinta do Condeâ (p<0.05), âQuinta da Areiaâ (p<0.001) and âCasal do Sapoâ (p<0.01). Beside the two parameters in study showed an increase in relation to unburned litter, the correlation between them is negative, but not significant at a p level of <0.05, Quinta do Condeâ(-0.04), âQuinta da Areiaâ(-0.11) and âCasal do Sapoâ (-0.29). We observed in laboratory simulations that at higher temperatures of exposition, EC dropped even if pH levels were rising, due the formation of calcite that capture ions in solution. This is logical explanation for this negative relationship. However future investigations will be done in order to validate this hypothesis, mainly the identification of the amount of calcite in the ashes.
Abstract: After a fire, the combusted organic matter release a large quantity of ions in soil surface leading to an increase of nutrients on soil solution and water resources. The type and amount of elements released depends on the combustion temperature of the organic matter. These ions could have coercive effects on soil physical status. Water with high Sodium Adsorption Rate (SAR) and low Ca:Mg ratio have a dispersive effect on soil clay and consequent soil disaggregation leading to a high vulnerability to erosion. Moreover, Ca:Mg ratios <1 are an indicator of a severe fire. The aim of this study is observe the SAR and Ca:Mg released from ashes generated in laboratory simulations at the temperatures of 150ºC, 200ºC, 250ºC, 300ºC, 350ºC, 400ºC, 450ºC, 500ºC and 550ºC during 2 hours of Quercus suber, Quercus robur and Pinus pinea and compare with ashes collected from a low-medium prescribed fire in a plot with 40x70m dominated by Quercus suber trees, located at Gavarres mountains, Catalonia. It is interesting to identify the behaviour of these indexes with temperature gradient and their differences between pre and post fire. The results showed that in laboratory experiments at reduced temperatures (<300ºC) SAR values are not substantial, increasing at middle and higher temperatures (>350ºC), mainly in Quercus robur and Pinus pinea. The relation between temperature gradient and SAR is for Quercus suber (r=0.85, p<0.01), Quercus robur (r=0.65, p<0.05) and Pinus pinea (r=0.91, p<0.001). Comparing a situation pre and post fire, we observed a significant increase of water with SAR released by the leaf litter combustion (p<0.05). Ca:Mg ratio decreased with temperature gradient, but not significatively, Quercus suber (-0.22, p>0.05), Quercus robur (-0.26 p>0.05) and Pinus pinea (-0.19 p>0.05). The fire temperatures had a higher severity in Pinus pinea litter, because Ca:Mg ratio is <1 at all temperatures. Although we identified a non significative reduction at a p level <0.05 of this ratio in litter combustion after the prescribed fire application. Overall, we observed that the water released by the organic matter combusted have a significa tive increase of SAR values, and on average in all plot, could cause slight to moderate problems in soil. Although, Ca:Mg levels do not decrease until critical values (<1) in all sample points, with the exception of the point where we collect Pinus pinea litter, as we observed in data obtained from laboratory simulations.
Abstract: The aim of this work is evaluate the physical and anthropogenic risks of wildfire in the Portuguese
maritime pine forests at the scale of municipalities. Since 1980 the fire incidents and the burned
area in Portugal have been increasing. The number of big fires (>500 ha) has also increased. The
Mediterranean climate is very susceptible to natural fire occurrences, mainly in the summer season,
but in the last years the great number of fire incidents is from anthropogenic origin. The main
causes of this catastrophic evolution are a consequence of human actions â land use change â
monoculture of eucalyptus(Eucalyptus globulus) and maritime pine (Pinus pinaster), rural exodus,,
land abandonment, the high level of garbage and criminal activity in the forests. Only minor
percentages are a result of natural causes. The maritime pine is one of the species with the widest
geographic distribution in Portuguese territory. This species has weak defences to fire incidences,
and as a consequence, very susceptible to their occurrence.
Here we want to assess, utilizing physical parameters (average temperature of the hottest month,
relative humidity, roughness and the distance to the artificial dams), what are the councils with
maritime pine forests â 235 municipalities â, more sensitive to wildfires and the degree of physical
obstacles to wildfire combat. With respect to human action, the normal profile of an arsonist is an
midle old age person with a low education level living under poor socio-economical conditions. We
want to evaluate the potential anthropogenic fire risk assessing the human development (IDH) but
also analysing the investment in the environment, using several variables (adult education index,
PIB (Gross domestic product) per capita, average life expectation and average years in school,
municipal expenditures on the environment, population density, number of firemen and ageing
index). Analysing the biophysical al parameters, the results show that the maritime pine forests in
mountain areas (Serra da Estrela, Marao, Peneda-Geres) and the littoral of Minho are the less
susceptible to fire occurrences because of the altitude and maritime influence on temperature and
humidity. On the other hand, the valleys of the rivers Tagus and Douro, have high temperatures and
a low humidity in summer season, and as consequence have a high physical risk of fire incidents.
The examination of anthropogenic variables demonstrate that, in general, Portugal has a high risk of
anthropogenic fires, mainly as a consequence of a low fire fighter number, and low investment in
the environment. Considering both the physical and anthropogenic risks, we can conclude that, in
general, Portuguese pine maritime forests have an elevated vulnerability to fire incidence. This high
risk is more a consequence of anthropogenic reasons than physical reasons.
